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1.  Evolutionary biology and anthropology suggest biome reconstitution as a necessary approach toward dealing with immune disorders 
Industrialized society currently faces a wide range of non-infectious, immune-related pandemics. These pandemics include a variety of autoimmune, inflammatory and allergic diseases that are often associated with common environmental triggers and with genetic predisposition, but that do not occur in developing societies. In this review, we briefly present the idea that these pandemics are due to a limited number of evolutionary mismatches, the most damaging being ‘biome depletion’. This particular mismatch involves the loss of species from the ecosystem of the human body, the human biome, many of which have traditionally been classified as parasites, although some may actually be commensal or even mutualistic. This view, evolved from the ‘hygiene hypothesis’, encompasses a broad ecological and evolutionary perspective that considers host-symbiont relations as plastic, changing through ecological space and evolutionary time. Fortunately, this perspective provides a blueprint, termed ‘biome reconstitution’, for disease treatment and especially for disease prevention. Biome reconstitution includes the controlled and population-wide reintroduction (i.e. domestication) of selected species that have been all but eradicated from the human biome in industrialized society and holds great promise for the elimination of pandemics of allergic, inflammatory and autoimmune diseases.
PMCID: PMC3868394  PMID: 24481190
allergy; autoimmunity; inflammation; helminths; microbiome; mutualism; autism
2.  A model for the induction of autism in the ecosystem of the human body: the anatomy of a modern pandemic? 
Microbial Ecology in Health and Disease  2015;26:10.3402/mehd.v26.26253.
The field of autism research is currently divided based on a fundamental question regarding the nature of autism: Some are convinced that autism is a pandemic of modern culture, with environmental factors at the roots. Others are convinced that the disease is not pandemic in nature, but rather that it has been with humanity for millennia, with its biological and neurological underpinnings just now being understood.
In this review, two lines of reasoning are examined which suggest that autism is indeed a pandemic of modern culture. First, given the widely appreciated derailment of immune function by modern culture, evidence that autism is strongly associated with aberrant immune function is examined. Second, evidence is reviewed indicating that autism is associated with ‘triggers’ that are, for the most part, a construct of modern culture. In light of this reasoning, current epidemiological evidence regarding the incidence of autism, including the role of changing awareness and diagnostic criteria, is examined. Finally, the potential role of the microbial flora (the microbiome) in the pathogenesis of autism is discussed, with the view that the microbial flora is a subset of the life associated with the human body, and that the entire human biome, including both the microbial flora and the fauna, has been radically destabilized by modern culture.
It is suggested that the unequivocal way to resolve the debate regarding the pandemic nature of autism is to perform an experiment: monitor the prevalence of autism after normalizing immune function in a Western population using readily available approaches that address the well-known factors underlying the immune dysfunction in that population.
PMCID: PMC4310853  PMID: 25634608
microbiome; fauna; autism; pandemic
3.  A Strategy to Identify de Novo Mutations in Common Disorders such as Autism and Schizophrenia 
There are several lines of evidence supporting the role of de novo mutations as a mechanism for common disorders, such as autism and schizophrenia. First, the de novo mutation rate in humans is relatively high, so new mutations are generated at a high frequency in the population. However, de novo mutations have not been reported in most common diseases. Mutations in genes leading to severe diseases where there is a strong negative selection against the phenotype, such as lethality in embryonic stages or reduced reproductive fitness, will not be transmitted to multiple family members, and therefore will not be detected by linkage gene mapping or association studies. The observation of very high concordance in monozygotic twins and very low concordance in dizygotic twins also strongly supports the hypothesis that a significant fraction of cases may result from new mutations. Such is the case for diseases such as autism and schizophrenia. Second, despite reduced reproductive fitness1 and extremely variable environmental factors, the incidence of some diseases is maintained worldwide at a relatively high and constant rate. This is the case for autism and schizophrenia, with an incidence of approximately 1% worldwide. Mutational load can be thought of as a balance between selection for or against a deleterious mutation and its production by de novo mutation. Lower rates of reproduction constitute a negative selection factor that should reduce the number of mutant alleles in the population, ultimately leading to decreased disease prevalence. These selective pressures tend to be of different intensity in different environments. Nonetheless, these severe mental disorders have been maintained at a constant relatively high prevalence in the worldwide population across a wide range of cultures and countries despite a strong negative selection against them2. This is not what one would predict in diseases with reduced reproductive fitness, unless there was a high new mutation rate. Finally, the effects of paternal age: there is a significantly increased risk of the disease with increasing paternal age, which could result from the age related increase in paternal de novo mutations. This is the case for autism and schizophrenia3. The male-to-female ratio of mutation rate is estimated at about 4–6:1, presumably due to a higher number of germ-cell divisions with age in males. Therefore, one would predict that de novo mutations would more frequently come from males, particularly older males4. A high rate of new mutations may in part explain why genetic studies have so far failed to identify many genes predisposing to complexes diseases genes, such as autism and schizophrenia, and why diseases have been identified for a mere 3% of genes in the human genome. Identification for de novo mutations as a cause of a disease requires a targeted molecular approach, which includes studying parents and affected subjects. The process for determining if the genetic basis of a disease may result in part from de novo mutations and the molecular approach to establish this link will be illustrated, using autism and schizophrenia as examples.
PMCID: PMC3197027  PMID: 21712793
4.  Age-Dependent Brain Gene Expression and Copy Number Anomalies in Autism Suggest Distinct Pathological Processes at Young Versus Mature Ages 
PLoS Genetics  2012;8(3):e1002592.
Autism is a highly heritable neurodevelopmental disorder, yet the genetic underpinnings of the disorder are largely unknown. Aberrant brain overgrowth is a well-replicated observation in the autism literature; but association, linkage, and expression studies have not identified genetic factors that explain this trajectory. Few studies have had sufficient statistical power to investigate whole-genome gene expression and genotypic variation in the autistic brain, especially in regions that display the greatest growth abnormality. Previous functional genomic studies have identified possible alterations in transcript levels of genes related to neurodevelopment and immune function. Thus, there is a need for genetic studies involving key brain regions to replicate these findings and solidify the role of particular functional pathways in autism pathogenesis. We therefore sought to identify abnormal brain gene expression patterns via whole-genome analysis of mRNA levels and copy number variations (CNVs) in autistic and control postmortem brain samples. We focused on prefrontal cortex tissue where excess neuron numbers and cortical overgrowth are pronounced in the majority of autism cases. We found evidence for dysregulation in pathways governing cell number, cortical patterning, and differentiation in young autistic prefrontal cortex. In contrast, adult autistic prefrontal cortex showed dysregulation of signaling and repair pathways. Genes regulating cell cycle also exhibited autism-specific CNVs in DNA derived from prefrontal cortex, and these genes were significantly associated with autism in genome-wide association study datasets. Our results suggest that CNVs and age-dependent gene expression changes in autism may reflect distinct pathological processes in the developing versus the mature autistic prefrontal cortex. Our results raise the hypothesis that genetic dysregulation in the developing brain leads to abnormal regional patterning, excess prefrontal neurons, cortical overgrowth, and neural dysfunction in autism.
Author Summary
Autism is a disorder characterized by aberrant social, communication, and restricted and repetitive behaviors. It develops clinically in the first years of life. Toddlers and children with autism often exhibit early brain enlargement and excess neuron numbers in the prefrontal cortex. Adults with autism generally do not display enlargement but instead may have a smaller brain size. Thus, we investigated DNA and mRNA patterns in prefrontal cortex from young versus adult postmortem individuals with autism to identify age-related gene expression differences as well as possible genetic correlates of abnormal brain enlargement, excess neuron numbers, and abnormal functioning in this disorder. We found abnormalities in genetic pathways governing cell number, neurodevelopment, and cortical lateralization in autism. We also found that the key pathways associated with autism are different between younger and older autistic individuals. These findings suggest that dysregulated gene pathways in the early stages of neurodevelopment could lead to later behavioral and cognitive deficits associated with autism.
PMCID: PMC3310790  PMID: 22457638
5.  Non-Specialist Psychosocial Interventions for Children and Adolescents with Intellectual Disability or Lower-Functioning Autism Spectrum Disorders: A Systematic Review 
PLoS Medicine  2013;10(12):e1001572.
In a systematic review, Brian Reichow and colleagues assess the evidence that non-specialist care providers in community settings can provide effective interventions for children and adolescents with intellectual disabilities or lower-functioning autism spectrum disorders.
Please see later in the article for the Editors' Summary
The development of effective treatments for use by non-specialists is listed among the top research priorities for improving the lives of people with mental illness worldwide. The purpose of this review is to appraise which interventions for children with intellectual disabilities or lower-functioning autism spectrum disorders delivered by non-specialist care providers in community settings produce benefits when compared to either a no-treatment control group or treatment-as-usual comparator.
Methods and Findings
We systematically searched electronic databases through 24 June 2013 to locate prospective controlled studies of psychosocial interventions delivered by non-specialist providers to children with intellectual disabilities or lower-functioning autism spectrum disorders. We screened 234 full papers, of which 34 articles describing 29 studies involving 1,305 participants were included. A majority of the studies included children exclusively with a diagnosis of lower-functioning autism spectrum disorders (15 of 29, 52%). Fifteen of twenty-nine studies (52%) were randomized controlled trials and just under half of all effect sizes (29 of 59, 49%) were greater than 0.50, of which 18 (62%) were statistically significant. For behavior analytic interventions, the best outcomes were shown for development and daily skills; cognitive rehabilitation, training, and support interventions were found to be most effective for improving developmental outcomes, and parent training interventions to be most effective for improving developmental, behavioral, and family outcomes. We also conducted additional subgroup analyses using harvest plots. Limitations include the studies' potential for performance bias and that few were conducted in lower- and middle-income countries.
The findings of this review support the delivery of psychosocial interventions by non-specialist providers to children who have intellectual disabilities or lower-functioning autism spectrum disorders. Given the scarcity of specialists in many low-resource settings, including many lower- and middle-income countries, these findings may provide guidance for scale-up efforts for improving outcomes for children with developmental disorders or lower-functioning autism spectrum disorders.
Protocol Registration
PROSPERO CRD42012002641
Please see later in the article for the Editors' Summary
Editors' Summary
Newborn babies are helpless, but over the first few years of life, they acquire motor (movement) skills, language (communication) skills, cognitive (thinking) skills, and social (interpersonal interaction) skills. Individual aspects of these skills are usually acquired at specific ages, but children with a development disorder such as an autism spectrum disorder (ASD) or intellectual disability (mental retardation) fail to reach these “milestones” because of impaired or delayed brain maturation. Autism, Asperger syndrome, and other ASDs (also called pervasive developmental disorders) affect about 1% of the UK and US populations and are characterized by abnormalities in interactions and communication with other people (reciprocal socio-communicative interactions; for example, some children with autism reject physical affection and fail to develop useful speech) and a restricted, stereotyped, repetitive repertoire of interests (for example, obsessive accumulation of facts about unusual topics). About half of individuals with an ASD also have an intellectual disability—a reduced overall level of intelligence characterized by impairment of the skills that are normally acquired during early life. Such individuals have what is called lower-functioning ASD.
Why Was This Study Done?
Most of the children affected by developmental disorders live in low- and middle-income countries where there are few services available to help them achieve their full potential and where little research has been done to identify the most effective treatments. The development of effective treatments for use by non-specialists (for example, teachers and parents) is necessary to improve the lives of people with mental illnesses worldwide, but particularly in resource-limited settings where psychiatrists, psychologists, and other specialists are scarce. In this systematic review, the researchers investigated which psychosocial interventions for children and adolescents with intellectual disabilities or lower-functioning ASDs delivered by non-specialist providers in community settings produce improvements in development, daily skills, school performance, behavior, or family outcomes when compared to usual care (the control condition). A systematic review identifies all the research on a given topic using predefined criteria; psychosocial interventions are defined as therapy, education, training, or support aimed at improving behavior, overall development, or specific life skills without the use of drugs.
What Did the Researchers Do and Find?
The researchers identified 29 controlled studies (investigations with an intervention group and a control group) that examined the effects of various psychosocial interventions delivered by non-specialist providers to children (under 18 years old) who had a lower-functioning ASD or intellectual disability. The researchers retrieved information on the participants, design and methods, findings, and intervention characteristics for each study, and calculated effect sizes—a measure of the effectiveness of a test intervention relative to a control intervention—for several outcomes for each intervention. Across the studies, three-quarters of the effect size estimates were positive, and nearly half were greater than 0.50; effect sizes of less than 0.2, 0.2–0.5, and greater than 0.5 indicate that an intervention has no, a small, or a medium-to-large effect, respectively. For behavior analytic interventions (which aim to improve socially significant behavior by systematically analyzing behavior), the largest effect sizes were seen for development and daily skills. Cognitive rehabilitation, training, and support (interventions that facilitates the relearning of lost or altered cognitive skills) produced good improvements in developmental outcomes such as standardized IQ tests in children aged 6–11 years old. Finally, parental training interventions (which teach parents how to provide therapy services for their child) had strong effects on developmental, behavioral, and family outcomes.
What Do These Findings Mean?
Because few of the studies included in this systematic review were undertaken in low- and middle-income countries, the review's findings may not be generalizable to children living in resource-limited settings. Moreover, other characteristics of the included studies may limit the accuracy of these findings. Nevertheless, these findings support the delivery of psychosocial interventions by non-specialist providers to children who have intellectual disabilities or a lower-functioning ASD, and indicate which interventions are likely to produce the largest improvements in developmental, behavioral, and family outcomes. Further studies are needed, particularly in low- and middle-income countries, to confirm these findings, but given that specialists are scarce in many resource-limited settings, these findings may help to inform the implementation of programs to improve outcomes for children with intellectual disabilities or lower-functioning ASDs in low- and middle-income countries.
Additional Information
Please access these websites via the online version of this summary at
This study is further discussed in a PLOS Medicine Perspective by Bello-Mojeed and Bakare
The US Centers for Disease Control and Prevention provides information (in English and Spanish) on developmental disabilities, including autism spectrum disorders and intellectual disability
The US National Institute of Mental Health also provides detailed information about autism spectrum disorders, including the publication “A Parent's Guide to Autism Spectrum Disorder”
Autism Speaks, a US non-profit organization, provides information about all aspects of autism spectrum disorders and includes information on the Autism Speaks Global Autism Public Health Initiative
The National Autistic Society, a UK charity, provides information about all aspects of autism spectrum disorders and includes personal stories about living with these conditions
The UK National Health Service Choices website has an interactive guide to child development and information about autism and Asperger syndrome, including personal stories, and about learning disabilities
The UK National Institute for Health and Care Excellence provides clinical guidelines for the management and support of children with autism spectrum disorders
The World Health Organization provides information on its Mental Health Gap Action Programme (mhGAP), which includes recommendations on the management of developmental disorders by non-specialist providers; the mhGAP Evidence Resource Center provides evidence reviews for parent skills training for management of children with intellectual disabilities and pervasive developmental disorders and interventions for management of children with intellectual disabilities
PROSPERO, an international prospective register of systematic reviews, provides more information about this systematic review
PMCID: PMC3866092  PMID: 24358029
6.  Potential Role of Decoy B7-H4 in the Pathogenesis of Rheumatoid Arthritis: A Mouse Model Informed by Clinical Data 
PLoS Medicine  2009;6(10):e1000166.
Finding an association between soluble B7-H4 and rheumatoid arthritis severity, Lieping Chen and colleagues use a mouse model to show that the soluble form blocks the inhibitory function of cell-surface B7-H4.
A pathogenic hallmark of rheumatoid arthritis (RA) is persistent inflammatory responses in target tissues and organs. Immune responses mediated by T cells and autoantibodies are known to play pivotal roles. A possible interpretation for this observation is a loss of negative regulation of autoimmune responses. Here we sought to investigate whether B7-H4, a cell surface inhibitory molecule of the B7-CD28 signaling pathway, may play a role in the pathogenesis of RA.
Methods and Findings
In a cross-sectional study of a clinical convenience sample using monoclonal antibodies against human B7-H4 molecules, we detected high levels of the soluble form of B7-H4 (sH4) in the sera of 65% of patients with RA (n = 68) versus only 13% of healthy donors (n = 24). Elevated sH4 was associated with an increased disease severity score (DAS28) in a cross-sectional analysis. In a mouse model of RA, transgenic expression of sH4 or genetic deletion of B7-H4 accelerated the progression of collagen-induced arthritis, accompanied by enhanced T and B cell–mediated autoimmune responses as well as increased activity of neutrophils. Expression in vivo of an agonist, a B7-H4-immunoglobulin Fc fusion protein, profoundly suppressed disease progression in the mouse model.
Our findings in mice indicate that sH4 acts as a decoy molecule to block the inhibitory functions of cell-surface B7-H4, leading to exacerbation of collagen-induced arthritis. If the preliminary correlation between sH4 levels and disease activity in patients with RA can be confirmed to reflect a similar mechanism, these findings suggest a novel target for treatment approaches.
Please see later in the article for the Editors' Summary
Editors' Summary
Rheumatoid arthritis (RA) is a chronic disease caused by abnormal immune responses. In RA, the body's own immune system mainly attacks the joints, causing inflammation in their lining, but can affect other tissues and organs in the body. About 1% of the population in developed countries suffer from RA, and it can result in long-term joint damage, causing significant illness and disability. Sufferers have chronic pain, loss of function of the joint, and loss of mobility. The cause of RA is unknown and there is no known cure. However, neutrophils (an immune cell important for inflammation) are thought to contribute to the initiation of RA. Understanding the primary mechanisms behind the development of RA, and where the body's immune system goes wrong, is fundamental not only to find new treatments for the disease but also to aid diagnosis to help patients get treatment to help control their often debilitating symptoms.
Why Was the Study Done?
Regulation of the immune system is necessary to prevent overactivity. Interruptions to the normal signals that moderate the immune response can lead to destruction of normal tissues. Previous studies have shown that the B7 family of proteins, which interact with CD28 signaling proteins on the surface of immune cells, are important regulators of the immune response. B7 proteins have also been found to exist in soluble forms that have been implicated in the development of rheumatoid diseases, but their exact role is not well understood. In the current study, researchers examined a member of the B7 family, B7-H4, which normally acts as an inhibitor of the immune response, to find out whether this signaling molecule affects the immune response and has a role in the development of RA.
What Did the Researchers Do and Find?
The researchers collected blood from 68 patients with RA and 24 healthy volunteers, and measured levels of soluble B7-H4, also known as sH4. They found sH4 in blood from 65% of patients with RA, compared with only 13% of healthy people. The levels of sH4 were significantly higher in RA patients (96.1 ng/ml) compared to healthy people (<5 ng/ml). Moreover, the highest levels of sH4 were found in patients with the most severe forms of RA, as measured by a standard index score that includes general health, the number of swollen joints, and the amount of inflammation. The researchers then used a mouse model of RA to explore how sH4 might contribute to RA. First, they injected mice with plasmids (circular pieces of DNA that can be used to transfer genes into organisms) carrying the gene for sH4 and looked at how overexpression of sH4 affected the development of arthritis. They also looked at how deleting the B7-H4 gene in mice affected symptoms. Both overexpression of sH4 and deletion of B7-H4 caused inflammation in the mice; symptoms appeared earlier and were more severe. Furthermore, the effects of sH4 were shown to be dependent on neutrophils. Finally, the researchers successfully prevented the development of disease in mice by using a protein to mimic the normal signaling by B7-H4, which inhibits the immune response.
What Do these Findings Mean?
These findings suggest that the signaling molecule B7-H4 may be involved in the development of RA. B7-H4 normally acts as an inhibitor of the immune response to suppress inflammation, but when its action is blocked the immune response is no longer suppressed, and an inappropriate and increased immune reaction occurs. sH4 is thought to act as a decoy that blocks binding of B7-H4 to its receptor, thereby preventing an inhibitory signal to the immune system. Overexpression of sH4 worsens the symptoms in the mouse model of RA. Intriguingly, high levels of sH4 were also present in RA patients and were associated with increased severity of disease. This study does not establish sH4 as a cause of RA but implicates sH4 as a cause in the progression of increased inflammation in this disease. Immune system signaling molecules have potential as novel targets for treatment of RA and other autoimmune disorders. However, further studies are needed to test whether sH4 has a direct role in the development of RA in humans.
Additional Information
Please access these Web sites via the online version of this summary at
MedlinePlus has a topic page on RA providing extensive information on symptoms and treatment for RA and access to related clinical trials and medical literature
The National Rheumatoid Arthritis Society (UK) is a patient-led charity to provide information, education, and support for people with RA
The Arthritis Foundation (US) is a national not-for-profit organization that supports public health education and research funding, and provides informational resources for people with arthritis
PMCID: PMC2760136  PMID: 19841745
7.  Application of Novel PCR-Based Methods for Detection, Quantitation, and Phylogenetic Characterization of Sutterella Species in Intestinal Biopsy Samples from Children with Autism and Gastrointestinal Disturbances 
mBio  2012;3(1):e00261-11.
Gastrointestinal disturbances are commonly reported in children with autism and may be associated with compositional changes in intestinal bacteria. In a previous report, we surveyed intestinal microbiota in ileal and cecal biopsy samples from children with autism and gastrointestinal dysfunction (AUT-GI) and children with only gastrointestinal dysfunction (Control-GI). Our results demonstrated the presence of members of the family Alcaligenaceae in some AUT-GI children, while no Control-GI children had Alcaligenaceae sequences. Here we demonstrate that increased levels of Alcaligenaceae in intestinal biopsy samples from AUT-GI children result from the presence of high levels of members of the genus Sutterella. We also report the first Sutterella-specific PCR assays for detecting, quantitating, and genotyping Sutterella species in biological and environmental samples. Sutterella 16S rRNA gene sequences were found in 12 of 23 AUT-GI children but in none of 9 Control-GI children. Phylogenetic analysis revealed a predominance of either Sutterella wadsworthensis or Sutterella stercoricanis in 11 of the individual Sutterella-positive AUT-GI patients; in one AUT-GI patient, Sutterella sequences were obtained that could not be given a species-level classification based on the 16S rRNA gene sequences of known Sutterella isolates. Western immunoblots revealed plasma IgG or IgM antibody reactivity to Sutterella wadsworthensis antigens in 11 AUT-GI patients, 8 of whom were also PCR positive, indicating the presence of an immune response to Sutterella in some children.
Autism spectrum disorders affect ~1% of the population. Many children with autism have gastrointestinal (GI) disturbances that can complicate clinical management and contribute to behavioral problems. Understanding the molecular and microbial underpinnings of these GI issues is of paramount importance for elucidating pathogenesis, rendering diagnosis, and administering informed treatment. Here we describe an association between high levels of intestinal, mucoepithelial-associated Sutterella species and GI disturbances in children with autism. These findings elevate this little-recognized bacterium to the forefront by demonstrating that Sutterella is a major component of the microbiota in over half of children with autism and gastrointestinal dysfunction (AUT-GI) and is absent in children with only gastrointestinal dysfunction (Control-GI) evaluated in this study. Furthermore, these findings bring into question the role Sutterella plays in the human microbiota in health and disease. With the Sutterella-specific molecular assays described here, some of these questions can begin to be addressed.
PMCID: PMC3252763  PMID: 22233678
8.  Exome sequencing of extended families with autism reveals genes shared across neurodevelopmental and neuropsychiatric disorders 
Molecular Autism  2014;5:1.
Autism spectrum disorders (ASDs) comprise a range of neurodevelopmental conditions of varying severity, characterized by marked qualitative difficulties in social relatedness, communication, and behavior. Despite overwhelming evidence of high heritability, results from genetic studies to date show that ASD etiology is extremely heterogeneous and only a fraction of autism genes have been discovered.
To help unravel this genetic complexity, we performed whole exome sequencing on 100 ASD individuals from 40 families with multiple distantly related affected individuals. All families contained a minimum of one pair of ASD cousins. Each individual was captured with the Agilent SureSelect Human All Exon kit, sequenced on the Illumina Hiseq 2000, and the resulting data processed and annotated with Burrows-Wheeler Aligner (BWA), Genome Analysis Toolkit (GATK), and SeattleSeq. Genotyping information on each family was utilized in order to determine genomic regions that were identical by descent (IBD). Variants identified by exome sequencing which occurred in IBD regions and present in all affected individuals within each family were then evaluated to determine which may potentially be disease related. Nucleotide alterations that were novel and rare (minor allele frequency, MAF, less than 0.05) and predicted to be detrimental, either by altering amino acids or splicing patterns, were prioritized.
We identified numerous potentially damaging, ASD associated risk variants in genes previously unrelated to autism. A subset of these genes has been implicated in other neurobehavioral disorders including depression (SLIT3), epilepsy (CLCN2, PRICKLE1), intellectual disability (AP4M1), schizophrenia (WDR60), and Tourette syndrome (OFCC1). Additional alterations were found in previously reported autism candidate genes, including three genes with alterations in multiple families (CEP290, CSMD1, FAT1, and STXBP5). Compiling a list of ASD candidate genes from the literature, we determined that variants occurred in ASD candidate genes 1.65 times more frequently than in random genes captured by exome sequencing (P = 8.55 × 10-5).
By studying these unique pedigrees, we have identified novel DNA variations related to ASD, demonstrated that exome sequencing in extended families is a powerful tool for ASD candidate gene discovery, and provided further evidence of an underlying genetic component to a wide range of neurodevelopmental and neuropsychiatric diseases.
PMCID: PMC3896704  PMID: 24410847
Autism spectrum disorder (ASD); Identical by descent (IBD); Single nucleotide variant (SNV); Whole exome sequencing
9.  Prenatal and perinatal analgesic exposure and autism: an ecological link 
Environmental Health  2013;12:41.
Autism and Autism Spectrum Disorder (ASD) are complex neurodevelopmental disorders. Susceptibility is believed to be the interaction of genetic heritability and environmental factors. The synchronous rises in autism/ASD prevalence and paracetamol (acetaminophen) use, as well as biologic plausibility have led to the hypothesis that paracetamol exposure may increase autism/ASD risk.
To explore the relationship of antenatal paracetamol exposure to ASD, population weighted average autism prevalence rates and paracetamol usage rates were compared. To explore the relationship of early neonatal paracetamol exposure to autism/ASD, population weighted average male autism prevalence rates for all available countries and U.S. states were compared to male circumcision rates – a procedure for which paracetamol has been widely prescribed since the mid-1990s. Prevalence studies were extracted from the U.S. Centers for Disease Control and Prevention Summary of Autism/ASD Prevalence Studies database. Maternal paracetamol usage and circumcision rates were identified by searches on Pub Med.
Using all available country-level data (n = 8) for the period 1984 to 2005, prenatal use of paracetamol was correlated with autism/ASD prevalence (r = 0.80). For studies including boys born after 1995, there was a strong correlation between country-level (n = 9) autism/ASD prevalence in males and a country’s circumcision rate (r = 0.98). A very similar pattern was seen among U.S. states and when comparing the 3 main racial/ethnic groups in the U.S. The country-level correlation between autism/ASD prevalence in males and paracetamol was considerably weaker before 1995 when the drug became widely used during circumcision.
This ecological analysis identified country-level correlations between indicators of prenatal and perinatal paracetamol exposure and autism/ASD. State level correlation was also identified for the indicator of perinatal paracetamol exposure and autism/ASD. Like all ecological analyses, these data cannot provide strong evidence of causality. However, biologic plausibility is provided by a growing body of experimental and clinical evidence linking paracetamol metabolism to pathways shown to be important in autism and related developmental abnormalities. Taken together, these ecological findings and mechanistic evidence suggest the need for formal study of the role of paracetamol in autism.
PMCID: PMC3673819  PMID: 23656698
Paracetamol; Acetaminophen; Autism spectrum disorder; Sulfation; Glucuronidation; Pro-inflammatory cytokines
10.  Spatial inequalities in life expectancy within postindustrial regions of Europe: a cross-sectional observational study 
BMJ Open  2014;4(6):e004711.
To compare spatial inequalities in life expectancy (LE) in West Central Scotland (WCS) with nine other postindustrial European regions.
A cross-sectional observational study.
WCS and nine other postindustrial regions across Europe.
Data for WCS and nine other comparably deindustrialised European regions were analysed. Male and female LEs at birth were obtained or calculated for the mid-2000s for 160 districts within selected regions. Districts were stratified into two groups: small (populations of between 141 000 and 185 000 people) and large (populations between 224 000 and 352 000). The range and IQR in LE were used to describe within-region disparities.
In small districts, the male LE range was widest in WCS and Merseyside, while the IQR was widest in WCS and Northern Ireland. For women, the LE range was widest in WCS, though the IQR was widest in Northern Ireland and Merseyside. In large districts, the range and IQR in LE was widest in WCS and Wallonia for both sexes.
Subregional spatial inequalities in LE in WCS are wide compared with other postindustrial mainland European regions, especially for men. Future research could explore the contribution of economic, social and political factors in reducing these inequalities.
PMCID: PMC4054650  PMID: 24889851
11.  Repair of naturally occurring mismatches can induce mutations in flanking DNA 
eLife  2014;3:e02001.
‘Normal’ genomic DNA contains hundreds of mismatches that are generated daily by the spontaneous deamination of C (U/G) and methyl-C (T/G). Thus, a mutagenic effect of their repair could constitute a serious genetic burden. We show here that while mismatches introduced into human cells on an SV40-based episome were invariably repaired, this process induced mutations in flanking DNA at a significantly higher rate than no mismatch controls. Most mutations involved the C of TpC, the substrate of some single strand-specific APOBEC cytidine deaminases, similar to the mutations that can typify the ‘mutator phenotype’ of numerous tumors. siRNA knockdowns and chromatin immunoprecipitation showed that TpC preferring APOBECs mediate the mutagenesis, and siRNA knockdowns showed that both the base excision and mismatch repair pathways are involved. That naturally occurring mispairs can be converted to mutators, represents an heretofore unsuspected source of genetic changes that could underlie disease, aging, and evolutionary change.
eLife digest
The inherent chemical instability of the four bases that are found in DNA leads to our genetic material being damaged on a daily basis. The sequence of these bases codes the genetic instructions necessary for all cellular functions, so damaged bases must be efficiently recognized and accurately repaired. The base excision repair pathway carries out these functions.
However, there are some circumstances in which random changes to the genetic code can be beneficial. In immune cells, for example, these changes enhance the diversity of antibodies generated to fight bacteria and viruses. In immune cells, a second repair pathway—the mismatch repair pathway—hijacks the base excision repair pathway. This gives enzymes belonging to the APOBEC family access to the DNA that is undergoing repair, and these enzymes change cytosine bases to uracil bases. Subsequent processing steps can lead to different bases substituted for the original cytosine. The recent discovery that APOBEC enzymes are abundant in other types of cells raised the possibility that these enzymes could be significant source of mutations in the DNA of cells where such mutations are not welcome.
To explore this possibility Chen et al. deliberately introduced a number of mutations (that are normally repaired by the base excision repair pathway) into non-immune human cells and observed what happened. The mutations were repaired, but the number of mutations in neighboring bases increased by a statistically significant amount. In particular, most of these mutations involved a cytosine base that was preceded by a thymine base. Chen et al. also showed that both APOBEC and the mismatch repair pathway are involved, as is the case for the mutations caused by APOBEC enzymes in immune cells. Similar APOBEC mutations are known to be involved in cancer.
The model system developed by Chen et al. not only shows that normally error-free DNA repair can be involved in generating these mutations, but also used to obtain a better understanding of these processes and thereby provide new insights in cancer biology.
PMCID: PMC3999860  PMID: 24843013
DNA repair; mutagenesis; APOBEC deaminase; human
12.  Zinc finger protein 804A (ZNF804A) and verbal deficits in individuals with autism 
In a genome-wide association study of autism, zinc finger protein 804A (ZNF804A) single nucleotide polymorphisms (SNPs) were found to be nominally associated in verbally deficient individuals with autism. Zinc finger protein 804A copy number variations (CNVs) have also been observed in individuals with autism. In addition, ZNF804A is known to be involved in theory of mind (ToM) tasks, and ToM deficits are deemed responsible for the communication and social challenges faced by individuals with autism. We hypothesized that ZNF804A could be a risk gene for autism.
We examined the genetic association and CNVs of ZNF804A in 841 families in which 1 or more members had autism. We compared the expression of ZNF804A in the postmortem brains of individuals with autism (n = 8) and controls (n = 13). We also assessed in vitro the effect of ZNF804A silencing on the expression of several genes known to be involved in verbal efficiency and social cognition.
We found that rs7603001 was nominally associated with autism (p = 0.018). The association was stronger (p = 0.008) in the families of individuals with autism who were verbally deficient (n = 761 families). We observed ZNF804A CNVs in 7 verbally deficient boys with autism. In ZNF804A knockdown cells, the expression of synaptosomal-associated protein, 25kDa (SNAP25) was reduced compared with controls (p = 0.009). The expression of ZNF804A (p = 0.009) and SNAP25 (p = 0.009) were reduced in the anterior cingulate gyrus (ACG) of individuals with autism. There was a strong positive correlation between the expression of ZNF804A and SNAP25 in the ACG (p < 0.001).
Study limitations include our small sample size of postmortem brains.
Our results suggest that ZNF804A could be a potential candidate gene mediating the intermediate phenotypes associated with verbal traits in individuals with autism.
PMCID: PMC4160358  PMID: 24866414
13.  Immune system gene dysregulation in autism & schizophrenia 
Developmental neurobiology  2012;72(10):1277-1287.
Gene*environment interactions play critical roles in the emergence of autism and schizophrenia pathophysiology. In both disorders, recent genetic association studies have provided evidence for disease-linked variation in immune system genes and post-mortem gene expression studies have shown extensive chronic immune abnormalities in brains of diseased subjects. Furthermore, peripheral biomarker studies revealed that both innate and adaptive immune systems are dysregulated. In both disorders symptoms of the disease correlate with the immune system dysfunction; yet, in autism this process appears to be chronic and sustained, while in schizophrenia it is exacerbated during acute episodes. Furthermore, since immune abnormalities endure into adulthood and anti-inflammatory agents appear to be beneficial, it is likely that these immune changes actively contribute to disease symptoms. Modeling these changes in animals provided further evidence that prenatal maternal immune activation alters neurodevelopment and leads to behavioral changes that are relevant for autism and schizophrenia. The converging evidence strongly argues that neurodevelopmental immune insults and genetic background critically interact and result in increased risk for either autism or schizophrenia. Further research in these areas may improve prenatal health screening in genetically at-risk families and may also lead to new preventive and/or therapeutic strategies.
PMCID: PMC3435446  PMID: 22753382
schizophrenia; autism; immune; environment; maternal immune activation
14.  Protein Interaction Networks Reveal Novel Autism Risk Genes within GWAS Statistical Noise 
PLoS ONE  2014;9(11):e112399.
Genome-wide association studies (GWAS) for Autism Spectrum Disorder (ASD) thus far met limited success in the identification of common risk variants, consistent with the notion that variants with small individual effects cannot be detected individually in single SNP analysis. To further capture disease risk gene information from ASD association studies, we applied a network-based strategy to the Autism Genome Project (AGP) and the Autism Genetics Resource Exchange GWAS datasets, combining family-based association data with Human Protein-Protein interaction (PPI) data. Our analysis showed that autism-associated proteins at higher than conventional levels of significance (P<0.1) directly interact more than random expectation and are involved in a limited number of interconnected biological processes, indicating that they are functionally related. The functionally coherent networks generated by this approach contain ASD-relevant disease biology, as demonstrated by an improved positive predictive value and sensitivity in retrieving known ASD candidate genes relative to the top associated genes from either GWAS, as well as a higher gene overlap between the two ASD datasets. Analysis of the intersection between the networks obtained from the two ASD GWAS and six unrelated disease datasets identified fourteen genes exclusively present in the ASD networks. These are mostly novel genes involved in abnormal nervous system phenotypes in animal models, and in fundamental biological processes previously implicated in ASD, such as axon guidance, cell adhesion or cytoskeleton organization. Overall, our results highlighted novel susceptibility genes previously hidden within GWAS statistical “noise” that warrant further analysis for causal variants.
PMCID: PMC4237351  PMID: 25409314
15.  Protection against Mycobacterium ulcerans Lesion Development by Exposure to Aquatic Insect Saliva 
PLoS Medicine  2007;4(2):e64.
Buruli ulcer is a severe human skin disease caused by Mycobacterium ulcerans. This disease is primarily diagnosed in West Africa with increasing incidence. Antimycobacterial drug therapy is relatively effective during the preulcerative stage of the disease, but surgical excision of lesions with skin grafting is often the ultimate treatment. The mode of transmission of this Mycobacterium species remains a matter of debate, and relevant interventions to prevent this disease lack (i) the proper understanding of the M. ulcerans life history traits in its natural aquatic ecosystem and (ii) immune signatures that could be correlates of protection. We previously set up a laboratory ecosystem with predatory aquatic insects of the family Naucoridae and laboratory mice and showed that (i) M. ulcerans-carrying aquatic insects can transmit the mycobacterium through bites and (ii) that their salivary glands are the only tissues hosting replicative M. ulcerans. Further investigation in natural settings revealed that 5%–10% of these aquatic insects captured in endemic areas have M. ulcerans–loaded salivary glands. In search of novel epidemiological features we noticed that individuals working close to aquatic environments inhabited by insect predators were less prone to developing Buruli ulcers than their relatives. Thus we set out to investigate whether those individuals might display any immune signatures of exposure to M. ulcerans-free insect predator bites, and whether those could correlate with protection.
Methods and Findings
We took a two-pronged approach in this study, first investigating whether the insect bites are protective in a mouse model, and subsequently looking for possibly protective immune signatures in humans. We found that, in contrast to control BALB/c mice, BALB/c mice exposed to Naucoris aquatic insect bites or sensitized to Naucoris salivary gland homogenates (SGHs) displayed no lesion at the site of inoculation of M. ulcerans coated with Naucoris SGH components. Then using human serum samples collected in a Buruli ulcer–endemic area (in the Republic of Benin, West Africa), we assayed sera collected from either ulcer-free individuals or patients with Buruli ulcers for the titre of IgGs that bind to insect predator SGH, focusing on those molecules otherwise shown to be retained by M. ulcerans colonies. IgG titres were lower in the Buruli ulcer patient group than in the ulcer-free group.
These data will help structure future investigations in Buruli ulcer–endemic areas, providing a rationale for research into human immune signatures of exposure to predatory aquatic insects, with special attention to those insect saliva molecules that bind to M. ulcerans.
Saliva from aquatic insects in areas where Buruli ulcer is endemic can protect mice against the disease's characteristic skin lesion and might play a role in natural immunity in humans.
Editors' Summary
Buruli ulcer disease is a severe skin infection caused by Mycobacterium ulcerans, a bacterium related to those that cause tuberculosis and leprosy. This poorly understood disease affects people living near slow-flowing or standing water in poor rural communities in tropical and subtropical countries. How people become infected with M. ulcerans is unclear but one possibility is that infected aquatic insects transmit it through their bites. The first sign of infection is usually a small painless swelling in the skin. Bacteria inside these swellings produce a toxin that damages nearby soft tissues until eventually the skin sloughs off to leave a large open sore. This usually heals but the resultant scar can limit limb movement. Consequently, 25% of people affected by Buruli ulcers—most of whom are children—are permanently disabled. If the disease is caught early, powerful antibiotics can prevent ulcer formation. But most patients do not seek help until the later stages when the only treatment is to cut out the infection and do a skin graft, a costly and lengthy treatment.
Why Was This Study Done?
There is currently no effective way to prevent Buruli ulcers. To develop an effective preventative strategy, researchers need to determine exactly how the infection is transmitted to people and what makes some individuals resistant to infection. Previous studies have indicated that 5%–10% of some aquatic insect predators that live in areas where Buruli ulcers occur have M. ulcerans in their salivary glands and that aquatic insects carrying M. ulcerans can transmit it to mice through bites. Furthermore, people working close to water inhabited by insect predators are less likely to develop Buruli ulcers than their relatives who do not work near water. In this study, therefore, the researchers investigated whether exposure to noninfected insect saliva provides some protection against M. ulcerans infection.
What Did the Researchers Do and Find?
The researchers let uninfected aquatic insects bite ten mice several times before exposing these mice and ten unbitten mice to M. ulcerans-infected water bugs. Only one pre-bitten mouse developed an M. ulcerans-containing lesion compared with eight control mice. Next, the researchers injected mice with insect salivary gland extracts before challenging them with “naked” M. ulcerans or bacteria coated with salivary gland extract. Most uninjected mice developed lesions when challenged with coated or naked M. ulcerans, as did experimental mice challenged with naked M. ulcerans. However, most experimental mice challenged with coated M. ulcerans remained lesion-free. In both experiments, the blood of the pre-bitten and extract-treated mice (but not the control mice) contained antibodies (immune system proteins that provide protection against infections and foreign proteins) to proteins in insect salivary gland extracts that stick to M. ulcerans. Finally, the researchers measured the blood concentration (the titer) of antibodies that bind insect salivary gland proteins in patients with Buruli ulcer and in healthy people living in the same area. People with high titers of these antibodies, they report, were less likely to have Buruli ulcers than those with low titers.
What Do These Findings Mean?
These findings suggest that exposure to aquatic insect saliva may provide some protection against M. ulcerans lesion development. However, the current results have several limitations. In particular they will only be relevant to human disease if M. ulcerans is normally transmitted by insect bites, and this has not been proven yet. Also, because the human study did not measure the overall immune status of the study participants, the people with Buruli ulcers may have had a general immune deficit rather than simply lacking antibodies against insect salivary gland proteins. However, if the human findings can be repeated and expanded, they suggest that low antibody titers to salivary gland proteins might identify those people who are most susceptible to M ulcerans infections and who would thus benefit most from regular tests for early signs of the disease. Finally, further work on the immune mechanism by which exposure to insect salivary gland proteins protects against M. ulcerans infections may help in the development of vaccines against Buruli ulcer disease.
Additional Information.
Please access these Web sites via the online version of this summary at
A related PLoS Medicine Perspective article by Manuel T. Silva and others discusses this study and others on insect-borne parasitic diseases
World Health Organization has information on Buruli ulcer disease
US Centers for Disease Control and Prevention has information on Buruli ulcer
The US Armed Forces Institute of Pathology Web site contains pages on Buruli ulcer
Leprosy Relief Emmaus Switzerland offers information on Buruli ulcer
Wikipedia contains pages on Buruli ulcer (note: Wikipedia is an online encyclopedia that anyone can edit)
PLoS Medicine has a detailed review article on Buruli ulcer by Paul D. R. Johnson and colleagues
PMCID: PMC1808094  PMID: 17326707
16.  A noise-reduction GWAS analysis implicates altered regulation of neurite outgrowth and guidance in autism 
Molecular Autism  2011;2:1.
Genome-wide Association Studies (GWAS) have proved invaluable for the identification of disease susceptibility genes. However, the prioritization of candidate genes and regions for follow-up studies often proves difficult due to false-positive associations caused by statistical noise and multiple-testing. In order to address this issue, we propose the novel GWAS noise reduction (GWAS-NR) method as a way to increase the power to detect true associations in GWAS, particularly in complex diseases such as autism.
GWAS-NR utilizes a linear filter to identify genomic regions demonstrating correlation among association signals in multiple datasets. We used computer simulations to assess the ability of GWAS-NR to detect association against the commonly used joint analysis and Fisher's methods. Furthermore, we applied GWAS-NR to a family-based autism GWAS of 597 families and a second existing autism GWAS of 696 families from the Autism Genetic Resource Exchange (AGRE) to arrive at a compendium of autism candidate genes. These genes were manually annotated and classified by a literature review and functional grouping in order to reveal biological pathways which might contribute to autism aetiology.
Computer simulations indicate that GWAS-NR achieves a significantly higher classification rate for true positive association signals than either the joint analysis or Fisher's methods and that it can also achieve this when there is imperfect marker overlap across datasets or when the closest disease-related polymorphism is not directly typed. In two autism datasets, GWAS-NR analysis resulted in 1535 significant linkage disequilibrium (LD) blocks overlapping 431 unique reference sequencing (RefSeq) genes. Moreover, we identified the nearest RefSeq gene to the non-gene overlapping LD blocks, producing a final candidate set of 860 genes. Functional categorization of these implicated genes indicates that a significant proportion of them cooperate in a coherent pathway that regulates the directional protrusion of axons and dendrites to their appropriate synaptic targets.
As statistical noise is likely to particularly affect studies of complex disorders, where genetic heterogeneity or interaction between genes may confound the ability to detect association, GWAS-NR offers a powerful method for prioritizing regions for follow-up studies. Applying this method to autism datasets, GWAS-NR analysis indicates that a large subset of genes involved in the outgrowth and guidance of axons and dendrites is implicated in the aetiology of autism.
PMCID: PMC3035032  PMID: 21247446
17.  Autism genetic database (AGD): a comprehensive database including autism susceptibility gene-CNVs integrated with known noncoding RNAs and fragile sites 
BMC Medical Genetics  2009;10:102.
Autism is a highly heritable complex neurodevelopmental disorder, therefore identifying its genetic basis has been challenging. To date, numerous susceptibility genes and chromosomal abnormalities have been reported in association with autism, but most discoveries either fail to be replicated or account for a small effect. Thus, in most cases the underlying causative genetic mechanisms are not fully understood. In the present work, the Autism Genetic Database (AGD) was developed as a literature-driven, web-based, and easy to access database designed with the aim of creating a comprehensive repository for all the currently reported genes and genomic copy number variations (CNVs) associated with autism in order to further facilitate the assessment of these autism susceptibility genetic factors.
AGD is a relational database that organizes data resulting from exhaustive literature searches for reported susceptibility genes and CNVs associated with autism. Furthermore, genomic information about human fragile sites and noncoding RNAs was also downloaded and parsed from miRBase, snoRNA-LBME-db, piRNABank, and the MIT/ICBP siRNA database. A web client genome browser enables viewing of the features while a web client query tool provides access to more specific information for the features. When applicable, links to external databases including GenBank, PubMed, miRBase, snoRNA-LBME-db, piRNABank, and the MIT siRNA database are provided.
AGD comprises a comprehensive list of susceptibility genes and copy number variations reported to-date in association with autism, as well as all known human noncoding RNA genes and fragile sites. Such a unique and inclusive autism genetic database will facilitate the evaluation of autism susceptibility factors in relation to known human noncoding RNAs and fragile sites, impacting on human diseases. As a result, this new autism database offers a valuable tool for the research community to evaluate genetic findings for this complex multifactorial disorder in an integrated format. AGD provides a genome browser and a web based query client for conveniently selecting features of interest. Access to AGD is freely available at .
PMCID: PMC2761880  PMID: 19778453
18.  Etiology of infantile autism: a review of recent advances in genetic and neurobiological research. 
The etiology of autism is complex, and in most cases the underlying pathologic mechanisms are unknown. Autism is a hetereogeneous disorder, diagnosed subjectively on the basis of a large number of criteria. Recent research has investigated genetics, in utero insults and brain function as well as neurochemical and immunological factors. On the basis of family and twin studies, there appears to be a genetic basis for a wide "autistic syndrome." About a quarter of cases of autism are associated with genetic disorders such as fragile X syndrome or with infectious diseases such as congenital rubella. Genetic studies have shown an association between autism markers of brain development such as 3 markers of the c-Harvey-ros oncogene and the homeobox gene EN2. In some cases, autism is associated with insults early in gestation, including thalidomide embryopathy. Autism may arise from abnormal central nervous system functioning, since most autistic patients have indications of brain dysfunction, and about half of them have abnormal electroencephalograms. Similarly, the pattern of evoked response potentials and conduction time is altered in autistic children. There is substantial evidence from neuroimaging studies that dysfunctions in the cerebellum and possibly the temporal lobe and association cortex occur in autistic symptoms. Neurochemical studies have investigated the role of serotonin, epinephrine and norepinephrine, since levels of these neurotransmitters are altered in autism, although other hypotheses implicate overactive brain opioid systems and changes in oxytocin neurotransmission. Autoimmunity may also play a role; antibodies against myelin basic protein are often found in children with autism, who also have increased eosinophil and basophil response to IgE-mediated reactions. In summary, the prevailing view is that autism is caused by a pathophysiologic process arising from the interaction of an early environmental insult and a genetic predisposition.
PMCID: PMC1188990  PMID: 10212552
19.  Glyoxalase I polymorphism rs2736654 causing the Ala111Glu substitution modulates enzyme activity—implications for autism 
Lay Abstract
Autism is a complex developmental disability characterized by abnormalities in spoken language, socialization and repetitive behaviors. In recent years, an increase in the number of autism cases worldwide has been reported. Researchers have found evidence that autism is caused by multiple genetic factors, and a number of potential risk genes have been identified. Earlier we have found an increased frequency in subject with autism of a form of the enzyme glyoxalase I (Glo1) that has glutamic acid at position 111. By using lymphoblastoid and neuronal cells in culture, we now present evidence that this form of Glo1 is reduced in function, and consequently accumulates a toxic metabolite called methylglyoxal (MG). MG can form conjugates with cellular proteins, thereby compromising their function. We propose that an increase in conjugated proteins causes over-expression of receptors that bind these altered proteins, which in turn can initiate cascades of potentially harmful events. These studies suggest that in a subset of individuals with autism, the occurrence of the Glo1 polymorphism may precipitate changes in cellular structure and function that support risk for autism.
Scientific Abstract
Autism is a pervasive, heterogeneous, neurodevelopmental disability characterized by impairments in verbal communications, reciprocal social interactions, and restricted repetitive stereotyped behaviors. Evidence suggests the involvement of multiple genetic factors in the etiology of autism, and extensive genome-wide association studies have revealed several candidate genes that bear single nucleotide polymorphisms (SNPs) in non-coding and coding regions. We have shown that a non-conservative, non-synonymous SNP in the glyoxalase I gene, GLOI, may be an autism susceptibility factor. The GLOI rs2736654 SNP is a C→A change that causes an Ala111Glu change in the Glo1 enzyme. To identify the significance of the SNP, we have conducted functional assays for Glo1. We now present evidence that the presence of the A-allele at rs2736654 results in reduced enzyme activity. Glo1 activity is decreased in lymphoblastoid cells that are homozygous for the A allele. The Glu-isoform of Glo1 in these cells is hyperphosphorylated. Direct HPLC measurements of the glyoxalase I substrate, methylglyoxal (MG), show an increase in MG in these cells. Western blot analysis revealed elevated levels of the receptor for advanced glycation end products (RAGEs). We also show that MG is toxic to the developing neuronal cells. We suggest that accumulation of MG results in the formation of AGEs, which induce expression of the RAGE that during crucial neuronal development may be a factor in the pathology of autism.
PMCID: PMC3138858  PMID: 21491613
autism; glyoxalase I; SNP; advanced glycation endproducts (AGEs); receptor for advanced glycation end products (RAGEs); methylglyoxal
20.  Children with Autism Show Reduced Somatosensory Response: An MEG Study 
Lay Abstract
Autism spectrum disorders are reported to affect nearly one out of every one hundred children, with over 90% of these children showing behavioral disturbances related to the processing of basic sensory information. Behavioral sensitivity to light touch, such as profound discomfort with clothing tags and physical contact, is a ubiquitous finding in children on the autism spectrum. In this study, we investigate the strength and timing of brain activity in response to simple, light taps to the fingertip. Our results suggest that children with autism show a diminished early response in the primary somatosensory cortex (S1). This finding is most evident in the left hemisphere. In exploratory analysis, we also show that tactile sensory behavior, as measured by the Sensory Profile, may be a better predictor of the intensity and timing of brain activity related to touch than a clinical autism diagnosis. We report that children with atypical tactile behavior have significantly lower amplitude somatosensory cortical responses in both hemispheres. Thus sensory behavioral phenotype appears to be a more powerful strategy for investigating neural activity in this cohort. This study provides evidence for atypical brain activity during sensory processing in autistic children and suggests that our sensory behavior based methodology may be an important approach to investigating brain activity in people with autism and neurodevelopmental disorders.
Scientific Abstract
The neural underpinnings of sensory processing differences in autism remain poorly understood. This prospective magnetoencephalography (MEG) study investigates whether children with autism show atypical cortical activity in the primary somatosensory cortex (S1) in comparison to matched controls. Tactile stimuli were clearly detectable, painless taps applied to the distal phalanx of the second (D2) and third (D3) fingers of the right and left hands. Three tactile paradigms were administered: an oddball paradigm (standard taps to D3 at an inter-stimulus interval (ISI) of 0.33 and deviant taps to D2 with ISI ranging from 1.32–1.64s); a slow-rate paradigm (D2) with an ISI matching the deviant taps in the oddball paradigm; and a fast-rate paradigm (D2) with an ISI matching the standard taps in the oddball. Study subjects were boys (age 7–11 years) with and without autism disorder. Sensory behavior was quantified using the Sensory Profile questionnaire. Boys with autism exhibited smaller amplitude left hemisphere S1 response to slow and deviant stimuli during the right hand paradigms. In post-hoc analysis, tactile behavior directly correlated with the amplitude of cortical response. Consequently, the children were re-categorized by degree of parent-report tactile sensitivity. This regrouping created a more robust distinction between the groups with amplitude diminution in the left and right hemispheres and latency prolongation in the right hemisphere in the deviant and slow-rate paradigms for the affected children. This study suggests that children with autism have early differences in somatosensory processing, which likely influence later stages of cortical activity from integration to motor response.
PMCID: PMC3474892  PMID: 22933354
Cognitive Neuroscience; Event Related Potential; School age; Low-level perception; Magnetoencephalography
21.  Global climate and the distribution of plant biomes. 
Biomes are areas of vegetation that are characterized by the same life-form. Traditional definitions of biomes have also included either geographical or climatic descriptors. This approach describes a wide range of biomes that can be correlated with characteristic climatic conditions, or climatic envelopes. The application of remote sensing technology to the frequent observation of biomes has led to a move away from the often subjective definition of biomes to one that is objective. Carefully characterized observations of life-form, by satellite, have been used to reconsider biome classification and their climatic envelopes. Five major tree biomes can be recognized by satellites based on leaf longevity and morphology: needleleaf evergreen, broadleaf evergreen, needleleaf deciduous, broadleaf cold deciduous and broadleaf drought deciduous. Observations indicate that broadleaf drought deciduous vegetation grades substantially into broadleaf evergreen vegetation. The needleleaf deciduous biome occurs in the world's coldest climates, where summer drought and therefore a drought deciduous biome are absent. Traditional biome definitions are quite static, implying no change in their life-form composition with time, within their particular climatic envelopes. However, this is not the case where there has been global ingress of grasslands and croplands into forested vegetation. The global spread of grasses, a new super-biome, was probably initiated 30-45 Myr ago by an increase in global aridity, and was driven by the natural spread of the disturbances of fire and animal grazing. These disturbances have been further extended over the Holocene era by human activities that have increased the land areas available for domestic animal grazing and for growing crops. The current situation is that grasses now occur in most, if not all biomes, and in many areas they dominate and define the biome. Croplands are also increasing, defining a new and relatively recent component to the grassland super-biome. In the case of both grassland and croplands, various forms of disturbance, particularly frequent disturbance, lead to continued range extensions of the biomes.
PMCID: PMC1693431  PMID: 15519965
22.  Association of autism with polymorphisms in the paired-like homeodomain transcription factor 1 (PITX1) on chromosome 5q31: a candidate gene analysis 
BMC Medical Genetics  2007;8:74.
Autism is a complex, heterogeneous, behaviorally-defined disorder characterized by disruptions of the nervous system and of other systems such as the pituitary-hypothalamic axis. In a previous genome wide screen, we reported linkage of autism with a 1.2 Megabase interval on chromosome 5q31. For the current study, we hypothesized that 3 of the genes in this region could be involved in the development of autism: 1) paired-like homeodomain transcription factor 1 (PITX1), which is a key regulator of hormones within the pituitary-hypothalamic axis, 2) neurogenin 1, a transcription factor involved in neurogenesis, and 3) histone family member Y (H2AFY), which is involved in X-chromosome inactivation in females and could explain the 4:1 male:female gender distortion present in autism.
A total of 276 families from the Autism Genetic Resource Exchange (AGRE) repository composed of 1086 individuals including 530 affected children were included in the study. Single nucleotide polymorphisms tagging the three candidate genes were genotyped on the initial linkage sample of 116 families. A second step of analysis was performed using tightly linked SNPs covering the PITX1 gene. Association was evaluated using the FBAT software version 1.7.3 for single SNP analysis and the HBAT command from the same package for haplotype analysis respectively.
Association between SNPs and autism was only detected for PITX1. Haplotype analysis within PITX1 showed evidence for overtransmission of the A-C haplotype of markers rs11959298 – rs6596189 (p = 0.0004). Individuals homozygous or heterozygous for the A-C haplotype risk allele were 2.54 and 1.59 fold more likely to be autistic than individuals who were not carrying the allele, respectively.
Strong and consistent association was observed between a 2 SNPs within PITX1 and autism. Our data suggest that PITX1, a key regulator of hormones within the pituitary-hypothalamic axis, may be implicated in the etiology of autism.
PMCID: PMC2222245  PMID: 18053270
23.  A Population Genetic Approach to Mapping Neurological Disorder Genes Using Deep Resequencing 
PLoS Genetics  2011;7(2):e1001318.
Deep resequencing of functional regions in human genomes is key to identifying potentially causal rare variants for complex disorders. Here, we present the results from a large-sample resequencing (n = 285 patients) study of candidate genes coupled with population genetics and statistical methods to identify rare variants associated with Autism Spectrum Disorder and Schizophrenia. Three genes, MAP1A, GRIN2B, and CACNA1F, were consistently identified by different methods as having significant excess of rare missense mutations in either one or both disease cohorts. In a broader context, we also found that the overall site frequency spectrum of variation in these cases is best explained by population models of both selection and complex demography rather than neutral models or models accounting for complex demography alone. Mutations in the three disease-associated genes explained much of the difference in the overall site frequency spectrum among the cases versus controls. This study demonstrates that genes associated with complex disorders can be mapped using resequencing and analytical methods with sample sizes far smaller than those required by genome-wide association studies. Additionally, our findings support the hypothesis that rare mutations account for a proportion of the phenotypic variance of these complex disorders.
Author Summary
It is widely accepted that genetic factors play important roles in the etiology of neurological diseases. However, the nature of the underlying genetic variation remains unclear. Critical questions in the field of human genetics relate to the frequency and size effects of genetic variants associated with disease. For instance, the common disease–common variant model is based on the idea that sets of common variants explain a significant fraction of the variance found in common disease phenotypes. On the other hand, rare variants may have strong effects and therefore largely contribute to disease phenotypes. Due to their high penetrance and reduced fitness, such variants are maintained in the population at low frequencies, thus limiting their detection in genome-wide association studies. Here, we use a resequencing approach on a cohort of 285 Autism Spectrum Disorder and Schizophrenia patients and preformed several analyses, enhanced with population genetic approaches, to identify variants associated with both diseases. Our results demonstrate an excess of rare variants in these disease cohorts and identify genes with negative (deleterious) selection coefficients, suggesting an accumulation of variants of detrimental effects. Our results present further evidence for rare variants explaining a component of the genetic etiology of autism and schizophrenia.
PMCID: PMC3044677  PMID: 21383861
Nature  2009;461(7265):802-808.
Although autism is a highly heritable neurodevelopmental disorder, attempts to identify specific susceptibility genes have thus far met with limited success 1. Genome-wide association studies (GWAS) using half a million or more markers, particularly those with very large sample sizes achieved through meta-analysis, have shown great success in mapping genes for other complex genetic traits ( Consequently, we initiated a linkage and association mapping study using half a million genome-wide SNPs in a common set of 1,031 multiplex autism families (1,553 affected offspring). We identified regions of suggestive and significant linkage on chromosomes 6q27 and 20p13, respectively. Initial analysis did not yield genome-wide significant associations; however, genotyping of top hits in additional families revealed a SNP on chromosome 5p15 (between SEMA5A and TAS2R1) that was significantly associated with autism (P = 2 × 10−7). We also demonstrated that expression of SEMA5A is reduced in brains from autistic patients, further implicating SEMA5A as an autism susceptibility gene. The linkage regions reported here provide targets for rare variation screening while the discovery of a single novel association demonstrates the action of common variants.
PMCID: PMC2772655  PMID: 19812673
25.  An Antibiotic-Responsive Mouse Model of Fulminant Ulcerative Colitis  
PLoS Medicine  2008;5(3):e41.
The constellation of human inflammatory bowel disease (IBD) includes ulcerative colitis and Crohn's disease, which both display a wide spectrum in the severity of pathology. One theory is that multiple genetic hits to the host immune system may contribute to the susceptibility and severity of IBD. However, experimental proof of this concept is still lacking. Several genetic mouse models that each recapitulate some aspects of human IBD have utilized a single gene defect to induce colitis. However, none have produced pathology clearly distinguishable as either ulcerative colitis or Crohn's disease, in part because none of them reproduce the most severe forms of disease that are observed in human patients. This lack of severe IBD models has posed a challenge for research into pathogenic mechanisms and development of new treatments. We hypothesized that multiple genetic hits to the regulatory machinery that normally inhibits immune activation in the intestine would generate more severe, reproducible pathology that would mimic either ulcerative colitis or Crohn's disease.
Methods and Findings
We generated a novel mouse line (dnKO) that possessed defects in both TGFβRII and IL-10R2 signaling. These mice rapidly and reproducibly developed a disease resembling fulminant human ulcerative colitis that was quite distinct from the much longer and more variable course of pathology observed previously in mice possessing only single defects. Pathogenesis was driven by uncontrolled production of proinflammatory cytokines resulting in large part from T cell activation. The disease process could be significantly ameliorated by administration of antibodies against IFNγ and TNFα and was completely inhibited by a combination of broad-spectrum antibiotics.
Here, we develop to our knowledge the first mouse model of fulminant ulcerative colitis by combining multiple genetic hits in immune regulation and demonstrate that the resulting disease is sensitive to both anticytokine therapy and broad-spectrum antibiotics. These findings indicated the IL-10 and TGFβ pathways synergize to inhibit microbially induced production of proinflammatory cytokines, including IFNγ and TNFα, which are known to play a role in the pathogenesis of human ulcerative colitis. Our findings also provide evidence that broad-spectrum antibiotics may have an application in the treatment of patients with ulcerative colitis. This model system will be useful in the future to explore the microbial factors that induce immune activation and characterize how these interactions produce disease.
Paul Allen and colleagues describe the development of a mouse model of fulminant ulcerative colitis with multiple genetic hits in immune regulation which can be moderated by anti-cytokine therapy and broad-spectrum antibiotics.
Editors' Summary
Inflammatory bowel disease (IBD), a group of disorders characterized by inflammation (swelling) of the digestive tract (the tube that runs from the mouth to the anus), affects about 1.4 million people in the US. There are two main types of IBD. In Crohn's disease, which can affect any area of the digestive tract but most commonly involves the lower part of the small intestine (small bowel), all the layers of the intestine become inflamed. In ulcerative colitis, which primarily affects the colon (large bowel) and the rectum (the part of the bowel closest to the anus), only the lining of the bowel becomes inflamed, the cells in this lining die, and sores or ulcers form. Both types of IBD most commonly develop between the ages of 15 and 35 years, often run in families, and carry an increased risk of cancer. Symptoms—usually diarrhea and abdominal cramps—can be mild or severe and the disorder can develop slowly or suddenly. There is no medical cure for IBD, but drugs that modulate the immune system (for example, corticosteroids) can help some people. Some people benefit from treatment with drugs that specifically inhibit “proinflammatory cytokines,” proteins made by the immune system that stimulate inflammation (for example, TNFα and INFγ). When medical therapy fails, surgery to remove the affected part of the bowel may be necessary.
Why Was This Study Done?
Exactly what causes IBD is not clear, but people with IBD seem to have an overactive immune system. The immune system normally protects the body from harmful substances but in IBD it mistakenly recognizes the food substances and “good” bacteria that are normally present in the human gut as foreign and hence reacts against them. As a result, immune system cells accumulate in the lining of the bowel and cause inflammation. Several different pathways usually prevent inappropriate immune activation, so could IBD be caused by alterations in one or several of these immune regulatory pathways? In previous studies, mice with a defect in just one pathway have developed mild intestinal abnormalities but not the problems seen in the most severe forms of IBD. In this study, therefore, the researchers have generated and characterized a new mouse line with defects in two immune regulatory pathways to see whether this might be a better animal model of human IBD.
What Did the Researchers Do and Find?
To make their new mouse line, the researchers mated mice that had a defective TGFβ signaling pathway in their T lymphocytes with mice that had a defective IL-10 signaling pathway. Both these pathways are anti-inflammatory, and mice with defects in either pathway develop mild and variable inflammation of the colon (colitis) by age 3–4 months. By contrast, the doubly defective mice (dnKO mice) failed to thrive, lost weight, and died by 4–6 weeks of age. The colons of 4- to 5-week old dnKO mice were inflamed and ulcerated (some changes were visible in 3-week-old mice) and contained many immune system cells. Mice with a single defective signaling pathway had no gut abnormalities at this age. The dnKO mice, just like people with IBD, had higher than normal blood levels of IFNγ, TNFα, and other proinflammatory cytokines; these raised levels were the result of abnormal lymphocyte activation. Treatment of the dnKO mice with a combination of agents that neutralize IFNγ and TNFα (anti-cytokine therapy) greatly reduced the colitis seen in these mice; neutralization of IFNγ alone had some beneficial effects, but neutralization of TNFα alone had no effect. Finally, early treatment of the dnKO mice with broad-spectrum antibiotics completely inhibited colitis.
What Do These Findings Mean?
These findings suggest that dnKO mice are a good model for fulminant (severe and rapidly progressing) ulcerative colitis and support the idea that IBD involves multiple genetic defects in immune regulation. They also indicate that the IL-10 and the TGFβ signaling pathways normally cooperate to inhibit the inappropriate immune responses to intestinal bacteria seen in IBD. This new mouse model should help researchers unravel what goes wrong in IBD and should also help them develop new treatments for ulcerative colitis. More immediately, these findings suggest that combined anti-cytokine therapy may be a better treatment for ulcerative colitis than single therapy. In addition, they suggest that clinical studies should be started to test whether broad-spectrum antibiotics can ameliorate ulcerative colitis in people.
Additional Information.
Please access these Web sites via the online version of this summary at
The Medline Plus Encyclopedia has pages on Crohn's disease and on ulcerative colitis (in English and Spanish)
Information is available from the UK National Health Service Direct Health Encyclopedia about Crohn's disease and ulcerative colitis
The US National Institute of Diabetes and Digestive and Kidney Diseases provides information on Crohn's disease and ulcerative colitis
Information and support for patients with inflammatory bowel disease and their caregivers is provided by the Crohn's and Colitis Foundation of America and by the UK National Association for Colitis and Crohn's Disease
PMCID: PMC2270287  PMID: 18318596

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