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author:("goat, Alison")
1.  Linkage analyses in Caribbean Hispanic families identifies novel loci associated with familial late-onset Alzheimer’s disease 
INTRODUCTION
We performed linkage analyses in Caribbean Hispanic families with multiple late-onset Alzheimer’s disease (LOAD) cases to identify regions that may contain disease causative variants.
METHODS
We selected 67 LOAD families to perform genome-wide linkage scan. Analysis of the linked regions was repeated using the entire sample of 282 families. Validated chromosomal regions were analyzed using joint linkage and association.
RESULTS
We identified 26 regions linked to LOAD (HLOD ≥ 3.6). We validated thirteen of the regions (HLOD ≥ 2.5) using the entire family sample. The strongest signal was at 11q12.3 (rs2232932: HLODmax= 4.7, Pjoint= 6.6 × 10−6), a locus located ~2Mb upstream of the MS4A gene cluster. We additional identified a locus at 7p14.3 (rs10255835: HLODmax= 4.9, Pjoint= 1.2 × 10−5), a region harboring genes associated with the nervous system (GARS, GHRHR and NEUROD6).
DISCUSSION
Future sequencing efforts should focus on these regions since they may harbor familial LOAD causative mutations.
doi:10.1016/j.jalz.2015.07.487
PMCID: PMC4690771  PMID: 26433351
Caribbean Hispanic families; Late Onset Alzheimer’s Disease; linkage analysis; joint linkage and association
2.  Common polygenic variation enhances risk prediction for Alzheimer’s disease 
Brain  2015;138(12):3673-3684.
Heritability estimates for Alzheimer’s disease in genome-wide association studies increase substantially when weak effect loci are also considered. Escott-Price et al. investigate the polygenic architecture of Alzheimer’s disease and the accuracy of prediction models, and show that including the polygenic component of risk significantly improves accuracy of case prediction.
Heritability estimates for Alzheimer’s disease in genome-wide association studies increase substantially when weak effect loci are also considered. Escott-Price et al. investigate the polygenic architecture of Alzheimer’s disease and the accuracy of prediction models, and show that including the polygenic component of risk significantly improves accuracy of case prediction.
The identification of subjects at high risk for Alzheimer’s disease is important for prognosis and early intervention. We investigated the polygenic architecture of Alzheimer’s disease and the accuracy of Alzheimer’s disease prediction models, including and excluding the polygenic component in the model. This study used genotype data from the powerful dataset comprising 17 008 cases and 37 154 controls obtained from the International Genomics of Alzheimer’s Project (IGAP). Polygenic score analysis tested whether the alleles identified to associate with disease in one sample set were significantly enriched in the cases relative to the controls in an independent sample. The disease prediction accuracy was investigated in a subset of the IGAP data, a sample of 3049 cases and 1554 controls (for whom APOE genotype data were available) by means of sensitivity, specificity, area under the receiver operating characteristic curve (AUC) and positive and negative predictive values. We observed significant evidence for a polygenic component enriched in Alzheimer’s disease (P = 4.9 × 10−26). This enrichment remained significant after APOE and other genome-wide associated regions were excluded (P = 3.4 × 10−19). The best prediction accuracy AUC = 78.2% (95% confidence interval 77–80%) was achieved by a logistic regression model with APOE, the polygenic score, sex and age as predictors. In conclusion, Alzheimer’s disease has a significant polygenic component, which has predictive utility for Alzheimer’s disease risk and could be a valuable research tool complementing experimental designs, including preventative clinical trials, stem cell selection and high/low risk clinical studies. In modelling a range of sample disease prevalences, we found that polygenic scores almost doubles case prediction from chance with increased prediction at polygenic extremes.
doi:10.1093/brain/awv268
PMCID: PMC5006219  PMID: 26490334
Alzheimer’s disease; polygenic score; predictive model
3.  Chitinase-3-like 1 protein (CHI3L1) locus influences cerebrospinal fluid levels of YKL-40 
BMC Neurology  2016;16:217.
Background
Alzheimer’s disease (AD) pathology appears several years before clinical symptoms, so identifying ways to detect individuals in the preclinical stage is imperative. The cerebrospinal fluid (CSF) Tau/Aβ42 ratio is currently the best known predictor of AD status and cognitive decline, and the ratio of CSF levels of chitinase-3-like 1 protein (CHI3L1, YKL-40) and amyloid beta (Aβ42) were reported as predictive, but individual variability and group overlap inhibits their utility for individual diagnosis making it necessary to find ways to improve sensitivity of these biomarkers.
Methods
We used linear regression to identify genetic loci associated with CSF YKL-40 levels in 379 individuals (80 cognitively impaired and 299 cognitively normal) from the Charles F and Joanne Knight Alzheimer’s Disease Research Center. We tested correlations between YKL-40 and CSF Tau/Aβ42 ratio, Aβ42, tau, and phosphorylated tau (ptau181). We used studentized residuals from a linear regression model of the log-transformed, standardized protein levels and the additive reference allele counts from the most significant locus to adjust YKL-40 values and tested the differences in correlations with CSF Tau/Aβ42 ratio, Aβ42, tau, and ptau181.
Results
We found that genetic variants on the CH13L1 locus were significantly associated with CSF YKL-40 levels, but not AD risk, age at onset, or disease progression. The most significant variant is a reported expression quantitative trait locus for CHI3L1, the gene which encodes YKL-40, and explained 12.74 % of the variance in CSF YKL-40 in our study. YKL-40 was positively correlated with ptau181 (r = 0.521) and the strength of the correlation significantly increased with the addition of genetic information (r = 0.573, p = 0.006).
Conclusions
CSF YKL-40 levels are likely a biomarker for AD, but we found no evidence that they are an AD endophenotype. YKL-40 levels are highly regulated by genetic variation, and by including genetic information the strength of the correlation between YKL-40 and ptau181 levels is significantly improved. Our results suggest that studies of potential biomarkers may benefit from including genetic information.
Electronic supplementary material
The online version of this article (doi:10.1186/s12883-016-0742-9) contains supplementary material, which is available to authorized users.
doi:10.1186/s12883-016-0742-9
PMCID: PMC5105244  PMID: 27832767
CHI3L1; YKL-40; Cerebrospinal fluid; Alzheimer disease
4.  Genetic variants associated with susceptibility to psychosis in Late Onset Alzheimer Disease families 
Neurobiology of aging  2015;36(11):3116.e9-3116.e16.
doi:10.1016/j.neurobiolaging.2015.08.006
PMCID: PMC4609604  PMID: 26359528
Late Onset Alzheimer Disease; psychosis; genome-wide linkage analysis; association analysis; Non-Hispanic Caucasian and Caribbean Hispanic ancestry populations
5.  Rare, low frequency, and common coding variants in CHRNA5 and their contribution to nicotine dependence in European and African Americans 
Molecular psychiatry  2015;21(5):601-607.
The common nonsynonymous variant rs16969968 in the α5 nicotinic receptor subunit gene (CHRNA5) is the strongest genetic risk factor for nicotine dependence in European Americans and contributes to risk in African Americans. To comprehensively examine whether other CHRNA5 coding variation influences nicotine dependence risk, we performed targeted sequencing on 1582 nicotine dependent cases (Fagerström Test for Nicotine Dependence score≥4) and 1238 non-dependent controls, with independent replication of common and low frequency variants using 12 studies with exome chip data. Nicotine dependence was examined using logistic regression with individual common variants (MAF≥0.05), aggregate low frequency variants (0.05>MAF≥0.005), and aggregate rare variants (MAF<0.005). Meta-analysis of primary results was performed with replication studies containing 12 174 heavy and 11 290 light smokers. Next-generation sequencing with 180X coverage identified 24 nonsynonymous variants and 2 frameshift deletions in CHRNA5, including 9 novel variants in the 2820 subjects. Meta-analysis confirmed the risk effect of the only common variant (rs16969968, European ancestry: OR=1.3, p=3.5×10−11; African ancestry: OR=1.3, p=0.01) and demonstrated that 3 low frequency variants contributed an independent risk (aggregate term, European ancestry: OR=1.3, p=0.005; African ancestry: OR=1.4, p=0.0006). The remaining 22 rare coding variants were associated with increased risk of nicotine dependence in the European American primary sample (OR=12.9, p=0.01) and in the same risk direction in African Americans (OR=1.5, p=0.37). Our results indicate that common, low frequency and rare CHRNA5 coding variants are independently associated with nicotine dependence risk. These newly identified variants likely influence risk for smoking-related diseases such as lung cancer.
doi:10.1038/mp.2015.105
PMCID: PMC4740321  PMID: 26239294
6.  Integrative network analysis of nineteen brain regions identifies molecular signatures and networks underlying selective regional vulnerability to Alzheimer’s disease 
Genome Medicine  2016;8:104.
Background
Alzheimer’s disease (AD) is the most common form of dementia, characterized by progressive cognitive impairment and neurodegeneration. However, despite extensive clinical and genomic studies, the molecular basis of AD development and progression remains elusive.
Methods
To elucidate molecular systems associated with AD, we developed a large scale gene expression dataset from 1053 postmortem brain samples across 19 cortical regions of 125 individuals with a severity spectrum of dementia and neuropathology of AD. We excluded brain specimens that evidenced neuropathology other than that characteristic of AD. For the first time, we performed a pan-cortical brain region genomic analysis, characterizing the gene expression changes associated with a measure of dementia severity and multiple measures of the severity of neuropathological lesions associated with AD (neuritic plaques and neurofibrillary tangles) and constructing region-specific co-expression networks. We rank-ordered 44,692 gene probesets, 1558 co-expressed gene modules and 19 brain regions based upon their association with the disease traits.
Results
The neurobiological pathways identified through these analyses included actin cytoskeleton, axon guidance, and nervous system development. Using public human brain single-cell RNA-sequencing data, we computed brain cell type-specific marker genes for human and determined that many of the abnormally expressed gene signatures and network modules were specific to oligodendrocytes, astrocytes, and neurons. Analysis based on disease severity suggested that: many of the gene expression changes, including those of oligodendrocytes, occurred early in the progression of disease, making them potential translational/treatment development targets and unlikely to be mere bystander result of degeneration; several modules were closely linked to cognitive compromise with lesser association with traditional measures of neuropathology. The brain regional analyses identified temporal lobe gyri as sites associated with the greatest and earliest gene expression abnormalities.
Conclusions
This transcriptomic network analysis of 19 brain regions provides a comprehensive assessment of the critical molecular pathways associated with AD pathology and offers new insights into molecular mechanisms underlying selective regional vulnerability to AD at different stages of the progression of cognitive compromise and development of the canonical neuropathological lesions of AD.
Electronic supplementary material
The online version of this article (doi:10.1186/s13073-016-0355-3) contains supplementary material, which is available to authorized users.
doi:10.1186/s13073-016-0355-3
PMCID: PMC5088659  PMID: 27799057
Alzheimer’s disease; Dementia; Differential expression; Gene co-expression network; Gene module; Systems biology; Selective vulnerability; Demyelination; Brain cell types
7.  A multiancestry study identifies novel genetic associations with CHRNA5 methylation in human brain and risk of nicotine dependence 
Human Molecular Genetics  2015;24(20):5940-5954.
Nicotine dependence is influenced by chromosome 15q25.1 single nucleotide polymorphisms (SNPs), including the missense SNP rs16969968 that alters function of the α5 nicotinic acetylcholine receptor (CHRNA5) and noncoding SNPs that regulate CHRNA5 mRNA expression. We tested for cis-methylation quantitative trait loci (cis-meQTLs) using SNP genotypes and DNA methylation levels measured across the IREB2-HYKK-PSMA4-CHRNA5-CHRNA3-CHRNB4 genes on chromosome 15q25.1 in the BrainCloud and Brain QTL cohorts [total N = 175 European-Americans and 65 African-Americans (AAs)]. We identified eight SNPs that were significantly associated with CHRNA5 methylation in prefrontal cortex: P ranging from 6.0 × 10−10 to 5.6 × 10−5. These SNP–methylation associations were also significant in frontal cortex, temporal cortex and pons: P ranging from 4.8 × 10−12 to 3.4 × 10−3. Of the eight cis-meQTL SNPs, only the intronic CHRNB4 SNP rs11636753 was associated with CHRNA5 methylation independently of the known SNP effects in prefrontal cortex, and it was the most significantly associated SNP with nicotine dependence across five independent cohorts (total N = 7858 European ancestry and 3238 AA participants): P = 6.7 × 10−4, odds ratio (OR) [95% confidence interval (CI)] = 1.11 (1.05–1.18). The rs11636753 major allele (G) was associated with lower CHRNA5 DNA methylation, lower CHRNA5 mRNA expression and increased nicotine dependence risk. Haplotype analyses showed that rs11636753-G and the functional rs16969968-A alleles together increased risk of nicotine dependence more than each variant alone: P = 3.1 × 10−12, OR (95% CI) = 1.32 (1.22–1.43). Our findings identify a novel regulatory SNP association with nicotine dependence and connect, for the first time, previously observed differences in CHRNA5 mRNA expression and nicotine dependence risk to underlying DNA methylation differences.
doi:10.1093/hmg/ddv303
PMCID: PMC4581607  PMID: 26220977
8.  Increased nicotine response in iPSC-derived human neurons carrying the CHRNA5 N398 allele 
Scientific Reports  2016;6:34341.
Genetic variation in nicotinic receptor alpha 5 (CHRNA5) has been associated with increased risk of addiction-associated phenotypes in humans yet little is known the underlying neural basis. Induced pluripotent stem cells (iPSCs) were derived from donors homozygous for either the major (D398) or the minor (N398) allele of the nonsynonymous single nucleotide polymorphism (SNP), rs16969968, in CHRNA5. To understand the impact of these nicotinic receptor variants in humans, we differentiated these iPSCs to dopamine (DA) or glutamatergic neurons and then tested their functional properties and response to nicotine. Results show that N398 variant human DA neurons differentially express genes associated with ligand receptor interaction and synaptic function. While both variants exhibited physiological properties consistent with mature neuronal function, the N398 neuronal population responded more actively with an increased excitatory postsynaptic current response upon the application of nicotine in both DA and glutamatergic neurons. Glutamatergic N398 neurons responded to lower nicotine doses (0.1 μM) with greater frequency and amplitude but they also exhibited rapid desensitization, consistent with previous analyses of N398-associated nicotinic receptor function. This study offers a proof-of-principle for utilizing human neurons to study gene variants contribution to addiction.
doi:10.1038/srep34341
PMCID: PMC5048107  PMID: 27698409
9.  ABCA7 p.G215S as potential protective factor for Alzheimer's disease 
Neurobiology of Aging  2016;46:235.e1-235.e9.
Genome-wide association studies (GWASs) have been effective approaches to dissect common genetic variability underlying complex diseases in a systematic and unbiased way. Recently, GWASs have led to the discovery of over 20 susceptibility loci for Alzheimer's disease (AD). Despite the evidence showing the contribution of these loci to AD pathogenesis, their genetic architecture has not been extensively investigated, leaving the possibility that low frequency and rare coding variants may also occur and contribute to the risk of disease. We have used exome and genome sequencing data to analyze the single independent and joint effect of rare and low-frequency protein coding variants in 9 AD GWAS loci with the strongest effect sizes after APOE (BIN1, CLU, CR1, PICALM, MS4A6A, ABCA7, EPHA1, CD33, and CD2AP) in a cohort of 332 sporadic AD cases and 676 elderly controls of British and North-American ancestry. We identified coding variability in ABCA7 as contributing to AD risk. This locus harbors a low-frequency coding variant (p.G215S, rs72973581, minor allele frequency = 4.3%) conferring a modest but statistically significant protection against AD (p-value = 0.024, odds ratio = 0.57, 95% confidence interval = 0.41–0.80). Notably, our results are not driven by an enrichment of loss of function variants in ABCA7, recently reported as main pathogenic factor underlying AD risk at this locus. In summary, our study confirms the role of ABCA7 in AD and provides new insights that should address functional studies.
doi:10.1016/j.neurobiolaging.2016.04.004
PMCID: PMC5024078  PMID: 27289440
Alzheimer's disease (AD); Genome-wide association studies (GWASs); ABCA7; Whole exome sequencing (WES); Whole genome sequencing (WGS); Protective variant
10.  Age and Amyloid Effects on Human CNS Amyloid-Beta Kinetics 
Annals of neurology  2015;78(3):439-453.
Objective
Age is the single greatest risk factor for Alzheimer’s disease with the incidence doubling every 5 years after age 65. However, our understanding of the mechanistic relationship between increasing age and the risk for Alzheimer’s disease is currently limited. We therefore sought to determine the relationship between age, amyloidosis, and amyloid-beta kinetics in the central nervous system (CNS) of humans
Methods
Amyloid-beta kinetics were analyzed in 112 participants and compared to the ages of participants and the amount of amyloid deposition.
Results
We found a highly significant correlation between increasing age and slowed amyloid-beta turnover rates (2.5-fold longer half-life over five decades of age). In addition, we found independent effects on amyloid-beta42 kinetics specifically in participants with amyloid deposition. Amyloidosis was associated with a higher (>50%) irreversible loss of soluble amyloid-beta42 and a 10-fold higher amyloid-beta42 reversible exchange rate.
Interpretation
These findings reveal a mechanistic link between human aging and the risk of amyloidosis which may be due to a dramatic slowing of amyloid-beta turnover, increasing the likelihood of protein misfolding that leads to deposition. Alterations in amyloid-beta kinetics associated with aging and amyloidosis suggest opportunities for diagnostic and therapeutic strategies. More generally, this study provides an example of how changes in protein turnover kinetics can be used to detect physiologic and pathophysiologic changes and may be applicable to other proteinopathies.
doi:10.1002/ana.24454
PMCID: PMC4546566  PMID: 26040676
11.  Cerebral amyloidosis associated with cognitive decline in autosomal dominant Alzheimer disease 
Neurology  2015;85(9):790-798.
Objective:
To investigate the associations of cerebral amyloidosis with concurrent cognitive performance and with longitudinal cognitive decline in asymptomatic and symptomatic stages of autosomal dominant Alzheimer disease (ADAD).
Methods:
Two hundred sixty-three participants enrolled in the Dominantly Inherited Alzheimer Network observational study underwent neuropsychological evaluation as well as PET scans with Pittsburgh compound B. One hundred twenty-one participants completed at least 1 follow-up neuropsychological evaluation. Four composite cognitive measures representing global cognition, episodic memory, language, and working memory were generated using z scores from a battery of 13 standard neuropsychological tests. General linear mixed-effects models were used to investigate the relationship between baseline cerebral amyloidosis and baseline cognitive performance and whether baseline cerebral amyloidosis predicts cognitive change over time (mean follow-up 2.32 years ± 0.92, range 0.89–4.19) after controlling for estimated years from expected symptom onset, APOE ε4 allelic status, and education.
Results:
In asymptomatic mutation carriers, amyloid burden was not associated with baseline cognitive functioning but was significantly predictive of longitudinal decline in episodic memory. In symptomatic mutation carriers, cerebral amyloidosis was correlated with worse baseline performance in multiple cognitive composites and predicted greater decline over time in global cognition, working memory, and Mini-Mental State Examination.
Conclusions:
Cerebral amyloidosis predicts longitudinal episodic memory decline in presymptomatic ADAD and multidomain cognitive decline in symptomatic ADAD. These findings imply that amyloidosis in the brain is an indicator of early cognitive decline and provides a useful outcome measure for early assessment and prevention treatment trials.
doi:10.1212/WNL.0000000000001903
PMCID: PMC4553024  PMID: 26245925
12.  Lack of an association of BDNF Val66Met polymorphism and plasma BDNF with hippocampal volume and memory 
Brain-derived neurotrophic factor (BDNF) has been shown to be important for neuronal survival and synaptic plasticity in the hippocampus in non-human animals. The Val66Met polymorphism in the BDNF gene, involving a valine (Val) to methionine (Met) substitution at codon 66, has been associated with lower BDNF secretion in vitro. However, there have been mixed results regarding associations between either circulating BDNF or the BDNF Val66Met polymorphism with hippocampal volume and memory in humans. The current study examined the association of BDNF genotype and plasma BDNF with hippocampal volume and memory in two large independent cohorts of middle-aged and older adults (both cognitively normal and early-stage dementia). Sample sizes ranged from 123 to 649. Measures of the BDNF genotype, plasma BDNF, MRI-based hippocampal volume and memory performance were obtained from the Knight Alzheimer Disease Research Center (ADRC) and the Alzheimer’s Disease Neuroimaging Initiative (ADNI). There were no significant differences between BDNF Met+ and Met- groups on either hippocampal volume or memory in either cohort. In addition, plasma BDNF was not significantly associated with either hippocampal volume or memory in either cohort. Neither age, cognitive status nor gender moderated any of the relationships. Overall, current findings suggest that BDNF genotype and plasma BDNF may not be robust predictors for variance in hippocampal volume and memory in middle age and older adult cohorts.
doi:10.3758/s13415-015-0343-x
PMCID: PMC4529376  PMID: 25784293
13.  A Genetic Variant (COMT) Coding Dopaminergic Activity Predicts Personality Traits in Healthy Elderly 
Association studies between the NEO five factor personality inventory and COMT rs4680 have focused on young adults and the results have been inconsistent. However, personality and cortical changes with age may put older adults in a more sensitive range for detecting a relationship. The present study examined associations of COMT rs4680 and personality in older adults.
Genetic association analyses were carried out between the NEO and the targeted COMT rs4680 in a large, well-characterized sample of healthy, cognitively normal older adults (N = 616, mean age = 69.26 years).
Three significant associations were found: participants with GG genotype showed lower mean scores on Neuroticism (p = 0.039) and higher scores on Agreeableness (p = 0.020) and Conscientiousness (p = 0.006) than participants with AA or AG genotypes.
These results suggest that older adults with higher COMT enzymatic activity (GG), therefore lower dopamine level, have lower Neuroticism scores, and higher Agreeableness and Conscientiousness scores. This is consistent with a recent model of phasic and tonic dopamine release suggesting that even though GG genotype is associated with lower tonic dopamine release, the phasic release of dopamine might be optimal for a more adaptive personality profile.
doi:10.1016/j.paid.2015.03.012
PMCID: PMC4422069  PMID: 25960587
Genetic association; Personality; Dopamine; COMT rs4680 polymorphism; Older adults
14.  Variants in CCL16 are associated with blood plasma and cerebrospinal fluid CCL16 protein levels 
BMC Genomics  2016;17(Suppl 3):437.
Background
CCL16 is a chemokine predominantly expressed in the liver, but is also found in the blood and brain, and is known to play important roles in immune response and angiogenesis. Little is known about the gene’s regulation.
Methods
Here, we test for potential causal SNPs that affect CCL16 protein levels in both blood plasma and cerebrospinal fluid in a genome-wide association study across two datasets. We then use METAL to performed meta-analyses with a significance threshold of p < 5x10−8. We removed SNPs where the direction of the effect was different between the two datasets.
Results
We identify 10 SNPs associated with increased CCL16 protein levels in both biological fluids.
Conclusions
Our results will help understand CCL16’s regulation, allowing researchers to better understand the gene’s effects on human health.
Electronic supplementary material
The online version of this article (doi:10.1186/s12864-016-2788-x) contains supplementary material, which is available to authorized users.
doi:10.1186/s12864-016-2788-x
PMCID: PMC4943476  PMID: 27357396
Blood; Brain; CCL16; Plasma; Cerebrospinal fluid; Genetics; Association
15.  Variants in ACPP are associated with cerebrospinal fluid Prostatic Acid Phosphatase levels 
BMC Genomics  2016;17(Suppl 3):439.
Background
Prostatic Acid Phosphatase (PAP) is an enzyme that is produced primarily in the prostate and functions as a cell growth regulator and potential tumor suppressor. Understanding the genetic regulation of this enzyme is important because PAP plays an important role in prostate cancer and is expressed in other tissues such as the brain.
Methods
We tested association between 5.8 M SNPs and PAP levels in cerebrospinal fluid across 543 individuals in two datasets using linear regression. We then performed meta-analyses using METAL =with a significance threshold of p < 5 × 10−8 and removed SNPs where the direction of the effect was different between the two datasets, identifying 289 candidate SNPs that affect PAP cerebrospinal fluid levels. We analyzed each of these SNPs individually and prioritized SNPs that had biologically meaningful functional annotations in wANNOVAR (e.g. non-synonymous, stop gain, 3’ UTR, etc.) or had a RegulomeDB score less than 3.
Results
Thirteen SNPs met our criteria, suggesting they are candidate causal alleles that underlie ACPP regulation and expression.
Conclusions
Given PAP’s expression in the brain and its role as a cell-growth regulator and tumor suppressor, our results have important implications in brain health such as cancer and other brain diseases including neurodegenerative diseases (e.g., Alzheimer’s disease and Parkinson’s disease) and mental health (e.g., anxiety, depression, and schizophrenia).
Electronic supplementary material
The online version of this article (doi:10.1186/s12864-016-2787-y) contains supplementary material, which is available to authorized users.
doi:10.1186/s12864-016-2787-y
PMCID: PMC4943489  PMID: 27357282
Brain; Cancer; CSF; PAP
16.  Genome-wide association study of prolactin levels in blood plasma and cerebrospinal fluid 
BMC Genomics  2016;17(Suppl 3):436.
Background
Prolactin is a polypeptide hormone secreted by the anterior pituitary gland that plays an essential role in lactation, tissue growth, and suppressing apoptosis to increase cell survival. Prolactin serves as a key player in many life-critical processes, including immune system and reproduction. Prolactin is also found in multiple fluids throughout the body, including plasma and cerebrospinal fluid (CSF).
Methods
In this study, we measured prolactin levels in both plasma and CSF, and performed a genome-wide association study. We then performed meta-analyses using METAL with a significance threshold of p < 5 × 10−8 and removed SNPs where the direction of the effect was different between the two datasets.
Results
We identified 12 SNPs associated with increased prolactin levels in both biological fluids.
Conclusions
Our efforts will help researchers understand how prolactin is regulated in both CSF and plasma, which could be beneficial in research for the immune system and reproduction.
Electronic supplementary material
The online version of this article (doi:10.1186/s12864-016-2785-0) contains supplementary material, which is available to authorized users.
doi:10.1186/s12864-016-2785-0
PMCID: PMC4943503  PMID: 27357110
Association; Genetics; CSF; Plasma; Prolactin
17.  Convergent genetic and expression data implicate immunity in Alzheimer's disease 
Jones, Lesley | Lambert, Jean-Charles | Wang, Li-San | Choi, Seung-Hoan | Harold, Denise | Vedernikov, Alexey | Escott-Price, Valentina | Stone, Timothy | Richards, Alexander | Bellenguez, Céline | Ibrahim-Verbaas, Carla A | Naj, Adam C | Sims, Rebecca | Gerrish, Amy | Jun, Gyungah | DeStefano, Anita L | Bis, Joshua C | Beecham, Gary W | Grenier-Boley, Benjamin | Russo, Giancarlo | Thornton-Wells, Tricia A | Jones, Nicola | Smith, Albert V | Chouraki, Vincent | Thomas, Charlene | Ikram, M Arfan | Zelenika, Diana | Vardarajan, Badri N | Kamatani, Yoichiro | Lin, Chiao-Feng | Schmidt, Helena | Kunkle, Brian | Dunstan, Melanie L | Ruiz, Agustin | Bihoreau, Marie-Thérèse | Reitz, Christiane | Pasquier, Florence | Hollingworth, Paul | Hanon, Olivier | Fitzpatrick, Annette L | Buxbaum, Joseph D | Campion, Dominique | Crane, Paul K | Becker, Tim | Gudnason, Vilmundur | Cruchaga, Carlos | Craig, David | Amin, Najaf | Berr, Claudine | Lopez, Oscar L | De Jager, Philip L | Deramecourt, Vincent | Johnston, Janet A | Evans, Denis | Lovestone, Simon | Letteneur, Luc | Kornhuber, Johanes | Tárraga, Lluís | Rubinsztein, David C | Eiriksdottir, Gudny | Sleegers, Kristel | Goate, Alison M | Fiévet, Nathalie | Huentelman, Matthew J | Gill, Michael | Emilsson, Valur | Brown, Kristelle | Kamboh, M Ilyas | Keller, Lina | Barberger-Gateau, Pascale | McGuinness, Bernadette | Larson, Eric B | Myers, Amanda J | Dufouil, Carole | Todd, Stephen | Wallon, David | Love, Seth | Kehoe, Pat | Rogaeva, Ekaterina | Gallacher, John | George-Hyslop, Peter St | Clarimon, Jordi | Lleὀ, Alberti | Bayer, Anthony | Tsuang, Debby W | Yu, Lei | Tsolaki, Magda | Bossù, Paola | Spalletta, Gianfranco | Proitsi, Petra | Collinge, John | Sorbi, Sandro | Garcia, Florentino Sanchez | Fox, Nick | Hardy, John | Naranjo, Maria Candida Deniz | Razquin, Cristina | Bosco, Paola | Clarke, Robert | Brayne, Carol | Galimberti, Daniela | Mancuso, Michelangelo | Moebus, Susanne | Mecocci, Patrizia | del Zompo, Maria | Maier, Wolfgang | Hampel, Harald | Pilotto, Alberto | Bullido, Maria | Panza, Francesco | Caffarra, Paolo | Nacmias, Benedetta | Gilbert, John R | Mayhaus, Manuel | Jessen, Frank | Dichgans, Martin | Lannfelt, Lars | Hakonarson, Hakon | Pichler, Sabrina | Carrasquillo, Minerva M | Ingelsson, Martin | Beekly, Duane | Alavarez, Victoria | Zou, Fanggeng | Valladares, Otto | Younkin, Steven G | Coto, Eliecer | Hamilton-Nelson, Kara L | Mateo, Ignacio | Owen, Michael J | Faber, Kelley M | Jonsson, Palmi V | Combarros, Onofre | O'Donovan, Michael C | Cantwell, Laura B | Soininen, Hilkka | Blacker, Deborah | Mead, Simon | Mosley, Thomas H | Bennett, David A | Harris, Tamara B | Fratiglioni, Laura | Holmes, Clive | de Bruijn, Renee FAG | Passmore, Peter | Montine, Thomas J | Bettens, Karolien | Rotter, Jerome I | Brice, Alexis | Morgan, Kevin | Foroud, Tatiana M | Kukull, Walter A | Hannequin, Didier | Powell, John F | Nalls, Michael A | Ritchie, Karen | Lunetta, Kathryn L | Kauwe, John SK | Boerwinkle, Eric | Riemenschneider, Matthias | Boada, Mercè | Hiltunen, Mikko | Martin, Eden R | Pastor, Pau | Schmidt, Reinhold | Rujescu, Dan | Dartigues, Jean-François | Mayeux, Richard | Tzourio, Christophe | Hofman, Albert | Nöthen, Markus M | Graff, Caroline | Psaty, Bruce M | Haines, Jonathan L | Lathrop, Mark | Pericak-Vance, Margaret A | Launer, Lenore J | Farrer, Lindsay A | van Duijn, Cornelia M | Van Broekhoven, Christine | Ramirez, Alfredo | Schellenberg, Gerard D | Seshadri, Sudha | Amouyel, Philippe | Williams, Julie | Holmans, Peter A
Background
Late–onset Alzheimer's disease (AD) is heritable with 20 genes showing genome wide association in the International Genomics of Alzheimer's Project (IGAP). To identify the biology underlying the disease we extended these genetic data in a pathway analysis.
Methods
The ALIGATOR and GSEA algorithms were used in the IGAP data to identify associated functional pathways and correlated gene expression networks in human brain.
Results
ALIGATOR identified an excess of curated biological pathways showing enrichment of association. Enriched areas of biology included the immune response (p = 3.27×10-12 after multiple testing correction for pathways), regulation of endocytosis (p = 1.31×10-11), cholesterol transport (p = 2.96 × 10-9) and proteasome-ubiquitin activity (p = 1.34×10-6). Correlated gene expression analysis identified four significant network modules, all related to the immune response (corrected p 0.002 – 0.05).
Conclusions
The immune response, regulation of endocytosis, cholesterol transport and protein ubiquitination represent prime targets for AD therapeutics.
doi:10.1016/j.jalz.2014.05.1757
PMCID: PMC4672734  PMID: 25533204
Alzheimer's disease; dementia; neurodegeneration; immune response; endocytosis; cholesterol metabolism; uniquitination; pathway analysis; ALIGATOR; Weighted gene coexpression network analysis
18.  Influence of Coding Variability in APP-Aβ Metabolism Genes in Sporadic Alzheimer’s Disease 
PLoS ONE  2016;11(6):e0150079.
The cerebral deposition of Aβ42, a neurotoxic proteolytic derivate of amyloid precursor protein (APP), is a central event in Alzheimer’s disease (AD)(Amyloid hypothesis). Given the key role of APP-Aβ metabolism in AD pathogenesis, we selected 29 genes involved in APP processing, Aβ degradation and clearance. We then used exome and genome sequencing to investigate the single independent (single-variant association test) and cumulative (gene-based association test) effect of coding variants in these genes as potential susceptibility factors for AD, in a cohort composed of 332 sporadic and mainly late-onset AD cases and 676 elderly controls from North America and the UK. Our study shows that common coding variability in these genes does not play a major role for the disease development. In the single-variant association analysis, the main hits, none of which statistically significant after multiple testing correction (1.9e-4
doi:10.1371/journal.pone.0150079
PMCID: PMC4889076  PMID: 27249223
Jun, Gyungah | Ibrahim-Verbaas, Carla A. | Vronskaya, Maria | Lambert, Jean-Charles | Chung, Jaeyoon | Naj, Adam C. | Kunkle, Brian W. | Wang, Li-San | Bis, Joshua C. | Bellenguez, Céline | Harold, Denise | Lunetta, Kathryn L. | Destefano, Anita L. | Grenier-Boley, Benjamin | Sims, Rebecca | Beecham, Gary W. | Smith, Albert V. | Chouraki, Vincent | Hamilton-Nelson, Kara L. | Ikram, M. Arfan | Fievet, Nathalie | Denning, Nicola | Martin, Eden R. | Schmidt, Helena | Kamatani, Yochiro | Dunstan, Melanie L | Valladares, Otto | Laza, Agustin Ruiz | Zelenika, Diana | Ramirez, Alfredo | Foroud, Tatiana M. | Choi, Seung-Hoan | Boland, Anne | Becker, Tim | Kukull, Walter A. | van der Lee, Sven J. | Pasquier, Florence | Cruchaga, Carlos | Beekly, Duane | Fitzpatrick, Annette L. | Hanon, Oliver | Gill, Michael | Barber, Robert | Gudnason, Vilmundur | Campion, Dominique | Love, Seth | Bennett, David A. | Amin, Najaf | Berr, Claudine | Tsolaki, Magda | Buxbaum, Joseph D. | Lopez, Oscar L. | Deramecourt, Vincent | Fox, Nick C | Cantwell, Laura B. | Tárraga, Lluis | Dufouil, Carole | Hardy, John | Crane, Paul K. | Eiriksdottir, Gudny | Hannequin, Didier | Clarke, Robert | Evans, Denis | Mosley, Thomas H. | Letenneur, Luc | Brayne, Carol | Maier, Wolfgang | De Jager, Philip | Emilsson, Valur | Dartigues, Jean-François | Hampel, Harald | Kamboh, M. Ilyas | de Bruijn, Renee F.A.G. | Tzourio, Christophe | Pastor, Pau | Larson, Eric B. | Rotter, Jerome I. | O’Donovan, Michael C | Montine, Thomas J. | Nalls, Michael A. | Mead, Simon | Reiman, Eric M. | Jonsson, Palmi V. | Holmes, Clive | St George-Hyslop, Peter H. | Boada, Mercè | Passmore, Peter | Wendland, Jens R. | Schmidt, Reinhold | Morgan, Kevin | Winslow, Ashley R. | Powell, John F | Carasquillo, Minerva | Younkin, Steven G. | Jakobsdóttir, Jóhanna | Kauwe, John SK | Wilhelmsen, Kirk C. | Rujescu, Dan | Nöthen, Markus M | Hofman, Albert | Jones, Lesley | Haines, Jonathan L. | Psaty, Bruce M. | Van Broeckhoven, Christine | Holmans, Peter | Launer, Lenore J. | Mayeux, Richard | Lathrop, Mark | Goate, Alison M. | Escott-Price, Valentina | Seshadri, Sudha | Pericak-Vance, Margaret A. | Amouyel, Philippe | Williams, Julie | van Duijn, Cornelia M. | Schellenberg, Gerard D. | Farrer, Lindsay A.
Molecular psychiatry  2015;21(1):108-117.
APOE ε4, the most significant genetic risk factor for Alzheimer disease (AD), may mask effects of other loci. We re-analyzed genome-wide association study (GWAS) data from the International Genomics of Alzheimer’s Project (IGAP) Consortium in APOE ε4+ (10,352 cases and 9,207 controls) and APOE ε4− (7,184 cases and 26,968 controls) subgroups as well as in the total sample testing for interaction between a SNP and APOE ε4 status. Suggestive associations (P<1x10−4) in stage 1 were evaluated in an independent sample (stage 2) containing 4,203 subjects (APOE ε4+: 1,250 cases and 536 controls; APOE ε4-: 718 cases and 1,699 controls). Among APOE ε4− subjects, novel genome-wide significant (GWS) association was observed with 17 SNPs (all between KANSL1 and LRRC37A on chromosome 17 near MAPT) in a meta-analysis of the stage 1 and stage 2 datasets (best SNP, rs2732703, P=5·8x10−9). Conditional analysis revealed that rs2732703 accounted for association signals in the entire 100 kilobase region that includes MAPT. Except for previously identified AD loci showing stronger association in APOE ε4+ subjects (CR1 and CLU) or APOE ε4− subjects (MS4A6A/MS4A4A/ MS4A6E), no other SNPs were significantly associated with AD in a specific APOE genotype subgroup. In addition, the finding in the stage 1 sample that AD risk is significantly influenced by the interaction of APOE with rs1595014 in TMEM106B (P=1·6x10−7) is noteworthy because TMEM106B variants have previously been associated with risk of frontotemporal dementia. Expression quantitative trait locus analysis revealed that rs113986870, one of the GWS SNPs near rs2732703, is significantly associated with four KANSL1 probes that target transcription of the first translated exon and an untranslated exon in hippocampus (P≤1.3x10−8), frontal cortex (P≤1.3x10−9), and temporal cortex (P≤1.2x10−11). Rs113986870 is also strongly associated with a MAPT probe that targets transcription of alternatively spliced exon 3 in frontal cortex (P=9.2x10−6) and temporal cortex (P=2.6x10−6). Our APOE-stratified GWAS is the first to show GWS association for AD with SNPs in the chromosome 17q21.31 region. Replication of this finding in independent samples is needed to verify that SNPs in this region have significantly stronger effects on AD risk in persons lacking APOE ε4 compared to persons carrying this allele, and if this is found to hold, further examination of this region and studies aimed at deciphering the mechanism(s) are warranted.
doi:10.1038/mp.2015.23
PMCID: PMC4573764  PMID: 25778476
Molecular psychiatry  2015;21(5):608-614.
Opioid dependence, a severe addictive disorder and major societal problem, has been demonstrated to be moderately heritable. We conducted a genome-wide association study in Comorbidity and Trauma Study data comparing opioid dependent daily injectors (N=1167) with opioid misusers who never progressed to daily injection (N=161). The strongest associations, observed for CNIH3 SNPs, were confirmed in two independent samples, the Yale-Penn genetic studies of opioid, cocaine, and alcohol dependence and the Study of Addiction: Genetics and Environment, which both contain non-dependent opioid misusers and opioid dependent individuals. Meta-analyses found 5 genome-wide significant CNIH3 SNPs. The A allele of rs10799590, the most highly associated SNP, was robustly protective [p=4.30E-9; OR 0.64 (95%CI 0.55 – 0.74)]. Epigenetic annotation predicts that this SNP is functional in fetal brain. Neuroimaging data from the Duke Neurogenetics Study (N=312) provide evidence of this SNP’s in vivo functionality; rs10799590 A allele carriers displayed significantly greater right amygdala habituation to threat-related facial expressions, a phenotype associated with resilience to psychopathology. Computational genetic analyses of physical dependence on morphine across 23 mouse strains yielded significant correlations for haplotypes in CNIH3 and functionally-related genes. These convergent findings support CNIH3 involvement in the pathophysiology of opioid dependence complementing prior studies implicating the AMPA glutamate system.
doi:10.1038/mp.2015.102
PMCID: PMC4740268  PMID: 26239289
Traylor, Matthew | Adib‐Samii, Poneh | Harold, Denise | Dichgans, Martin | Williams, Julie | Lewis, Cathryn M. | Markus, Hugh S. | Fornage, Myriam | Holliday, Elizabeth G | Sharma, Pankaj | Bis, Joshua C | Psaty, Bruce M | Seshadri, Sudha | Nalls, Mike A | Devan, William J | Boncoraglio, Giorgio | Malik, Rainer | Mitchell, Braxton D | Kittner, Steven J | Ikram, M Arfan | Clarke, Robert | Rosand, Jonathan | Meschia, James F | Sudlow, Cathie | Rothwell, Peter M | Levi, Christopher | Bevan, Steve | Kilarski, Laura L | Walters, Matthew | Thijs, Vincent | Slowik, Agnieszka | Lindgren, Arne | de Bakker, Paul I W | Lambert, Jean‐Charles | Ibrahim‐Verbaas, Carla A | Harold, Denise | Naj, Adam C | Sims, Rebecca | Bellenguez, Céline | Jun, Gyungah | DeStefano, Anita L | Bis, Joshua C | Beecham, Gary W | Grenier‐Boley, Benjamin | Russo, Giancarlo | Thornton‐Wells, Tricia A | Jones, Nicola | Smith, Albert V | Chouraki, Vincent | Thomas, Charlene | Ikram, M Arfan | Zelenika, Diana | Vardarajan, Badri N | Kamatani, Yoichiro | Lin, Chiao‐Feng | Gerrish, Amy | Schmidt, Helena | Kunkle, Brian | Dunstan, Melanie L | Ruiz, Agustin | Bihoreau, Marie‐Thçrèse | Choi, Seung‐Hoan | Reitz, Christiane | Pasquier, Florence | Hollingworth, Paul | Ramirez, Alfredo | Hanon, Olivier | Fitzpatrick, Annette L | Buxbaum, Joseph D | Campion, Dominique | Crane, Paul K | Baldwin, Clinton | Becker, Tim | Gudnason, Vilmundur | Cruchaga, Carlos | Craig, David | Amin, Najaf | Berr, Claudine | Lopez, Oscar L | De Jager, Philip L | Deramecourt, Vincent | Johnston, Janet A | Evans, Denis | Lovestone, Simon | Letenneur, Luc | Morón, Francisco J | Rubinsztein, David C | Eiriksdottir, Gudny | Sleegers, Kristel | Goate, Alison M | Fiçvet, Nathalie | Huentelman, Matthew J | Gill, Michael | Brown, Kristelle | Kamboh, M Ilyas | Keller, Lina | Barberger‐Gateau, Pascale | McGuinness, Bernadette | Larson, Eric B | Green, Robert | Myers, Amanda J | Dufouil, Carole | Todd, Stephen | Wallon, David | Love, Seth | Rogaeva, Ekaterina | Gallacher, John | St George‐Hyslop, Peter | Clarimon, Jordi | Lleo, Alberto | Bayer, Anthony | Tsuang, Debby W | Yu, Lei | Tsolaki, Magda | Bossù, Paola | Spalletta, Gianfranco | Proitsi, Petroula | Collinge, John | Sorbi, Sandro | Sanchez‐Garcia, Florentino | Fox, Nick C | Hardy, John | Deniz Naranjo, Maria Candida | Bosco, Paolo | Clarke, Robert | Brayne, Carol | Galimberti, Daniela | Mancuso, Michelangelo | Matthews, Fiona | Moebus, Susanne | Mecocci, Patrizia | Del Zompo, Maria | Maier, Wolfgang | Hampel, Harald | Pilotto, Alberto | Bullido, Maria | Panza, Francesco | Caffarra, Paolo | Nacmias, Benedetta | Gilbert, John R | Mayhaus, Manuel | Lannfelt, Lars | Hakonarson, Hakon | Pichler, Sabrina | Carrasquillo, Minerva M | Ingelsson, Martin | Beekly, Duane | Alvarez, Victoria | Zou, Fanggeng | Valladares, Otto | Younkin, Steven G | Coto, Eliecer | Hamilton‐Nelson, Kara L | Gu, Wei | Razquin, Cristina | Pastor, Pau | Mateo, Ignacio | Owen, Michael J | Faber, Kelley M | Jonsson, Palmi V | Combarros, Onofre | O'Donovan, Michael C | Cantwell, Laura B | Soininen, Hilkka | Blacker, Deborah | Mead, Simon | Mosley, Thomas H | Bennett, David A | Harris, Tamara B | Fratiglioni, Laura | Holmes, Clive | de Bruijn, Renee F A G | Passmore, Peter | Montine, Thomas J | Bettens, Karolien | Rotter, Jerome I | Brice, Alexis | Morgan, Kevin | Foroud, Tatiana M | Kukull, Walter A | Hannequin, Didier | Powell, John F | Nalls, Michael A | Ritchie, Karen | Lunetta, Kathryn L | Kauwe, John S K | Boerwinkle, Eric | Riemenschneider, Matthias | Boada, Mercè | Hiltunen, Mikko | Martin, Eden R | Schmidt, Reinhold | Rujescu, Dan | Wang, Li‐San | Dartigues, Jean‐François | Mayeux, Richard | Tzourio, Christophe | Hofman, Albert | Nöthen, Markus M | Graff, Caroline | Psaty, Bruce M | Jones, Lesley | Haines, Jonathan L | Holmans, Peter A | Lathrop, Mark | Pericak‐Vance, Margaret A | Launer, Lenore J | Farrer, Lindsay A | van Duijn, Cornelia M | Van Broeckhoven, Christine | Moskvina, Valentina | Seshadri, Sudha | Williams, Julie | Schellenberg, Gerard D | Amouyel, Philippe
Annals of Neurology  2016;79(5):739-747.
Objective
Increasing evidence suggests epidemiological and pathological links between Alzheimer's disease (AD) and ischemic stroke (IS). We investigated the evidence that shared genetic factors underpin the two diseases.
Methods
Using genome‐wide association study (GWAS) data from METASTROKE + (15,916 IS cases and 68,826 controls) and the International Genomics of Alzheimer's Project (IGAP; 17,008 AD cases and 37,154 controls), we evaluated known associations with AD and IS. On the subset of data for which we could obtain compatible genotype‐level data (4,610 IS cases, 1,281 AD cases, and 14,320 controls), we estimated the genome‐wide genetic correlation (rG) between AD and IS, and the three subtypes (cardioembolic, small vessel, and large vessel), using genome‐wide single‐nucleotide polymorphism (SNP) data. We then performed a meta‐analysis and pathway analysis in the combined AD and small vessel stroke data sets to identify the SNPs and molecular pathways through which disease risk may be conferred.
Results
We found evidence of a shared genetic contribution between AD and small vessel stroke (rG [standard error] = 0.37 [0.17]; p = 0.011). Conversely, there was no evidence to support shared genetic factors in AD and IS overall or with the other stroke subtypes. Of the known GWAS associations with IS or AD, none reached significance for association with the other trait (or stroke subtypes). A meta‐analysis of AD IGAP and METASTROKE + small vessel stroke GWAS data highlighted a region (ATP5H/KCTD2/ICT1) associated with both diseases (p = 1.8 × 10−8). A pathway analysis identified four associated pathways involving cholesterol transport and immune response.
Interpretation
Our findings indicate shared genetic susceptibility to AD and small vessel stroke and highlight potential causal pathways and loci. Ann Neurol 2016;79:739–747
doi:10.1002/ana.24621
PMCID: PMC4864940  PMID: 26913989
Addiction biology  2014;20(3):617-627.
Alcohol and drug use disorders are individually heritable (50%). Twin studies indicate that alcohol and substance use disorders share common genetic influences, and therefore may represent a more heritable form of addiction and thus be more powerful for genetic studies. This study utilized data from 2,322 subjects from 118 European-American families in the COGA sample to conduct genomewide association analysis of a binary and a continuous index of general substance dependence liability. The binary phenotype (ANYDEP) was based on meeting lifetime criteria for any DSM-IV dependence on alcohol, cannabis, cocaine or opioids. The quantitative trait (QUANTDEP) was constructed from factor analysis based on endorsement across the 7 DSM-IV criteria for each of the 4 substances. Heritability was estimated to be 54% for ANYDEP and 86% for QUANTDEP. One SNP, rs2952621 in the uncharacterized gene LOC151121 on chromosome 2, was associated with ANYDEP (p=1.8×10−8), with support from surrounding imputed SNPs and replication in an independent sample (SAGE; p=0.02). One SNP, rs2567261 in ARHGAP28 (Rho GTPase activating protein 28), was associated with QUANTDEP (p=3.8×10−8), and supported by imputed SNPs in the region, but did not replicate in an independent sample (SAGE; p=0.29). The results of this study provide evidence that there are common variants that contribute to the risk for a general liability to substance dependence.
doi:10.1111/adb.12153
PMCID: PMC4233207  PMID: 24832863
alcohol dependence; cannabis dependence; cocaine dependence; common genetic liability; drug dependence; opioid dependence
Brain  2015;138(4):1036-1045.
Ringman et al. characterize behavioural changes in individuals with preclinical and early familial Alzheimer's disease. Significant behavioural changes do not occur prior to cognitive decline but, in common with late-onset Alzheimer’s disease, increased rates of depression, anxiety, apathy and other behavioural changes are seen early in manifest familial disease.
Prior studies indicate psychiatric symptoms such as depression, apathy and anxiety are risk factors for or prodromal symptoms of incipient Alzheimer’s disease. The study of persons at 50% risk for inheriting autosomal dominant Alzheimer’s disease mutations allows characterization of these symptoms before progressive decline in a population destined to develop illness. We sought to characterize early behavioural features in carriers of autosomal dominant Alzheimer’s disease mutations. Two hundred and sixty-one persons unaware of their mutation status enrolled in the Dominantly Inherited Alzheimer Network, a study of persons with or at-risk for autosomal dominant Alzheimer’s disease, were evaluated with the Neuropsychiatric Inventory-Questionnaire, the 15-item Geriatric Depression Scale and the Clinical Dementia Rating Scale (CDR). Ninety-seven asymptomatic (CDR = 0), 25 mildly symptomatic (CDR = 0.5), and 33 overtly affected (CDR > 0.5) autosomal dominant Alzheimer’s disease mutation carriers were compared to 106 non-carriers with regard to frequency of behavioural symptoms on the Neuropsychiatric Inventory-Questionnaire and severity of depressive symptoms on the Geriatric Depression Scale using generalized linear regression models with appropriate distributions and link functions. Results from the adjusted analyses indicated that depressive symptoms on the Neuropsychiatric Inventory-Questionnaire were less common in cognitively asymptomatic mutation carriers than in non-carriers (5% versus 17%, P = 0.014) and the odds of experiencing at least one behavioural sign in cognitively asymptomatic mutation carriers was lower than in non-carriers (odds ratio = 0.50, 95% confidence interval: 0.26–0.98, P = 0.042). Depression (56% versus 17%, P = 0.0003), apathy (40% versus 4%, P < 0.0001), disinhibition (16% versus 2%, P = 0.009), irritability (48% versus 9%, P = 0.0001), sleep changes (28% versus 7%, P = 0.003), and agitation (24% versus 6%, P = 0.008) were more common and the degree of self-rated depression more severe (mean Geriatric Depression Scale score of 2.8 versus 1.4, P = 0.006) in mildly symptomatic mutation carriers relative to non-carriers. Anxiety, appetite changes, delusions, and repetitive motor activity were additionally more common in overtly impaired mutation carriers. Similar to studies of late-onset Alzheimer’s disease, we demonstrated increased rates of depression, apathy, and other behavioural symptoms in the mildly symptomatic, prodromal phase of autosomal dominant Alzheimer’s disease that increased with disease severity. We did not identify any increased psychopathology in mutation carriers over non-carriers during the presymptomatic stage, suggesting these symptoms result when a threshold of neurodegeneration is reached rather than as life-long qualities. Unexpectedly, we found lower rates of depressive symptoms in cognitively asymptomatic mutation carriers.
doi:10.1093/brain/awv004
PMCID: PMC4963801  PMID: 25688083
behaviour; depression; Alzheimer; prodromal; familial
PLoS ONE  2016;11(2):e0148717.
Late onset Alzheimer’s disease (LOAD) is a genetically complex and clinically heterogeneous disease. Recent large-scale genome wide association studies (GWAS) have identified more than twenty loci that modify risk for AD. Despite the identification of these loci, little progress has been made in identifying the functional variants that explain the association with AD risk. Thus, we sought to determine whether the novel LOAD GWAS single nucleotide polymorphisms (SNPs) alter expression of LOAD GWAS genes and whether expression of these genes is altered in AD brains. The majority of LOAD GWAS SNPs occur in gene dense regions under large linkage disequilibrium (LD) blocks, making it unclear which gene(s) are modified by the SNP. Thus, we tested for brain expression quantitative trait loci (eQTLs) between LOAD GWAS SNPs and SNPs in high LD with the LOAD GWAS SNPs in all of the genes within the GWAS loci. We found a significant eQTL between rs1476679 and PILRB and GATS, which occurs within the ZCWPW1 locus. PILRB and GATS expression levels, within the ZCWPW1 locus, were also associated with AD status. Rs7120548 was associated with MTCH2 expression, which occurs within the CELF1 locus. Additionally, expression of several genes within the CELF1 locus, including MTCH2, were highly correlated with one another and were associated with AD status. We further demonstrate that PILRB, as well as other genes within the GWAS loci, are most highly expressed in microglia. These findings together with the function of PILRB as a DAP12 receptor supports the critical role of microglia and neuroinflammation in AD risk.
doi:10.1371/journal.pone.0148717
PMCID: PMC4769299  PMID: 26919393
JAMA neurology  2015;72(2):209-216.
IMPORTANCE
Recently, a rare variant in the amyloid precursor protein gene (APP) was described in a population from Iceland. This variant, in which alanine is replaced by threonine at position 673 (A673T), appears to protect against late-onset Alzheimer disease (AD). We evaluated the frequency of this variant in AD cases and cognitively normal controls to determine whether this variant will significantly contribute to risk assessment in individuals in the United States.
OBJECTIVE
To determine the frequency of the APP A673T variant in a large group of elderly cognitively normal controls and AD cases from the United States and in 2 case-control cohorts from Sweden.
DESIGN, SETTING, AND PARTICIPANTS
Case-control association analysis of variant APP A673T in US and Swedish white individuals comparing AD cases with cognitively intact elderly controls. Participants were ascertained at multiple university-associated medical centers and clinics across the United States and Sweden by study-specific sampling methods. They were from case-control studies, community-based prospective cohort studies, and studies that ascertained multiplex families from multiple sources.
MAIN OUTCOMES AND MEASURES
Genotypes for the APP A673T variant were determined using the Infinium HumanExome V1 Beadchip (Illumina, Inc) and by TaqMan genotyping (Life Technologies).
RESULTS
The A673T variant genotypes were evaluated in 8943 US AD cases, 10 480 US cognitively normal controls, 862 Swedish AD cases, and 707 Swedish cognitively normal controls. We identified 3 US individuals heterozygous for A673T, including 1 AD case (age at onset, 89 years) and 2 controls (age at last examination, 82 and 77 years). The remaining US samples were homozygous for the alanine (A673) allele. In the Swedish samples, 3 controls were heterozygous for A673T and all AD cases were homozygous for the A673 allele. We also genotyped a US family previously reported to harbor the A673T variant and found a mother-daughter pair, both cognitively normal at ages 72 and 84 years, respectively, who were both heterozygous for A673T; however, all individuals with AD in the family were homozygous for A673.
CONCLUSIONS AND RELEVANCE
The A673T variant is extremely rare in US cohorts and does not play a substantial role in risk for AD in this population. This variant may be primarily restricted to Icelandic and Scandinavian populations.
doi:10.1001/jamaneurol.2014.2157
PMCID: PMC4324097  PMID: 25531812

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