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1.  Extensive regulation of the non-coding transcriptome by hypoxia: role of HIF in releasing paused RNApol2 
EMBO Reports  2013;15(1):70-76.
Hypoxia is central to both ischaemic and neoplastic diseases. However, the non-coding transcriptional response to hypoxia is largely uncharacterized. We undertook integrated genomic analyses of both non-coding and coding transcripts using massively parallel sequencing and interfaced this data with pan-genomic analyses of hypoxia-inducible factor (HIF) and RNApol2 binding in hypoxic cells. These analyses revealed that all classes of RNA are profoundly regulated by hypoxia and implicated HIF as a major direct regulator of both the non-coding and coding transcriptome, acting predominantly through release of pre-bound promoter-paused RNApol2. These findings indicate that the transcriptional response to hypoxia is substantially more extensive than previously considered.
PMCID: PMC3983684  PMID: 24363272
HIF; hypoxia; non-coding; RNApol2; transcription
2.  The histone demethylase JMJD2B is regulated by estrogen receptor alpha and hypoxia and is a key mediator of estrogen induced growth 
Cancer research  2010;70(16):6456-6466.
ERα plays an important role in breast cancer. Up-regulation of HIF-1α in ERα-positive cancers suggests that HIF-1α may cooperate with ERα to promote breast cancer progression and consequently affect breast cancer treatment. Here we show the histone demethylase JMJD2B is regulated by both ERα and HIF-1α, and drives breast cancer cell proliferation in normoxia and hypoxia, and epigenetically regulates the expression of cell cycle genes such as CCND1, CCNA1 and WEE1. We also demonstrate that JMJD2B and the hypoxia marker CA9 together stratify a subclass of breast cancer patients and predicts a worse outcome of these breast cancers. Our findings provide a biological rationale to support the therapeutic targeting of histone demethylases in breast cancer patients.
PMCID: PMC4261152  PMID: 20682797
Hypoxia; ERα; HIF-1α; Histone demethylase; JMJD2B; breast cancer
3.  The molecular biology of the olive fly comes of age 
BMC Genetics  2014;15(Suppl 2):S8.
Olive cultivation blends with the history of the Mediterranean countries since ancient times. Even today, activities around the olive tree constitute major engagements of several people in the countryside of both sides of the Mediterranean basin. The olive fly is, beyond doubt, the most destructive pest of cultivated olives. The female fly leaves its eggs in the olive fruit. Upon emergence, the larvae feed on the olive sap, thus destroying the fruit. If untreated, practically all olives get infected. The use of chemical insecticides constitutes the principal olive fly control approach. The Sterile Insect Technique (SIT), an environmentally friendly alternative control method, had been tried in pilot field applications in the 1970's, albeit with no practical success. This was mainly attributed to the low, non-antagonistic quality of the mixed-sex released insects. Many years of experience from successful SIT applications in related species, primarily the Mediterranean fruit fly, Ceratitis capitata, demonstrated that efficient SIT protocols require the availability of fundamental genetic and molecular information.
Among the primary systems whose understanding can contribute towards novel SIT approaches (or its recently developed alternative RIDL: Release of Insects carrying a Dominant Lethal) is the reproductive, since the ability to manipulate the reproductive system would directly affect the insect's fertility. In addition, the analysis of early embryonic promoters and apoptotic genes would provide tools that confer dominant early-embryonic lethality during mass-rearing. Here we report the identification of several genes involved in these systems through whole transcriptome analysis of female accessory glands (FAGs) and spermathecae, as well as male testes. Indeed, analysis of differentially expressed genes in these tissues revealed higher metabolic activity in testes than in FAGs/spermathecae. Furthermore, at least five olfactory-related genes were shown to be differentially expressed in the female and male reproductive systems analyzed. Finally, the expression profile of the embryonic serendipity-α locus and the pre-apoptotic head involution defective gene were analyzed during embryonic developmental stages.
Several years of molecular studies on the olive fly can now be combined with new information from whole transcriptome analyses and lead to a deep understanding of the biology of this notorious insect pest. This is a prerequisite for the development of novel embryonic lethality female sexing strains for successful SIT efforts which, combined with improved mass-reared conditions, give new hope for efficient SIT applications for the olive fly.
PMCID: PMC4255830  PMID: 25472866
Tephritidae; Bactrocera oleae; sry-α; hid
5.  Olive fly transcriptomics analysis implicates energy metabolism genes in spinosad resistance 
BMC Genomics  2014;15(1):714.
The olive fly, Bactrocera oleae, is the most devastating pest of cultivated olives. Its control has been traditionally based on insecticides, mainly organophosphates and pyrethroids. In recent years, the naturalyte spinosad is used against the olive fly. As with other insecticides, spinosad is subject to selection pressures that have led to resistance development. Mutations in the α6 subunit of the nicotinic acetylcholine receptor (nAChR) have been implicated in spinosad resistance in several species (e.g., Drosophila melanogaster) but excluded in others (e.g., Musca domestica). Yet, additional mechanisms involving enhanced metabolism of detoxification enzymes (such as P450 monooxygenases or mixed function oxidases) have also been reported. In order to clarify the spinosad resistance mechanisms in the olive fly, we searched for mutations in the α6-subunit of the nAChR and for up-regulated genes in the entire transcriptome of spinosad resistant olive flies.
The olive fly α6-subunit of the nAChR was cloned from the laboratory sensitive strain and a spinosad selected resistant line. The differences reflected silent nucleotide substitutions or conserved amino acid changes. Additionally, whole transcriptome analysis was performed in the two strains in order to reveal any underlying resistance mechanisms. Comparison of over 13,000 genes showed that in spinosad resistant flies nine genes were significantly over-expressed, whereas ~40 were under-expressed. Further functional analyses of the nine over-expressed and eleven under-expressed loci were performed. Four of these loci (Yolk protein 2, ATP Synthase FO subunit 6, Low affinity cationic amino acid transporter 2 and Serine protease 6) showed consistently higher expression both in the spinosad resistant strain and in wild flies from a resistant California population. On the other side, two storage protein genes (HexL1 and Lsp1) and two heat-shock protein genes (Hsp70 and Hsp23) were unfailingly under-expressed in resistant flies.
The observed nucleotide differences in the nAChR-α6 subunit between the sensitive and spinosad resistant olive fly strains did not advocate for the involvement of receptor mutations in spinosad resistance. Instead, the transcriptome comparison between the two strains indicated that several immune system loci as well as elevated energy requirements of the resistant flies might be necessary to lever the detoxification process.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-714) contains supplementary material, which is available to authorized users.
PMCID: PMC4168201  PMID: 25156405
Insecticide tolerance; Spinosyns; Next generation sequencing; Expression analysis
6.  High-resolution analysis of cis-acting regulatory networks at the α-globin locus 
We have combined the circular chromosome conformation capture protocol with high-throughput, genome-wide sequence analysis to characterize the cis-acting regulatory network at a single locus. In contrast to methods which identify large interacting regions (10–1000 kb), the 4C approach provides a comprehensive, high-resolution analysis of a specific locus with the aim of defining, in detail, the cis-regulatory elements controlling a single gene or gene cluster. Using the human α-globin locus as a model, we detected all known local and long-range interactions with this gene cluster. In addition, we identified two interactions with genes located 300 kb (NME4) and 625 kb (FAM173a) from the α-globin cluster.
PMCID: PMC3682726  PMID: 23650635
α-globin locus; cis-regulatory elements; chromatin conformation capture
7.  Microarray-based ultra-high resolution discovery of genomic deletion mutations 
BMC Genomics  2014;15:224.
Oligonucleotide microarray-based comparative genomic hybridization (CGH) offers an attractive possible route for the rapid and cost-effective genome-wide discovery of deletion mutations. CGH typically involves comparison of the hybridization intensities of genomic DNA samples with microarray chip representations of entire genomes, and has widespread potential application in experimental research and medical diagnostics. However, the power to detect small deletions is low.
Here we use a graduated series of Arabidopsis thaliana genomic deletion mutations (of sizes ranging from 4 bp to ~5 kb) to optimize CGH-based genomic deletion detection. We show that the power to detect smaller deletions (4, 28 and 104 bp) depends upon oligonucleotide density (essentially the number of genome-representative oligonucleotides on the microarray chip), and determine the oligonucleotide spacings necessary to guarantee detection of deletions of specified size.
Our findings will enhance a wide range of research and clinical applications, and in particular will aid in the discovery of genomic deletions in the absence of a priori knowledge of their existence.
PMCID: PMC3998191  PMID: 24655320
Mutation; Deletion; Microarray; Genome; Comparative genomic hybridization; Probe density
8.  Next-generation sequencing (NGS) as a diagnostic tool for retinal degeneration reveals a much higher detection rate in early-onset disease 
Inherited retinal degeneration (IRD) is a common cause of visual impairment (prevalence ∼1/3500). There is considerable phenotype and genotype heterogeneity, making a specific diagnosis very difficult without molecular testing. We investigated targeted capture combined with next-generation sequencing using Nimblegen 12plex arrays and the Roche 454 sequencing platform to explore its potential for clinical diagnostics in two common types of IRD, retinitis pigmentosa and cone-rod dystrophy. 50 patients (36 unknowns and 14 positive controls) were screened, and pathogenic mutations were identified in 25% of patients in the unknown, with 53% in the early-onset cases. All patients with new mutations detected had an age of onset <21 years and 44% had a family history. Thirty-one percent of mutations detected were novel. A de novo mutation in rhodopsin was identified in one early-onset case without a family history. Bioinformatic pipelines were developed to identify likely pathogenic mutations and stringent criteria were used for assignment of pathogenicity. Analysis of sequencing metrics revealed significant variability in capture efficiency and depth of coverage. We conclude that targeted capture and next-generation sequencing are likely to be very useful in a diagnostic setting, but patients with earlier onset of disease are more likely to benefit from using this strategy. The mutation-detection rate suggests that many patients are likely to have mutations in novel genes.
PMCID: PMC3573204  PMID: 22968130
retinal degeneration; molecular diagnostics; next-generation sequencing
9.  Integrated analysis of microRNA and mRNA expression and association with HIF binding reveals the complexity of microRNA expression regulation under hypoxia 
Molecular Cancer  2014;13:28.
In mammalians, HIF is a master regulator of hypoxia gene expression through direct binding to DNA, while its role in microRNA expression regulation, critical in the hypoxia response, is not elucidated genome wide. Our aim is to investigate in depth the regulation of microRNA expression by hypoxia in the breast cancer cell line MCF-7, establish the relationship between microRNA expression and HIF binding sites, pri-miRNA transcription and microRNA processing gene expression.
MCF-7 cells were incubated at 1% Oxygen for 16, 32 and 48 h. SiRNA against HIF-1α and HIF-2α were performed as previously published. MicroRNA and mRNA expression were assessed using microRNA microarrays, small RNA sequencing, gene expression microarrays and Real time PCR. The Kraken pipeline was applied for microRNA-seq analysis along with Bioconductor packages. Microarray data was analysed using Limma (Bioconductor), ChIP-seq data were analysed using Gene Set Enrichment Analysis and multiple testing correction applied in all analyses.
Hypoxia time course microRNA sequencing data analysis identified 41 microRNAs significantly up- and 28 down-regulated, including hsa-miR-4521, hsa-miR-145-3p and hsa-miR-222-5p reported in conjunction with hypoxia for the first time. Integration of HIF-1α and HIF-2α ChIP-seq data with expression data showed overall association between binding sites and microRNA up-regulation, with hsa-miR-210-3p and microRNAs of miR-27a/23a/24-2 and miR-30b/30d clusters as predominant examples. Moreover the expression of hsa-miR-27a-3p and hsa-miR-24-3p was found positively associated to a hypoxia gene signature in breast cancer. Gene expression analysis showed no full coordination between pri-miRNA and microRNA expression, pointing towards additional levels of regulation. Several transcripts involved in microRNA processing were found regulated by hypoxia, of which DICER (down-regulated) and AGO4 (up-regulated) were HIF dependent. DICER expression was found inversely correlated to hypoxia in breast cancer.
Integrated analysis of microRNA, mRNA and ChIP-seq data in a model cell line supports the hypothesis that microRNA expression under hypoxia is regulated at transcriptional and post-transcriptional level, with the presence of HIF binding sites at microRNA genomic loci associated with up-regulation. The identification of hypoxia and HIF regulated microRNAs relevant for breast cancer is important for our understanding of disease development and design of therapeutic interventions.
PMCID: PMC3928101  PMID: 24517586
MicroRNA; Hypoxia; HIF; Transcription factor; Gene regulation
10.  MicroRNA expression profile in head and neck cancer: HOX-cluster embedded microRNA-196a and microRNA-10b dysregulation implicated in cell proliferation 
BMC Cancer  2013;13:533.
Current evidence implicates aberrant microRNA expression patterns in human malignancies; measurement of microRNA expression may have diagnostic and prognostic applications. Roles for microRNAs in head and neck squamous cell carcinomas (HNSCC) are largely unknown. HNSCC, a smoking-related cancer, is one of the most common malignancies worldwide but reliable diagnostic and prognostic markers have not been discovered so far. Some studies have evaluated the potential use of microRNA as biomarkers with clinical application in HNSCC.
MicroRNA expression profile of oral squamous cell carcinoma samples was determined by means of DNA microarrays. We also performed gain-of-function assays for two differentially expressed microRNA using two squamous cell carcinoma cell lines and normal oral keratinocytes. The effect of the over-expression of these molecules was evaluated by means of global gene expression profiling and cell proliferation assessment.
Altered microRNA expression was detected for a total of 72 microRNAs. Among these we found well studied molecules, such as the miR-17-92 cluster, comprising potent oncogenic microRNA, and miR-34, recently found to interact with p53. HOX-cluster embedded miR-196a/b and miR-10b were up- and down-regulated, respectively, in tumor samples. Since validated HOX gene targets for these microRNAs are not consistently deregulated in HNSCC, we performed gain-of-function experiments, in an attempt to outline their possible role. Our results suggest that both molecules interfere in cell proliferation through distinct processes, possibly targeting a small set of genes involved in cell cycle progression.
Functional data on miRNAs in HNSCC is still scarce. Our data corroborate current literature and brings new insights into the role of microRNAs in HNSCC. We also show that miR-196a and miR-10b, not previously associated with HNSCC, may play an oncogenic role in this disease through the deregulation of cell proliferation. The study of microRNA alterations in HNSCC is an essential step to the mechanistic understanding of tumor formation and could lead to the discovery of clinically relevant biomarkers.
PMCID: PMC3826519  PMID: 24209638
11.  Next generation sequencing for molecular diagnosis of neurological disorders using ataxias as a model 
Brain  2013;136(10):3106-3118.
Many neurological conditions are caused by immensely heterogeneous gene mutations. The diagnostic process is often long and complex with most patients undergoing multiple invasive and costly investigations without ever reaching a conclusive molecular diagnosis. The advent of massively parallel, next-generation sequencing promises to revolutionize genetic testing and shorten the ‘diagnostic odyssey’ for many of these patients. We performed a pilot study using heterogeneous ataxias as a model neurogenetic disorder to assess the introduction of next-generation sequencing into clinical practice. We captured 58 known human ataxia genes followed by Illumina Next-Generation Sequencing in 50 highly heterogeneous patients with ataxia who had been extensively investigated and were refractory to diagnosis. All cases had been tested for spinocerebellar ataxia 1–3, 6, 7 and Friedrich’s ataxia and had multiple other biochemical, genetic and invasive tests. In those cases where we identified the genetic mutation, we determined the time to diagnosis. Pathogenicity was assessed using a bioinformatics pipeline and novel variants were validated using functional experiments. The overall detection rate in our heterogeneous cohort was 18% and varied from 8.3% in those with an adult onset progressive disorder to 40% in those with a childhood or adolescent onset progressive disorder. The highest detection rate was in those with an adolescent onset and a family history (75%). The majority of cases with detectable mutations had a childhood onset but most are now adults, reflecting the long delay in diagnosis. The delays were primarily related to lack of easily available clinical testing, but other factors included the presence of atypical phenotypes and the use of indirect testing. In the cases where we made an eventual diagnosis, the delay was 3–35 years (mean 18.1 years). Alignment and coverage metrics indicated that the capture and sequencing was highly efficient and the consumable cost was ∼£400 (€460 or US$620). Our pathogenicity interpretation pathway predicted 13 different mutations in eight different genes: PRKCG, TTBK2, SETX, SPTBN2, SACS, MRE11, KCNC3 and DARS2 of which nine were novel including one causing a newly described recessive ataxia syndrome. Genetic testing using targeted capture followed by next-generation sequencing was efficient, cost-effective, and enabled a molecular diagnosis in many refractory cases. A specific challenge of next-generation sequencing data is pathogenicity interpretation, but functional analysis confirmed the pathogenicity of novel variants showing that the pipeline was robust. Our results have broad implications for clinical neurology practice and the approach to diagnostic testing.
PMCID: PMC3784284  PMID: 24030952
ataxia; genetics; autosomal dominant cerebellar ataxia; autosomal recessive cerebellar ataxia; diagnosis
12.  Cross-species Analysis Reveals Evolving and Conserved Features of the Nuclear Factor κB (NF-κB) Proteins*  
The Journal of Biological Chemistry  2013;288(16):11546-11554.
Background: NF-κB regulates transcription via binding to DNA and interactions with cofactors.
Results: NF-κB binding to DNA and cytosolic IκBs is conserved, whereas binding to nuclear IκBs has evolved.
Conclusion: There is distinct evolutionary pressure on two NF-κB/IκB binding interfaces.
Significance: The results provide inroads into IκB-specific modulation of NF-κB activity.
NF-κB is a key regulator of immune gene expression in metazoans. It is currently unclear what changes occurred in NF-κB during animal evolution and what features remained conserved. To address this question, we compared the biochemical and functional properties of NF-κB proteins derived from human and the starlet sea anemone (Nematostella vectensis) in 1) a high-throughput assay of in vitro preferences for DNA sequences, 2) ChIP analysis of in vivo recruitment to the promoters of target genes, 3) a LUMIER-assisted examination of interactions with cofactors, and 4) a transactivation assay. We observed a remarkable evolutionary conservation of the DNA binding preferences of the animal NF-κB orthologs. We also show that NF-κB dimerization properties, nuclear localization signals, and binding to cytosolic IκBs are conserved. Surprisingly, the Bcl3-type nuclear IκB proteins functionally pair up only with NF-κB derived from their own species. The basis of the differential NF-κB recognition by IκB subfamilies is discussed.
PMCID: PMC3630861  PMID: 23508954
Cell Signaling; Evolution; Protein/Nucleic Acid Interaction; Protein/Protein Interactions; Transcription; IκB; NF-κB; Nematostella vectensis; Immune
13.  TGF-β/Smad2/3 Signaling Directly Regulates Several miRNAs in Mouse ES Cells and Early Embryos 
PLoS ONE  2013;8(1):e55186.
The Transforming Growth Factor-β (TGF-β) signaling pathway is one of the major pathways essential for normal embryonic development and tissue homeostasis, with anti-tumor but also pro-metastatic properties in cancer. This pathway directly regulates several target genes that mediate its downstream functions, however very few microRNAs (miRNAs) have been identified as targets. miRNAs are modulators of gene expression with essential roles in development and a clear association with diseases including cancer. Little is known about the transcriptional regulation of the primary transcripts (pri-miRNA, pri-miR) from which several mature miRNAs are often derived. Here we present the identification of miRNAs regulated by TGF-β signaling in mouse embryonic stem (ES) cells and early embryos. We used an inducible ES cell system to maintain high levels of the TGF-β activated/phosphorylated Smad2/3 effectors, which are the transcription factors of the pathway, and a specific inhibitor that blocks their activation. By performing short RNA deep-sequencing after 12 hours Smad2/3 activation and after 16 hours inhibition, we generated a database of responsive miRNAs. Promoter/enhancer analysis of a subset of these miRNAs revealed that the transcription of pri-miR-181c/d and the pri-miR-341∼3072 cluster were found to depend on activated Smad2/3. Several of these miRNAs are expressed in early mouse embryos, when the pathway is known to play an essential role. Treatment of embryos with TGF-β inhibitor caused a reduction of their levels confirming that they are targets of this pathway in vivo. Furthermore, we showed that pri-miR-341∼3072 transcription also depends on FoxH1, a known Smad2/3 transcription partner during early development. Together, our data show that miRNAs are regulated directly by the TGF-β/Smad2/3 pathway in ES cells and early embryos. As somatic abnormalities in functions known to be regulated by the TGF-β/Smad2/3 pathway underlie tumor suppression and metastasis, this research also provides a resource for miRNAs involved in cancer.
PMCID: PMC3559380  PMID: 23390484
14.  Cellular interference in craniofrontonasal syndrome: males mosaic for mutations in the X-linked EFNB1 gene are more severely affected than true hemizygotes 
Human Molecular Genetics  2013;22(8):1654-1662.
Craniofrontonasal syndrome (CFNS), an X-linked disorder caused by loss-of-function mutations of EFNB1, exhibits a paradoxical sex reversal in phenotypic severity: females characteristically have frontonasal dysplasia, craniosynostosis and additional minor malformations, but males are usually more mildly affected with hypertelorism as the only feature. X-inactivation is proposed to explain the more severe outcome in heterozygous females, as this leads to functional mosaicism for cells with differing expression of EPHRIN-B1, generating abnormal tissue boundaries—a process that cannot occur in hemizygous males. Apparently challenging this model, males occasionally present with a more severe female-like CFNS phenotype. We hypothesized that such individuals might be mosaic for EFNB1 mutations and investigated this possibility in multiple tissue samples from six sporadically presenting males. Using denaturing high performance liquid chromatography, massively parallel sequencing and multiplex-ligation-dependent probe amplification (MLPA) to increase sensitivity above standard dideoxy sequencing, we identified mosaic mutations of EFNB1 in all cases, comprising three missense changes, two gene deletions and a novel point mutation within the 5′ untranslated region (UTR). Quantification by Pyrosequencing and MLPA demonstrated levels of mutant cells between 15 and 69%. The 5′ UTR variant mutates the stop codon of a small upstream open reading frame that, using a dual-luciferase reporter construct, was demonstrated to exacerbate interference with translation of the wild-type protein. These results demonstrate a more severe outcome in mosaic than in constitutionally deficient males in an X-linked dominant disorder and provide further support for the cellular interference mechanism, normally related to X-inactivation in females.
PMCID: PMC3605834  PMID: 23335590
15.  Recessive Mutations in SPTBN2 Implicate β-III Spectrin in Both Cognitive and Motor Development 
PLoS Genetics  2012;8(12):e1003074.
β-III spectrin is present in the brain and is known to be important in the function of the cerebellum. Heterozygous mutations in SPTBN2, the gene encoding β-III spectrin, cause Spinocerebellar Ataxia Type 5 (SCA5), an adult-onset, slowly progressive, autosomal-dominant pure cerebellar ataxia. SCA5 is sometimes known as “Lincoln ataxia,” because the largest known family is descended from relatives of the United States President Abraham Lincoln. Using targeted capture and next-generation sequencing, we identified a homozygous stop codon in SPTBN2 in a consanguineous family in which childhood developmental ataxia co-segregates with cognitive impairment. The cognitive impairment could result from mutations in a second gene, but further analysis using whole-genome sequencing combined with SNP array analysis did not reveal any evidence of other mutations. We also examined a mouse knockout of β-III spectrin in which ataxia and progressive degeneration of cerebellar Purkinje cells has been previously reported and found morphological abnormalities in neurons from prefrontal cortex and deficits in object recognition tasks, consistent with the human cognitive phenotype. These data provide the first evidence that β-III spectrin plays an important role in cortical brain development and cognition, in addition to its function in the cerebellum; and we conclude that cognitive impairment is an integral part of this novel recessive ataxic syndrome, Spectrin-associated Autosomal Recessive Cerebellar Ataxia type 1 (SPARCA1). In addition, the identification of SPARCA1 and normal heterozygous carriers of the stop codon in SPTBN2 provides insights into the mechanism of molecular dominance in SCA5 and demonstrates that the cell-specific repertoire of spectrin subunits underlies a novel group of disorders, the neuronal spectrinopathies, which includes SCA5, SPARCA1, and a form of West syndrome.
Author Summary
β-III spectrin is present in the brain and is known to be important in the function of the cerebellum. Mutations in β-III spectrin cause spinocerebellar ataxia type 5 (SCA5), sometimes called Lincoln ataxia because it was first described in the relatives of United States President Abraham Lincoln. This is generally an adult-onset progressive cerebellar disorder. Recessive mutations have not previously been described in any of the brain spectrins. We identified a homozygous mutation in SPTBN2, which causes a more severe disorder than SCA5, with a developmental cerebellar ataxia, which is present from childhood; in addition there is marked cognitive impairment. We call this novel condition SPARCA1 (Spectrin-associated Autosomal Recessive Cerebellar Ataxia type 1). This condition could be caused by two separate gene mutations; but we show, using a combination of genome-wide mapping, whole-genome sequencing, and detailed behavioural and neuropathological analysis of a β-III spectrin mouse knockout, that both the ataxia and cognitive impairment are caused by the recessive mutations in β-III spectrin. SPARCA1 is one of a family of neuronal spectrinopathies and illustrates the importance of spectrins in brain development and function.
PMCID: PMC3516553  PMID: 23236289
16.  Individual common variants exert weak effects on the risk for autism spectrum disorderspi 
Anney, Richard | Klei, Lambertus | Pinto, Dalila | Almeida, Joana | Bacchelli, Elena | Baird, Gillian | Bolshakova, Nadia | Bölte, Sven | Bolton, Patrick F. | Bourgeron, Thomas | Brennan, Sean | Brian, Jessica | Casey, Jillian | Conroy, Judith | Correia, Catarina | Corsello, Christina | Crawford, Emily L. | de Jonge, Maretha | Delorme, Richard | Duketis, Eftichia | Duque, Frederico | Estes, Annette | Farrar, Penny | Fernandez, Bridget A. | Folstein, Susan E. | Fombonne, Eric | Gilbert, John | Gillberg, Christopher | Glessner, Joseph T. | Green, Andrew | Green, Jonathan | Guter, Stephen J. | Heron, Elizabeth A. | Holt, Richard | Howe, Jennifer L. | Hughes, Gillian | Hus, Vanessa | Igliozzi, Roberta | Jacob, Suma | Kenny, Graham P. | Kim, Cecilia | Kolevzon, Alexander | Kustanovich, Vlad | Lajonchere, Clara M. | Lamb, Janine A. | Law-Smith, Miriam | Leboyer, Marion | Le Couteur, Ann | Leventhal, Bennett L. | Liu, Xiao-Qing | Lombard, Frances | Lord, Catherine | Lotspeich, Linda | Lund, Sabata C. | Magalhaes, Tiago R. | Mantoulan, Carine | McDougle, Christopher J. | Melhem, Nadine M. | Merikangas, Alison | Minshew, Nancy J. | Mirza, Ghazala K. | Munson, Jeff | Noakes, Carolyn | Nygren, Gudrun | Papanikolaou, Katerina | Pagnamenta, Alistair T. | Parrini, Barbara | Paton, Tara | Pickles, Andrew | Posey, David J. | Poustka, Fritz | Ragoussis, Jiannis | Regan, Regina | Roberts, Wendy | Roeder, Kathryn | Roge, Bernadette | Rutter, Michael L. | Schlitt, Sabine | Shah, Naisha | Sheffield, Val C. | Soorya, Latha | Sousa, Inês | Stoppioni, Vera | Sykes, Nuala | Tancredi, Raffaella | Thompson, Ann P. | Thomson, Susanne | Tryfon, Ana | Tsiantis, John | Van Engeland, Herman | Vincent, John B. | Volkmar, Fred | Vorstman, JAS | Wallace, Simon | Wing, Kirsty | Wittemeyer, Kerstin | Wood, Shawn | Zurawiecki, Danielle | Zwaigenbaum, Lonnie | Bailey, Anthony J. | Battaglia, Agatino | Cantor, Rita M. | Coon, Hilary | Cuccaro, Michael L. | Dawson, Geraldine | Ennis, Sean | Freitag, Christine M. | Geschwind, Daniel H. | Haines, Jonathan L. | Klauck, Sabine M. | McMahon, William M. | Maestrini, Elena | Miller, Judith | Monaco, Anthony P. | Nelson, Stanley F. | Nurnberger, John I. | Oliveira, Guiomar | Parr, Jeremy R. | Pericak-Vance, Margaret A. | Piven, Joseph | Schellenberg, Gerard D. | Scherer, Stephen W. | Vicente, Astrid M. | Wassink, Thomas H. | Wijsman, Ellen M. | Betancur, Catalina | Buxbaum, Joseph D. | Cook, Edwin H. | Gallagher, Louise | Gill, Michael | Hallmayer, Joachim | Paterson, Andrew D. | Sutcliffe, James S. | Szatmari, Peter | Vieland, Veronica J. | Hakonarson, Hakon | Devlin, Bernie
Human Molecular Genetics  2012;21(21):4781-4792.
While it is apparent that rare variation can play an important role in the genetic architecture of autism spectrum disorders (ASDs), the contribution of common variation to the risk of developing ASD is less clear. To produce a more comprehensive picture, we report Stage 2 of the Autism Genome Project genome-wide association study, adding 1301 ASD families and bringing the total to 2705 families analysed (Stages 1 and 2). In addition to evaluating the association of individual single nucleotide polymorphisms (SNPs), we also sought evidence that common variants, en masse, might affect the risk. Despite genotyping over a million SNPs covering the genome, no single SNP shows significant association with ASD or selected phenotypes at a genome-wide level. The SNP that achieves the smallest P-value from secondary analyses is rs1718101. It falls in CNTNAP2, a gene previously implicated in susceptibility for ASD. This SNP also shows modest association with age of word/phrase acquisition in ASD subjects, of interest because features of language development are also associated with other variation in CNTNAP2. In contrast, allele scores derived from the transmission of common alleles to Stage 1 cases significantly predict case status in the independent Stage 2 sample. Despite being significant, the variance explained by these allele scores was small (Vm< 1%). Based on results from individual SNPs and their en masse effect on risk, as inferred from the allele score results, it is reasonable to conclude that common variants affect the risk for ASD but their individual effects are modest.
PMCID: PMC3471395  PMID: 22843504
17.  Principles of dimer-specific gene regulation revealed by a comprehensive characterization of NF-κB family DNA binding 
Nature Immunology  2011;13(1):95-102.
The unique DNA-binding properties of distinct NF-κB dimers are known to influence the selective regulation of NF-κB target genes. To gain a stronger appreciation for these dimer-specific differences, we have combined protein-binding microarrays (PBM) and surface plasmon resonance (SPR) to evaluate DNA sites recognized by eight different NF-κB dimers. We observed three distinct binding-specificity classes and provide insight into mechanisms by which dimers might regulate distinct sets of genes. We identified many new non-traditional κB site sequences and highlight an under-appreciated plasticity of NF-κB dimers in recognizing κB sites with a single consensus half-site. This study provides a database that will be of broad utility in efforts to identify NF-κB target sites and uncover gene regulatory circuitry.
PMCID: PMC3242931  PMID: 22101729
18.  Principles of dimer-specific gene regulation revealed by a comprehensive characterization of NF-κB family DNA binding 
Nature immunology  2011;13(1):95-102.
The unique DNA-binding properties of distinct NF-κB dimers are known to influence the selective regulation of NF-κB target genes. To gain a stronger appreciation for these dimer-specific differences, we have combined protein-binding microarrays (PBM) and surface plasmon resonance (SPR) to evaluate DNA sites recognized by eight different NF-κB dimers. We observed three distinct binding-specificity classes and provide insight into mechanisms by which dimers might regulate distinct sets of genes. We identified many new non-traditional κB site sequences and highlight an under-appreciated plasticity of NF-κB dimers in recognizing κB sites with a single consensus half-site. This study provides a database that will be of broad utility in efforts to identify NF-κB target sites and uncover gene regulatory circuitry.
PMCID: PMC3242931  PMID: 22101729
19.  Direct targeting of Sec23a by miR-200s influences cancer cell secretome and promotes metastatic colonization 
Nature medicine  2011;17(9):1101-1108.
Although the role of miR-200s in regulating E-cadherin expression and epithelial-mesenchymal transition is well established, their influence on metastatic colonization remains controversial. Here, we use clinical and experimental models of breast cancer metastasis to discover a pro-metastatic role of miR-200s that goes beyond their regulation of E-cadherin and epithelial phenotype. Overexpression of miR-200s is associated with increased risk of metastasis in breast cancer and promotes metastatic colonization in mouse models, phenotypes that cannot be recapitulated by E-cadherin expression alone. Genomic and proteomic analyses revealed global shifts in gene expression upon miR-200 overexpression toward that of highly metastatic cells. MiR-200s promote metastatic colonization partly through direct targeting of Sec23a, which mediates secretion of metastasis suppressive proteins, including Igfbp4 and Tinagl1, as validated by functional and clinical correlation studies. Overall, these findings suggest a pleiotropic role of miR-200s in promoting metastatic colonization by influencing E-cadherin-dependent epithelial traits and Sec23a-mediated tumor cell secretome.
PMCID: PMC3169707  PMID: 21822286
miR-200; metastasis; Sec23a; secretome; epithelial-mesenchymal transition
21.  Polycomb Associates Genome-wide with a Specific RNA Polymerase II Variant, and Regulates Metabolic Genes in ESCs 
Cell Stem Cell  2012;10(2):157-170.
Polycomb repressor complexes (PRCs) are important chromatin modifiers fundamentally implicated in pluripotency and cancer. Polycomb silencing in embryonic stem cells (ESCs) can be accompanied by active chromatin and primed RNA polymerase II (RNAPII), but the relationship between PRCs and RNAPII remains unclear genome-wide. We mapped PRC repression markers and four RNAPII states in ESCs using ChIP-seq, and found that PRC targets exhibit a range of RNAPII variants. First, developmental PRC targets are bound by unproductive RNAPII (S5p+S7p−S2p−) genome-wide. Sequential ChIP, Ring1B depletion, and genome-wide correlations show that PRCs and RNAPII-S5p physically bind to the same chromatin and functionally synergize. Second, we identify a cohort of genes marked by PRC and elongating RNAPII (S5p+S7p+S2p+); they produce mRNA and protein, and their expression increases upon PRC1 knockdown. We show that this group of PRC targets switches between active and PRC-repressed states within the ESC population, and that many have roles in metabolism.
Graphical Abstract
► A unique RNAPII variant (S5p+S7p−S2p−) binds PRC targets genome-wide in ESCs ► RNAPII-S5p and PRC coincide in time and localization, and show proportional abundance ► Novel, active PRC-target genes identified in ESCs include metabolic genes ► Active PRC targets switch between on/off (active/PRC) states in the ESC population
PMCID: PMC3682187  PMID: 22305566
22.  A novel approach of homozygous haplotype sharing identifies candidate genes in autism spectrum disorder 
Casey, Jillian P. | Magalhaes, Tiago | Conroy, Judith M. | Regan, Regina | Shah, Naisha | Anney, Richard | Shields, Denis C. | Abrahams, Brett S. | Almeida, Joana | Bacchelli, Elena | Bailey, Anthony J. | Baird, Gillian | Battaglia, Agatino | Berney, Tom | Bolshakova, Nadia | Bolton, Patrick F. | Bourgeron, Thomas | Brennan, Sean | Cali, Phil | Correia, Catarina | Corsello, Christina | Coutanche, Marc | Dawson, Geraldine | de Jonge, Maretha | Delorme, Richard | Duketis, Eftichia | Duque, Frederico | Estes, Annette | Farrar, Penny | Fernandez, Bridget A. | Folstein, Susan E. | Foley, Suzanne | Fombonne, Eric | Freitag, Christine M. | Gilbert, John | Gillberg, Christopher | Glessner, Joseph T. | Green, Jonathan | Guter, Stephen J. | Hakonarson, Hakon | Holt, Richard | Hughes, Gillian | Hus, Vanessa | Igliozzi, Roberta | Kim, Cecilia | Klauck, Sabine M. | Kolevzon, Alexander | Lamb, Janine A. | Leboyer, Marion | Le Couteur, Ann | Leventhal, Bennett L. | Lord, Catherine | Lund, Sabata C. | Maestrini, Elena | Mantoulan, Carine | Marshall, Christian R. | McConachie, Helen | McDougle, Christopher J. | McGrath, Jane | McMahon, William M. | Merikangas, Alison | Miller, Judith | Minopoli, Fiorella | Mirza, Ghazala K. | Munson, Jeff | Nelson, Stanley F. | Nygren, Gudrun | Oliveira, Guiomar | Pagnamenta, Alistair T. | Papanikolaou, Katerina | Parr, Jeremy R. | Parrini, Barbara | Pickles, Andrew | Pinto, Dalila | Piven, Joseph | Posey, David J. | Poustka, Annemarie | Poustka, Fritz | Ragoussis, Jiannis | Roge, Bernadette | Rutter, Michael L. | Sequeira, Ana F. | Soorya, Latha | Sousa, Inês | Sykes, Nuala | Stoppioni, Vera | Tancredi, Raffaella | Tauber, Maïté | Thompson, Ann P. | Thomson, Susanne | Tsiantis, John | Van Engeland, Herman | Vincent, John B. | Volkmar, Fred | Vorstman, Jacob A. S. | Wallace, Simon | Wang, Kai | Wassink, Thomas H. | White, Kathy | Wing, Kirsty | Wittemeyer, Kerstin | Yaspan, Brian L. | Zwaigenbaum, Lonnie | Betancur, Catalina | Buxbaum, Joseph D. | Cantor, Rita M. | Cook, Edwin H. | Coon, Hilary | Cuccaro, Michael L. | Geschwind, Daniel H. | Haines, Jonathan L. | Hallmayer, Joachim | Monaco, Anthony P. | Nurnberger, John I. | Pericak-Vance, Margaret A. | Schellenberg, Gerard D. | Scherer, Stephen W. | Sutcliffe, James S. | Szatmari, Peter | Vieland, Veronica J. | Wijsman, Ellen M. | Green, Andrew | Gill, Michael | Gallagher, Louise | Vicente, Astrid | Ennis, Sean
Human Genetics  2011;131(4):565-579.
Autism spectrum disorder (ASD) is a highly heritable disorder of complex and heterogeneous aetiology. It is primarily characterized by altered cognitive ability including impaired language and communication skills and fundamental deficits in social reciprocity. Despite some notable successes in neuropsychiatric genetics, overall, the high heritability of ASD (~90%) remains poorly explained by common genetic risk variants. However, recent studies suggest that rare genomic variation, in particular copy number variation, may account for a significant proportion of the genetic basis of ASD. We present a large scale analysis to identify candidate genes which may contain low-frequency recessive variation contributing to ASD while taking into account the potential contribution of population differences to the genetic heterogeneity of ASD. Our strategy, homozygous haplotype (HH) mapping, aims to detect homozygous segments of identical haplotype structure that are shared at a higher frequency amongst ASD patients compared to parental controls. The analysis was performed on 1,402 Autism Genome Project trios genotyped for 1 million single nucleotide polymorphisms (SNPs). We identified 25 known and 1,218 novel ASD candidate genes in the discovery analysis including CADM2, ABHD14A, CHRFAM7A, GRIK2, GRM3, EPHA3, FGF10, KCND2, PDZK1, IMMP2L and FOXP2. Furthermore, 10 of the previously reported ASD genes and 300 of the novel candidates identified in the discovery analysis were replicated in an independent sample of 1,182 trios. Our results demonstrate that regions of HH are significantly enriched for previously reported ASD candidate genes and the observed association is independent of gene size (odds ratio 2.10). Our findings highlight the applicability of HH mapping in complex disorders such as ASD and offer an alternative approach to the analysis of genome-wide association data.
Electronic supplementary material
The online version of this article (doi:10.1007/s00439-011-1094-6) contains supplementary material, which is available to authorized users.
PMCID: PMC3303079  PMID: 21996756
23.  Regenerant Arabidopsis Lineages Display a Distinct Genome-Wide Spectrum of Mutations Conferring Variant Phenotypes 
Current Biology  2011;21(16):1385-1390.
Multicellular organisms can be regenerated from totipotent differentiated somatic cell or nuclear founders [1–3]. Organisms regenerated from clonally related isogenic founders might a priori have been expected to be phenotypically invariant. However, clonal regenerant animals display variant phenotypes caused by defective epigenetic reprogramming of gene expression [2], and clonal regenerant plants exhibit poorly understood heritable phenotypic (“somaclonal”) variation [4–7]. Here we show that somaclonal variation in regenerant Arabidopsis lineages is associated with genome-wide elevation in DNA sequence mutation rate. We also show that regenerant mutations comprise a distinctive molecular spectrum of base substitutions, insertions, and deletions that probably results from decreased DNA repair fidelity. Finally, we show that while regenerant base substitutions are a likely major genetic cause of the somaclonal variation of regenerant Arabidopsis lineages, transposon movement is unlikely to contribute substantially to that variation. We conclude that the phenotypic variation of regenerant plants, unlike that of regenerant animals, is substantially due to DNA sequence mutation.
► Regenerant Arabidopsis lineages display heritable phenotypic variation ► Regenerant Arabidopsis lineages display elevated genome-wide DNA sequence mutation ► Regenerant DNA sequence mutations comprise a distinct molecular spectrum ► Regenerant base substitution mutations confer heritable phenotypic variation
PMCID: PMC3162137  PMID: 21802297
24.  Extensive characterization of NF-κB binding uncovers non-canonical motifs and advances the interpretation of genetic functional traits 
Genome Biology  2011;12(7):R70.
Genetic studies have provided ample evidence of the influence of non-coding DNA polymorphisms on trait variance, particularly those occurring within transcription factor binding sites. Protein binding microarrays and other platforms that can map these sites with great precision have enhanced our understanding of how a single nucleotide polymorphism can alter binding potential within an in vitro setting, allowing for greater predictive capability of its effect on a transcription factor binding site.
We have used protein binding microarrays and electrophoretic mobility shift assay-sequencing (EMSA-Seq), a deep sequencing based method we developed to analyze nine distinct human NF-κB dimers. This family of transcription factors is one of the most extensively studied, but our understanding of its DNA binding preferences has been limited to the originally described consensus motif, GGRRNNYYCC. We highlight differences between NF-κB family members and also put under the spotlight non-canonical motifs that have so far received little attention. We utilize our data to interpret the binding of transcription factors between individuals across 1,405 genomic regions laden with single nucleotide polymorphisms. We also associated binding correlations made using our data with risk alleles of disease and demonstrate its utility as a tool for functional studies of single nucleotide polymorphisms in regulatory regions.
NF-κB dimers bind specifically to non-canonical motifs and these can be found within genomic regions in which a canonical motif is not evident. Binding affinity data generated with these different motifs can be used in conjunction with data from chromatin immunoprecipitation-sequencing (ChIP-Seq) to enable allele-specific analyses of expression and transcription factor-DNA interactions on a genome-wide scale.
PMCID: PMC3218832  PMID: 21801342
25.  The Use of Genome-Wide eQTL Associations in Lymphoblastoid Cell Lines to Identify Novel Genetic Pathways Involved in Complex Traits 
PLoS ONE  2011;6(7):e22070.
The integrated analysis of genotypic and expression data for association with complex traits could identify novel genetic pathways involved in complex traits. We profiled 19,573 expression probes in Epstein-Barr virus-transformed lymphoblastoid cell lines (LCLs) from 299 twins and correlated these with 44 quantitative traits (QTs). For 939 expressed probes correlating with more than one QT, we investigated the presence of eQTL associations in three datasets of 57 CEU HapMap founders and 86 unrelated twins. Genome-wide association analysis of these probes with 2.2 m SNPs revealed 131 potential eQTLs (1,989 eQTL SNPs) overlapping between the HapMap datasets, five of which were in cis (58 eQTL SNPs). We then tested 535 SNPs tagging the eQTL SNPs, for association with the relevant QT in 2,905 twins. We identified nine potential SNP-QT associations (P<0.01) but none significantly replicated in five large consortia of 1,097–16,129 subjects. We also failed to replicate previous reported eQTL associations with body mass index, plasma low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides levels derived from lymphocytes, adipose and liver tissue. Our results and additional power calculations suggest that proponents may have been overoptimistic in the power of LCLs in eQTL approaches to elucidate regulatory genetic effects on complex traits using the small datasets generated to date. Nevertheless, larger tissue-specific expression data sets relevant to specific traits are becoming available, and should enable the adoption of similar integrated analyses in the near future.
PMCID: PMC3137612  PMID: 21789213

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