Recurrent Copy Number Variations Research Articles

Contrasting mechanisms of de novo copy number mutagenesis suggest the existence of different classes of environmental copy number mutagens.

While gene copy number variations (CNVs) are abundant in the human genome, and often are associated with disease consequences, the mutagenic pathways and environmental exposures that cause these large structural mutations are understudied relative to conventional nucleotide substitutions in DNA. The members of the environmental mutagenesis community are currently seeking to remedy this deficiency, and there is a renewed interest in the development of mutagenicity assays to identify and characterize compounds that may induce de novo CNVs in humans. To achieve this goal, it is critically important to acknowledge that CNVs exist in two very distinct classes: nonrecurrent and recurrent CNVs. The goal of this commentary is to emphasize the deep contrasts that exist between the proposed pathways that lead to these two mutation classes. Nonrecurrent de novo CNVs originate primarily in mitotic cells through replication-dependent DNA repair pathways that involve microhomologies (<10 bp), and are detected at higher frequency in children of older fathers. In contrast, recurrent de novo CNVs are most often formed in meiotic cells through homologous recombination between nonallelic large low-copy repeats (>10,000 bp), without an associated paternal age effect. Given the biological differences between the two CNV classes, it is our belief that nonrecurrent and recurrent CN mutagens will probably differ substantially in their modes of action. Therefore, each CNV class may require their own uniquely designed assays, so that we as a field may succeed in uncovering the broadest possible spectrum of environmental CN mutagens.

Recurrent deletions and duplications of chromosome 2q11.2 and 2q13 are associated with variable outcomes.

Copy number variation (CNV) in the long arm of chromosome 2 has been implicated in developmental delay (DD), intellectual disability (ID), autism spectrum disorder (ASD), congenital anomalies, and psychiatric disorders. Here we describe 14 new subjects with recurrent deletions and duplications of chromosome 2q11.2, 2q13, and 2q11.2-2q13. Though diverse phenotypes are associated with these CNVs, some common features have emerged. Subjects with 2q11.2 deletions often exhibit DD, speech delay, and attention deficit hyperactivity disorder (ADHD), whereas those with 2q11.2 duplications have DD, gastroesophageal reflux, and short stature. Congenital heart defects (CHDs), hypotonia, dysmorphic features, and abnormal head size are common in those with 2q13 deletions. In the 2q13 duplication cohort, we report dysmorphic features, DD, and abnormal head size. Two individuals with large duplications spanning 2q11.2-2q13 have dysmorphic features, hypotonia, and DD. This compilation of clinical features associated with 2q CNVs provides information that will be useful for healthcare providers and for families of affected children. However, the reduced penetrance and variable expressivity associated with these recurrent CNVs makes genetic counseling and prediction of outcomes challenging. © 2015 Wiley Periodicals, Inc.

A Screen for Genomic Disorders of Infertility Identifies MAST2 Duplications Associated with Nonobstructive Azoospermia in Humans.

Since the cytogenetic identification of azoospermia factor regions 40 years ago, the Y chromosome has dominated research on the genetics of male infertility. We hypothesized that hotspots of structural rearrangement, which are dispersed across the genome, may mediate rare, recurrent copy number variations (CNVs), leading to severe infertility. We tested this hypothesis by contrasting patterns of rare CNVs in 970 Han Chinese men with idiopathic nonobstructive azoospermia and 1661 ethnicity-matched controls. Our results strongly support our previous claim that sperm production is modulated by genetic variation across the entire genome. The X chromosome in particular was enriched for loci modulating spermatogenesis--rare X-linked deletions larger than 100 kb were twice as common in patients compared with controls (odds ratio [OR] = 2.05, P = 0.01). At rearrangement hotspots across the genome, we observed a 2.4-fold enrichment of singleton CNVs in patients (P < 0.02), and we identified 117 testis genes, such as SYCE1, contained within 47 hotspots that may plausibly mediate genomic disorders of fertility. In our discovery sample we observed 3 case-specific duplications of the autosomal gene MAST2, and in a replication phase we found another 11 duplications in 1457 patients and 1 duplication in 1590 controls (P < 5 × 10(-5), combined data). With a large, polygenic genetic basis, new ways of establishing the pathogenicity of rare, large-effect mutations will be needed to fully reap the benefit of genome data in the management of azoospermia.

A recurrent copy number variation of the NEB triplicate region: only revealed by the targeted nemaline myopathy CGH array.

Recently, new large variants have been identified in the nebulin gene (NEB) causing nemaline myopathy (NM). NM constitutes a heterogeneous group of disorders among the congenital myopathies, and disease-causing variants in NEB are a main cause of the recessively inherited form of NM. NEB consists of 183 exons and it includes homologous sequences such as a 32-kb triplicate region (TRI), where eight exons are repeated three times (exons 82-89, 90-97, 98-105). In human, the normal copy number of NEB TRI is six (three copies in each allele). Recently, we described a custom NM-CGH microarray designed to detect copy number variations (CNVs) in the known NM genes. The array has now been updated to include all the currently known 10 NM genes. The NM-CGH array is superior in detecting CNVs, especially of the NEB TRI, that is not included in the exome capture kits. To date, we have studied 266 samples from 196 NM families using the NM-CGH microarray, and identified a novel recurrent NEB TRI variation in 13% (26/196) of the families and in 10% of the controls (6/60). An analysis of the breakpoints revealed adjacent repeat elements, which are known to predispose for rearrangements such as CNVs. The control CNV samples deviate only one copy from the normal six copies, whereas the NM samples include CNVs of up to four additional copies. Based on this study, NEB seems to tolerate deviations of one TRI copy, whereas addition of two or more copies might be pathogenic.

Comparative mapping of the 22q11.2 deletion region and the potential of simple model organisms.

Background22q11.2 deletion syndrome (22q11.2DS) is the most common micro-deletion syndrome. The associated 22q11.2 deletion conveys the strongest known molecular risk for schizophrenia. Neurodevelopmental phenotypes, including intellectual disability, are also prominent though variable in severity. Other developmental features include congenital cardiac and craniofacial anomalies. Whereas existing mouse models have been helpful in determining the role of some genes overlapped by the hemizygous 22q11.2 deletion in phenotypic expression, much remains unknown. Simple model organisms remain largely unexploited in exploring these genotype-phenotype relationships.MethodsWe first developed a comprehensive map of the human 22q11.2 deletion region, delineating gene content, and brain expression. To identify putative orthologs, standard methods were used to interrogate the proteomes of the zebrafish (D. rerio), fruit fly (D. melanogaster), and worm (C. elegans), in addition to the mouse. Spatial locations of conserved homologues were mapped to examine syntenic relationships. We systematically cataloged available knockout and knockdown models of all conserved genes across these organisms, including a comprehensive review of associated phenotypes.ResultsThere are 90 genes overlapped by the typical 2.5 Mb deletion 22q11.2 region. Of the 46 protein-coding genes, 41 (89.1 %) have documented expression in the human brain. Identified homologues in the zebrafish (n = 37, 80.4 %) were comparable to those in the mouse (n = 40, 86.9 %) and included some conserved gene cluster structures. There were 22 (47.8 %) putative homologues in the fruit fly and 17 (37.0 %) in the worm involving multiple chromosomes. Individual gene knockdown mutants were available for the simple model organisms, but not for mouse. Although phenotypic data were relatively limited for knockout and knockdown models of the 17 genes conserved across all species, there was some evidence for roles in neurodevelopmental phenotypes, including four of the six mitochondrial genes in the 22q11.2 deletion region.ConclusionsSimple model organisms represent a powerful but underutilized means of investigating the molecular mechanisms underlying the elevated risk for neurodevelopmental disorders in 22q11.2DS. This comparative multi-species study provides novel resources and support for the potential utility of non-mouse models in expression studies and high-throughput drug screening. The approach has implications for other recurrent copy number variations associated with neurodevelopmental phenotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s11689-015-9113-x) contains supplementary material, which is available to authorized users.

Clinical phenotype of the recurrent 1q21.1 copy-number variant.

To characterize the clinical phenotype of the recurrent copy-number variation (CNV) at 1q21.1, we assessed the psychiatric and medical phenotypes of 1q21.1 deletion and duplication carriers ascertained through clinical genetic testing and family member cascade testing, with particular emphasis on dimensional assessment across multiple functional domains. Nineteen individuals with 1q21.1 deletion, 19 individuals with the duplication, and 23 familial controls (noncarrier siblings and parents) spanning early childhood through adulthood were evaluated for psychiatric, neurologic, and other medical diagnoses, and their cognitive, adaptive, language, motor, and neurologic domains were also assessed. Twenty-eight individuals with 1q21.1 CNVs (15 deletion, 13 duplication) underwent structural magnetic resonance brain imaging. Probands with 1q21.1 CNVs presented with a range of psychiatric, neurologic, and medical disorders. Deletion and duplication carriers shared several features, including borderline cognitive functioning, impaired fine and gross motor functioning, articulation abnormalities, and hypotonia. Increased frequency of Autism Spectrum Disorder (ASD) diagnosis, increased ASD symptom severity, and increased prevalence of macrocephaly were observed in the duplication relative to deletion carriers, whereas reciprocally increased prevalence of microcephaly was observed in the deletion carriers. Individuals with 1q21.1 deletions or duplications exhibit consistent deficits on motor and cognitive functioning and abnormalities in head circumference.Genet Med 18 4, 341-349.

Genetic Evaluation of Copy Number Variations, Loss of Heterozygosity, and Single-Nucleotide Variant Levels in Human Embryonic Stem Cells With or Without Skewed X Chromosome Inactivation.

Human embryonic stem cells (hESCs) exhibiting skewed X chromosome inactivation (XCI) have been reported. The copy number variations (CNVs), loss of heterozygosity (LOH), or single-nucleotide variant (SNV) events in those epigenetically distinct cells remain unknown, and whether such genetic abnormalities will influence the XCI status of hESCs is unclear. In this study, three hESCs with skewed XCI, three with random XCI, and two male hESC lines at different passages were analyzed for CNVs and LOH levels using a high-resolution genotyping microarray. Whole-exome sequencing was used to investigate the potentially damaging SNVs. On average, 17.6 CNVs and 5.3 cases of LOH were identified in the skewed hESCs, which were similar to the rates observed in random hESCs. Five recurrent CNV regions were uniquely identified in the skewed hESCs, but all of them were considered polymorphisms. With the exception of a nongenic CNV, no additional CNVs were detected on the X chromosome in the skewed hESCs. Although the XCI status in two hESC lines was observed to be changed from random to skewed, no significant CNV difference was identified before and after the XCI change. SNV analysis indicated that normal alleles are maintained for most genes within copy-neutral LOH regions. Three types of expression patterns were observed in heterozygous alleles, and the damaging SNVs in skewed hESCs favored the expression of the wild-type alleles. In conclusion, in the present study, we did not find genetic differences in the CNV and LOH levels between hESCs with and without skewed XCI. Wild-type allele expression in the presence of damaging SNVs on the X chromosome in skewed hESCs might alleviate adverse effects in those hESCs.

Deletion of 15q11.2(BP1-BP2) region: further evidence for lack of phenotypic specificity in a pediatric population.

Microdeletion of the BP1-BP2 region at 15q11.2 is a recurrent copy number variant (CNV) frequently found in patients undergoing chromosomal microarray (CMA). Genetic counselling regarding this CNV is challenging due to the wide range of phenotypic presentation in reported patients and lack of general population-based data. As one of the most common reasons for CMA is childhood developmental delay, clinicians need to be cognizant of the inherent ascertainment bias in the literature. We performed a detailed medical record review for 55 patients with this 15q11.2 microdeletion and report the clinical features of the 35 patients for whom information was available. We compared our results to the recent report by Cafferkey et al. in this journal. Our conclusion is that the phenotypic spectrum is too broad and non-specific to constitute a bona fide "syndrome" and that further research must be done to delineate the contribution of this CNV to phenotype.

Whole genome sequencing of elite rice cultivars as a comprehensive information resource for marker assisted selection.

Current advances in sequencing technologies and bioinformatics revealed the genomic background of rice, a staple food for the poor people, and provided the basis to develop large genomic variation databases for thousands of cultivars. Proper analysis of this massive resource is expected to give novel insights into the structure, function, and evolution of the rice genome, and to aid the development of rice varieties through marker assisted selection or genomic selection. In this work we present sequencing and bioinformatics analyses of 104 rice varieties belonging to the major subspecies of Oryza sativa. We identified repetitive elements and recurrent copy number variation covering about 200 Mbp of the rice genome. Genotyping of over 18 million polymorphic locations within O. sativa allowed us to reconstruct the individual haplotype patterns shaping the genomic background of elite varieties used by farmers throughout the Americas. Based on a reconstruction of the alleles for the gene GBSSI, we could identify novel genetic markers for selection of varieties with high amylose content. We expect that both the analysis methods and the genomic information described here would be of great use for the rice research community and for other groups carrying on similar sequencing efforts in other crops.

An efficient screening method for simultaneous detection of recurrent copy number variants associated with psychiatric disorders

Several recurrent copy number variants (CNVs) increasing risk to neuropsychiatric diseases have been identified in recent years. They show variable clinical expressivity, being associated with different disorders, and incomplete penetrance. However, due to its very low frequency, the full variety of clinical outcomes associated with each one of these CNVs is unknown. Current methods for detection of CNVs are labor intensive, expensive or not suitable for high throughput analysis. Quantitative interspecies competitive PCR linked to variant minisequencing and detection by mass-spectrometry may overcome these limitations. Here, we present two multiplex assays based on this method to screen for eleven psychiatric risk CNVs, such as 1q21, 16p11.2, 3q29, or 16p13.11 regions, among others. The assays were tested in our collection of 514 schizophrenia patients. Results were compared with MLPA at two CNVs. Additional positive results were confirmed by exome sequencing. A total of fourteen patients were CNV carriers. The method presents high sensitivity and specificity, showing its utility as a cheap, accurate, high throughput screening tool for recurrent CNVs. The method may be very useful for management of psychiatric patients as well as screening of different collections of samples to better identify the full spectrum of clinical variability.

A Bayesian Analysis of Copy Number Variations in Array Comparative Genomic Hybridization Data

Array Comparative Genomic Hybridization (CGH) has been widely used for detecting genomic copy number variations (CNVs). The central goal of array CGH data analysis is to accurately detect homogeneous regions of log intensity ratios which represent relative changes in DNA copy number. Various methods have been proposed in recent years. Most methods, however, do not consider correlations of neighboring probe measurements, and are usually designed for analysis at single sample level rather than detecting common or recurrent CNVs among multiple samples. We propose a Bayesian segment-based approach for efficient analysis of array CGH data. The proposed method is based on simple assumptions but is general enough to accommodate various spatial correlations among probe measurements. It also allows for multiple samples with recurrent CNVs, therefore is able to borrow strength across samples. In contrast to another probe-based approach developed in the same Bayesian framework, the segment-based approach parameterizes the mean log intensity ratios in a more appropriate way, which leads to a posterior sampling scheme based on reversible-jump Markov chain Monte Carlo. We perform a simulation study to compare these two approaches and the commonly-used circular binary segmentation method and Bayesian hidden Markov model method. The segment-based approach achieves better estimation accuracy and higher computational efficiency compared to the probe-based approach, and also provides improved results compared to the other two methods, especially for data with relatively low signal to noise ratio and high correlation. The segment-based approach is further applied to the Corriel cell lines data and Pancreatic Adenocarcinoma data.

Recurrent benign copy number variants & issues in interpretation of variants of unknown significance identified by cytogenetic microarray in Indian patients with intellectual disability.

Background & objectives:Cytogenetic microarray (CMA) is now recommended as a first-tier clinical diagnostic test in cases with idiopathic intellectual disability and/or developmental delay (ID/DD). Along with clinically relevant variants, CMA platforms also identify variants of unknown significance (VUS). This study was done to look for utility and various issues in interpretation of copy number variants (CNVs) in Indian patients with ID/DD.Methods:The CMA was performed in 86 Indian patients with idiopathic ID/DD with or without dysmorphic features. CNV was reported if copy number gain was >400 kb in size and copy number loss was > 200 kb in size.Results:Pathogenic CNVs were found in 18 of 86 (20.9%) patients. One large (14 Mb size) de novo heterozygous copy number gain was found in one patient. VUS (total 31) were present in 17 of 86 (19.7%) patients. Five novel recurrent benign CNVs were also present in our patients.Interpretation & conclusions:Our findings highlight the difficulties in interpretation of CNVs identified by CMA. More Indian data on VUS and recurrent benign CNVs will be helpful in the interpretation of CMA in patients with ID/DD.

Copy number variation in schizophrenia.

Copy number variation contributes substantially to human evolution, normal phenotypic variation, and human disease (Malhotra and Sebat, 2012). To date, thousands of different genomic duplications and deletions, each spanning hundreds to millions of basepairs, have been mapped genome-wide, and collectively account for a significant fraction of human genetic variation. By reorganizing broad swaths of DNA, structural mutations potentially create new genes and regulatory motifs while also disrupting established genes. Copy number variants (CNVs) tend to occur in regions rich in genes, segmental duplications, and mobile elements(Malhotra and Sebat, 2012). Some arise repeatedly as de novo mutations in genomic ‘hotspots.' The genomic architecture of hotspots is typically characterized by large repeated segments that increase the risk for errors in replication, a process known as nonallelic homologous recombination. If a CNV is pathogenic, it may persist for only a few generations given negative selection. At the same time, in each generation many de novo CNVs are introduced given the highly repetitive nature of the human genome. The importance of rare copy number mutations for neuropsychiatric disease is now well-established (Malhotra and Sebat, 2012). Our group was the first to demonstrate that individuals with schizophrenia are significantly more likely than unaffected persons to harbor rare gene-impacting CNVs, with greater effect for patients with illness onset before age 18 years. Genes disrupted by CNVs in patients function disproportionately in signaling and neurodevelopmental processes, including neuregulin and glutamate pathways (Walsh et al, 2008). Subsequent research replicated and extended these findings. Most rare copy number mutations implicated in schizophrenia are unique, and many arose de novo or in recent generations. Others recur at genomic hotspots, including chromosomes 1q21.1, 3q29, 15q11.2, 15q13.3, 16p11.2, 16p12.1, 16p13.11, 17p12, 22q11.2, and the neuropeptide receptor VIPR2 (Malhotra and Sebat, 2012) (Figure 1). Figure 1 CNVs in schizophrenia. The figure depicts the cytogenetic locations of known genomic hotspots (Malhotra and Sebat, 2012) (red), case-specific CNVs (Walsh et al, 2008) (blue), and case-specific CNVs that created chimeric genes (Rippey et al, 2013) (green). ... One novel mechanism by which CNVs may cause schizophrenia is the creation of chimeric genes (Rippey et al, 2013). We recently found that persons with schizophrenia were more likely than controls to carry genomic duplications or deletions that resulted in a fusion gene. Each of the chimeric genes in patients differed from their parent genes in ways likely to be important to brain function, including differences in neuronal subcellular localization, levels of expression, and/or protein interactions. For example, one patient harbored a 150-kb deletion that resulted in a MAP3K3–DDX42 fusion gene. The MAP3K3–DDX42 chimera produced a novel protein isoform that binds activated MEK5 and likely acts as a dominant-negative inhibitor of ERK5 signaling, a key pathway regulating neuronal differentiation and adult neurogenesis. By interfering with parent gene function, chimeras potentially disrupt critical brain processes important to schizophrenia. Rare deletions and duplications, including in the same recurrent hotspot CNVs associated with schizophrenia, are also enriched in other neuropsychiatric conditions, including autism, intellectual disability, and idiopathic generalized epilepsy (Malhotra and Sebat, 2012). Many clinical laboratories now have assays that can detect hundreds of potentially pathogenic CNVs. Each disorder is associated with many different structural mutations. Each pathogenic CNV is associated with different phenotypes in different persons, including cognitive deficits in individuals characterized as ‘unaffected' (Stefansson et al, 2014). Variable phenotypic expression of pathogenic events is likely mediated by a variety of different factors, including dose effects, epistasis, epigenetic mechanisms, and environmental exposures (McClellan and King, 2010). Genes and loci disrupted by pathogenic CNVs provide a window to study key neurobiological mechanisms important to brain development and pathophysiology. For example, rare de novo CNVs in persons with schizophrenia were found to be enriched for genes that function within N-methyl-D-aspartate receptor postsynaptic signaling complexes (Kirov et al, 2012). Given the extreme genetic heterogeneity, such research is critical towards delineating specific genomically defined neurobiological subtypes within large clinically heterogeneous diagnostic groups, and ultimately towards developing biologically informed targeted treatments.

Integrated Genome Sequencing Reveals Frequent Loss of Function Alterations of ARID1A and Other Epigenetic Modifiers in Sezary Syndrome

IntroductionSezary Syndrome (SS) is an aggressive mature T-cell neoplasm characterized by erythroderma, generalized lymphadenopathy and circulating T-cells. SS cells are characterized by complex karyotypes with numerous structural alterations and copy-number variants. Previous studies have implicated disruption and/or haploinsufficiency of TP53, CDKN2A, RB1 and PTEN in SS. Nevertheless, the comprehensive genetic alterations underlying the pathogenesis of SS are unknown. In this study, we used an integrated genomic sequencing approach to characterize the genetic basis of SS.MethodsSS cases that fulfilled established diagnostic criteria including characteristic cytologic, immunophenotypic and karyotypic features were analyzed. We performed genomic analysis on 84 primary SS cases using whole genome sequencing (WGS; n = 6), high-resolution array comparative genome hybridization (aCGH using NimbleGen 270K Feature Array; n = 80) and whole exome sequencing (WES) using Illumina TruSeq Exome Capture (n = 66). We filtered this combined dataset to identify 463 genes within regions of recurrent copy-number variations that were also impacted by protein coding mutations. We focused on 16 of these genes and confirmed 75 mutations in these genes by Sanger sequencing. For 35 of these mutations, normal tissue was available to confirm somatic acquisition.ResultsWGS revealed a complex structural genome with numerous regions of chromothrypsis and aneuploidy with over 1,000 inter- and intra-chromosomal translocations in the 6 SS genomes but did not reveal recurrent structural alterations. Array CGH identified many aneuploidies reported previously including 8+, 10-, 17p-/iso17 and 19q-. These results were corroborated by aCGH analysis which also revealed recurrent genomic losses at 9p21.3 (CDKN2A), 10p11.22 (PTEN) and 13q14.2 (RB1). Importantly, exome sequencing further identified several novel somatic, deleterious mutations in these three genes. Strikingly, in addition to confirming loss of function alterations of genes previously implicated in SS pathogenesis, we identified genetic alterations in genes involved in epigenetic modification including chromatin/histone modification (including ARID1A, ARID5B, MLL, MLL2, MLL4, SETD1A, SETD1B, SETD6) and DNA methylation (including NCOR1, TET1, TET2, DNMT3A, DNMT3B) not previously implicated in SS pathogenesis.Among the most frequent and most restricted regions of recurrent deletion was the 1p36.11 region. Of the 18 genes within this region, ARID1A showed the highest frequency of disruption (27/80 showing deletion; 7/66 showing novel mutations including a frameshift mutation at residue 1449 within the GR binding domain of ARID1A). Of the SS genomes for which both WES and aCGH analysis were performed, 25/62 (40.3%) showed disruption of ARID1A either by deletion or mutation or both. Moreover ARID5B was also targeted by deletions of region 10q21.2 in 23/80 genomes and 3/66 SS genomes showed mutations. We also identified a narrow region of recurrent aneuploidy affecting the SWI/SNF family-member of SMARC genes known to interact with ARID-family SMARCC1at 3p21.31. This gene was recurrently targeted by a deletion in 17/80 (21.3%) SS genomes by highly restricted deletional events (<4Mb).Altogether, deletions and/or mutations in ARID1A, ARID5B or SMARCC1 were identified in 38 of 62 (61.3%) of SS genomes. Further analysis revealed that other members of the ARID- and SMARC-families, ARID1B, ARID2 and ARID4A, were mutated. Moreover, ARID3A and SMARCA4 (both located on 19p) were targeted by recurrent deletions in 29/80 and 18/80 SS genomes, respectively. Altogether, deletions and/or mutations in at least one of the ARID- or SMARC-family genes were identified in 91.9% of SS.ConclusionThis study is the first to comprehensively profile the genomic landscape in SS. Integration of high-resolution aCGH with mutational analysis reveals alterations in epigenetic regulators through loss-of-function lesions in ARID- and SMARC-family genes in over 90% of SS. The results of our study offer further insights into the pathogenesis of SS and provide support for use of drugs targeting deregulated chromatin remodeling pathways in the treatment of SS patients. DisclosuresNo relevant conflicts of interest to declare.

Copy number variation analysis based on AluScan sequences.

BackgroundAluScan combines inter-Alu PCR using multiple Alu-based primers with opposite orientations and next-generation sequencing to capture a huge number of Alu-proximal genomic sequences for investigation. Its requirement of only sub-microgram quantities of DNA facilitates the examination of large numbers of samples. However, the special features of AluScan data rendered difficult the calling of copy number variation (CNV) directly using the calling algorithms designed for whole genome sequencing (WGS) or exome sequencing.ResultsIn this study, an AluScanCNV package has been assembled for efficient CNV calling from AluScan sequencing data employing a Geary-Hinkley transformation (GHT) of read-depth ratios between either paired test-control samples, or between test samples and a reference template constructed from reference samples, to call the localized CNVs, followed by use of a GISTIC-like algorithm to identify recurrent CNVs and circular binary segmentation (CBS) to reveal large extended CNVs. To evaluate the utility of CNVs called from AluScan data, the AluScans from 23 non-cancer and 38 cancer genomes were analyzed in this study. The glioma samples analyzed yielded the familiar extended copy-number losses on chromosomes 1p and 9. Also, the recurrent somatic CNVs identified from liver cancer samples were similar to those reported for liver cancer WGS with respect to a striking enrichment of copy-number gains in chromosomes 1q and 8q. When localized or recurrent CNV-features capable of distinguishing between liver and non-liver cancer samples were selected by correlation-based machine learning, a highly accurate separation of the liver and non-liver cancer classes was attained.ConclusionsThe results obtained from non-cancer and cancerous tissues indicated that the AluScanCNV package can be employed to call localized, recurrent and extended CNVs from AluScan sequences. Moreover, both the localized and recurrent CNVs identified by this method could be subjected to machine-learning selection to yield distinguishing CNV-features that were capable of separating between liver cancers and other types of cancers. Since the method is applicable to any human DNA sample with or without the availability of a paired control, it can also be employed to analyze the constitutional CNVs of individuals.Electronic supplementary materialThe online version of this article (doi:10.1186/s13336-014-0015-z) contains supplementary material, which is available to authorized users.

Copy number variations and human genetic disease.

Recent studies clearly demonstrate that copy number variations (CNVs) are widespread in our genome and play an important role in human genetic variation, accounting for both human population diversity and human genetic disease. This review will discuss the most current knowledge regarding our understanding of the biology of CNVs in relation to human genetic disease. CNVs associated with human genetic disease can be either recurrent, with a common size and breakpoint clustering, or nonrecurrent, with different sizes and variable breakpoints. Two types of recurrent CNVs have been distinguished, including the syndromic forms in which the phenotypic features are relatively consistent, and those in which the same recurrent CNV can be associated with a diverse set of diagnoses. Recently, the 'Two-hit model' was used to explain the phenotypic variability associated with the latter group of recurrent CNVs. Nonrecurrent CNVs, on the contrary, occur at a relatively lower frequency at the individual locus level but collectively they are as common as recurrent CNVs. Finally, the study of CNV burden in different diseases demonstrated a clear trend of an increasing CNV burden in diseases with more severe phenotypes. In spite of the advances in the study of the CNV landscape associated with human genetic disease, there still remain many unexplored questions especially regarding the role of CNVs in the pathogenesis of complex human genetic diseases.

Abstract 16160: Common Autosomal Variants are Associated With Bicuspid Aortic Valve in Turner Syndrome

Introduction: The prevalence of bicuspid aortic valves (BAV) is enriched thirty-fold in women with Turner Syndrome (TS) in comparison with the general population. Hypothesis: Common autosomal variants influence the development of BAV in TS women, who may be uniquely sensitized to these variants by the loss of one X chromosome. We sought to identify autosomal BAV susceptibility genes in a cohort of TS women (average age 30 years, 38% BAV, 18% coarctation). Methods: A total of 106 TS women of European ancestry with BAV and 173 TS women with tricuspid aortic valves were genotyped on Illumina Omni-Express arrays. Valve phenotypes were determined by independent review of echocardiograms from the enrolling sites. Tests of association were performed using logistic regression without adjustment for covariates and were summarized in a meta-analysis. Results: Xp dosage was inversely and quantitatively associated with BAV status (P=0.02). Large, recurrent copy number variants in 1p36.13, 3q29, 8p23.1 and 9p24.3 were significantly enriched in BAV cases. After exclusion of 26 outlier samples in multidimensional scaling analysis, there was no significant genomic inflation (lambda= 1.02). The strongest genome-wide association signals were observed in 1p36.23, 3q23, 12q21.2, 18q21 and 22q13.31, and did not overlap with previously reported loci for BAV. A total of 13 SNPs in 18q21 were positively associated with BAV (OR=2.5-4.3) with a minimum P value of 1x10-7. Replication of these regions in independent groups of cases is ongoing. Conclusion: Our results demonstrate that autosomal variants with large magnitudes of effect contribute to BAV in TS women, confirming our hypothesis, and provide evidence for gene-gene interactions in BAV formation.

A rare duplication on chromosome 16p11.2 is identified in patients with psychosis in Alzheimer's disease.

Epidemiological and genetic studies suggest that schizophrenia and autism may share genetic links. Besides common single nucleotide polymorphisms, recent data suggest that some rare copy number variants (CNVs) are risk factors for both disorders. Because we have previously found that schizophrenia and psychosis in Alzheimer's disease (AD+P) share some genetic risk, we investigated whether CNVs reported in schizophrenia and autism are also linked to AD+P. We searched for CNVs associated with AD+P in 7 recurrent CNV regions that have been previously identified across autism and schizophrenia, using the Illumina HumanOmni1-Quad BeadChip. A chromosome 16p11.2 duplication CNV (chr16: 29,554,843-30,105,652) was identified in 2 of 440 AD+P subjects, but not in 136 AD subjects without psychosis, or in 593 AD subjects with intermediate psychosis status, or in 855 non-AD individuals. The frequency of this duplication CNV in AD+P (0.46%) was similar to that reported previously in schizophrenia (0.46%). This duplication CNV was further validated using the NanoString nCounter CNV Custom CodeSets. The 16p11.2 duplication has been associated with developmental delay, intellectual disability, behavioral problems, autism, schizophrenia (SCZ), and bipolar disorder. These two AD+P patients had no personal of, nor any identified family history of, SCZ, bipolar disorder and autism. To the best of our knowledge, our case report is the first suggestion that 16p11.2 duplication is also linked to AD+P. Although rare, this CNV may have an important role in the development of psychosis.

Investigation of selected genomic deletions and duplications in a cohort of 338 patients presenting with syndromic obesity by multiplex ligation-dependent probe amplification using synthetic probes.

BackgroundCertain rare syndromes with developmental delay or intellectual disability caused by genomic copy number variants (CNVs), either deletions or duplications, are associated with higher rates of obesity. Current strategies to diagnose these syndromes typically rely on phenotype-driven investigation. However, the strong phenotypic overlap between syndromic forms of obesity poses challenges to accurate diagnosis, and many different individual cytogenetic and molecular approaches may be required. Multiplex ligation-dependent probe amplification (MLPA) enables the simultaneous analysis of multiple targeted loci in a single test, and serves as an important screening tool for large cohorts of patients in whom deletions and duplications involving specific loci are suspected. Our aim was to design a synthetic probe set for MLPA analysis to investigate in a cohort of 338 patients with syndromic obesity deletions and duplications in genomic regions that can cause this phenotype.ResultsWe identified 18 patients harboring copy number imbalances; 18 deletions and 5 duplications. The alterations in ten patients were delineated by chromosomal microarrays, and in the remaining cases by additional MLPA probes incorporated into commercial kits. Nine patients showed deletions in regions of known microdeletion syndromes with obesity as a clinical feature: in 2q37 (4 cases), 9q34 (1 case) and 17p11.2 (4 cases). Four patients harbored CNVs in the DiGeorge syndrome locus at 22q11.2. Two other patients had deletions within the 22q11.2 ‘distal’ locus associated with a variable clinical phenotype and obesity in some individuals. The other three patients had a recurrent CNV of one of three susceptibility loci: at 1q21.1 ‘distal’, 16p11.2 ‘distal’, and 16p11.2 ‘proximal’.ConclusionsOur study demonstrates the utility of an MLPA-based first line screening test to the evaluation of obese patients presenting with syndromic features. The overall detection rate with the synthetic MLPA probe set was about 5.3% (18 out of 338). Our experience leads us to suggest that MLPA could serve as an effective alternative first line screening test to chromosomal microarrays for diagnosis of syndromic obesity, allowing for a number of loci (e.g., 1p36, 2p25, 2q37, 6q16, 9q34, 11p14, 16p11.2, 17p11.2), known to be clinically relevant for this patient population, to be interrogated simultaneously.

Common microRNAs Target Established ASD Genes.

COMPLEX GENETIC ARCHITECTURE IN AUTISM Autism spectrum disorder (ASD) encompasses a range of early-onset neurodevelopmental disorders characterized by impaired social interactions and communications, together with repetitive stereotypic behaviors (MIM20895; DSM5). Individuals with ASD can display a broad clinical profile ranging in symptom severity and comorbidities. A strong genetic component underlying ASD has been firmly established; hundreds of genes and chromosomal loci are known to be associated with the disorder and have been cataloged in ASD-specific genetic databases such as AutDB (1). The potential genetic risk factors range from candidate genes reported from genetic association studies to rare, recurrent gene-disruptive mutations identified in ASD individuals using high-throughput technologies such as whole exome sequencing (2). A number of recurrent copy number variants (CNVs) that overlap with related neurodevelopmental and neuropsychiatric disorders such as intellectual disability and schizophrenia have been implicated in ASD as well. Two recent studies, in particular, provide a deeper understanding of the complex genetic architecture of ASD. First, a genome-wide analysis revealed shared risk loci between five major psychiatric disorders including ASD, attention deficit hyperactivity disorder (ADHD), bipolar disorder, major depressive disorder, and schizophrenia (3). The second study examined the detailed structure of the type of genetic liability in ASD and showed that inherited common variants contributed to 49.4% heritability, whereas rare de novo variants accounted for only 2.6% (4). Despite this progress in ASD genetics, the underlying perturbations in brain development that contributes to the emergence of specific symptoms along developmental time points, whether in the first years of life in ASD or during adolescence in the case of schizophrenia, remains largely unresolved. The regulatory mechanisms that orchestrate the precise temporal and spatial patterns of gene expression in the brain are at the forefront of research for brain-based disorders. The importance of various types of non-coding RNAs is being increasingly recognized in this regulatory process, with microRNAs (miRNAs) emerging as a leading candidate. miRNAs are highly conserved small non-coding RNAs approximately 22 nucleotides in length that regulate gene expression mostly by binding to the 3 UTR of target messenger RNAs (mRNAs). miRNAs recognize their targets primarily through complementarity with the seed sequence at nucleotides 2–8 of the 5 end of the miRNA. A distinguishing feature of miRNAs lies in the ability of a single miRNA molecule to bind to the recognition site on many mRNAs and subsequently regulate their expression (5). By this mechanism, miRNA–mRNA interactions can potentially modulate expression of hundreds of target genes and influence the corresponding cellular networks. Any disturbances of such a system within a neuronal context could lead to altered brain circuits and synaptic function – processes implicated in disorders such as autism or schizophrenia.