Search

We assessed the relationship of gene copy number variation (CNV) in mental health/neurodevelopmental traits and diagnoses, physical health and cognition in a community sample of 7100 unrelated children and youth of European or East Asian ancestry (Spit for Science). Clinically significant or susceptibility CNVs were present in 3.9% of participants and were associated with elevated scores on a continuous measure of attention-deficit/hyperactivity disorder (ADHD) traits (P = 5.0 × 10−3), longer response inhibition (a cognitive deficit found in several mental health and neurodevelopmental disorders; P = 1.0 × 10−2) and increased prevalence of mental health diagnoses (P = 1.9 × 10−6, odds ratio: 3.09), specifically ADHD, autism spectrum disorder anxiety and learning problems/learning disorder (P’s

Defining different genetic subtypes of autism spectrum disorder (ASD) can enable the prediction of developmental outcomes. Based on minor physical and major congenital anomalies, we categorized 325 Canadian children with ASD into dysmorphic and nondysmorphic subgroups. We developed a method for calculating a patient-level, genome-wide rare variant score (GRVS) from whole-genome sequencing (WGS) data. GRVS is a sum of the number of variants in morphology-associated coding and non-coding regions, weighted by their effect sizes. Probands with dysmorphic ASD had a significantly higher GRVS compared to those with nondysmorphic ASD (P= 0.027). Using the polygenic transmission disequilibrium test, we observed an over-transmission of ASD-associated common variants in nondysmorphic ASD probands (P= 2.9×10−3). These findings replicated using WGS data from 442 ASD probands with accompanying morphology data from the Simons Simplex Collection. Our results provide support for an alternative genomic classification of ASD subgroups using morphology data, which may inform intervention protocols.

BACKGROUND: The Personal Genome Project Canada is a comprehensive public data resource that integrates whole genome sequencing data and health information. We describe genomic variation identified in the initial recruitment cohort of 56 volunteers. METHODS: Volunteers were screened for eligibility and provided informed consent for open data sharing. Using blood DNA, we performed whole genome sequencing and identified all possible classes of DNA variants. A genetic counsellor explained the implication of the results to each participant. RESULTS: Whole genome sequencing of the first 56 participants identified 207 662 805 sequence variants and 27 494 copy number variations. We analyzed a prioritized disease-associated data set (n = 1606 variants) according to standardized guidelines, and interpreted 19 variants in 14 participants (25%) as having obvious health implications. Six of these variants (e.g., in BRCA1 or mosaic loss of an X chromosome) were pathogenic or likely pathogenic. Seven were risk factors for cancer, cardiovascular or neurobehavioural conditions. Four other variants — associated with cancer, cardiac or neurodegenerative phenotypes — remained of uncertain significance because of discrepancies among databases. We also identified a large structural chromosome aberration and a likely pathogenic mitochondrial variant. There were 172 recessive disease alleles (e.g., 5 individuals carried mutations for cystic fibrosis). Pharmacogenomics analyses revealed another 3.9 potentially relevant genotypes per individual. INTERPRETATION: Our analyses identified a spectrum of genetic variants with potential health impact in 25% of participants. When also considering recessive alleles and variants with potential pharmacologic relevance, all 56 participants had medically relevant findings. Although access is mostly limited to research, whole genome sequencing can provide specific and novel information with the potential of major impact for health care.

Purpose Hemiplegia is a subtype of cerebral palsy (CP) in which one side of the body is affected. Our earlier study of unselected children with CP demonstrated de novo and clinically relevant rare inherited genomic copy-number variations (CNVs) in 9.6% of participants. Here, we examined the prevalence and types of CNVs specifically in hemiplegic CP. Methods We genotyped 97 unrelated probands with hemiplegic CP and their parents. We compared their CNVs to those of 10,851 population controls, in order to identify rare CNVs (

A major contribution to the genome variability among individuals comes from deletions and duplications - collectively termed copy number variations (CNVs) - which alter the diploid status of DNA. These alterations may have no phenotypic effect, account for adaptive traits or can underlie disease. We have compiled published high-quality data on healthy individuals of various ethnicities to construct an updated CNV map of the human genome. Depending on the level of stringency of the map, we estimated that 4.8-9.5% of the genome contributes to CNV and found approximately 100 genes that can be completely deleted without producing apparent phenotypic consequences. This map will aid the interpretation of new CNV findings for both clinical and research applications.

A remaining hurdle to whole-genome sequencing (WGS) becoming a first-tier genetic test has been accurate detection of copy-number variations (CNVs). Here, we used several datasets to empirically develop a detailed workflow for identifying germline CNVs >1 kb from short-read WGS data using read depth-based algorithms. Our workflow is comprehensive in that it addresses all stages of the CNV-detection process, including DNA library preparation, sequencing, quality control, reference mapping, and computational CNV identification. We used our workflow to detect rare, genic CNVs in individuals with autism spectrum disorder (ASD), and 120/120 such CNVs tested using orthogonal methods were successfully confirmed. We also identified 71 putative genic de novo CNVs in this cohort, which had a confirmation rate of 70%; the remainder were incorrectly identified as de novo due to false positives in the proband (7%) or parental false negatives (23%). In individuals with an ASD diagnosis in which both microarray and WGS experiments were performed, our workflow detected all clinically relevant CNVs identified by microarrays, as well as additional potentially pathogenic CNVs < 20 kb. Thus, CNVs of clinical relevance can be discovered from WGS with a detection rate exceeding microarrays, positioning WGS as a single assay for genetic variation detection.

We are performing whole genome sequencing (WGS) of families with Autism Spectrum Disorder (ASD) to build a resource, named MSSNG, to enable the sub-categorization of phenotypes and underlying genetic factors involved. Here, we report WGS of 5,205 samples from families with ASD, accompanied by clinical information, creating a database accessible in a cloud platform, and through an internet portal with controlled access. We found an average of 73.8 de novo single nucleotide variants and 12.6 de novo insertion/deletions (indels) or copy number variations (CNVs) per ASD subject. We identified 18 new candidate ASD-risk genes such as MED13 and PHF3, and found that participants bearing mutations in susceptibility genes had significantly lower adaptive ability (p=6×10−4). In 294/2,620 (11.2%) of ASD cases, a molecular basis could be determined and 7.2% of these carried CNV/chromosomal abnormalities, emphasizing the importance of detecting all forms of genetic variation as diagnostic and therapeutic targets in ASD.

Background Rare Copy Number Variants (CNVs) likely play an important role in common childhood neuropsychiatric disorders such as ADHD and OCD. These disorders represent the extremes of broadly distributed behavioural traits that are influenced by underlying variation in fundamental cognitive processes such as response inhibition. Using behavioural and cognitive trait-based approaches in population samples can help reduce heterogeneity and improve power to detect rare CNVs associated with these disorders. Currently we do not know the prevalence of CNVs related to neuropsychiatric disorders in youth in the general population. Using the Spit for Science sample (Toronto, Canada), we examined the association of rare CNVs with ADHD, OCD and response inhibition traits. Methods We collected DNA and quantitative trait measures from 16,718 youth (ages 6–17 years) at a local science museum. We measured ADHD traits using the Strengths and Weaknesses of ADHD and Normal Behavior (SWAN) scale, obsessive-compulsive traits using the Toronto Obsessive-Compulsive scale (TOCS) and response inhibition, a putative endophenotype for ADHD, using the Stop-Task. We genotyped unrelated Caucasians (n=5,320) using Illumina HumanCoreExome beadchips. CNVs were called using three algorithms: iPattern (ipn), PennCNV (pcnv), and QuantiSNP (qsnp) and a high confidence dataset was generated by retaining variants detected by two or more algorithms and at least 10 kb in size. We defined rare variants as those with less than 0.1% frequency against our population controls. Using linear regression, we examined whether CNV burden, overall and within psychiatrically relevant gene sets (e.g., brain expression, synaptic function), is associated with response inhibition, ADHD and OCD traits. Results After stringent quality control, 4815 (90.5%) of participants remained with a total of 9,490 rare CNVs (1.97/individual on average). We observed CNVs affecting 23 genomic loci previously implicated in neurodevelopmental conditions (e.g. 22q11.2) in 59 (1.2%) of participants. Other large CNVs affecting known psychiatric genes (e.g., ASTN2, NRXN1) were also identified. Significantly more deletions (>500 kb; p=0.04) and enrichment of deletions in genes involved in synapse structure, neuron projection and neurophenotypes in mice (p Discussion In a large pediatric general population sample, brain-related CNVs were associated with neuropsychiatric traits in children although the pattern of enrichment differed between ADHD, OCD and response inhibition. Our results replicate several previous CNV burden findings for ADHD and OCD suggesting a similar genetic architecture between traits and disorders. Our approach shows the feasibility of CNV analysis and quality of CNV data from the HumanCoreExome array in a large population based sample.

IMMP2L, the gene encoding the inner mitochondrial membrane peptidase subunit 2-like protein, has been reported as a candidate gene for Tourette syndrome, autism spectrum disorder (ASD) and additional neurodevelopmental disorders. Here we genotyped 100 trio families with an index proband with autism spectrum disorder in Han Chinese population and found three cases with rare exonic IMMP2L deletions. We have conducted a comprehensive meta-analysis to quantify the association of IMMP2L deletions with ASD using 5,568 cases and 10,279 controls. While the IMMP2L deletions carried non-recurrent breakpoints, in contrast to previous reports, our meta-analysis found no evidence of association (P > 0.05) between IMMP2L deletions and ASD. We also observed common exonic deletions impacting IMMP2L in a separate control (5,971 samples) cohort where subjects were screened for psychiatric conditions. This is the first systematic review and meta-analysis regarding the effect of IMMP2L deletions on ASD, but further investigations in different populations, especially Chinese population may be still needed to confirm our results.

Numerous types of DNA variation exist, ranging from SNPs to larger structural alterations such as copy number variants (CNVs) and inversions. Alignment of DNA sequence from different sources has been used to identify SNPs1,2 and intermediate-sized variants (ISVs)3. However, only a small proportion of total heterogeneity is characterized, and little is known of the characteristics of most smaller-sized (1.5 million SNPs. Some differences were simple insertions and deletions, but in regions containing CNVs, segmental duplication and repetitive DNA, they were more complex. Our results uncover substantial undescribed variation in humans, highlighting the need for comprehensive annotation strategies to fully interpret genome scanning and personalized sequencing projects.

We observed that current high-throughput sequencing approaches only detected a fraction of the full size-spectrum of insertions, deletions, and copy number variants compared with a previously published, Sanger-sequenced human genome. The sensitivity for detection was the lowest in the 100- to 10,000-bp size range, and at DNA repeats, with copy number gains harder to delineate than losses. We discuss strategies for discovering the full spectrum of genetic variation necessary for disease association studies.

Chromosomal microarray analysis to assess copy-number variation has become a first-tier genetic diagnostic test for individuals with unexplained neurodevelopmental disorders or multiple congenital anomalies. More than 100 cytogenetic laboratories worldwide use the new ultra-high resolution Affymetrix CytoScan-HD array to genotype hundreds of thousands of samples per year. Our aim was to develop a copy-number variation resource from a new population sample that would enable more accurate interpretation of clinical genetics data on this microarray platform and others. Genotyping of 1,000 adult volunteers who are broadly representative of the Ontario population (as obtained from the Ontario Population Genomics Platform) was performed with the CytoScan-HD microarray system, which has 2.7 million probes. Four independent algorithms were applied to detect copy-number variations. Reproducibility and validation metrics were quantified using sample replicates and quantitative-polymerase chain reaction, respectively. DNA from 873 individuals passed quality control and we identified 71,178 copy-number variations (81 copy-number variations/individual); 9.8% (6,984) of these copy-number variations were previously unreported. After applying three layers of filtering criteria, from our highest confidence copy-number variation data set we obtained >95% reproducibility and >90% validation rates (73% of these copy-number variations overlapped at least one gene). The genotype data and annotated copy-number variations for this largely Caucasian population will represent a valuable public resource enabling clinical genetics research and diagnostics. Genet Med 17 9, 747–752.

Rare copy number variants (CNVs) disrupting ASTN2 or both ASTN2 and TRIM32 have been reported at 9q33.1 by genome-wide studies in a few individuals with neurodevelopmental disorders (NDDs). The vertebrate-specific astrotactins, ASTN2 and its paralog ASTN1, have key roles in glial-guided neuronal migration during brain development. To determine the prevalence of astrotactin mutations and delineate their associated phenotypic spectrum, we screened ASTN2/TRIM32 and ASTN1 (1q25.2) for exonic CNVs in clinical microarray data from 89 985 individuals across 10 sites, including 64 114 NDD subjects. In this clinical dataset, we identified 46 deletions and 12 duplications affecting ASTN2. Deletions of ASTN1 were much rarer. Deletions near the 3' terminus of ASTN2, which would disrupt all transcript isoforms (a subset of these deletions also included TRIM32), were significantly enriched in the NDD subjects (P = 0.002) compared with 44 085 population-based controls. Frequent phenotypes observed in individuals with such deletions include autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), speech delay, anxiety and obsessive compulsive disorder (OCD). The 3'-terminal ASTN2 deletions were significantly enriched compared with controls in males with NDDs, but not in females. Upon quantifying ASTN2 human brain RNA, we observed shorter isoforms expressed from an alternative transcription start site of recent evolutionary origin near the 3' end. Spatiotemporal expression profiling in the human brain revealed consistently high ASTN1 expression while ASTN2 expression peaked in the early embryonic neocortex and postnatal cerebellar cortex. Our findings shed new light on the role of the astrotactins in psychopathology and their interplay in human neurodevelopment.

De novo mutations (DNMs) are important in autism spectrum disorder (ASD), but so far analyses have mainly been on the ~1.5% of the genome encoding genes. Here, we performed whole-genome sequencing (WGS) of 200 ASD parent–child trios and characterised germline and somatic DNMs. We confirmed that the majority of germline DNMs (75.6%) originated from the father, and these increased significantly with paternal age only (P=4.2×10−10). However, when clustered DNMs (those within 20 kb) were found in ASD, not only did they mostly originate from the mother (P=7.7×10−13), but they could also be found adjacent to de novo copy number variations where the mutation rate was significantly elevated (P=2.4×10−24). By comparing with DNMs detected in controls, we found a significant enrichment of predicted damaging DNMs in ASD cases (P=8.0×10−9; odds ratio=1.84), of which 15.6% (P=4.3×10−3) and 22.5% (P=7.0×10−5) were non-coding or genic non-coding, respectively. The non-coding elements most enriched for DNM were untranslated regions of genes, regulatory sequences involved in exon-skipping and DNase I hypersensitive regions. Using microarrays and a novel outlier detection test, we also found aberrant methylation profiles in 2/185 (1.1%) of ASD cases. These same individuals carried independently identified DNMs in the ASD-risk and epigenetic genes DNMT3A and ADNP. Our data begins to characterize different genome-wide DNMs, and highlight the contribution of non-coding variants, to the aetiology of ASD.

Even with significant advances in technology, few studies of structural variation have yet resolved to the level of the precise nucleotide junction. We examined the sequence of 408,532 gains, 383,804 losses, and 166 inversions from the first sequenced personal genome, to quantify the relative proportion of mutational mechanisms. Among small variants (1 kb), we observed that 72.6% of them were associated with nonhomologous processes and 24.9% with microsatellites events. Medium-size variants (10 kb) were commonly related to minisatellites (25.8%) and retrotransposons (24%), whereas 46.2% of large variants (10 kb) were associated with nonallelic homologous recombination. We genotyped eight new breakpoint-resolved inversions at (3q26.1, Xp11.22, 7q11.22, 16q23.1, 4q22.1, 1q31.3, 6q27, and 16q24.1) in human populations to elucidate the structure of these presumed benign variants. Three of these inversions (3q26.1, 7q11.22, and 16q23.1) were accompanied by unexpected complex rearrangements. In particular, the 16q23.1 inversion and an accompanying deletion would create conjoined chymotrypsinogen genes (CTRB1 and CTRB2), disrupt their gene structure, and exhibit differentiated allelic frequencies among populations. Also, two loci (Xp11.3 and 6q27) of potential reference assembly orientation errors were found. This study provides a thorough account of formation mechanisms for structural variants, and reveals a glimpse of the dynamic structure of inversions.

Background There are four known pericentromeric euchromatic variants of chromosome 9 in the literature that are increasingly being observed in diagnostic cytogenetic laboratories. These variants pose diagnostic and counselling dilemmas, especially in prenatal settings, as distinction of a pathogenic alteration from a euchromatic variant is difficult. The molecular characterisation of three of these four variants has been reported. In this study, the genomic structure of the fourth variant, an additional G-positive band at 9q13-q21, is characterised. Methods Two unrelated families with the 9q13-q21 duplication variant, and a third individual with a cytogenetically visible 9q13-q21 deletion, were studied using conventional and molecular cytogenetics techniques, as well as microarrays. The highly repetitive nature of the segmental duplications in the region also necessitated the use of both interphase and metaphase fluorescence in situ hybridisation (FISH). Results It was determined that the DNA that constitutes this variant was ∼15–20 megabases in size and tandemly repeated as 3–4 cassettes of intrachromosomal segmental duplication. The variant appeared constitutively similar in sequence content and organisation between the two unrelated individuals, and it was inherited without apparent change. Sequences found amplified in the two duplication carriers were absent in the carrier of the deletion variant. Conclusions The sequences involved in both the 9q13-q21 duplication and deletion appear the same, implying reciprocity and suggesting non-allelic homologous recombination as the underlying mechanism. All four known euchromatic variants of chromosome 9 have now been shown to encompass segmental duplications. Importantly, a set of validated FISH probes was defined for the detection and characterisation of this 9q13-q21 amplification in the context of other chromosome 9 variants, allowing apparently benign variants to be distinguished from pathogenic changes.

The term monoclonal B-cell lymphocytosis (MBL) is used to characterize individuals with a circulating population of clonal B-cells and no other features of a lymphoproliferative disorder. Although several recent studies have examined the molecular basis of this condition, the subgroup of MBL lacking CD5 expression has been largely overlooked. In this study, we sequenced a t(2;7) in a patient with persistent but non-progressing CD5 − MBL. This revealed a breakpoint at 2p11.2 localized to the recombination signal sequence (RSS) of the immunoglobulin κ ( IGK ) variable gene IGKV3-15 , and a breakpoint at 7q21.2 located 520 base pairs (bp) upstream of the transcription start site of cyclin-dependent kinase 6 ( CDK6 ). The 7q breakpoint showed perfect sequence homology to the immunoglobulin RSS heptamer, and was located within 3 bp of a t(2;7) junction previously characterized in splenic marginal zone lymphoma (SMZL). These findings highlight a genetic link between CD5 − MBL and SMZL, and implicate the dysregulation of CDK6 in the emergence of this preclinical disorder.

Structural variations of DNA greater than 1 kilobase in size account for most bases that vary among human genomes, but are still relatively under-ascertained. Here we use tiling oligonucleotide microarrays, comprising 42 million probes, to generate a comprehensive map of 11,700 copy number variations (CNVs) greater than 443 base pairs, of which most (8,599) have been validated independently. For 4,978 of these CNVs, we generated reference genotypes from 450 individuals of European, African or East Asian ancestry. The predominant mutational mechanisms differ among CNV size classes. Retrotransposition has duplicated and inserted some coding and non-coding DNA segments randomly around the genome. Furthermore, by correlation with known trait-associated single nucleotide polymorphisms (SNPs), we identified 30 loci with CNVs that are candidates for influencing disease susceptibility. Despite this, having assessed the completeness of our map and the patterns of linkage disequilibrium between CNVs and SNPs, we conclude that, for complex traits, the heritability void left by genome-wide association studies will not be accounted for by common CNVs.

Presented here is a genome sequence of an individual human. It was produced from ∼32 million random DNA fragments, sequenced by Sanger dideoxy technology and assembled into 4,528 scaffolds, comprising 2,810 million bases (Mb) of contiguous sequence with approximately 7.5-fold coverage for any given region. We developed a modified version of the Celera assembler to facilitate the identification and comparison of alternate alleles within this individual diploid genome. Comparison of this genome and the National Center for Biotechnology Information human reference assembly revealed more than 4.1 million DNA variants, encompassing 12.3 Mb. These variants (of which 1,288,319 were novel) included 3,213,401 single nucleotide polymorphisms (SNPs), 53,823 block substitutions (2–206 bp), 292,102 heterozygous insertion/deletion events (indels)(1–571 bp), 559,473 homozygous indels (1–82,711 bp), 90 inversions, as well as numerous segmental duplications and copy number variation regions. Non-SNP DNA variation accounts for 22% of all events identified in the donor, however they involve 74% of all variant bases. This suggests an important role for non-SNP genetic alterations in defining the diploid genome structure. Moreover, 44% of genes were heterozygous for one or more variants. Using a novel haplotype assembly strategy, we were able to span 1.5 Gb of genome sequence in segments >200 kb, providing further precision to the diploid nature of the genome. These data depict a definitive molecular portrait of a diploid human genome that provides a starting point for future genome comparisons and enables an era of individualized genomic information., Author Summary We have generated an independently assembled diploid human genomic DNA sequence from both chromosomes of a single individual (J. Craig Venter). Our approach, based on whole-genome shotgun sequencing and using enhanced genome assembly strategies and software, generated an assembled genome over half of which is represented in large diploid segments (>200 kilobases), enabling study of the diploid genome. Comparison with previous reference human genome sequences, which were composites comprising multiple humans, revealed that the majority of genomic alterations are the well-studied class of variants based on single nucleotides (SNPs). However, the results also reveal that lesser-studied genomic variants, insertions and deletions, while comprising a minority (22%) of genomic variation events, actually account for almost 74% of variant nucleotides. Inclusion of insertion and deletion genetic variation into our estimates of interchromosomal difference reveals that only 99.5% similarity exists between the two chromosomal copies of an individual and that genetic variation between two individuals is as much as five times higher than previously estimated. The existence of a well-characterized diploid human genome sequence provides a starting point for future individual genome comparisons and enables the emerging era of individualized genomic information., Comparison of the DNA sequence of an individual human from the reference sequence reveals a surprising amount of difference.

Background Neoplasia can be driven by mutations resulting in dysregulation of transcription. In the mesenchymal neoplasm, aggressive fibromatosis, subtractive hybridization identified sterile alpha motif domain 9 (SAMD9) as a substantially down regulated gene in neoplasia. SAMD9 was recently found to be mutated in normophosphatemic familial tumoral calcinosis. In this study, we studied the gene structure and function of SAMD9, and its paralogous gene, SAMD9L, and examined these in a variety of species. Results SAMD9 is located on human chromosome 7q21.2 with a paralogous gene sterile alpha motif domain 9 like (SAMD9L) in the head-to-tail orientation. Although both genes are present in a variety of species, the orthologue for SAMD9 is lost in the mouse lineage due to a unique genomic rearrangement. Both SAMD9 and SAMD9L are ubiquitously expressed in human tissues. SAMD9 is expressed at a lower level in a variety of neoplasms associated with β-catenin stabilization, such as aggressive fibromatosis, breast, and colon cancers. SAMD9 and SAMD9L contain an amino-terminal SAM domain, but the remainder of the predicted protein structure does not exhibit substantial homology to other known protein motifs. The putative protein product of SAMD9 localizes to the cytoplasm. In vitro data shows that SAMD9 negatively regulates cell proliferation. Over expression of SAMD9 in the colon cancer cell line, SW480, reduces the volume of tumors formed when transplanted into immune-deficient mice. Conclusion SAMD9 and SAMD9L are a novel family of genes, which play a role regulating cell proliferation and suppressing the neoplastic phenotype. This is the first report as far as we know about a human gene that exists in rat, but is lost in mouse, due to a mouse specific rearrangement, resulting in the loss of the SAMD9 gene.

International audience; Copy number variation (CNV) of DNA sequences is functionally significant but has yet to be fully ascertained. We have constructed a first-generation CNV map of the human genome through the study of 270 individuals from four populations with ancestry in Europe, Africa or Asia (the HapMap collection). DNA from these individuals was screened for CNV using two complementary technologies: single-nucleotide polymorphism (SNP) genotyping arrays, and clone-based comparative genomic hybridization. A total of 1,447 copy number variable regions (CNVRs), which can encompass overlapping or adjacent gains or losses, covering 360 megabases (12% of the genome) were identified in these populations. These CNVRs contained hundreds of genes, disease loci, functional elements and segmental duplications. Notably, the CNVRs encompassed more nucleotide content per genome than SNPs, underscoring the importance of CNV in genetic diversity and evolution. The data obtained delineate linkage disequilibrium patterns for many CNVs, and reveal marked variation in copy number among populations. We also demonstrate the utility of this resource for genetic disease studies.

The aim of this chapter is to provide instruction for analyzing and mapping recent segmental and gene duplications in eukaryotic genomes. We describe a bioinformatics-based approach utilizing computational tools to manage eukaryotic genome sequences to characterize and understand the evolutionary fates and trajectories of duplicated genes. An introduction to bioinformatics tools and programs such as BLAST, Perl, BioPerl, and the GFF specification provides the necessary background to complete this analysis for any eukaryotic genome of interest.

With a draft genome-sequence assembly for the chimpanzee available, it is now possible to perform genome-wide analyses to identify, at a submicroscopic level, structural rearrangements that have occurred between chimpanzees and humans. The goal of this study was to investigate chromosomal regions that are inverted between the chimpanzee and human genomes. Using the net alignments for the builds of the human and chimpanzee genome assemblies, we identified a total of 1,576 putative regions of inverted orientation, covering more than 154 mega-bases of DNA. The DNA segments are distributed throughout the genome and range from 23 base pairs to 62 mega-bases in length. For the 66 inversions more than 25 kilobases (kb) in length, 75% were flanked on one or both sides by (often unrelated) segmental duplications. Using PCR and fluorescence in situ hybridization we experimentally validated 23 of 27 (85%) semi-randomly chosen regions; the largest novel inversion confirmed was 4.3 mega-bases at human Chromosome 7p14. Gorilla was used as an out-group to assign ancestral status to the variants. All experimentally validated inversion regions were then assayed against a panel of human samples and three of the 23 (13%) regions were found to be polymorphic in the human genome. These polymorphic inversions include 730 kb (at 7p22), 13 kb (at 7q11), and 1 kb (at 16q24) fragments with a 5%, 30%, and 48% minor allele frequency, respectively. Our results suggest that inversions are an important source of variation in primate genome evolution. The finding of at least three novel inversion polymorphisms in humans indicates this type of structural variation may be a more common feature of our genome than previously realized., Synopsis Chimpanzee is the closest relative to humans having DNA sequences about 98% identical to each other. Small DNA sequence changes and probably more importantly, larger structural changes of chromosomes, led to the divergence of the two species some 6 million years ago. Until recently, there were ten structural differences visible under the microscope between chimpanzee and human, and nine of these were inversions of DNA. Through computational comparisons of genome sequences, the current study identifies another 1,576 putative inversion events. Thirty-three of these were larger than 100,000 base pairs in size and 29 intersect genes, prioritizing them for evolutionary studies. Twenty-three of the inversions have been confirmed experimentally with the largest being 4.3 million base pairs in size on human Chromosome 7. Surprisingly, three of the “inverted” regions were found to be variable in their orientation in the human population (in some cases the inversion was in the ancestral orientation found in chimpanzee). These observations indicate the human genome is still evolving in structure. Moreover, since such variable inversions have been shown to predispose to other (sometimes deleterious) changes in chromosomes, the new data delineate potential disease-associated genes.

7 páginas, 2 figuras, 1 tabla., We have identified C7orf11, which localizes to the nucleus and is expressed in fetal hair follicles, as the first disease gene for nonphotosensitive trichothiodystrophy (TTD). C7orf11 maps to chromosome 7p14, and the disease locus has been designated “TTDN1” (TTDnonphotosensitive 1). Mutations were found in patients with Amish brittle-hair syndrome and in other nonphotosensititive TTD cases with mental retardation and decreased fertility but not in patients with Sabinas syndrome or Pollitt syndrome. Therefore, genetic heterogeneity in nonphotosensitive TTD is a feature similar to that observed in photosensitive TTD, which is caused by mutations in transcription factor II H (TFIIH) subunit genes. Comparative immunofluorescence analysis, however, suggests that C7orf11 does not influence TFIIH directly. Given the absence of cutaneous photosensitivity in the patients with C7orf11 mutations, together with the protein’s nuclear localization, C7orf11 may be involved in transcription but not DNA repair., We acknowledge The Centre for Applied Genomics, the Genome Canada/Ontario Genome Institute, the Hospital for Sick Children Foundation, the Association Française contre les Myopathies, and the Dykstra Foundation in Detroit (grant to C.E.J.). S.W.S. is an Investigator of the Canadian Institutes of Health Research, a Scholar of the McLaughlin Centre for Molecular Medicine, and an International Scholar of the Howard Hughes Medical Institute.

DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism., link_to_OA_fulltext

BACKGROUND: Previous studies have suggested that recent segmental duplications, which are often involved in chromosome rearrangements underlying genomic disease, account for some 5% of the human genome. We have developed rapid computational heuristics based on BLAST analysis to detect segmental duplications, as well as regions containing potential sequence misassignments in the human genome assemblies. RESULTS: Our analysis of the June 2002 public human genome assembly revealed that 107.4 of 3,043.1 megabases (Mb) (3.53%) of sequence contained segmental duplications, each with size equal or more than 5 kb and 90% identity. We have also detected that 38.9 Mb (1.28%) of sequence within this assembly is likely to be involved in sequence misassignment errors. Furthermore, we have identified a significant subset (199,965 of 2,327,473 or 8.6%) of single-nucleotide polymorphisms (SNPs) in the public databases that are not true SNPs but are potential paralogous sequence variants. CONCLUSION: Using two distinct computational approaches, we have identified most of the sequences in the human genome that have undergone recent segmental duplications. Near-identical segmental duplications present a major challenge to the completion of the human genome sequence. Potential sequence misassignments detected in this study would require additional efforts to resolve., published_or_final_version

Objective To develop a novel clinical test using microarray technology as a high-resolution alternative to current methods for detection of known and novel microdeletions on the Y chromosome. Design Custom Agilent 8x15K array comparative genomic hybridization (aCGH) with 10,162 probes on an average probe spacing of 2.5 kb across the euchromatic region of the Y chromosome. Setting Clinical diagnostic laboratory. Patient(s) Men with infertility (n = 104) and controls with proven fertility (n = 148). Intervention(s) Microarray genotyping of DNA. Main Outcome Measure(s) Gene copy number variation determined by log ratio of probe signal intensity against a DNA reference. Result(s) Our aCGH experiments found all known AZF microdeletions as well as additional unbalanced structural alterations. In addition to complete AZF microdeletions, we found that AZFc partial deletions represent a risk factor for male infertility. In total, aCGH-based detection achieved a diagnostic yield of ∼11% and also revealed additional potentially etiologic copy number variations requiring further characterization. Conclusion(s) The aCGH approach is a reliable high-resolution alternative to multiplex polymerase chain reaction for the discovery of pathogenic chromosome Y microdeletions in male infertility.

Abstract 1191 Efforts to decipher the biological basis of lymphoid malignancy have recently been accentuated by the discovery of clonal B-cells in otherwise healthy individuals, an entity now referred to as monoclonal B-cell lymphocytosis (MBL). However, while considerable attention has been devoted towards characterizing this pervasive condition, the subgroup of MBL lacking CD5 expression has been largely overlooked. To address this imbalance, our group previously examined a series of cases presenting with persistent but non-progressing CD5- clonal lymphocytosis (Amato D et al, Am J Clin Pathol 2007). Herein, karyotypic analysis revealed a unique case harboring the translocation t(2;7)(p11;q22), a genetic abnormality which has been documented in association with splenic marginal zone lymphoma (SMZL). The present study set out to further characterize the t(2;7) breakpoint of this novel case study in order to test whether the translocation represents a common genetic link between CD5- MBL and SMZL. Using fluorescent in situ hybridization (FISH), the breakpoint on chromosome 7 was initially narrowed down to a 41 kilobase (kb) candidate region at 7q21.2, as inferred by a split signal from the cosmid probe cos130a6. Based on the proximity of the chromosome 2 breakpoint to the immunoglobulin kappa (IGK) locus on 2p11, long-range polymerase chain reaction (L-PCR) was subsequently performed according to the hypothesis that the t(2;7) translocation had arisen from aberrant VJ recombination. Primers targeting conserved sequences within the IGK variable genes were sequentially juxtaposed with primers on chromosome 7 located at 6 kb intervals across the 41 kb candidate region, and L-PCR conducted using both patient and reference DNA as a template. This process gave rise to a single instance of strong patient-specific amplification, thereby indicating successful targeting of the t(2;7) breakpoint. Sanger sequencing of the corresponding PCR product confirmed this result, revealing a breakpoint at 2p11.2 localized to the heptamer recombination signal sequence (RSS) of the IGK variable gene V3-15, alongside a breakpoint at 7q21.2 located 3.6 kb upstream of the transcription start site of the cell cycle regulator cyclin dependent kinase 6 (CDK6). Remarkably, the breakpoint on chromosome 7 showed perfect sequence homology to the immunoglobulin RSS heptamer, and was within 3 base pairs of a breakpoint previously characterized in association with SMZL (Corcoran M et al, Oncogene 1999). Hence, this result implicates the dysregulation of CDK6 during the clonal expansion observed in CD5- MBL, and highlights the potential role of aberrant VJ recombination during the formation of this genetic abnormality. By establishing a clear genetic link between CD5- MBL and SMZL, this study supports the notion of CD5- MBL as a precursor of overt malignancy within a ‘multi-hit’ model of oncogenesis. Finally, the sequence-level characterization of a novel translocation breakpoint by L-PCR strongly validates the potential utility of this approach during future studies of immunoglobulin-associated translocations. Disclosures: No relevant conflicts of interest to declare.

A comprehensive map of structural variation in the human genome provides a reference dataset for analyses of future personal genomes., Background Several genomes have now been sequenced, with millions of genetic variants annotated. While significant progress has been made in mapping single nucleotide polymorphisms (SNPs) and small (24% of structural variants would not be imputed by SNP-association. Conclusions Our results indicate that a large number of structural variants have been unreported in the individual genomes published to date. This significant extent and complexity of structural variants, as well as the growing recognition of their medical relevance, necessitate they be actively studied in health-related analyses of personal genomes. The new catalogue of structural variants generated for this genome provides a crucial resource for future comparison studies.

The high quality of the mouse genome draft sequence and its associated annotations are an invaluable biological resource. Identifying recent duplications in the mouse genome, especially in regions containing genes, may highlight important events in recent murine evolution. In addition, detecting recent sequence duplications can reveal potentially problematic regions of the genome assembly. We use BLAST-based computational heuristics to identify large (≥ 5 kb) and recent (≥ 90% sequence identity) segmental duplications in the mouse genome sequence. Here we present a database of recently duplicated regions of the mouse genome found in the mouse genome sequencing consortium (MGSC) February 2002 and February 2003 assemblies. We determined that 33.6 Mb of 2,695 Mb (1.2%) of sequence from the February 2003 mouse genome sequence assembly is involved in recent segmental duplications, which is less than that observed in the human genome (around 3.5-5%). From this dataset, 8.9 Mb (26%) of the duplication content consisted of 'unmapped' chromosome sequence. Moreover, we suspect that an additional 18.5 Mb of sequence is involved in duplication artifacts arising from sequence misassignment errors in this genome assembly. By searching for genes that are located within these regions, we identified 675 genes that mapped to duplicated regions of the mouse genome. Sixteen of these genes appear to have been duplicated independently in the human genome. From our dataset we further characterized a 42 kb recent segmental duplication of Mater, a maternal-effect gene essential for embryogenesis in mice. Our results provide an initial analysis of the recently duplicated sequence and gene content of the mouse genome. Many of these duplicated loci, as well as regions identified to be involved in potential sequence misassignment errors, will require further mapping and sequencing to achieve accuracy. A Genome Browser database was set up to display the identified duplication content presented in this work. This data will also be relevant to the growing number of investigators who use the draft genome sequence for experimental design and analysis.