Gene CNVs genetically mapped and linked to adaptation in spruce
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ABSTRACT: Following previous work, we extend the use of a reliable detection method to a wide progeny in white spruce in order to genetically map a maximum of inherited gene CNVs and linked those to phenotypic traits related to adaptation. We selected probes targeting 3911 genes likely in CNV in this progeny and performed genetic mapping for those harboring a 1:1 segregation. In addition, the link between gene CNVs and phenotypic variation was tested using budburst, budset and growth data for the same samples. Results: We genetically mapped 82 gene CNVs inherited from the previous generation and harboring the expected segregation ratio. This mapping allowed to delineate a few hotspots of CNV that are likely shared with other conifer species. In addition, individual-specific gene CNVs likely representing de novo variation supported the hypothesis of a purifying selection against copy losses. Finally, 29 gene CNVs were significantly associated to adaptive trait variation; 13 were located on the genetic map, including 4 located within hotspots of CNVs.
Project description:This study examines genomic copy-number variation among African cichlids spanning multiple tribes and radiations. We map CNVs and hotspots throughout the Oreochromis niloticus reference genome, categorize gene ontology enrichment within CNV regions, and compare results with sequence-based cichlid phylogenies.
Project description:Background: Detecting genetic variation is a critical step in elucidating the molecular mechanisms underlying phenotypic diversity. Until recently, such detection has mostly focused on single nucleotide polymorphisms (SNPs) because of the ease in screening complete genomes. Another type of variant, copy number variation (CNV), is emerging as a significant contributor to phenotypic variation in many species. Here we describe a genome-wide CNV study using array comparative genomic hybridization (aCGH) in a wide variety of chicken breeds. Results: We identified 3,154 CNVs, grouped into 1,556 CNV regions (CNVRs). Thirty percent of the CNVs were detected in at least 2 individuals. The average size of the CNVs detected was 46.3 kb with the largest CNV, located on GGAZ, being 4.3 Mb. Approximately 75% of the CNVs are copy number losses relatively to the Red Jungle Fowl reference genome. The genome coverage of CNVRs in this study is 60 Mb, which represents almost 5.4% of the chicken genome. In particular large gene families such as the keratin gene family and the MHC show extensive CNV. Conclusions: A relative large group of the CNVs are line-specific, several of which were previously shown to be related to the causative mutation for a number of phenotypic variants. The chance that inter-specific CNVs fall into CNVRs detected in chicken is related to the evolutionary distance between the species. Our results provide a valuable resource for the study of genetic and phenotypic variation in this phenotypically diverse species.
Project description:Copy number variants (CNVs) reshape gene structure, modulate gene expression, and contribute to significant phenotypic variation. Previous studies have revealed CNV patterns in natural populations of Drosophila melanogaster and suggested that selection and mutational bias shape genomic patterns of CNV. While previous CNV studies focused on heterogeneous strains, here we established a number of second-chromosome substitution lines to uncover CNV characteristics when homozygous. The percentage of genes harboring CNVs is higher than found in previous studies. More CNVs are detected in homozygous than heterozygous substitution strains, suggesting the comparative genomic hybridization arrays underestimate CNV owing to heterozygous masking. We incorporated previous gene expression data collected from some of the same substitution lines to investigate relationships between CNV gene dosage and expression. Most genes present in CNVs show no evidence of increased or diminished transcription, and the fraction of such dosage-insensitive CNVs is greater in heterozygotes. More than 70% of the dosage-sensitive CNVs are recessive with undetectable effects on transcription in heterozygotes. A deficiency of singletons in recessive dosage-sensitive CNVs supports the hypothesis that most CNVs are subject to negative selection. On the other hand, relaxed purifying selection might account for the higher number of protein-protein interactions in dosage insensitive CNVs than in dosage-sensitive CNVs. Dosage-sensitive CNVs that are up-regulated and down-regulated coincide with copy number increases and decreases. Our results help clarify the relation between CNV dosage and gene expression in the D. melanogaster genome.
Project description:Copy number variants (CNVs) reshape gene structure, modulate gene expression, and contribute to significant phenotypic variation. Previous studies have revealed CNV patterns in natural populations of Drosophila melanogaster and suggested that selection and mutational bias shape genomic patterns of CNV. While previous CNV studies focused on heterogeneous strains, here we established a number of second-chromosome substitution lines to uncover CNV characteristics when homozygous. The percentage of genes harboring CNVs is higher than found in previous studies. More CNVs are detected in homozygous than heterozygous substitution strains, suggesting the comparative genomic hybridization arrays underestimate CNV owing to heterozygous masking. We incorporated previous gene expression data collected from some of the same substitution lines to investigate relationships between CNV gene dosage and expression. Most genes present in CNVs show no evidence of increased or diminished transcription, and the fraction of such dosage-insensitive CNVs is greater in heterozygotes. More than 70% of the dosage-sensitive CNVs are recessive with undetectable effects on transcription in heterozygotes. A deficiency of singletons in recessive dosage-sensitive CNVs supports the hypothesis that most CNVs are subject to negative selection. On the other hand, relaxed purifying selection might account for the higher number of protein-protein interactions in dosage insensitive CNVs than in dosage-sensitive CNVs. Dosage-sensitive CNVs that are up-regulated and down-regulated coincide with copy number increases and decreases. Our results help clarify the relation between CNV dosage and gene expression in the D. melanogaster genome. To determine copy number variation, the genomic DNA from five homozygous and two heterozygous second chromosome substitution lines were extracted and compared to another second chromosome substitution line. Gene expression levels can be referred to at Series GSE12191 (Lemos et al. (2008) PMID:18791071).
Project description:Background: Detecting genetic variation is a critical step in elucidating the molecular mechanisms underlying phenotypic diversity. Until recently, such detection has mostly focused on single nucleotide polymorphisms (SNPs) because of the ease in screening complete genomes. Another type of variant, copy number variation (CNV), is emerging as a significant contributor to phenotypic variation in many species. Here we describe a genome-wide CNV study using array comparative genomic hybridization (aCGH) in a wide variety of chicken breeds. Results: We identified 3,154 CNVs, grouped into 1,556 CNV regions (CNVRs). Thirty percent of the CNVs were detected in at least 2 individuals. The average size of the CNVs detected was 46.3 kb with the largest CNV, located on GGAZ, being 4.3 Mb. Approximately 75% of the CNVs are copy number losses relatively to the Red Jungle Fowl reference genome. The genome coverage of CNVRs in this study is 60 Mb, which represents almost 5.4% of the chicken genome. In particular large gene families such as the keratin gene family and the MHC show extensive CNV. Conclusions: A relative large group of the CNVs are line-specific, several of which were previously shown to be related to the causative mutation for a number of phenotypic variants. The chance that inter-specific CNVs fall into CNVRs detected in chicken is related to the evolutionary distance between the species. Our results provide a valuable resource for the study of genetic and phenotypic variation in this phenotypically diverse species. In total 62 chicken DNA samples (derived from 15 lines) were analyzed against the chicken reference animal UCD001 (the same induvidual that was used to generate the chicken genome reference sequence (ICGSC, 2004)
Project description:Copy number variants (CNVs) represent a substantial source of genomic variation in vertebrates, but the zebrafish reference genome has no annotated CNV information. We developed a zebrafish CNV map using 80 zebrafish genomes from laboratory strains (AB, Tubingen, and WIK) and one native population, identifying 6,080 CNV elements. Overlapping or adjacent CNVs account for 14.6% of the genome, representing four times the CNV levels from other vertebrates including humans. Highest intra-specific CNV levels were observed for Tubingen, a common laboratory strain due to high fecundity. Tubingen variation likely represents higher initial population size and composite population founders initiating the laboratory strain. Extensive zebrafish CNVs, along with associated phenotypic impacts, advocates for increased usage of isogenic strains for genetic studies intended for human disease translation.
Project description:Copy number variants (CNVs) represent a substantial source of genomic variation in vertebrates, but the zebrafish reference genome has no annotated CNV information. We developed a zebrafish CNV map using 80 zebrafish genomes from laboratory strains (AB, Tubingen, and WIK) and one native population, identifying 6,080 CNV elements. Overlapping or adjacent CNVs account for 14.6% of the genome, representing four times the CNV levels from other vertebrates including humans. Highest intra-specific CNV levels were observed for Tubingen, a common laboratory strain due to high fecundity. Tubingen variation likely represents higher initial population size and composite population founders initiating the laboratory strain. Extensive zebrafish CNVs, along with associated phenotypic impacts, advocates for increased usage of isogenic strains for genetic studies intended for human disease translation.
Project description:Copy number variants (CNVs) represent a substantial source of genomic variation in vertebrates, but the zebrafish reference genome has no annotated CNV information. We developed a zebrafish CNV map using 80 zebrafish genomes from laboratory strains (AB, Tubingen, and WIK) and one native population, identifying 6,080 CNV elements. Overlapping or adjacent CNVs account for 14.6% of the genome, representing four times the CNV levels from other vertebrates including humans. Highest intra-specific CNV levels were observed for Tubingen, a common laboratory strain due to high fecundity. Tubingen variation likely represents higher initial population size and composite population founders initiating the laboratory strain. Extensive zebrafish CNVs, along with associated phenotypic impacts, advocates for increased usage of isogenic strains for genetic studies intended for human disease translation.
Project description:Genetic variation is responsible for the generation of phenotypic diversity, including susceptibility to disease. Two major types of variation are known: single nucleotide polymorphisms (SNPs) and a more recently discovered structural variation, involving changes in copy number (CNVs) of kilobase- to megabase-sized chromosomal segments. Variation caused by CNVs has exceeded the amount of SNP-based differences expected to exist between two unrelated humans. Furthermore, many CNVs have been associated with disease predisposition. It is unknown whether CNVs arise in somatic cells, but it is, however, generally assumed that normal cells are genetically identical. Here we show that CNVs are frequent in healthy somatic cells of adult humans. We tested 34 tissue samples from three subjects and, having analyzed for each tissue <10-6 of all cells expected in an adult human, we observed at least six CNVs, affecting a single organ or one or more tissues of the same subject. The CNVs ranged from 82-176 kb, often encompassing known genes, potentially affecting gene function. Our results point to a paradigm shift in the genetics of somatic cells and indicate that humans are commonly affected by somatic mosaicism for stochastic CNVs, which occur in a substantial fraction of cells. A considerable number of phenotypes and diseases affecting humans are a consequence of a somatic process. Thus, our conclusions will be important for the delineation of genetic factors behind these phenotypes. Consequently, biobanks should consider sampling multiple tissues in order to better address mosaicism in the studies of somatic disorders. Furthermore, forensic medicine laboratories should be sensitized to the issue of underestimated frequency of somatic CNV mosaicism. Keywords: copy number variation (CNV), phenotype diversity, somatic cells
Project description:Rare DNA copy-number variation (CNV) plays an important role in the underlying genetic etiology of autism and intellectual disability. Although large numbers of copy-number variants (CNVs) have been recently implicated in autism, most are large affecting many genes and specificity of these lesions with respect to classically defined autism as opposed to more broadly defined developmental delay is unclear. We exploited the repeat architecture of the genome to target smaller regions (n=1340 hotspots, median size 15 kbp) flanked by repetitive sequence among 2,240 autism simplex patients and a subset of unaffected parents.