Dataset Information

Computational detection and experimental validation of segmental duplications and associated copy number variants in river buffalo (Bubalus bubalis)

ABSTRACT: Duplicated sequences are the important source of gene innovation and structural variation within mammalian genomes. Using a read depth approach based on next-generation sequencing, we performed a genome-wide analysis of segmental duplications (SDs) and associated copy number variants (CNVs) in water buffalo (Bubalus bubalis). Aligning to the UMD3.1 cattle genome, we estimated 44.6 Mb (~1.73% of cattle genome) segmental duplications in the autosomes and X chromosome using the sequencing reads of Olimpia (the sequenced water buffalo). 70.3% (70/101) duplications were experimentally validated using the fluorescent in situ hybridization. We also detected a total of 1344 CNV regions across 14 additional water buffalos as well as Olimpia, amounting to 59.8Mb of variable sequence or 2.2% of the cattle genome. The CNV regions overlap 1245 genes and are significantly enriched for specific biological functions such as immune response, oxygen transport, sensory system and signalling transduction. Additionally, we performed array Comparative Genomic Hybridization (aCGH) experiments using the 14 water buffalos as test samples and Olimpia as the reference. Using a linear regression model, significant and high Pearson correlations (r = 0.781) were observed between the digital aCGH values and aCGH probe log2 ratios. We further designed Quantitative PCR assays to confirm CNV regions within or near annotated genes and found 74.2% agreement with our CNV predictions.

ORGANISM(S): Bubalus bubalis

PROVIDER: GSE118117 | GEO | 2019/02/28

REPOSITORIES: GEO

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Project description:Genomic structural variation is an important and abundant source of genetic and phenotypic variation. Here we describe the first systematic and genome-wide analysis of copy number variations (CNVs) in modern domesticated cattle using array comparative genomic hybridization (array CGH), quantitative PCR (qPCR) and fluorescent in situ hybridization (FISH). The array CGH panel included 90 animals from 11 Bos taurus, 3 Bos indicus and 3 composite breeds for beef, dairy or dual purpose. We identified over 200 candidate CNV regions (CNVRs) in total and 177 within known chromosomes, which harbor or are adjacent to gains or losses. These 177 high-confidence CNVRs cover 28.1 mega bases or ~1.07% of the genome. Over 50% of the CNVRs (89/177) were found in multiple animals or breeds and analysis revealed breed-specific frequency differences and reflected aspects of the known ancestry of these cattle breeds. Selected CNVs were further validated by independent methods using qPCR and FISH. Approximately 67% of the CNVRs (119/177) completely or partially span cattle genes and 61% of the CNVRs (108/177) directly overlap with segmental duplications. The CNVRs span about 400 annotated cattle genes that are significantly enriched for specific biological functions such as immunity, lactation, reproduction and rumination. Multiple gene families, including ULBP, have gone through ruminant lineage-specific gene amplification. We detected and confirmed marked differences in their CNV frequencies across diverse breeds, indicating that some cattle CNVs are likely to arise independently in breeds and contribute to breed differences. Our results provide a valuable resource beyond microsatellites and single nucleotide polymorphisms to explore the full dimension of genetic variability for future cattle genomic research. The custom aCGH chips that interrogated the whole genome CNVs were build for 90 cattles from diverse breeds, with Hereford L1 Dominette 01449 as refference sample.

Dataset Information

Computational detection and experimental validation of segmental duplications and associated copy number variants in river buffalo (Bubalus bubalis)

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