Exome of Holstein Friesian Cows. Bos taurus

Despite the large amounts of transcriptome data generated for many non-model organisms, there has been a much lesser uptake of individual genomic sequencing for detecting SNPs and determining haplotypes in these species. Transcriptome data represents a source of variant information, specifically for coding DNA, however there is little information on the accuracy, coverage and limitations of using transcriptomic data for the identification of single nucleotide polymorphisms (SNPs) in non-model organisms. To investigate this, we generated the first whole exome design for bovine using the Roche Nimblegen Developer system (Roche, USA) and used it to sequence and call SNPs from a lactating dairy cow model with genetically divergent fertility phenotypes (Fert+, n=8; Fert-, n=8). We compared these results to SNPs called from liver and muscle transcriptomes from the same animals. Our exome demonstrated 99.1% coverage of the target design of 56.7MB, whereas the transcriptomes only covered 60 and 54.5% of 44.2 and 42.8MB in liver and muscle respectively. We found that specificity of SNP detection in the transcriptome data is ~75% following basic hard-filtering, but could be increased marginally to ~80% by increasing the minimum threshold of reads covering a SNP, and number of samples in which it was found. Functional annotation of non-synonymous SNPs specific to both the high and low fertility phenotype identified immune response-related genes, supporting previous work that identified this process as key to the phenotype. Overall design: 16 samples total; 8 Fert+ ('high fertility'), 8 Fert- ('low fertility')