Sequencing and annotated analysis of full genome of Holstein breed bull.

In the present study, we describe the deep sequencing and structural analysis of the Holstein breed bull genome. Our aim was to receive a high-quality Holstein bull genome reference sequence and to describe different types of variations in its genome compared to Hereford breed as a reference. We generated four mate-paired libraries and one fragment library from 30 μg of genomic DNA. Colour space fasta were mapped and paired to the reference cow (Bos taurus) genome assembly from Oct. 2011 (Baylor 4.6.1/bosTau7). Initial sequencing resulted in the 4,864,054,296 of 50-bp reads. Average mapping efficiency was 71.7 % and altogether 3,494,534,136 reads and 157,928,163,086 bp were successfully mapped, resulting in 60 × coverage. This is the highest coverage for bovine genome published so far. Tertiary analysis found 6,362,988 SNPs in the bull's genome, 4,045,889 heterozygous and 2,317,099 homozygous variants. Annotation revealed that 4,330,337 of all discovered SNPs were annotated in the dbSNP database (build 137) and therefore 2,032,651 SNPs were novel. Large indel variations accounted for the 245,947,845 bp of the variation in entire genome and their number was 312,879. We also found that small indels (number was 633,310) accounted for the total variation of 2,542,552 nucleotides in the genome. Only 106,768 small indels were listed in the dbSNP. Finally, we identified 2,758 inversions in the genome of the bull covering in total 23,099,054 bp of genome's variation. The largest inversion was 87,440 bp in size. In conclusion, the present study discovered different types of novel variants in bull's genome after high-coverage sequencing. Better knowledge of the functions of these variations is needed.