A synaptojanin 1 (SYNJ1) single nucleotide polymorphism not responsible for polledness in German Holstein, Limousin, Charolais and Pinzgauer cattle

Genome-wide association study provides insights into genes related with horn development in Nelore beef cattle

The causal mutation for polledness in Nelore (Bos taurus indicus) breed seems to have appeared first in Brazil in 1957. The expression of the polled trait is known to be ruled by a few groups of alleles in taurine breeds; however, the genetic basis of this trait in indicine cattle is still unclear. The aim of this study was to identify genomic regions associated with the hornless trait in a commercial Nelore population. A total of 107,294 animals had phenotypes recorded and 2,238 were genotyped/imputed for 777k SNP. The weighted single-step approach for genome-wide association study (WssGWAS) was used to estimate the SNP effects and variances accounted for by 1 Mb sliding SNP windows. A centromeric region of chromosome 1 with 3.11 Mb size (BTA1: 878,631–3,987,104 bp) was found to be associated with hornless in the studied population. A total of 28 protein-coding genes are mapped in this region, including the taurine Polled locus and the IFNAR1, IFNAR2, IFNGR2, KRTAP11-1, MIS18A, OLIG1, OLIG2, and SOD1 genes, which expression can be related to the horn formation as described in literature. The functional enrichment analysis by DAVID tool revealed cytokine-cytokine receptor interaction, JAK-STAT signaling, natural killer cell mediated cytotoxicity, and osteoclast differentiation pathways as significant (P < 0.05). In addition, a runs of homozygosity (ROH) analysis identified a ROH island in polled animals with 2.47 Mb inside the region identified by WssGWAS. Polledness in Nelore cattle is associated with one region in the genome with 3.1 Mb size in chromosome 1. Several genes are harbored in this region, and they may act together in the determination of the polled/horned phenotype. Fine mapping the locus responsible for polled trait in Nelore breed and the identification of the molecular mechanisms regulating the horn growth deserve further investigation.

Associations of single nucleotide polymorphisms in candidate genes with the polled trait in Datong domestic yaks

The domestic yak (Bos grunniens) is an iconic symbol of animal husbandry at high altitudes. Yaks exhibit unique external characteristics including long hair and large horns. However, hornless yaks can be found in different breeds and different populations. The hornless trait is also known as polled, and the POLL locus has been fine-mapped to chromosome 1 in cattle (Bos taurus), although the underlying genetic basis of the polled trait is still unclear in the yak. Thus, we performed an association study to identify the genetic polymorphisms responsible for the polled trait in the yak. Fifty polled Datong domestic yaks and 51 horned individuals were selected randomly from a huge herd and were used as the case and control groups respectively for the association analysis. Twelve genes located in the candidate region of the POLL locus in cattle were used as references to detect DNA polymorphisms related to yak polledness, which were analyzed by sequencing and a high-resolution melting test. We applied Fisher's exact test and haplotype analysis to show that a 147-kb segment that included three protein-coding genes C1H21orf62, GCFC1 and SYNJ1 was the most likely location of the POLL mutation in domestic yaks.