247 Unraveling molecular functions underlying age at puberty in a composite beef cattle population.

Abstract The objective of this study was to identify genomic makers associated with age at puberty in a composite beef cattle breed. The data used consisted of 3,902 Composite Gene Combination animals (CGC; 1/2 Red Angus, 1/4 Charolais, 1/4 Tarentaise) born from 2002 to 2015 genotyped with Illumina BovineSNP50. Phenotypic records of age at puberty were analyzed for 1,365 heifers. Pedigree information tracing back up to 4 generations consisted of 4,983 records. A single-step GBLUP approach was applied to identify candidate regions and markers associated with the age at puberty. SNP markers were weighted based on three iterations, the variance of which was used to emphasize genomic regions in each iteration. Genomic regions explaining more than 0.5% were assumed to be significantly associated with the age at puberty based on visual inspection of the Manhattan plots. The results indicated that peaks on chromosomes 1, 3, 14, and 24 were associated with age at puberty in CGC cows. The largest peak was observed in BTA14, and multiple protein-coding candidate genes in that region could explain such relationships. The enriched genes list includes CHD7, CLVS1, RAB2A, EMILIN2, among others. Additionally, this window contains regions annotated as long noncoding RNAs, which could also be modulating target genes associated with age at puberty. Similar features were identified for other windows associated with the trait. Given the complexity and multifactorial basis of fertility traits, such as age at puberty, further work on genome annotation, including functional and pathway analysis of enriched regions, is planned. The findings from this study provide insights for enhancing the detection of genomic variants influencing complex traits in livestock and that using weighted approaches may help emphasize important regions.