Showing results for: [ Animal Developmental and Reproductive Biology ]
X chromosome variants are associated with male fertility traits in two bovine populations. Fortes, Porto-Neto et al. 2020.
Twenty-five phenotypes were measured as indicators of bull fertility (1099 Br... moreahman and 1719 Tropical Composite bulls). Measurements included sperm morphology, scrotal circumference, and sperm chromatin phenotypes such as DNA fragmentation and protamine deficiency. We estimated the heritability of these phenotypes and carried genome-wide association studies (GWAS) within breed, using the bovine high-density chip, to detect quantitative trait loci (QTL). Our analyses suggested that both sperm DNA fragmentation and sperm protamine deficiency are heritable (h2 ranging from 0.10 to 0.22). To confirm these first estimates of heritability further studies on sperm chromatin traits, with larger datasets are desirable. Our GWAS identified QTL for bull fertility traits, based on at least five polymorphisms (P < 10-8) for each QTL. Most of the significant polymorphisms detected in both breeds were on the X chromosome. The QTL were breed-specific, but for some traits, a closer inspection of GWAS results revealed suggestive SNP associations (P < 10-7) in both breeds. For example, the QTL for inhibin in Braham could be relevant to Tropical Composites too (many polymorphisms reached P < 10-7 in the same region). The QTL for sperm midpiece morphological abnormalities on X (QTL peak at 4.92 Mb, P < 10-17) is an example of a breed-specific QTL, supported by several significant SNPs (P < 10-8) in Brahman, but absent in Tropical Composites. The reported GWAS results add evidence to the mammalian specialization of the X chromosome, which during evolution has accumulated genes linked to spermatogenesis. Some of the polymorphisms on X were associated to more than one genetically correlated trait (correlations ranged from 0.33 to 0.51). Correlations and shared polymorphism associations support the hypothesis that these phenotypes have the same underlying cause, i.e. defective spermatogenesis. Genetic improvement for bull fertility is possible through genomic selection, which is likely more accurate if the QTL on X are considered in the predictions. Polymorphisms associated with male fertility accumulate on X in cattle, as in humans and mice, suggesting specialization of this chromosome.less
MLA: L.GEN.1818 Bull fertility update: historical data, new cohort and advanced genomics - Livestock genetics and genomics - Published 20 Jul 2020