Genome-Wide Association Studies for Immunoglobulins in Colostrum and Serum in Chinese Holstein

Abstract

<jats:title>Abstract</jats:title> <jats:p><jats:bold>Background</jats:bold>Immunoglobulins (Igs) are important components of the innate immune system, and fight pathogens as a part of the first defense line. Newborn dairy calves get maternal antibodies from colostrum. Therefore, contents of immunoglobulins in colostrum and serum of cows are essential traits when estimating potential natural disease resistance of calves. In this study, a genome-wide association study (GWAS) was performed to identify candidate genes that are responsible for the observed genetic variation of immunoglobulins contents in colostrum and blood in Holstein cows.<jats:bold>Results</jats:bold>Colostrum, blood and hair follicle samples were collected from the 620 Chinese Holstein cows within 24 hours after calving. The concentration of IgG, IgG1, IgG2, IgA and IgM in both colostrum and serum were detected via ELISA methods, respectively. Using GCTA software, GWASs were performed with 88,934 SNPs genotyped by using Illumina 50K (54,609 SNPs) and GeneSeek 150K (140,668 SNPs) chips in which 50K chip were imputed to 150K SNPs with BEAGLE 3.0.4 software. As a result, 20 and 5 SNPs were detected genome-wide significantly associated with contents of the IgG and IgM in colostrum and serum (P&lt;3.16E–6). In addition, 57, 11 and 10 SNPs were suggestive significantly associated with IgG, IgA and IgM traits (P&lt;6.32E–5). Next, a total of 1,083 functional genes were identified that included or adjacent to these significant SNPs with a distance less than 1 Mb. Functional enrichment analysis showed that these genes were involved in immune related pathways, such as immune response, Fc gamma R-mediated phagocytosis, negative regulation of immunoglobulin secretion, humoral immune response, Fc-epsilon receptor and NF-kappaB signaling pathways. By integrating analysis of the functional enrichment and the known QTL data, we identified 21 candidate genes associated with contents of immunoglobulins in colostrum and serum, including<jats:italic> ABR, TIMM22, CRK, MYO1C, RILP, SERPINF2, AKT1, BCL11B, HHIPL1, DYNC1H1, HSP90AA1, TRAF3, KLC1, IL6, PYCARD, ITGAM, TGFB1I1, GUSB, CRCP, RABGEF1</jats:italic> and <jats:italic>SBDS</jats:italic>.<jats:bold>Conclusions</jats:bold>In this study, we identified 21 candidate genes associated with immunoglobulins level in colostrum and serum in dairy cattle. This founding demonstrated the possibility of increasing immunity through selective breeding and provided an important information for molecular breeding of dairy cattle.</jats:p>