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

Abstract

BackgroundThe early death and health problems of calves caused substantial economic losses in dairy industry. As the immune system has not been fully developed in the neonates, transport of passive immune substance such as immunoglobulins (Ig) from mothers to newborn calves is essential in protecting neonates from infections in their early life. Therefore, concentrations of immunoglobulins in the colostrum and serum of dairy cows are critical traits when estimating potential disease resistance of its offspring. ResultsColostrum, blood and hair follicle samples were collected from the 620 Chinese Holstein cows within 24 hours after calving. The concentration of total IgG, IgG1, IgG2, IgA and IgM in both colostrum and serum were detected via ELISA methods. With GCTA software, genome-wide association studies (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. As a result, 20, 1 and 4 significant SNPs were detected associated with the concentrations of IgG2, IgA and IgM at genome-wide level (P < 3.16E–6); 11, 11, 35, 11 and 10 significant SNPs were identified associated with total IgG, IgG1, IgG2, IgA and IgM at suggestive level (P < 6.32E–5). Such SNPs were located in or proximate to (±1 Mb) 1,083 genes, which were functionally implicated in biological processes and pathways, such as immune response, negative regulation of immunoglobulin secretion, Fc-epsilon receptor and NF-kappaB signaling pathways. By combining the biological functions and the known QTL data for immune traits in bovine, 21 promising candidate functional genes were identified for immunoglobulins concentrations in colostrum and serum in dairy cattle, they were ABR, TIMM22, CRK, MYO1C, RILP, SERPINF2, AKT1, BCL11B, HHIPL1, DYNC1H1, HSP90AA1, TRAF3, KLC1, IL6, PYCARD, ITGAM, TGFB1I1, GUSB, CRCP, RABGEF1 and SBDS.ConclusionsIn this study, we identified 21 candidate genes related to concentrations of immunoglobulins in colostrum and serum in dairy cattle by performing GWASs. Our findings provide a groundwork for unraveling the key genes and causal mutations affecting immunoglobulins levels in colostrum and important information for genetic improvement of such traits in dairy cattle.