Analysis of Fcgrt gene polymorphism in indigenous Chinese sheep and its association with colostrum IgG concentration

The neonatal Fc receptor (FcRn) plays an important role in regulating IgG homeostasis in the body and passive protection to the offspring. Changes in FcRn expression levels caused by genetic polymorphisms of Fcgrt, which encodes FcRn, may lead to inter-individual differences in colostrum IgG levels in sheep. In this study, we sequenced the FcRn partial heavy chain from 179 sheep from Xinjiang Province, China, and detected the differences in colostrum IgG levels and Fcgrt genotypes to identify the correlation between the Fcgrt genotype and colostrum IgG levels in 4 sheep breeds. The DNA sequencing of a 680-bp fragment of the Fcgrt gene revealed various patterns depending on the single-strand conformation in the Suffolk breed. Sequencing analysis revealed a total of 3 patterns, AA, BB, AB, in this fragment, among which the absence of AB and BB genotype acted as a marker for breed identification and characterization, while the AA genotype was shared by Suffolk and 3 other breeds. The only allele found in all 4 breeds was allele A, indicating that natural selection may be favoring the AB and BB genotypes in general and B allele in particular, as the colostrum IgG concentration was relatively higher in the Suffolk breed compared to the other 3 breeds.