Allele mining in gene encoding fc fragment of IgG receptor, transporter, alpha (FCGRT) and association of nucleotide variants with passive transfer of immunity in neonatal buffalo calves.

BACKGROUND: Neonatal Fc receptors (FcRn) mediate the transcytosis of IgG present in colostrum across absorptive gut epithelium of newborn calves. FcRn receptor is a heterodimer composed of two polypeptides encoded by FCGRT (Fc fragment of IgG Receptor Transporter neonatal) and B2M (Beta 2 microglobulin) genes. Polymorphism in FCGRT gene may have a bearing on absorption of colostral immunoglobulins by neonatal buffalo calves, thereby affecting their immune status and susceptibility to diseases. The primary aim of our study was to mine alleles and single nucleotide polymorphs in the FCGRT gene and determine their association with the levels of IgG in serum of neonatal buffalo calves. METHODS AND RESULTS: On the basis of serum IgG levels estimated by indirect ELISA in 80 newborn calves, 20 calves each with highest and lowest IgG concentration were selected to study polymorphism in the FCGRT gene. The exonic regions of this gene were amplified in nine fragments which were subjected to PCR-SSCP to detect variations followed by the sequencing of variants to locate the SNPs. A total of nine SNPs (7 in introns and 2 in exons) were detected in four polymorphic fragments. Association study based on Odds ratios (ORs) with 95% Confidence Interval (CIs) established that the SNP G40T in fragment 3 has a significant (P < 0.05) bearing on IgG level in serum of neonatal buffalo calves. CONCLUSION: Genetic variation in FCGRT gene in buffalo calves was found to be associated with their serum IgG levels in neonatal stage which may have implications in calf survival and growth vis-à-vis inadequate transfer of passive immunity.

Detection of nucleotide variants in FCGRT (Fc fragment of IgG, receptor, transporter, alpha) gene and their influence on colostral IgG concentration in Indian water buffalo (Bubalus bubalis).

BACKGROUND: The neonatal Fc receptors (FcRn) mediate the transfer of immunoglobulin G (IgG) molecules from a dam's circulation to the colostrum produced by it immediately after parturition. In ruminants, the calves born are agammaglobulinemic therefore, ingestion of colostrum with high concentration of IgG imparts passive immunity to the newborn. The FcRn molecule is a heterodimer, coded by FCGRT (Fc fragment of IgG Receptor Transporter neonatal) and B2M (Beta 2 microglobulin) genes. Present study attempted to identify single nucleotide polymorphisms (SNPs) in the FCGRT gene in 40 buffaloes of Murrah breed and evaluated the association of these nucleotide variations and haplotypes with IgG concentration in their colostrum. METHODS AND RESULTS: Animals producing colostrum with high IgG and low IgG levels were identified by indirect ELISA and selected. SNPs were detected in the FCGRT gene sequence of selected animals by amplifying it in nine fragments covering all exons (with flanking introns) followed by PCR-single strand conformational polymorphism (PCR-SSCP). A total of nine SNPs were observed of which seven were present in flanking introns and two in exon 4 of the gene. The SNP A75G was non-synonymous and produced an amino acid change from isoleucine to valine. The exonic SNPs and corresponding haplotypes were found to be significantly (P < 0.01 and 0.05 respectively) associated with colostral IgG concentration based on Odds ratios at 95% confidence interval. CONCLUSION: Polymorphism in FCGRT gene is found to be associated with IgG concentration in colostrum and identification of females with desirable variations may prevent failure of passive transfer in neonatal ruminants.