Polymorphism of the porcine CGA gene and its association with growth and carcass traits

Glycoprotein hormones in the pituitary gland affect a myriad of biological processes such as development, growth, metabolic control and gametogenesis. The quantitative trait loci (QTL) near their common glycoprotein alpha(A) subunit gene (CGA) have been reported inconsistently. The aim of this study was to dissect potential genetic factors for these unstable results and validate the association or linkage relationship of CGA gene with growth and carcass traits. By resequencing all the exons and part of the introns of the porcine CGA gene, 22 polymorphisms in total were identified in this study. Five single nucleotide polymorphism (SNP) markers were chosen and evaluated in six pure-bred pig breeds (n = 228). Breed-specific haplotypes were found and a map of the porcine CGA polymorphisms' evolution history was inferred. A resource family (n = 365) with different genetic backgrounds from those used in other papers was used to perform an association study. The resource family was created based on crosses of Pietrain and Jinhua pigs (Central China type pigs). Results indicated that a low correlation between haplotype blocks may abolish each other's effects. Moreover, a significant association of SNP C-925T with growth rate and back-fat thickness in this study confirmed the existence of previously reported QTL. SNP C-925T and SNP A+15599G could be useful linkage markers and SNP C-925T may also be a candidate causative SNP for the corresponding traits. Further investigation for variants within of the CGA promoter region and their association with growth rate and back-fat traits is suggested.