Novel mutation in TGA stop-codon of bovine SIX6 gene

Abstract

As a transcriptional regulatory gene of the SIX family, SIX6 (also known as OPTX2, SIX9), probably affects pituitary development and secretion of hormones, suggesting that this gene is a potential candidate gene for studying association with growth trait in animals. Therefore, this study is first of all focused on detecting sequence variations in a bovine SIX6 gene and on its effects on growth traits in 1087 cattle from five Chinese cattle breeds using DNA sequencing and HhaI-ACRS-PCR methods. Herein, a novel mutation (NC_007308: g 2015T > C) in the TGA stop-codon of a bovine SIX6 gene was found, which leads to an ORF shift and extension of the encoded protein for four amino acids (Arg223-Gln224-Arg225-Val226). The frequency of allele "C" varied from 0.255 (Chinese Holsteins) to 0.614 (Hasake). They all were in the Hardy-Weinberg equilibrium except Jiaxian Red and Hasake cattle. Using amino acid sequence alignment and online prediction software, a new helix in the C-terminal domain of the mutated bovine SIX6 protein was revealed, which possibly affects pituitary development and hormone secretion. So, relationship analysis between this polymorphism and growth traits in the Nanyang breed was carried out based on a proper linear model. Although no statistically significant associations were observed (P > 0.05), the presented work preliminarily demonstrated a novel mutation in the TGA stop-codon which extends the spectrum of genetic variations of the bovine SIX6 gene and might be of interest in terms of its association with other biophysical and biochemical indexes.