Genetic Variation Of Pituitary Gland Transcriptional Factors SIX3 & SIX6 Genes In Yellow Cattle And Their Association With Growth Traits

Mixture DNA pools sequencing, PCR-SSCP, PCR-RFLP and PCR-ACRS techniques were applied to detect SNPs of anterior pituitary key transcriptional factors SIX3 and SIX6 genes in 1075 individuals from five cattle populations (Nanyang, Qinchuan, Jiaxian Red cattle, Chinese Holstein and Hasake cattle), subsequently analyzed their genetic structure and diversity in these populations as well as association with growth traits of three Chinese cattle (Nanyang, Qinchuan and Jiaxian Red cattle). The objects were to discovery the hereditary characteristics and to explore molecular markers with significant effects on economic important traits for efficient selection and improvement of Chinese cattle, and to provide genetic information for foundation of molecular marker database, protection and usage of breed resource of Chinese cattle. Meanwhile, the space secondary structure and domain of bovine SIX6 homeoprotein were predicted by biological software so as to study the change of structure for the effects of functionThe results were as follows:1 Association between genetic variation of SIX3 gene in five breeds of cattle and growth traits in Nanyang, Jiaxian and Qinchuan cattlePolymorphisms of SIX3 gene within all exon, partial intron and flanking region were detected in five cattle population. Two novel SNPs (IVS1+2791:g.T>C, IVS1+2699:g.G>A) were identified in intron1 for the first time. There were three genetypes in the Alw26I-RFLP loci of SIX3 gene: TT, TC and CC. Genetype CC were not dected in Qinchuan cattle. The frequency of C allele varied from 0.025 to 0.386 in Qinchuan, Nanyang, Jiaxian Red, Chinese Holstein and Hasake cattle respectively. There were three genetypes in the TaqI-ACRS-RFLP loci of SIX3 gene: GG, GA and AA. Genetype AA just were dected in Chinese Holstein and Hasake cattle, the frequency of allele A respectively were 0.042, 0.046, 0.044, 0.309 and 0.375 in Qinchuan, Nanyang, Jiaxian Red, Chinese Holstein and Hasake cattle. Theχ2 test showed that Chinese Holstein and Hasake population were in Hardy-Weinberg disequilibrium (P<0.05) at these two locus. Theχ2 test of genotype distributions showed that there was significant difference between Chinese Holstein, Hasake cattle and Qinchuan, Nanyang, Jiaxian Red cattle.(P<0.01). The result of linkage disequilibrium analysis in the five cattle population indicated that there was an intermediate linkage in Chinese Holstein population (r2>0.3).The model of GLM analysis result between Alw26I-RFLP loci with TaqI-ACRS-RFLP loci and growth traits showed that different genotypes significantly affect on body weight and average daily gain at 18months old in Nanyang cattle (P<0.05), and the individuals with GG-TC genotype had greater body weight and average daily gain than GG-CC at 18 months old. Therefore, SIX3 gene was considered as the candidate SNP of growth traits.2 Association between genetic variation of SIX6 gene in five breeds of cattle and growth traits in Nanyang, Jiaxian and Qinchuan cattlePolymorphisms of SIX6 gene within all exon, partial intron and flanking region were detected in five cattle population. A novel mutation (NC₀07308: g 2015T>C) in TGA stop-codon of bovine SIX6 gene was found, which lead to the ORF shift and extension of the encoded protein for four amino acids (Arg223-Gln224-Arg225-Val226). Another mutation (NC₀07308: g 2068A>T) were dected in mRNA 3'untranslate region. There were three genetypes in the HhaI- ACRS-PCR loci of SIX6 gene: TT, TC and CC. the frequency of allele C respectively were 0.263, 0.262, 0.310, 0.255 and 0.614 in Qinchuan, Nanyang, Jiaxian Red, Chinese Holstein and Hasake cattle. There were also moderate polymorphic in this locus in this five populations (0.25