绵羊季节性繁殖相关基因TSHR外显子多态性研究

Study on Exon Polymorphism of Seasonal Breeding Related Gene TSHRin Sheep

旨在研究乌珠穆沁羊与湖羊这两种具有不同繁殖性能和发情周期绵羊的促甲状腺激素受体（Thyroid stimulating hormone receptor,TSHR）基因外显子区遗传变异特性及其构建的单倍型在品种间的分布和对mRNA和蛋白质二级结构的影响,为进一步揭示其对TSHR表达调控的影响及表型效应奠定基础。本研究采用直接测序的方法对中国蒙古系2个绵羊品种共172个个体TSHR基因的遗传变异情况进行分析。共发现了6个突变位点,独立性卡方检验发现SNP1、SNP3、SNP4和SNP5 4个多态位点的基因型在两个绵羊群体间的分布存在极显著差异（P〈0.01）,其中SNP5为错义突变,其余为同义突变;对这4个位点进行连锁不平衡分析发现,SNP3和SNP4两个位点完全连锁,其余位点两两之间存在不同程度连锁关系;生物信息学分析发现不同的单倍型使TSHR基因的mRNA二级结构发生改变,SNP5使受体蛋白的二级结构发生改变。结果提示：（1）TSHR基因外显子区存在4个在两个绵羊品种中具有潜在生物学功能和表型效应的突变位点,可组成H1～H6共6种单倍型,其中H1（CGCC）和H4（TTTG）分别在乌珠穆沁羊和湖羊群体中为优势单倍型,这可能与这两种绵羊不同的发情周期有关。（2）外显子区SNP5位点突变影响mRNA和蛋白质二级结构的稳定性,可能是具有潜在表型效应的重要功能位点。

The study aimed to investigate the genetic variation of thyroid stimulating hormone receptor（TSHR）gene in Ujumqin sheep and Hu sheep,which had different reproductive performance and oestrous cycle,and the distribution of different haplotypes caused by the polymorphic site and its effects on mRNA and secondary structure of protein.This study provided a theoretical basis for seeking the influence of the mutation on TSHRgene expression and phenotype.Direct sequencing was taken to study genetic variation of the TSHR gene in 172 sheep of 2Chinese Mongolian sheep strains.6mutant sites were found and genotyped.Chi-square test for independence was performed to find the genotypes of the 4SNPs（SNP1,SNP3,SNP4 and SNP5）which were significantly different between the 2sheep populations（P0.01）.The SNP5 was missense mutation,the other sites were synonymous mutations.Linkage disequilibrium analysis was used to screen the 4sites,complete linkage happened between SNP3 and SNP4,and the other sites present different degrees of interlocking relationship.Bioinformatics analysis revealed that not only the mutations occured in the TSHR,but also different haplotypes could result in the changes of mR-NA and the secondary structure of protein.These results indicate that：（1）The genotypes distribution of 4sites in TSHRgene have significant differences between the 2sheep populations.They form 6haplotypes,among which H1（CGCC）is the advantage haplotype in Ujumqin sheep,and H4（TTTG）is the advantage haplotype in Hu sheep.（2）The SNP5 site affects the stability of mRNA and protein secondary structure of TSHRgene,which may be one of the important functional sites with potential phenotypic effects.