甘肃肉羊新品种选育群GnRHR基因多态性及其与产羔性状关联分析

Polymorphism of GnRHR Gene and Its Relationship with Litter Size Trait of Gansu Meat Sheep New Breed Population

根据GenBank发布的绵羊促性腺激素释放激素受体(gonadotropin releasing hormone receptor,GnRHR)基因序列设计2对引物,采用聚合酶链式反应-单链构象多态性(PCR-SSCP)技术分析GnRHR基因外显子2和3在甘肃肉羊新品种选育群中的单核苷酸多态性,并与产羔性状进行关联分析。结果表明,在甘肃肉羊新品种选育群GnRHR基因外显子2检测到GG、GH、HH基因型,基因型频率分别为0.784(160)、0.206(42)0、.010(2),序列测序结果发现在编码区第198位碱基发生突变G→C,导致G变成R(甘氨酸→精氨酸)变化;GnRHR基因外显子3检测到MM、MN基因型,基因型频率分别为0.882(180)0、.118(24),序列测序结果发现在第257位碱基发生突变A→G,导致Q变成R(谷氨酰胺→精氨酸)。GnRHR基因外显子2突变对新品种群羊繁殖力高低影响极显著,突变纯合基因型(HH)绵羊平均产羔数比野生纯合型(GG)多0.981只(P=0.006<0.01);外显子3突变对新品种群羊繁殖力高低也有显著影响,MN基因型羊平均产羔数比MM基因型多0.688只(P=0.029<0.05)。由此可推测GnRHR基因可能是控制新品种群羊产羔性能的一个主效基因或是与之存在紧密连锁的一个遗传标记。

The GnRHR gene was studied as a candidate gene for the high prolificacy of sheep.Two pairs of primers were designed according to the sequence of exon 2 and exon 3 of GnRHR gene published in Genbank.Single nucleotide polymorphisms（SNPs）of exon 2 and exon 3 of GnRHR gene were detected in Gansu meat sheep new breed population and Poll Dorset by polymerase chain reaction（PCR）-single strand conformation polymorphism（SSCP）.The results showed that there were three genotypes（GG,GH and HH）detected in GnRHR gene exon 2 of the new breed population,frequencies of GG,GH and HH genotypes were 0.784（160）,0.206（42）,0.010（2）,respectively.The polymorphic fragment amplified was sequenced and there was one nucleotide mutation（G→C）at cDNA 198 of GnRHR gene,the mutation resulted amino acid change（Gly→Arg）.and the difference of litter size among GG adn HH was very significant（P0.01）.Another mutation（A→G）was found in GnRHR exon 3 at cDNA 257,the mutation resulted in amino acid change（Gln→Arg） and the difference of litter size among MM and MN was significant（P0.05）.So the GnRHR gene may be one of the main effective gene controlling the prolificacy of Gansu meat sheep new breed population or a genetic marker linked with it closely.