绵羊PRLR基因内含子9和外显子10多态性与产羔数的关系研究

本研究采用PCR-SSCP技术对绵羊催乳素受体（PRLR）基因内含子9和外显子10部分核苷酸多态性及其与小尾寒羊、中国美利奴（新疆型）绵羊多胎品系、肉用品系、体大品系、萨福克、无角陶赛特、中国美利奴（新疆型）和德国肉用美利奴产羔数间的关系进行了分析。结果发现：①在绵羊PRLR基因内含子9的第259 bp处，存在C→T转换，BB基因型的小尾寒羊平均产羔数分别较AA和AB基因型提高0.81和0.87只（P<0.05）；②在绵羊PRLR基因外显子10的第304 bp处存在一个G→A转换，该突变导致PRLR基因第387位氨基酸残基由Glu突变为Lys，并使中国美利奴（新疆型）多胎品系中AB基因型的平均产羔数较AA和BB基因型增加0.58和0.80只（P<0.05）；③在绵羊PRLR基因外显子10第571、585和606 bp处分别存在G→A、C→G和C→T突变；其中前2处突变分别导致PRLR基因的第476位氨基酸由Ala突变为Thr，第480位氨基酸由Ser突变为Arg。其中第571 bp处突变导致小尾寒羊AB基因型的平均窝产羔数显著高于AA基因型的窝产羔数，增加0.8 只（P<0.05）。以上结果提示，PRLR基因可能是控制小尾寒羊和中国美利奴（新疆型）绵羊多胎品系产羔数的主效基因或与之存在紧密的遗传连锁。

Relationships between Genetic Polymorphisms of Intron 9 and Exon 10 of Prolactin Rceptor Gene and Litter Size of Sheep

In the present research, the genetic polymorphisms of intron 9 and exon 10 of prolactin receptor (PRLR) gene of eight breeds or strains sheep, which including Small Tail Han, Poll Dorset, Suffolk, Germany Mutton Merino and Chinese Merino (Xinjiang type) (including Prolific strain, Meat strain and Large Frame strain), were detected by polymerase chain reaction- single strand conformation polymorphism（PCR-SSCP） and the relationship between genotypes and average litter size were analyzed. The results as follows：①There was a C→T transition at 259 in intron 9 of sheep PRLR gene. In Small Tail Han, the average litter size of BB genotype was 0.81 and 0.87 more than that of AA and AB genotypes respectively (P<0.05). ②There was a G→A transition at 304 in exon 10 of PRLR gene and this mutation cause an amino acid residue change of Glu→Lys at No. 387 of PRLR. Further research showed that average litter size of Chinese Merino (Xinjiang type) Prolific strain ewes with AB genotype was 0.58 and 0.80 more than that of ewes with AA and BB genotypes respectively (P<0.05). ③Moreover, three mutations (571G→A，585C→G and 606C→T) were identified in exon 10 of PRLR gene. The former two mutations resulted in two amino acid residues change of Ala→Thr and Ser→Arg at No. 476 and 480 of PRLR. In Small Tail Han, the average litter size of AB genotype of the 571G→A mutation increased 0.8 than that of AA genotype (P<0.05). These results preliminarily indicated that the prolactin receptor locus was either a major gene that influences the prolificacy in Small Tail Han sheep and Chinese Merino (Xinjiang type) prolific strain sheep or was in close linkage with such a gene.