猪MC4R基因Asp298Asn位点的多态性及其与商品猪背膘厚的关系

黑素皮质素受体4 ( melanocortin 4 receptor, MC4R) 是G 蛋白耦联受体( G protein coupled receptors,GPCRs) 超家族的一个成员, 在人和小鼠的体重、能量稳态和采食量的调控中发挥重要作用。本研究采用PCR-RFLP技术对MC4R的298位点错义突变（Asp298Asn）在莱芜猪、大莱二元杂交猪和商品猪中的多态性进行了检测，对该突变与商品猪背膘厚的关系进行了关联分析。结果表明，在33头莱芜猪中只检测到11基因型，而在大莱二元杂交猪和商品猪中11、12和22基因型均有分布，且等位基因1的频率均高于等位基因2；在该突变位点三个群体均处于Hardy-Weinberg平衡状态（P>0.05）。商品猪不同基因型个体背膘厚差异显著，22基因型个体的背膘厚显著高于12基因型（P <0.01）和11基因型（P <0.05）个体。因此，MC4R基因298位点的Asp298Asn错义突变与商品猪的背膘厚有关，可以作为以西方猪种为杂交亲本的商品猪背膘厚的分子标记。

Polymorphism of MC4R Asp298Asn Site and Its Relationship with Backfat Thickness in Commercial Pigs

Melanocortin- 4 receptor (MC4R) is a member of the superfamily of G protein coupled receptors (GPCRs), which affects body weight, energy homeostasis and food intake in human and mouse. In this study, the Asp298Asn polymorphism of MC4R gene in Laiwu, Yorkshire×Laiwu and commercial crossbred pig populations was investigated using PCR-RFLP method, and, the relationship of this mutation with backfat thickness was analyzed. The results indicated that only genotype 11 exist in 33 individuals of Laiwu pigs, whereas in Yorkshire×Laiwu and commercial crossbred populations, three genotypes of 11, 12 and 22 were detected. The distributions of allele and genotype frequencies in Yorkshire×Laiwu and commercial crossbred populations were similar with the frequency of allele 1 being higher than that of allele 2. All of the three populations were at Hardy-Weinberg equilibrium with respect to this mutation site（P>0.05）. In commercial crossbred pigs, individuals with genotype 22 had significant higher backfat thickness than the ones with genotypes 12 and 11 (P < 0.05). This study provide evidence that the Asp298Asn polymorphism of MC4R is associated with backfat thickness in commercial crossbred pigs with western pigs as parental lines, and therefore, can be used as a DNA marker for pig breeding in such kind of populations.