Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.
Poult Sci. 2010 Mar;89(3):428-38. doi: 10.3382/ps.2009-00428.
Chicken broodiness is a polygenic trait controlled by autosomal genes. Prolactin gene is a candidate of great interest in molecular studies of broodiness. However, another candidate dopamine D2 receptor (DRD2) gene has not been studied extensively. The objective of this study was to analyze the genetic effects of the DRD2 gene on chicken broodiness through linkage disequilibrium analyses, tag SNP selection, genetic diversity observation, 2-tailed test, and association analyses. In this study, we assayed 27 variations of this gene in 456 individuals from 6 chicken populations to observe linkage disequilibrium pattern, the tag SNP, and genetic diversity. Among the 6 populations, Taihe Silkies exhibited no characteristic between the square of the correlation coefficient of gene frequencies (r(2)) and physical distance. The other populations including Red Jungle Fowls, Xinghua chickens, Ningdu Sanhuang chickens (NDH), Baier Huang chickens, and Leghorn layers exhibited conspicuous characteristic of decreasing r(2) value over physical distance. Linkage disequilibrium decayed more rapidly in Red Jungle Fowls, Xinghua, and NDH than in Baier Huang and Leghorn layers. Allelic frequencies and genotype distributions in the 5 populations showed that A-38600G, I-38463D, T-32751C, A-16105G, A-6543G, C-6539T, and A+2794G were possibly associated with broodiness. Besides the above 7 sites, another 2 sites that might be associated with broodiness were screened by 2-tailed test. All 9 sites were used for association analyses with broodiness in 644 NDH chickens. A significant association (P < 0.05) was found between A-16105G and broody frequency (%), and the T+619C in intron 1 was significantly associated with duration of broodiness (P < 0.05). These findings suggested that the DRD2 gene should be included in future genetic studies of chicken broodiness and 2 SNP of A-16105G and T+619C might be markers for breeding against broodiness.
鸡抱窝性是一个由常染色体基因控制的多基因性状。催乳素基因是分子研究抱窝性的一个重要候选基因。然而，另一个候选基因多巴胺 D2 受体（DRD2）基因尚未得到广泛研究。本研究旨在通过连锁不平衡分析、标记 SNP 选择、遗传多样性观察、双尾检验和关联分析，分析 DRD2 基因对鸡抱窝性的遗传效应。本研究在 6 个鸡群体的 456 只个体中检测了该基因的 27 个变异，观察连锁不平衡模式、标记 SNP 和遗传多样性。在 6 个群体中，泰和丝鸡的基因频率平方相关系数（r²）与物理距离之间没有特征性。其他种群包括红原鸡、兴化鸡、宁都三黄鸡（NDH）、柏艾黄鸡和来亨层鸡表现出 r²值随物理距离减小的明显特征。在红原鸡、兴化和 NDH 中，连锁不平衡的衰减速度快于柏艾黄鸡和来亨层鸡。在 5 个群体中，等位基因频率和基因型分布表明，A-38600G、I-38463D、T-32751C、A-16105G、A-6543G、C-6539T 和 A+2794G 可能与抱窝性有关。除了上述 7 个位点外，通过双尾检验还筛选出另外 2 个可能与抱窝性有关的位点。在 644 只 NDH 鸡中，用这 9 个位点与抱窝性进行关联分析。A-16105G 与抱窝频率（%）显著相关（P < 0.05），内含子 1 中的 T+619C 与抱窝持续时间显著相关（P < 0.05）。这些发现表明，DRD2 基因应该包含在未来的鸡抱窝性遗传研究中，A-16105G 和 T+619C 的 2 个 SNP 可能是抗抱窝性育种的标记。
