Takeuchi S, Suzuki H, Yabuuchi M, Takahashi S
Department of Biology, Faculty of Science, Okayama University, Japan.
Biochim Biophys Acta. 1996 Aug 14;1308(2):164-8. doi: 10.1016/0167-4781(96)00100-5.
The Extended black (E) locus on chromosome 1 acts within the melanocyte to regulate feather color pigmentation in the chicken. Several alleles exhibiting different pigmentation have been described and their phenotypes are similar to those of the murine extension locus which encodes melanocortin 1-receptor (MC1-R), the receptor for alpha-melanocyte-stimulating hormone (alpha-MSH). To investigate whether the MC1-R gene is responsible for E-locus function, we examined the structure of MC1-R in E-locus mutants by RFLP analysis and genomic DNA sequencing. In the most recessive allele (ey), which exhibits a uniformly red-yellow pigmentation, MC1-R was found to contain amino acid substitutions possibly causing functional deficiency. On the other hand, in the most dominant allele (E), which confers a uniformly black pigmentation, MC1-R possessed mutation responsible for a constitutively active MC1-R and resultant black coat color in mice. Our finding that the structure of MC1-R was affected by individual E-locus alleles strongly suggests that MC1-R is associated with the E-locus. Furthermore, since the same mutation of MC1-R was found in mice and chickens that exhibit the same pigmentation, it is possible that the regulatory mechanism of MC1-R function is shared in chickens and mammals.
位于1号染色体上的扩展黑色（E）基因座在黑素细胞内发挥作用，调节鸡的羽毛色素沉着。已经描述了几个表现出不同色素沉着的等位基因，它们的表型与编码黑素皮质素1受体（MC1-R）的小鼠扩展基因座的表型相似，黑素皮质素1受体是α-黑素细胞刺激激素（α-MSH）的受体。为了研究MC1-R基因是否负责E基因座的功能，我们通过RFLP分析和基因组DNA测序检查了E基因座突变体中MC1-R的结构。在表现出均匀红黄色素沉着的最隐性等位基因（ey）中，发现MC1-R含有可能导致功能缺陷的氨基酸替换。另一方面，在赋予均匀黑色色素沉着的最显性等位基因（E）中，MC1-R具有导致小鼠组成型活性MC1-R和由此产生的黑色皮毛颜色的突变。我们发现MC1-R的结构受单个E基因座等位基因的影响，这强烈表明MC1-R与E基因座相关。此外，由于在表现出相同色素沉着的小鼠和鸡中发现了相同的MC1-R突变，因此MC1-R功能的调节机制在鸡和哺乳动物中可能是共享的。
