Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Kitaku Tsushimanaka, Okayama 700-8530, Japan.
Gen Comp Endocrinol. 2011 Mar 1;171(1):46-51. doi: 10.1016/j.ygcen.2010.12.018. Epub 2010 Dec 25.
Feather coloration in chickens mainly depends on melanin produced by melanocytes located in the feather follicles. The melanocortin 1 receptor (MC1R) on follicular melanocytes regulates melanin synthesis; however, the source of the melanocortins that interact with the receptors remains unclear. In this study, we examine the potential expression of melanocortins and characterize the mRNAs for the precursor pro-opiomelanocortin (POMC) in chicken feather follicles. Reverse transcription-polymerase chain reaction (RT-PCR) revealed the expression of mRNAs for POMC, prohormone convertase 1 (PC1) and PC2, and western blotting detected adrenocorticotropic hormone (ACTH)-related products of POMC processing in feather follicles, suggesting that melanocortins are produced locally in the tissues of chickens. A combination of 5'RACE (rapid amplification of cDNA 5' end), 3'RACE and RT-PCR analyzes identified two classes of POMC mRNA, class a and class b, which encode the same full-length POMC protein but have different non-coding leader exons. Class a mRNAs were expressed specifically in feather follicles, whereas class b mRNAs were expressed in the pituitary, hypothalamus, and various peripheral tissues that we examined. Within the feather follicles, the class a mRNAs were distributed in epidermal layers from middle to distal locations, whereas the class b mRNAs were mainly expressed in pulp at proximal locations. Our findings suggest that feather pigmentation is regulated by locally produced melanocortins, and indicate that the melanocortins encoded by the different classes of POMC mRNAs may play different intra-follicular roles in chickens. This is the first report that demonstrates alternative promoter usage generating different full-length POMC mRNAs in vertebrates.
鸡的羽毛颜色主要取决于位于毛囊中的黑素细胞产生的黑色素。毛囊黑素细胞上的黑素皮质素 1 受体（MC1R）调节黑色素的合成；然而，与受体相互作用的黑素皮质素的来源尚不清楚。在这项研究中，我们检查了黑素皮质素的潜在表达，并对鸡羽毛毛囊中前阿黑皮素原（POMC）的 mRNA 进行了特征描述。反转录-聚合酶链反应（RT-PCR）显示 POMC、前激素转化酶 1（PC1）和 PC2 的 mRNA 表达，Western blot 检测到羽毛毛囊中 POMC 加工的促肾上腺皮质激素（ACTH）相关产物，表明黑素皮质素在鸡组织中局部产生。5'RACE（cDNA 5'端快速扩增）、3'RACE 和 RT-PCR 分析的组合鉴定了两类 POMC mRNA，a 类和 b 类，它们编码相同的全长 POMC 蛋白，但具有不同的非编码前导外显子。a 类 mRNA 特异性表达于羽毛毛囊，而 b 类 mRNA 表达于垂体、下丘脑和我们检查的各种外周组织。在羽毛毛囊中，a 类 mRNA 分布在从中部到远端的表皮层，而 b 类 mRNA 主要在近端的髓质中表达。我们的发现表明，羽毛色素沉着受局部产生的黑素皮质素调节，并表明不同 POMC mRNA 类编码的黑素皮质素可能在鸡的毛囊内发挥不同的作用。这是第一个证明脊椎动物中不同全长 POMC mRNA 通过不同启动子使用产生的报告。
