Takeuchi S, Takahashi S
Faculty of Science, Okayama University, Okayama, 700-8530, Japan.
Gen Comp Endocrinol. 1998 Nov;112(2):220-31. doi: 10.1006/gcen.1998.7167.
Two receptor genes belonging to the melanocortin receptor (MC-R) family were isolated in the chicken, the CMC4 and CMC5, each of which is a chicken homologue of the mammalian MC4-R and MC5-R, respectively. The CMC4 encodes a 331 amino acid protein, sharing 86. 4-88.1% identity with mammalian analogs, and the CMC5 encodes a 325 amino acid protein, which is 72.3-79.1% identical to mammalian counterparts. Both genes contain no intron in their coding regions and exist in the chicken genome as single copy genes. Reverse transcription-PCR analysis revealed that the CMC4 mRNA is expressed in a wide variety of peripheral tissues, including the adrenal, gonads, spleen, and adipose tissues, as well as in the brain, where mammalian counterparts are exclusively expressed in the brain, indicating that the regulation of MC4-R gene expression differs between mammals and chickens. The CMC5 mRNA, on the other hand, is expressed in the liver, gonads, adrenal, kidney, brain, and adipose tissues as well as in the uropygial gland. These findings raise the possibility that melanocortins affect a variety of functions both in the brain and in the peripheral tissues of the chicken.
在鸡体内分离出了两个属于黑皮质素受体（MC-R）家族的受体基因，即CMC4和CMC5，它们分别是哺乳动物MC4-R和MC5-R的鸡同源物。CMC4编码一种由331个氨基酸组成的蛋白质，与哺乳动物的类似物具有86.4%-88.1%的同一性，而CMC5编码一种由325个氨基酸组成的蛋白质，与哺乳动物的对应物具有72.3%-79.1%的同一性。这两个基因在其编码区域均无内含子，在鸡基因组中以单拷贝基因形式存在。逆转录-聚合酶链反应分析显示，CMC4 mRNA在多种外周组织中表达，包括肾上腺、性腺、脾脏和脂肪组织，以及在大脑中表达，而其哺乳动物对应物仅在大脑中表达，这表明MC4-R基因表达的调控在哺乳动物和鸡之间存在差异。另一方面，CMC5 mRNA在肝脏、性腺、肾上腺、肾脏、大脑和脂肪组织以及尾脂腺中表达。这些发现增加了黑皮质素影响鸡大脑和外周组织多种功能的可能性。
