University of Denver, Department of Biological Sciences, Denver, CO 80210, USA.
Gen Comp Endocrinol. 2013 Jan 15;181:4-9. doi: 10.1016/j.ygcen.2012.08.016. Epub 2012 Aug 31.
There is general agreement that the presence of five melanocortin receptor genes in tetrapods is the result of two genome duplications that occurred prior to the emergence of the gnathostomes, and at least one local gene duplication that occurred early in the radiation of the ancestral gnathostomes. Hence, it is assumed that representatives from the extant classes of gnathostomes (i.e., Chondrichthyes, Actinopterygii, Sarcopterygii) should also have five paralogous melanocortin genes. Current studies on cartilaginous fishes indicate that while there is evidence for five paralogous melanocortin receptor genes in this class, to date all five paralogs have not been detected in the genome of a single species. This mini-review will discuss the ligand selectivity properties of the melanocortin-3 receptor of the elephant shark (subclass Holocephali) and the ligand selectivity properties of the melanocortin-3 receptor, melanocortin-4 receptor, and the melanocortin-5 receptor of the dogfish (subclass Elasmobranchii). The potential relationship of these melanocortin receptors to the hypothalamus/pituitary/interrenal axis will be discussed.
普遍认为，四足动物中存在的五个黑皮质素受体基因是在颌口动物出现之前发生的两次基因组复制的结果，并且至少发生了一次早期的局部基因复制，发生在祖颌口动物的辐射中。因此，人们假设现存的颌口动物类群（即软骨鱼纲、硬骨鱼纲、肉鳍鱼纲）也应该有五个同源的黑皮质素基因。目前对软骨鱼类的研究表明，虽然有证据表明在该类群中有五个同源的黑皮质素受体基因，但迄今为止，在单个物种的基因组中尚未检测到所有五个同源基因。这篇迷你综述将讨论象鲨（全头亚纲）的黑皮质素-3 受体的配体选择性特性，以及狗鲨（软骨鱼纲）的黑皮质素-3 受体、黑皮质素-4 受体和黑皮质素-5 受体的配体选择性特性。还将讨论这些黑皮质素受体与下丘脑/垂体/肾上腺轴的潜在关系。
