Ficele G, Heinig J A, Kawauchi H, Youson J H, Keeley F W, Wright G M
Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island, Canada.
Gen Comp Endocrinol. 1998 May;110(2):212-25. doi: 10.1006/gcen.1998.7071.
Two POMC-like pituitary prohormones proopiocortin (POC) and proopiomelanotropin (POM) have been characterized from adult sea lampreys (Petromyzon marinus). POC encodes a nasohypophysial factor (NHF), ACTH, an MSH, and beta-END; and POM encodes MSH-A, MSH-B, and beta-END. Two radiolabeled riboprobes, one encoding a unique portion of POC mRNA and the other encoding the MSH-B domain unique to POM mRNA, were generated in order to examine the expression of POC and POM during the life cycle of the sea lamprey by in situ hybridization. POC expression appears evenly distributed throughout most cells of the rostral pars distalis (RPD) during the entire life cycle. POC expression also occurs in scattered cells of the caudal (proximal) pars distalis (CPD) at stage 5 of metamorphosis. By the prespawner period, POC expression is mainly distributed in the dorsal aspect of this region. POM expression was completely confined to most cells of the pars intermedia (PI) at all periods examined. Quantitative, computer-assisted, image analysis of POM expression revealed high signal densities in all larvae which decreased by early metamorphosis, steadily increased and reached high levels by late metamorphosis (stages 6 and 7), and attained even higher levels in prespawners. Volumetric analysis revealed that the net volume of POM expressing cells is at its lowest in larvae and increases during subsequent development. Analysis of signal density and volumetric measurements of POC expression revealed that POC expression in the RPD is low in larvae and steadily increases during subsequent intervals of the life cycle reaching very high levels by the prespawning period. POC expression in the CPD, first visible at stage 5, increases steadily throughout the remainder of metamorphosis and reaches the highest levels of expression in prespawning animals. These results would implicate the role of POM and POC in some developmental processes but not in the initiation of metamorphosis. The very high levels of POM and POC expression in prespawner animals suggest that the two genes may have important roles at this time in the life cycle of lampreys.
在成年海七鳃鳗（海七鳃鳗）中已鉴定出两种类似促肾上腺皮质激素原的垂体前体激素，即阿黑皮素原（POC）和阿黑皮素黑素细胞刺激素原（POM）。POC编码一种鼻垂体因子（NHF）、促肾上腺皮质激素（ACTH）、一种促黑素（MSH）和β-内啡肽（beta-END）；而POM编码MSH-A、MSH-B和β-内啡肽。为了通过原位杂交研究海七鳃鳗生命周期中POC和POM的表达情况，制备了两种放射性标记的核糖探针，一种编码POC mRNA的独特部分，另一种编码POM mRNA特有的MSH-B结构域。在整个生命周期中，POC的表达似乎均匀分布于吻部远侧部（RPD）的大多数细胞中。在变态第5阶段，POC的表达也出现在尾侧（近端）远侧部（CPD）的散在细胞中。到产卵前期，POC的表达主要分布在该区域的背侧。在所有检测阶段，POM的表达完全局限于中间部（PI）的大多数细胞。对POM表达的定量、计算机辅助图像分析显示，所有幼虫中的信号密度都很高，到变态早期降低，在变态后期（第6和7阶段）稳步增加并达到高水平，在产卵前期达到更高水平。体积分析表明，表达POM的细胞的净体积在幼虫中最低，并在随后的发育过程中增加。对POC表达的信号密度和体积测量分析表明，RPD中POC的表达在幼虫中较低，并在生命周期的后续阶段稳步增加，到产卵前期达到非常高的水平。CPD中POC的表达在第5阶段首次可见，在变态的其余阶段稳步增加，并在产卵前动物中达到最高表达水平。这些结果表明POM和POC在某些发育过程中起作用，但与变态的启动无关。产卵前动物中POM和POC的极高表达水平表明这两个基因在七鳃鳗生命周期的这个阶段可能具有重要作用。
