Department of Biological Sciences, Texas Tech University, Lubbock, TX, 79409, USA.
Department of Biology, University of Massachusetts, Amherst, MA, USA.
Sci Rep. 2020 Feb 3;10(1):1674. doi: 10.1038/s41598-020-58344-5.
Growth hormone receptor (GHR) and prolactin receptor (PRLR) in jawed vertebrates were thought to arise after the divergence of gnathostomes from a basal vertebrate. In this study we have identified two genes encoding putative GHR and PRLR in sea lamprey (Petromyzon marinus) and Arctic lamprey (Lethenteron camtschaticum), extant members of one of the oldest vertebrate groups, agnathans. Phylogenetic analysis revealed that lamprey GHR and PRLR cluster at the base of gnathostome GHR and PRLR clades, respectively. This indicates that distinct GHR and PRLR arose prior to the emergence of the lamprey branch of agnathans. In the sea lamprey, GHR and PRLR displayed a differential but overlapping pattern of expression; GHR had high expression in liver and heart tissues, whereas PRLR was expressed highly in the brain and moderately in osmoregulatory tissues. Branchial PRLR mRNA levels were significantly elevated by stage 5 of metamorphosis and remained elevated through stage 7, whereas levels of GHR mRNA were only elevated in the final stage (7). Branchial expression of GHR increased following seawater (SW) exposure of juveniles, but expression of PRLR was not significantly altered. The results indicate that GHR and PRLR may both participate in metamorphosis and that GHR may mediate SW acclimation.
在颌脊椎动物中，生长激素受体 (GHR) 和催乳素受体 (PRLR) 被认为是在颌脊椎动物与基础脊椎动物分化之后出现的。在这项研究中，我们在七鳃鳗 (Petromyzon marinus) 和北极七鳃鳗 (Lethenteron camtschaticum) 中鉴定出两个编码假定的 GHR 和 PRLR 的基因，这两种鱼都是最古老的脊椎动物群体之一——无颌类的现存成员。系统发育分析表明，七鳃鳗的 GHR 和 PRLR 分别位于颌脊椎动物 GHR 和 PRLR 进化枝的基部。这表明，在无颌类分支出现之前，就已经出现了不同的 GHR 和 PRLR。在七鳃鳗中，GHR 和 PRLR 的表达模式存在差异但有重叠；GHR 在肝脏和心脏组织中高表达，而 PRLR 在大脑中高表达，在渗透压调节组织中中度表达。变态阶段 5 的鳃 PRLR mRNA 水平显著升高，并一直升高到阶段 7，而 GHR mRNA 水平仅在最后一个阶段 (7) 升高。幼鱼暴露于海水中后，GHR 在鳃中的表达增加，但 PRLR 的表达没有明显改变。结果表明，GHR 和 PRLR 可能都参与了变态，而 GHR 可能介导了海水适应。
