Medaka receptors for somatolactin and growth hormone: Phylogenetic paradox among fish growth hormone receptors
Medaka receptors for somatolactin and growth hormone: Phylogenetic paradox among fish growth hormone receptors
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DOI：
10.1534/genetics.105.048819
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发表时间：
2005-12-01
期刊：
影响因子：
3.3
通讯作者：
Mitani, H
中科院分区：
文献类型：
--
作者：
Fukamachi, S;Yada, T;Mitani, H
鱼类中的生长激素（SL）属于生长激素/催乳素家族。其在四足动物中的直系同源物尚未被鉴定，其功能在很大程度上仍然未知。最近在鲑鱼中发现的青鳉SL缺陷突变体（color interferor，ci）和SL受体（SL receptor，SLR）为研究SL在体内的功能提供了一个有趣的领域。在这里，我们分离的青鳉直系同源的鲑鱼SLR的mRNA转录在可变的器官。CI中的甘油三酯和胆固醇含量显著高于野生型，这为SL抑制脂质向器官积累的功能提供了第一个证据。有趣的是，青鳉SLR和生长激素受体（GHR）之间的系统发育比较，这也是在这项研究中分离的，与其他鱼类的GHR有关，表明所有报告的GHR从nonsalmonid物种，至少在遗传学上的SLR。在青鳉和河豚的SLR和比目鱼和海鲷的GHRs插入一个额外的内含子也支持他们的orthopathic关系，但不与四足动物的GHRs。这些结果可能表明，在鱼类中，SLR和GHR功能的谱系特异性多样化，或者只是这些受体的命名不恰当。为解决这一问题，有必要进行进一步的功能和比较重新评估。
Somatolactin (SL) in fish belongs to the growth hormone/prolactin family. Its ortholog in tetrapods has not been identified and its function(s) remains largely unknown. The SL-deficient mutant of medaka (color interfere, ci) and an SL receptor (SLR) recently identified in salmon provide a fascinating field for investigating SL's function (s) in vivo. Here we isolated a medaka ortholog of the salmon SLR The mRNA is transcribed in variable organs. Triglycerides and cholesterol contents in the ci are significantly higher than those in the wild type, providing the first evidence of SL's function in suppressing lipid accumulation to organs. Interestingly, phylogenetic comparisons between the medaka SLR and growth hormone receptor (GHR), which is also isolated in this study, in relation to GHRs of other fish, suggested that all GHRs reported from nonsalmonid species are, at least phylogenetically SLRs. An extra intron inserted in medaka and pufferfish SLRs and flounder and sea bream GHRs also supports their orthologous relationship, but not with tetrapod GHRs. These results may indicate lineage-specific diversification of SLR and GHR functions among fish or just an inappropriate naming of these receptors. Further functional and comparative reassessments are necessary to address this question.