Yamaguchi Yoko, Takagi Wataru, Kuraku Shigehiro, Moriyama Shunsuke, Bell Justin D, Seale Andre P, Lerner Darren T, Grau E Gordon, Hyodo Susumu
Hawai'i Institute of Marine Biology, University of Hawai'i, Kaneohe, HI 96744, USA.
Laboratory of Physiology, Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba 277-8564, Japan.
Gen Comp Endocrinol. 2015 Dec 1;224:216-27. doi: 10.1016/j.ygcen.2015.08.020. Epub 2015 Aug 29.
The conventional prolactin (PRL), also known as PRL1, is an adenohypophysial hormone that critically regulates various physiological events in reproduction, metabolism, growth, osmoregulation, among others. PRL1 shares its evolutionary origin with PRL2, growth hormone (GH), somatolactin and placental lactogen, which together form the GH/PRL hormone family. Previously, several bioassays implied the existence of PRL1 in elasmobranch pituitaries. However, to date, all attempts to isolate PRL1 from chondrichthyans have been unsuccessful. Here, we cloned PRL1 from the pituitary of the holocephalan elephant fish, Callorhinchus milii, as the first report of chondrichthyan PRL1. The putative mature protein of elephant fish PRL1 (cmPRL1) consists of 198 amino acids, containing two conserved disulfide bonds. The orthologous relationship of cmPRL1 to known vertebrate PRL1s was confirmed by the analyses of molecular phylogeny and gene synteny. The cmPRL1 gene was similar to teleost PRL1 genes in gene synteny, but was distinct from amniote PRL1 genes, which most likely arose in an early amphibian by duplication of the ancestral PRL1 gene. The mRNA of cmPRL1 was predominantly expressed in the pituitary, but was considerably less abundant than has been previously reported for bony fish and tetrapod PRL1s; the copy number of cmPRL1 mRNA in the pituitary was less than 1% and 0.1% of that of GH and pro-opiomelanocortin mRNAs, respectively. The cells expressing cmPRL1 mRNA were sparsely distributed in the rostral pars distalis. Our findings provide a new insight into the studies on molecular and functional evolution of PRL1 in vertebrates.
传统催乳素（PRL），也称为PRL1，是一种腺垂体激素，对生殖、代谢、生长、渗透压调节等各种生理过程起着关键调节作用。PRL1与PRL2、生长激素（GH）、生长催乳素和胎盘催乳素有着共同的进化起源，它们共同构成了GH/PRL激素家族。此前，多项生物测定表明板鳃亚纲动物垂体中存在PRL1。然而，迄今为止，从软骨鱼类中分离PRL1的所有尝试均未成功。在此，我们从全头亚纲银鲛（Callorhinchus milii）的垂体中克隆出PRL1，这是软骨鱼类PRL1的首次报道。银鲛PRL1（cmPRL1）的推定成熟蛋白由198个氨基酸组成，含有两个保守的二硫键。通过分子系统发育和基因共线性分析，证实了cmPRL1与已知脊椎动物PRL1的直系同源关系。cmPRL1基因在基因共线性方面与硬骨鱼PRL1基因相似，但与羊膜动物PRL1基因不同，后者很可能是在早期两栖动物中通过祖先PRL1基因的复制产生的。cmPRL1的mRNA主要在垂体中表达，但其丰度远低于先前报道的硬骨鱼和四足动物PRL1；垂体中cmPRL1 mRNA的拷贝数分别不到GH和促肾上腺皮质激素原mRNA拷贝数的1%和0.1%。表达cmPRL1 mRNA的细胞稀疏分布于远侧部前端。我们的研究结果为脊椎动物PRL1的分子和功能进化研究提供了新的见解。
