Laboratory of Aquacultural Biology, Graduate School of Agricultural Science, Tohoku University, 1-1 Amamiya-Machi, Tsutsumidori, Aoba-Ku, Sendai, Miyagi 981 8555, Japan.
Gen Comp Endocrinol. 2012 Apr 1;176(2):167-72. doi: 10.1016/j.ygcen.2012.01.008. Epub 2012 Feb 2.
Gonadotropin-releasing hormone (GnRH) is central to the control of vertebrate reproductive cycles and since GnRH orthologs are also present in invertebrates, it is likely that the common ancestor of bilateral animals possessed a GnRH-like peptide. In order to understand the evolutionary and comparative biology of GnRH peptides we cloned the cDNA transcripts of prepro GnRH-like peptides from two species of bivalve molluscs, the Yesso scallop Patinopecten yessoensis and the Pacific oyster Crassostrea gigas. We compared their deduced uncleaved and mature amino acid sequences with those from other invertebrates and vertebrates, and determined their sites of expression and biological activity. The two molluscan GnRH sequences increased the number of known protostome GnRHs to six different forms, indicating the current classification of protostome GnRHs requires further revision. In both molluscs, RT-PCR analysis showed that the genes were highly expressed in nervous tissue with lower levels present in peripheral tissues including the gonads, while immunocytochemistry, using anti-octopus GnRH-like peptide, demonstrated the presence of GnRH-like peptide in neural tissue. Putative scallop GnRH-like peptide stimulated spermatogonial cell division in cultured scallop testis, but the scallop GnRH-like peptide did not stimulate LH release from cultured quail pituitary cells. This is the first report of the cloning of bivalve GnRH-like peptide genes and of molluscan GnRH-like peptides that are biologically active in molluscs, but not in a vertebrate.
促性腺激素释放激素（GnRH）是脊椎动物生殖周期调控的核心，由于 GnRH 同源物也存在于无脊椎动物中，因此双侧动物的共同祖先很可能拥有 GnRH 样肽。为了了解 GnRH 肽的进化和比较生物学，我们从两种双壳贝类，即日本真珠贝（Patinopecten yessoensis）和太平洋牡蛎（Crassostrea gigas）中克隆了 prepro GnRH 样肽的 cDNA 转录本。我们将它们推断的未切割和成熟氨基酸序列与其他无脊椎动物和脊椎动物的序列进行了比较，并确定了它们的表达和生物活性位点。这两种软体动物的 GnRH 序列将已知的原口动物 GnRH 增加到六种不同的形式，表明原口动物 GnRH 的当前分类需要进一步修订。在这两种软体动物中，RT-PCR 分析表明，这些基因在神经组织中高度表达，在包括性腺在内的外周组织中表达水平较低，而使用抗章鱼 GnRH 样肽的免疫细胞化学显示神经组织中存在 GnRH 样肽。推测的扇贝 GnRH 样肽刺激培养的扇贝睾丸精原细胞分裂，但扇贝 GnRH 样肽不能刺激培养的鹌鹑脑垂体细胞释放 LH。这是首次报道双壳类 GnRH 样肽基因的克隆，以及在软体动物中具有生物活性但在脊椎动物中没有活性的软体动物 GnRH 样肽。
