UMR 7221 CNRS/MNHN Evolution des Régulations Endocriniennes, Muséum National d'Histoire Naturelle, 75231 Paris, France.
Gen Comp Endocrinol. 2011 Feb 1;170(3):575-81. doi: 10.1016/j.ygcen.2010.11.017. Epub 2010 Nov 29.
The neuropeptide gonadotropin-releasing hormone (GnRH) plays an important role in the control of reproductive functions. Vertebrates possess multiple GnRH isoforms that are classified into three main groups, namely GnRH1, GnRH2 and GnRH3. In the present study, we show that the chromosomal organization of the three GnRH loci is very well conserved among gnathostome species. We analyzed genes belonging to several other multigenic families that are present in the vicinity of GnRH genes. Five of them were seen to occur in four chromosomal regions that clearly form a paralogon. Moreover, we show that the homologous regions in the amphioxus genome are present on a single locus. Taken together, these observations indicate that GnRH1, GnRH2 and GnRH3 genes represent three paralogous genes that resulted from the two rounds of tetraploidization that took place early in vertebrate evolution. They confirm that the GnRH3 gene which is currently known only in teleost has most likely been lost in the tetrapod lineage. Finally, they suggest the existence of a fourth GnRH gene, named GnRH4. Whether the GnRH4 gene still exists in extant vertebrates is currently unknown. A search for this putative gene would be particularly useful in basal groups such as agnathans and cartilaginous fish.
神经肽促性腺激素释放激素（GnRH）在生殖功能的控制中起着重要作用。脊椎动物具有多种 GnRH 同工型，可分为 GnRH1、GnRH2 和 GnRH3 三个主要组。在本研究中，我们表明三种 GnRH 基因座的染色体组织在颌口动物物种中非常保守。我们分析了属于几种其他多基因家族的基因，这些基因存在于 GnRH 基因附近。其中有五个基因出现在四个明确形成旁系同源的染色体区域中。此外，我们表明文昌鱼基因组中的同源区域存在于一个单一基因座上。总之，这些观察结果表明，GnRH1、GnRH2 和 GnRH3 基因代表了三个来自脊椎动物进化早期发生的两轮四倍体化的旁系同源基因。它们证实了目前仅在硬骨鱼中已知的 GnRH3 基因很可能在四足动物谱系中丢失。最后，它们表明存在第四种 GnRH 基因，命名为 GnRH4。这种 GnRH4 基因是否仍然存在于现存的脊椎动物中目前尚不清楚。在无颌类和软骨鱼类等基础群中寻找这个假定的基因将特别有用。
