A study of molecular evolutionary and population genetics of olfactory receptor genes family : Cloning of putative olfactory receptor genesin Medaka, Oryzias latipes.

为了阐明嗅觉的遗传基础、维持遗传多样性的机制以及脊椎动物嗅觉受体基因家族的起源，我们试图克隆果蝇和米达卡鱼的嗅觉受体基因。从medaka基因组DNA中，利用一组简并寡核苷酸作为引物，成功克隆出mfOR1、mfOR2、mfOR3和mfOR4 4个受体基因。他们推导出的所有氨基酸序列都包含7个疏水结构域和几个在嗅觉受体中常见的序列基序。四种medaka受体序列相似性为19 ~ 91%。在氨基酸水平上，4个受体基因与鲶鱼和斑马鱼的嗅觉受体序列具有高度同源性。这些结果表明它们编码了嗅觉受体基因家族的新成员。连锁分析表明，这四个受体基因被分为两个簇。mfOR3和mfOR4基因簇在medaka连锁组XX中连锁，显示出与哺乳动物的同源性。此外，NJ方法的系统发育分析表明，medaka嗅觉受体在四足脊椎动物中分支良好。

To elucidate the genetic basis of olfaction, the mechanisms that maintain genetic diversity and the origin of vertebrate olfactory receptor gene family, we have tried to clone the olfactory receptor genes of Drosophila and medaka fish (Oryzias latipes).From medaka genomic DNA,four receptor genes, named mfOR1, mfOR2, mfOR3 and mfOR4, were successfully cloned using a set of degenerate oligonucleotides as PCR primers. All of their deduced amino acid sequences contained seven hydrophobic domains and several sequence motifs commonly seen in the olfactory receptors. The four medaka receptors exhibit from 19-91% sequence similarity to each other. At amino acid level, four receptor genes show high homologies with the olfactory receptor sequences from catfish and zebra fish. These results suggested that they encode novel members of olfactory receptor gene family.Linkage analysis have revealed that the four receptor genes are grouped into two clusters. The cluster of mfOR3 and mfOR4 linked in medaka linkage group XX which showed synteny with the mammals. Furthermore, phylogenetic analysis by NJ method revealed that medaka olfactory receptors branches well from the tetrapod vertebrate.