A novel olfactory receptor gene family in teleost fish
A novel olfactory receptor gene family in teleost fish
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DOI：
10.1101/gr.6553207
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发表时间：
2007-10-01
期刊：
影响因子：
7
通讯作者：
Korsching, Sigrun I.
中科院分区：
文献类型：
--
作者：
Saraiva, Luis R.;Korsching, Sigrun I.
虽然已经确定了三个哺乳动物嗅觉受体家族中的两个（OR和V2R），但第三个家族（V1R）被认为是由一个紧密相连的基因对代表的。我们在每一种被分析的硬骨鱼（Danio rerio, Gasterosteus aculeatus, Oryzias latipes, Tetraodon nigroviridis, takifupes）中发现了4个V1R- like基因。在系统发育分析中，这些ora基因（嗅觉受体A类相关）形成一个单一的进化支，包括整个哺乳动物V1R超家族。相似物的同源性比直系物的同源性低得多，这表明所有六个家庭成员在进化上比本文分析的硬骨鱼谱系的物种形成事件要早得多。这些ora基因处于强烈的负选择下，这一点可以从直系同源间比较的非常小的d(N)/ d(S)值中得到证明。系统发育树的成对结构表明存在三个祖先的奥拉亚支，其中一个在两栖动物中消失了，另一个在哺乳动物中消失了。出乎意料的是，在所有研究的鱼类中，两个ora基因表现出高度保守的多外显子结构，四个ora基因组织在紧密相连的基因对中。所有的ora基因在斑马鱼嗅觉上皮中特异表达，在感觉表面的稀疏细胞中，与嗅觉受体的预期一致。ora基因库在硬骨鱼中高度保守，这与在四足动物中观察到的频繁的物种特异性扩展形成鲜明对比，特别是哺乳动物的V1Rs，这可能反映了基因调控和基因功能在向四足动物过渡时的重大转变。
While for two of three mammalian olfactory receptor families ( OR and V2R) ortholog teleost families have been identified, the third family ( V1R) has been thought to be represented by a single, closely linked gene pair. We identified four further V1R- like genes in every teleost species analyzed ( Danio rerio, Gasterosteus aculeatus, Oryzias latipes, Tetraodon nigroviridis, Takifugu rubripes). In the phylogenetic analysis these ora genes ( olfactory receptor class A- related) form a single clade, which includes the entire mammalian V1R superfamily. Homologies are much lower in paralogs than in orthologs, indicating that all six family members are evolutionarily much older than the speciation events in the teleost lineage analyzed here. These ora genes are under strong negative selection, as evidenced by very small d(N)/ d(S) values in comparisons between orthologs. A pairwise configuration in the phylogenetic tree suggests the existence of three ancestral Ora subclades, one of which has been lost in amphibia, and a further one in mammals. Unexpectedly, two ora genes exhibit a highly conserved multi- exonic structure and four ora genes are organized in closely linked gene pairs across all fish species studied. All ora genes are expressed specifically in the olfactory epithelium of zebrafish, in sparse cells within the sensory surface, consistent with the expectation for olfactory receptors. The ora gene repertoire is highly conserved across teleosts, in striking contrast to the frequent species- specific expansions observed in tetrapod, especially mammalian V1Rs, possibly reflecting a major shift in gene regulation as well as gene function upon the transition to tetrapods.