The mammalian Crx genes are highly divergent representatives of the Otx5 gene family, a gnathostome orthology class of orthodenticle-related homeogenes involved in the differentiation of retinal photoreceptors and circadian entrainment
The mammalian Crx genes are highly divergent representatives of the Otx5 gene family, a gnathostome orthology class of orthodenticle-related homeogenes involved in the differentiation of retinal photoreceptors and circadian entrainment
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DOI：
10.1093/molbev/msg085
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发表时间：
2003-04-01
影响因子：
10.7
通讯作者：
Mazan, S
中科院分区：
文献类型：
--
作者：
Plouhinec, JL;Sauka-Spengler, T;Mazan, S
哺乳动物Crx基因是高度分化的与正畸相关的同源基因，在视网膜光感受器的分化和昼夜节律中起重要作用。然而，它们的进化起源和与其他otd相关基因的同源关系仍不清楚。这些基因与在鱼类和两栖动物中发现的高度保守的Otx5基因，以及在眼睛和骨骺中表达的基因之间的同源关系，此前已被提出，但仍存在争议。为了验证这一假设，我们在许多哺乳动物中发现了Crx基因，包括三种有袋动物，在蜥蜴、海龟和两种祖龙（鳄鱼和小鸡）以及河豚中发现了otx5相关基因。编码序列的系统发育分析表明，哺乳动物Crx基因与其他颌口动物中分离的otx5相关基因同源。它们还表明，在分支体分裂之后，放线翼类中发生了复制事件，并且在哺乳动物谱系的早期，作用于基因编码区域的结构约束的放松已经发生。这一过程可能不仅与原肠形成过程中或视网膜色素上皮中祖先Otx5/Crx功能的丧失有关，还与哺乳动物光诱导机制的进化有关。
The mammalian Crx genes are highly divergent orthodenticle (otd)-related homeogenes that play important roles in the differentiation of retinal photoreceptors and the circadian entrainment. However, their evolutionary origin and orthological relationships with other otd-related genes remain unclear. An orthology relationship of these genes with the highly conserved Otx5 genes identified in fish and amphibians, and also expressed in the eye and epiphysis, has been proposed previously but remains controversial. To test this hypothesis, we have identified Crx genes in a wide range of mammals, including three marsupials, and Otx5-related genes in a lizard, a turtle, and two archosaurs (crocodile and chick), as well as in the pufferfish. Phylogenetic analyses of the coding sequences show that the mammalian Crx genes are orthologous to the Otx5-related genes isolated in other gnathostomes. They also indicate that a duplication event has taken place in actinopterygians, after the splitting of the Cladistia, and that a relaxation of the structural constraints acting on the gene coding region has occurred early in the mammalian lineage. This process may be linked not only to the loss of ancestral Otx5/Crx functions during gastrulation or in the retinal pigmented epithelium, but also to the evolution of photic entrainment mechanisms in mammals.