Evolutionary analysis on regulatory mechanism of the Dlx3-7 gene cluster regarding evolution of morphological novelty.

哺乳动物的d1×3和d1×7基因被组织成一个双烯簇，它们各自的表达模式在时间和空间上都受该簇基因间隔区的顺式元件控制。以前的工作表明，其中一个保守的元件(137-2)确实是一个内脏弓形增强子，能够概括嵌套表达模式。为了研究哺乳动物中非编码功能元件的进化，我们将这些分析扩展到另外12个哺乳动物分类群(包括一个有袋类和一个单孔目)。大规模的序列比较和随后通过进化刚性分析(ERA)提取的保守基序表明，每个顺式元件基序在哺乳动物物种之间表现出不同程度的进化保守性。137-1含有文昌鱼远端缺失基因所共有的IL非常古老的保守基序。另一方面，137-2在有袋类/真兽类物种中高度保守，但在单孔动物和有袋类/真兽类祖先之间的保守性较低。由于137-2已被证明对颅面表情是重要的，这种137-2元件的间歇性进化可能与哺乳动物的颅面创新有关。

The mammalian D1×3 and D1×7 genes are organized as a bigene cluster, and their respective expression patterns are controlled temporally and spatially by cis-elements that have been identified in the intergenic region of the cluster. Previous work showed that one of the conserved elements (137-2) was indeed a visceral arch enhancer that was able to recapitulate the nested expression pattern. We have extended these analyses to include twelve additional mammalian taxa (including a marsupial and a monotreme) in order to study evolution of the non-coding functional elements in mammals. Large-scale sequence comparisons and subsequent conservative motif extraction by the evolutionary rigidity assay (ERA) showed that each cis-element motif exhibited different degrees of evolutionary conservation among mammalian species. 137-1 harbored IL very old conservative motif that was shared by amphioxus distal-less gene. On the other hand, 137-2 exhibited less conservation between monotreme and marsupial/eutherian ancestor despite being highly conserved among marsupial/eutherian species. Since 137-2 has been shown to be important for the craniofacial expression, this intermittent evolution of 137-2 element may possibly be related to craniofacial innovation of mammals.