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基因簇，它们各自的表达模式在时间和空间上都受到已在该簇基因间区域鉴定的顺式元件的控制。先前的工作表明，保守元件之一（137-2）确实是一个内脏弓增强子，能够概括嵌套表达模式。我们已经扩展了这些分析，包括12个额外的哺乳动物类群（包括有袋动物和单孔目动物），以研究哺乳动物的非编码功能元件的进化。大规模的序列比较和随后的保守基序提取的进化刚性分析（ERA）表明，每个顺式元件基序表现出不同程度的进化保守哺乳动物物种。137-1具有与文昌鱼无末端基因相同的IL非常古老的保守基序。另一方面，尽管137-2在有袋动物/真兽目物种中高度保守，但在单孔目和有袋动物/真兽目祖先之间表现出较少的保守性。由于137-2在颅面表情中起重要作用，137-2的这种间歇性进化可能与哺乳动物颅面的创新有关。

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.