Shashikant C S, Kim C B, Borbély M A, Wang W C, Ruddle F H
Department of Molecular, Cellular, and Developmental Biology, P.O. Box 208103, New Haven, CT 06520, USA.
Proc Natl Acad Sci U S A. 1998 Dec 22;95(26):15446-51. doi: 10.1073/pnas.95.26.15446.
Variations in regulatory regions of developmental control genes have been implicated in the divergence of axial morphologies. To find potentially significant changes in cis-regulatory regions, we compared nucleotide sequences and activities of mammalian Hoxc8 early enhancers. The nucleotide sequence of the early enhancer region is extremely conserved among mammalian clades, with five previously described cis-acting elements, A-E, being invariant. However, a 4-bp deletion within element C of the Hoxc8 early enhancer sequence is observed in baleen whales. When assayed in transgenic mouse embryos, a baleen whale enhancer (unlike other mammalian enhancers) directs expression of the reporter gene to more posterior regions of the neural tube but fails to direct expression to posterior mesoderm. We suggest that regulation of Hoxc8 in baleen whales differs from other mammalian species and may be associated with variation in axial morphology.
发育控制基因调控区域的变异与轴向形态的差异有关。为了寻找顺式调控区域中潜在的显著变化，我们比较了哺乳动物Hoxc8早期增强子的核苷酸序列和活性。早期增强子区域的核苷酸序列在哺乳动物进化枝中极其保守，之前描述的五个顺式作用元件A - E是不变的。然而，在须鲸中观察到Hoxc8早期增强子序列的元件C内有一个4碱基对的缺失。当在转基因小鼠胚胎中进行检测时，须鲸增强子（与其他哺乳动物增强子不同）将报告基因的表达导向神经管更靠后的区域，但未能将表达导向中胚层后部。我们认为须鲸中Hoxc8的调控与其他哺乳动物物种不同，可能与轴向形态的变化有关。
