Logan C, Hanks M C, Noble-Topham S, Nallainathan D, Provart N J, Joyner A L
Department of Molecular and Medical Genetics, University of Toronto, Canada.
Dev Genet. 1992;13(5):345-58. doi: 10.1002/dvg.1020130505.
We have isolated and characterized genomic DNA clones for the human and chicken homologues of the mouse En-1 and En-2 genes and determined the genomic structure and predicted protein sequences of both En genes in all three species. Comparison of these vertebrate En sequences with the Xenopus En-2 [Hemmati-Brivanlou et al., 1991) and invertebrate engrailed-like genes showed that the two previously identified highly conserved regions within the En protein ]reviewed in Joyner and Hanks, 1991] can be divided into five distinct subregions, designated EH1 to EH5. Sequences 5' and 3' to the predicted coding regions of the vertebrate En genes were also analyzed in an attempt to identify cis-acting DNA sequences important for the regulation of En gene expression. Considerable sequence similarity was found between the mouse and human homologues both within the putative 5' and 3' untranslated as well as 5' flanking regions. Between the mouse and Xenopus En-2 genes, shorter stretches of sequence similarity were found within the 3' untranslated region. The 5' untranslated regions of the mouse, chicken and Xenopus En-2 genes, however, showed no similarly conserved stretches. In a preliminary analysis of the expression pattern of the human En genes, En-2 protein and RNA were detected in the embryonic and adult cerebellum respectively and not in other tissues tested. These patterns are analogous to those seen in other vertebrates. Taken together these results further strengthen the suggestion that En gene function and regulation has been conserved throughout vertebrate evolution and, along with the five highly conserved regions within the En protein, raise an interesting question about the presence of conserved genetic pathways.
我们已经分离并鉴定了小鼠En-1和En-2基因的人类和鸡同源基因的基因组DNA克隆，并确定了这三个物种中两个En基因的基因组结构和预测的蛋白质序列。将这些脊椎动物的En序列与非洲爪蟾的En-2 [Hemmati-Brivanlou等人，1991] 和无脊椎动物的engrailed样基因进行比较，结果表明，En蛋白中先前确定的两个高度保守区域 [Joyner和Hanks，1991年综述] 可分为五个不同的亚区域，分别命名为EH1至EH5。我们还分析了脊椎动物En基因预测编码区域5' 和' 3端的序列，试图确定对En基因表达调控重要的顺式作用DNA序列。在假定的5' 和3' 非翻译区域以及5' 侧翼区域内，小鼠和人类同源基因之间发现了相当大的序列相似性。在小鼠和非洲爪蟾的En-2基因之间，在3' 非翻译区域内发现了较短的序列相似片段。然而，小鼠、鸡和非洲爪蟾En-2基因的5' 非翻译区域没有显示出类似的保守片段。在对人类En基因表达模式的初步分析中，分别在胚胎和成年小脑而非其他测试组织中检测到了En-2蛋白和RNA。这些模式与在其他脊椎动物中观察到的模式相似。综合这些结果进一步支持了以下观点，即En基因的功能和调控在整个脊椎动物进化过程中得以保留，并且与En蛋白内的五个高度保守区域一起，引发了一个关于保守遗传途径存在的有趣问题。
