The analysis of dharma/bozozok gene function in vertebrates body axis formation.

体轴的背腹侧特化需要母体来源的Wnt信号激活。母体来源的Wnt信号激活参与Nieuwkoop中心形成和随后诱导背侧组织者的基因。同源异型盒基因dharma/bozozok（dha/boz）是母系Wnt信号的直接靶基因，在斑马鱼背侧组织器的形成和/或功能中起重要作用。Dha/Boz含有与Engrailed的阻遏物结构域（Ehl基序）相似的氨基酸基序。我们发现Dha/Boz通过Eh 1基序与辅阻遏物Groucho相互作用。Dha/Boz的阻遏活性是组织者基因表达和胚胎背侧化所必需的。利用有序差异显示技术，我们分离到了一个新的腹侧表达的同源异型盒基因ved，该基因与vox和vent具有序列相似性，ved是转录抑制因子Dha/Boz的靶基因。转录激活子和抑制子结构域融合蛋白的分析表明，Ved作为一个转录抑制因子。通过反义吗啉介导的功能丧失实验，我们发现ved，vox和vent是背侧组织者形成的冗余阻遏物。这些结果表明，dha/boz通过抑制ved、vox和vent的表达来促进背侧命运，这些基因的作用是限制背侧组织者基因在适当区域的表达。

Specification of dorso-ventral body axis requires the maternally-derived Wnt signal activation. The maternally-derived Wnt signal activates genes that are involved in formation of the Nieuwkoop center and subsequently induction of the dorsal organizer. The homeobox gene dharma/bozozok (dha/boz) is a direct target gene of the maternal Wnt signal and plays an important role in the formation and/or function of the zebra fish dorsal organizer. Dha/Boz contains an amino acid motif similar to the repressor domain of Engrailed (Ehl motif). We found that Dha/Boz interacted with a co-repressor Groucho through the Eh1 motif. The repressor activity of Dha/Boz was required for expression of organizer genes and dha/boz-dependent dorsalization of the embryos. By ordered differential display method, we isolated a novel ventrally-expressed homeobox gene ved, which displays sequence similarities with vox and vent, ved is a target of the transcriptional repressors Dha/Boz. The analysis of transcriptional activator and repressor domain fusion proteins suggested that Ved acts as a transcriptional repressor. By antisense morpholino-mediated loss of function experiments, we showed that ved, vox and vent were redundant repressors of the dorsal organizer formation. These results suggested that dha/boz promoted the dorsal fate by suppressing the expression of ved, vox, and vent which act to restrict the expression of the dorsal organizer genes in appropriate region.