Itoh Motoyuki, Kudoh Tetsuhiro, Dedekian Michael, Kim Cheol-Hee, Chitnis Ajay B
Laboratory of Molecular Genetics, NICHD/NIH, Bethesda, MD 20892, USA.
Development. 2002 May;129(10):2317-27. doi: 10.1242/dev.129.10.2317.
We have identified a novel Iroquois (Iro) gene, iro7, in zebrafish. iro7 is expressed during gastrulation along with iro1 in a compartment of the dorsal ectoderm that includes the prospective midbrain-hindbrain domain, the adjacent neural crest and the trigeminal placodes in the epidermis. The iro1 and iro7 expression domain is expanded in headless and masterblind mutants, which are characterized by exaggerated Wnt signaling. Early expansion of iro1 and iro7 expression in these mutants correlates with expansion of the midbrain-hindbrain boundary (MHB) domain, the neural crest and trigeminal neurons, raising the possibility that iro1 and iro7 have a role in determination of these ectodermal derivatives. A knockdown of iro7 function revealed that iro7 is essential for the determination of neurons in the trigeminal placode. In addition, a knockdown of both iro1 and iro7 genes uncovered their essential roles in neural crest development and establishment of the isthmic organizer at the MHB. These results suggest a new role for Iro genes in establishment of an ectodermal compartment after Wnt signaling in vertebrate development. Furthermore, analysis of activator or repressor forms of iro7 suggests that iro1 and iro7 are likely to function as repressors in establishment of the isthmic organizer and neural crest, and Iro genes may have dual functions as repressors and activators in neurogenesis.
我们在斑马鱼中鉴定出一个新的易洛魁族（Iro）基因——iro7。iro7在原肠胚形成期与iro1一起表达于背侧外胚层的一个区域，该区域包括预期的中脑-后脑区域、相邻的神经嵴以及表皮中的三叉神经基板。在无头和主盲突变体中，iro1和iro7的表达域扩大，这些突变体的特征是Wnt信号过度激活。在这些突变体中，iro1和iro7表达的早期扩展与中脑-后脑边界（MHB）区域、神经嵴和三叉神经元的扩展相关，这增加了iro1和iro7在这些外胚层衍生物的决定过程中发挥作用的可能性。对iro7功能的敲低显示，iro7对于三叉神经基板中神经元的决定至关重要。此外，对iro1和iro7基因的同时敲低揭示了它们在神经嵴发育以及MHB处峡部组织者的建立中的重要作用。这些结果表明Iro基因在脊椎动物发育中Wnt信号之后的外胚层区域建立中具有新的作用。此外，对iro7激活或抑制形式的分析表明，iro1和iro7在峡部组织者和神经嵴的建立中可能作为抑制因子发挥作用，并且Iro基因在神经发生中可能具有作为抑制因子和激活因子的双重功能。
