Kawahara A, Wilm T, Solnica-Krezel L, Dawid I B
Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 2000 Oct 24;97(22):12121-6. doi: 10.1073/pnas.97.22.12121.
During zebrafish development, zygotic gene expression initiated at the midblastula transition converts maternal information on embryo polarity into a transcriptional read-out. Expression of a homeobox gene, vega1, is activated at midblastula transition in all blastomeres, but is down-regulated dorsally before gastrulation. Ubiquitous expression of vega1 is maintained in bozozok mutants, in which the dorsal-specific homeobox gene bozozok/dharma (boz/dha) is disrupted and organizer formation is impaired. Vega1 inhibits expression of boz/dha and organizer-specific genes, and causes ventralization resulting in a headless phenotype. In contrast, VP16-vega1, a fusion including the Vega1 homeodomain and VP16 activation domain, elicits ectopic expression of organizer genes and suppresses several aspects of the boz mutant phenotype. We propose that boz/dha-dependent down-regulation of vega1 in the dorsal region is an early essential step in organizer formation in zebrafish.
在斑马鱼发育过程中，合子基因表达于中囊胚转换期起始，将胚胎极性的母体信息转化为转录输出。同源框基因vega1的表达在中囊胚转换期于所有卵裂球中被激活，但在原肠胚形成之前在背侧下调。vega1在bozozok突变体中维持普遍表达，其中背侧特异性同源框基因bozozok/dharma（boz/dha）被破坏且组织者形成受损。Vega1抑制boz/dha和组织者特异性基因的表达，并导致腹侧化，从而产生无头表型。相反，VP16-vega1是一种包含Vega1同源结构域和VP16激活结构域的融合蛋白，可引发组织者基因的异位表达，并抑制boz突变体表型的多个方面。我们提出，背侧区域中vega1依赖于boz/dha的下调是斑马鱼组织者形成的早期关键步骤。
