Antagonistic role of vega1 and bozozok/dharma homeobox genes in organizer formation.
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.
Kawahara
A
A
Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Wilm
T
T
Solnica-Krezel
L
L
Dawid
I B
IB
D000595:Amino Acid Sequence; D000818:Animals; D019521:Body Patterning; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish / Q000235:genetics*; D029961:Zebrafish Proteins
D018398:Homeodomain Proteins; D029961:Zebrafish Proteins; C113874:dharma protein, zebrafish