fork head domain, Drosophila embryo, zebrafish, evolution, genes, vertebrate
Okamoto, H.M., Nakayama, I., Nagoya, H., and Araki, K. (2001) Predicted protein structure of medaka FoxA3 and its expression in polster. Zool. Sci.. 18(6):823-832.
The forkhead box genes (Fox genes) are expressed in many tissues during embryogenesis and their products play a key role in organogenesis. We cloned two Fox genes from an embryonic cDNA library of medaka (Oryzias latipes). One was MeHNF3 beta, a homologue of HNF3 beta (FoxA2). The other was Mefkh1 (medaka-forkhead1), related to HNF3 gamma (FoxA3). We found that the expression pattern of FoxA3 differs in some aspects between medaka and zebrafish. Mefkh1 is expressed in the dorsal marginal zone, embryonic shield, polster, gut and slightly axial mesoderm, whereas zebrafish FoxA3 is expressed in the yolk syncytial layer (YSL), axial mesoderm, polster, gut and posterior neural crest cells (Odenthal and Nusslein-Volhard, 1998, Dev Genes Evol 208, 245-258). In zebrafish, the level of expression of FoxA3 in the axial mesoderm is similar to that of FoxA2 (axial); in medaka, FoxA3 (Mefkh1) expression is mainly detected in the polster, and FoxA2 (MeHNF3 beta) is expressed in the axial mesoderm. This indicates that the combined functioning of FoxA2 and FoxA3 in the organogenesis of the polster and axial mesoderm differs between medaka and zebrafish.