○Haichang Li1,2 Ichiro Masai3 Yasuhiro Nojima1,2 Atsuko Komori3 Hideomi Tanaka1,2 Yuko Nishiwaki3 Hironori Wada2 Hitoshi Okamoto1,2
CREST, Japan Science and Technology Corporation (JST)1，Lab. for Developmental Gene Regulation, RIKEN BSI2，Masai Initiative Research Unit, RIKEN3
In vertebrate, brain development is a complex process. During gastrulation, the neural plate is induced in the dorsal side of ectoderm by signals from Spemann organizer. Next, a dorsal edge of the neural plate converge and fuse to form the neural tube, which shows vertebrate-specific brain structure through subsequent morphological change. Finally, neuronal differentiation and synaptic connections lead to establishment of functional neural circuits. To identify genes involved in CNS development, we have performed ENU-induced large-scale mutagenesis and identified zebrafish mutants showing defects in brain development. Here we show a novel brain mutant, kaitou (kat, メopen-headモ in Chinese/Japanese). Morphological analysis combined with molecular marker labeling has revealed that neural plate fail to close in mid/hindbrain territory and specification of midbrain and MHB seems to be normal in kat. These data suggest that dorsal rim of neural plate corresponding to mid/hindbrain fails to converge or fuse properly in kat. To elucidate whether the differentiation of neural crest cells, which derive from dorsal edge of neural tube, is affected or not, we examined formation of neural crest-derivative tissues such as cartilage and pigment in kat. However, the two structures show normal in kat, suggesting that specification of dorsal area of the neural tube is normal in the mutant. To clone kat gene, we mapped kat mutational locus to LG1 where there has been reported no gene involved in brain morphogenesis, suggesting that kat might be a novel gene.
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