| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2002: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2001: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
We have completed the DMA sequencing of Tryptophan hydroxylase gene (HpTPH) that is expressed exclusively in serotonin cells at apical ganglion during very early moment of gangliogenesis in sea urchin pluteus larvae. The gene encoded 479 amino acids, and its catalytic domain preserved the homology to vertebrates' domain. According to phylogenetic analysis conducted based on the present result, HpTPH was closer to that of vertebrate than those found in invertebrates. In situ hybridization analysis that was used with tyramide signal amplification system showed that the gene expression was limited to serotonin cells that were initially detected immunohistochemically. Potential function of HpTPHwasexaminedbyp-Chlorphynylalanine.aTPHinhib'rtor.treatmentontotheplutei. These larvae did not swim, implicating that ciliary beating that promotes larval swimming is under the control of serotonin.
During serotonergic ganglion formation, serotonin cells extends axons, initially toward the midline of the larvae. To elucidate this mechanism, potential involvement of Netrin 1 that is known to function in axon guidance cue in vertebrates: We have cloned sea urchin Netrin 1 gene (Hpnetrin), and completed the entire DNA sequence. In situ hybridization located the gene expression site at the midline of the larvae during early period of serotonin axon elongation, strongly implicated sea urchin possesses similar molecular mechanism of axon guidance to that of vertebrates. We also cloned hedgehog gene, and completing the entire DNA sequence. In situ hybridization showed the transcription site at very close to apical ganglion forming area of the larvae.
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