| Budget Amount *help |
¥4,110,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥510,000)
Fiscal Year 2007: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2006: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
Denticle is a special cuticle structure of larval epithelial cells in Drosophila, which is prepatterned by protrusion of embryonic epidermal cells. In previous studies, we have shown that the polished rice(pri) gene plays an important role in denticle formation. To elucidate molecular basis of pattern formation in Drosophila, we characterized the pri gene by a series of genetic experiments.
pri transcript does not contains any ORFs longer than 49 aa, but five of ten short ORFs are evolutionarily conserved. Reporter assays using series of pri transgenes showed that the first four ORFs(11, 11, 11 and 32 aa), which share a common septamer motif LDPTGQ/TY, were independently translated from the full-length pri cDNA transgenes. When each of any four ORFs was introduced in pri mutants, the denticle phenotype was completely rescued. On the other hands, a control transgene containing frame-shift mutation did not show any effects on the phenotype. These results suggest that pri encode multiple small peptides polycistronically, which share redundant function during denticle formation.
By time-lapse imaging analysis, we found that pri mutant shows evident defects of actin dynamics during denticle formation. In control embryos, intracellular localization of actin fibers prefigured cell protrusions in denticle cells, while pri mutants did not show any sign of the localized signal. We also found that pri is required for expression of several actin regulators controlled by transcriptional factor Shavenbaby(SVB), although expression of SVB itself is not affected by pri mutation, suggesting that pri is involved in transcriptional regulation by SVB protein.
Taken together, we conclude that pri encodes multiple small peptides that regulate denticle formation via intercellular interaction. Taking account of the fact that eukaryotic genomes contain a number of short ORF genes, our results suggest that potent importance of small peptide genes in developmental events.
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