| Summary: | 碩士 === 國立臺灣大學 === 分子與細胞生物學研究所 === 93 === Myf5 is the first expressed muscle regulatory factor in many species and the transcription mechanism is dedicated controlled. In zebrafish, myf5 is activated in presomitic mesoderm (PSM); prolong expression at newly forming somites and down-regulation in the elder one. However, the activation mechanism of myf5 in PSM has never been reported. Mesp family, including mespo, mesp-a, are expressed in PSM or somitomere that function as transcription factors. Here, we performed morpholino (MO) knockdown experiments to examine the transcriptional effects of Mesp family on zebrafish myf5 gene. Treatment the Myf5:BAC:gfp transgenic line with mespo-MO revealed that Myf5-positive green fluorescent cells were restricted in the PSM. We furthermore using whole mount in situ hybridization to examine the expression patterns of myf5 and found that myf5 transcripts were also restricted to tail buds in mespo knockdown embryos. Compared to the wild type, myoD transcripts were unaffected, indicating that mespo played important role in regulating myf5. Similar results were observed in mesp-a knockdown embryos. Interestingly, we also found that mespo is able to activate mesp-a in somitomeres. When mespo and mesp-a were double knockdown, myf5 transcripts were down-regulated significantly. Besides, down-regulated her1 and fgf8 transcripts in mespo-morphants also showed that mespo was able to regulate her1 oscillation in anterior PSM and fgf8 expression in somites, indicating that mespo could regulate somite segmentation indirectly through regulating both her1 and fgf8. Based on these observations, we propose that transcription of myf5 on PSM is maintained by mespo through mesp-a and her1 signaling.
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