| Summary: | 碩士 === 國立臺灣師範大學 === 生命科學研究所 === 92 === During animal embryogenesis, heart is the first funtional organ to be formed. Heart provides pulsative power for circulation of blood cells, therefore, heart is considered as one of the most important organs in animal. Despide the morphological difference, cardiogenesis in both Drosophila and vertebrates are quite similar. For instance: hearts of both fly and vertebrates are derived from mesoderm. Furthmore, most genes involved in cardogenesis, such as tinman, gata4 and mef2, are evolutionary conserved in different species. The homeobox containing gene, tinman plays a vital role in developing heart. The heart precursor cells are missing in tinamn mutant embryos, which leads to abolish of the mature heart. Tinman homologs, Nkx 2 group genes, were also discovered in dirrerence organisms, including mouse, Xenopus and Zerbra fish, which shown to play essential roles during heart development. Acummulate evidences suggested that tinman exerts its function by activating down-stream genes or acting synergistically with other genes to specify different cardial cell types. Disseting the interaction of these genes will assist us greatly in understanding the cardiogenesis of aninmals. The major objective of this study is to identified more cadiogenic genes, and elucidate their fndtion during heart development. From the platform of gene expression in Drosophila which is provided by Berkeley Drosophila Genome Project, we have identified a candidate gene, him, that may participate in heart development of Drosophila. Expression of Him in mesoderm is later than that of tinman. Later both tinman and Him are expressed restrictly in heart. As tinman is an essential gene in heart morphogenesis, we would like to address whether Him and tinman plays same roles as suggested by their expression profiles in this study. Using in situ hybridization we have found that Him is expressed in cardial and pericardial cells. Numbers of cardial cells are increased in loss-of-funtion embryos of Him. Similar phenotypes had been observed in him RNAi transgenic flies. In addition, we have characterized the mesoderm enhancer of Him and demonstrated that Him is regulated by tinman, pannier and Dmef2. Further studies are needed to show if Him is a direct target of these gene.
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