| Summary: | 碩士 === 國立臺灣海洋大學 === 水產養殖學系 === 95 === Member of the T-box family of transcription factors, tbx5, expresses in the heart, pectoral fins and eyes of zebrafish during embryonic development. In zebrafish, injection of tbx5 morpholino antisense RNA caused changes of heart conformation, defect of heart looping, pericardium effusion, dropsy of ventral position and decreased in heart rate. Meanwhile, expression of cardiac myogenesis genes amhc, vmhc and cmlc2 was decreased dramatically by the knockdown of tbx5 gene. As a result, we demonstrated that cardiac myogenesis genes might responsible for these phenomenons. Hence, zebrafish was used as our model organism in order to ascertain the relationship between cardiac myogenesis genes and heart defect. In previous study, we have established 5 levels of heart defects: Grade 0, Grade I, Grade II, Grade III and Grade IV. Experimental results indicated that cardiac myogenesis genes express constantly at the early embryonic development and reach highest right before cardiac looping. These cardiac myogenesis genes show insufficient expressions within different heart defect degree embryos, especially at Grade IV. Myogenesis genes of heart defective embryos showed ectopic expression of these genes in addition to heart looping defect. Moreover, slower heart rate was observed in these heart defect embryos. Previous studies reviewed that growth related hormones play important roles throughout heart development and cardiomyogenesis. Early and late treatments of hGH, IGF-I and Ghrelin can reduce certain amount of heart defect and survival rate in tbx5 knockdown zebrafish embryos, especially 10 fmole Ghrelin. In addition, hGH, IGF-I and Ghrelin treatments could improve heart rate and decrease the occurrence of leftward-looping heart in tbx5 gene knockdown embryos. Abnormal zebrafish embryos could be detected after over dosage of hGH, IGF-I and Ghrelin treatments, and decreased the expression of amhc, vmhc and cmlc2 gene expression was also found.
|
|---|
