| Summary: | 博士 === 國立陽明大學 === 臨床醫學研究所 === 107 === The Tbx5 mutation in human causes Holt-Oram syndrome, an autosomal dominant disease characterized by a familial history of congenital heart defects and pre-axial radial upper limb defects. Several phenotypes including heart or limb/pectoral fin anomalies consistently exist in zebrafish with TBX5 deficiency, as some different species. We have established a Tbx5 knockdown embryonic zebrafish model by morpholino, which also known as a morpholino oligomer and as a phophorodiomidate morpholino oligomer (PMO). We also have reported that aberrant apoptosis and dormant cell growth over head, heart, trunk, fin, and tail of zebrafish embryos with TBX5 deficiency correspond to the dysmorphogenesis of Tbx5 morphants. Since exogenous human growth hormone is able to enhance expression of downstream mediators in the growth hormone and insulin-like growth factor I pathway, we try to study effects of GH/IGF-I on Tbx5 morphants during embryonic and developmental stages with heart-fin dysmorphogenesis.
Microarray revealed the attenuating effects of GH and IGF-I in Tbx5 -MO knockdown embryos throughout different developmental stages. Exogenous GH, or IGF-I, supplied to Tbx5 knockdown zebrafish embryos to enhance the expression of downstream mediators in the GH and IGF-I pathway including gh, ghra, ghrb, ifg1, igf1-ra and ifg-rb and signal transductors such as erk1 and akt2. GH and IGF-I, respectively, have effects to decrease expression of apopotosis-related genes and proteins, and to enhance expression of cell cycle-related genes and cardiomyogenetic genes, revealed by TUNEL assay, semi-quantitative RT-PCR, and immunohistochemical analysis,
Supplementary GH/IGF-1 could enhance cell and individual survival, reduce apoptosis and eventually correct dysmorphogensis in various organs, especially heart, trunk, and pectoral fins. That is, GH/IGF-I could play a survival factor to rescue the mortality and the dysmorphogenesis in zebrafish embryos with TBX5 deficiency. It implies a promising embryonic treatment for congenital anomalies by hereditary genetic defects.
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