Abstract 1570: HIF-1α-Dependent Expression of Nkx2.5 is Required on Normal Heart Development in Xenopus
[Background] Hypoxia inducible factor-1α (HIF-1α) is a transcription factor that regulates oxygen homeostasis, and is globally activated during embryonic development in organs. It is well known that HIF-1α induces the expression of many angiogenesis factors such as VEGF, ETS-1 and FLT-1 in adults. Analysis of HIF-1α knockout mice, which are embryonic lethal due to a defect in vasculogenesis, revealed that HIF-1α signaling is essential for proper vascular development. In this study, using Xenopus we analyzed the role of HIF-1α during embryonic development.
[Methods and Results] For loss-of-function experiments, we injected HIF-1α antisense morpholino into one blastomere at the 8-cell stage of Xenopus embryos. Then we performed whole-mount in situ hybridization for TnC that revealed the knockdown of HIF-1α caused cardia bifida at stage 32 embryos. These defects may result from abnormal cardiomyocyte differentiation. To determine where in the cardiogenic regulatory network HIF-1α might act, we examined the expression of several heart markers. It was found that reduced expression of Nkx2.5 was observed with the knockdown of HIF-1α Luciferase reporter assay using the Nkx2.5 promoter showed that the knockdown of HIF-1α decreased its promoter activity. Furthermore, overexpression of Nkx2.5 could rescue the cardiac abnormality in Hif-1α morpholino injected embryos.
[Conclusions] These results indicated that HIF-1α signaling regulate the expression of Nkx2.5 for cardiac differentiation during embryonic development.