| 其他摘要 | Post-transcriptional regulation, including the regulation of pre-mRNA alternative splicing, mRNA stability, localization and translation, play important roles in embryonic development. Post-transcriptional control is often achieved through elements in its 5’- or 3’-untranslated region (UTR) of an mRNA. Recent studies show that post-transcriptional control is also crucial for vertebrate neural development. Sox2 gene encodes one transcriptional factor and is one of the earlist neural determinants of the neural system in vertebrate. Sox2 is expressed strongly in the neuroepithelium of the developing central nervous system and has been shown to function in neural stem cells. Through bioinformatical analysis, we found that the 3’UTR sequences of vertebrate Sox2 genes are highly conserved and contained four conserved AU rich fragments. Through reporter gene analysis, we analyzed the ability of the elements in Sox2 3’UTR to regulate gene expression in Xenopus embryos and cultured cells. Our results showed that two of these elements were able to promote reporter expression significantly, suggesting that the expression of Sox2 might be regulated post-transcriptionally. We also identified one element from Xenopus fhl3 3’UTR that was highly conserved in the 3’UTR of about 20 different genes. Interestingly, so far this element is found only in Xenopus. To study its possibile involvement in post-transcriptional regulation, we compared the expression of reporter genes with or without this element in Xenopus embryos and 293T cells. This element was found able to reduce the expression of reporter genes. Since it is found only in amphibians, we speculated that it might be involved in the regulation of certain amphian specific process, such as metamorphosis. To check this possibility, we checked the responsiveness of the reporter genes to thyroid hormone, the key regulator of metamorphosis in amphibian. Our results showed that thyroid hormone treatment could significantly enhance the expression of the reporter genes with this element, but not the control reporter. The results suggested the possibility for this conserved element to mediate thyroid hormone induced post-transcriptional control of the target genes. Vertebrate eye development is controlled by a complex regulatory network. Several transcription factors that pattern the anterior neural plate of the early vertebrate embryo are essential for normal eye development. We studied the temporal and spatial expression pattern of Sox1 and MGC85160 genes during Xenopus laevis early development, and compared the expression patterns of Sox1-3 in the developing eye and brain. Sox1 was expressed maternally and was detected in the animal pole at cleavage to blastrula stages and in the central nervous system (CNS) and the developing eye from neurula stage on. At neurula to tailbud stages, MGC85160 was also strongly expressed in the CNS and the developing eye. Anabarilius grahami is a cyprinoid fish endemic to Fuxian Lake, Yunnan, China. In this study, we also produced a comprehensive staging series of A. grahami. The embryonic development of A. grahami was divided into six main periods: zygote period, cleavage period, blastula period, gastrula period, segmentation period and hatching period. Its embryonic development is essentially similar to that of zebrafish but relatively slower. We have also cloned and checked the expression patterns of A. grahami Sox2, Pax6a, Six3a and Rx2 genes during eye development. The four genes showed similar expression patterns to their zebrafish homologs, suggesting the evolutionary conservation of the regulatory network of eye development. |
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