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题名	Akirin及ZFP36L1在非洲爪蛙神经发育中的表达及功能研究
作者	夏英杰
学位类别	博士
答辩日期	2011-12
授予单位	中国科学院研究生院
授予地点	北京
导师	毛炳宇
关键词	神经发育 Akirin BMP ZFP36L1 RNA结合蛋白
其他题名	The expression patterns and functions of Akirin and ZFP36L1 genes in Xenopus neural development
中文摘要	在脊椎动物的原肠胚中，原肠背部中央的脊索与其上方覆盖的预定神经外胚层细胞之间通过相互作用，使外胚层发育为神经组织的过程即为神经诱导。脊椎动物的神经诱导是一个复杂有序，受多种信号通路和转录因子共同调控的过程。其中BMP信号通路发挥最重要的作用。 Akirin是一类核因子，可参与免疫反应、肌肉发生、肿瘤发生等多种生理过程的调控。我们发现非洲爪蛙的Akirin1和Akirin2在神经系统内特异性表达，二者都表达于爪蛙胚胎的神经板（管）和神经嵴，且表达区域基本重叠。注射特异的morpholino抑制这两个基因的表达后，胚胎都会产生较严重的神经发育缺陷。注射Akirin1 MO的胚胎，头部发育异常，注射侧眼睛明显减小甚至不能形成。而Akirin2表达被抑制后，胚胎在尾芽期出现体轴缩短弯曲等表型，在神经板期检测发现注射侧Sox2、Pax3、Nkx6.2和FoxD3等神经和神经嵴特异基因表达明显增强，这一表型可较好地被非洲爪蛙Akirin2 mRNA挽救。在动物帽的半定量PCR实验中Akirin2的敲低可以上调Sox2的表达，暗示其可能参与神经诱导。此外,在动物帽实验中，注射Akirin2的morpholino可抑制BMP信号的活性，在HEK-293细胞中转染Akirin2的表达质粒，BMP信号的活性被上调。虽然爪蛙Akirin1和Akirin2在胚胎发育早期具有相似的表达模式，但分别抑制这两个基因会导致不同的表型，说明二者在胚胎发育中具有不同的作用。Akirin2对非洲爪蛙神经发育调节的具体机制，及其是否依赖于BMP信号通路的活性，仍需进一步的实验验证。 ZFP36家族蛋白是一类RNA结合蛋白，它们均含有两个或两个以上串联的CCCH锌指结构域，并可通过此结构域与特异mRNA的3’非编码区的AU富集元件（ARE）相结合，促进其多聚腺苷酸尾巴的降解，从而降低靶标mRNA的稳定性。ZFP36蛋白家族参与动物发育的多个生理过程。其成员ZFP36L1已有多个靶标RNA被发现，并且在小鼠中此基因的敲除是胚胎致死的，而ZFP36L1在非洲爪蛙胚胎发育中的表达模式及其功能是未知的。我们研究了ZFP36L1在非洲爪蛙胚胎神经系统中的特异表达及其潜在的功能。在爪蛙早期胚胎中过表达ZFP36L1可导致严重的神经管缺陷（NTD），并伴随着神经标记基因表达水平的降低。ZFP36L1蛋白的锌指结构域和C末端区域对这一功能都是必不可少的，而这也与其在细胞质中的定位相符。这些结果提示，非洲爪蛙的ZFP36L1蛋白可能参与早期神经分化的过程，且此活性可能与其在细胞内的定位相关。
英文摘要	Neural induction is the process by which the gastrula embryonic ectoderm is induced to become neural tissue via signaling interactions with the adjacent midline mesoderm (notochord). This process is complicated but ordered, involving several signaling pathways and lots of transcription factors. In Chapter 1, I reviewed the roles of BMP, FGF, Wnt and IGF pathways and a series of transcription factors including Sox, FoxD5 and Zic during vertebrates’ neural induction. Akirins are nucleus factors reported to participate in immune response, muscle genesis, carcinogenesis and other developmental processes. In Chapter 2, I report that Xenopus laevis Akirin1 and Akirin2 are expressed in the neural system, including the central neural system and neural crest, and they have very similar expression patterns. Knockdown of either Akirin in Xenopus embryos leads to severe defects in neural development. Akirin1 MO injected embryos shows deformed heads, with small eyes or even no eyes on the injected sides. Akirin2 knockdown in Xenopus embryos results in short and bended body axes at tailbud stages, and expansion of the neural markers Sox2, Pax3, Nkx6.2 and FoxD3. The different phenotypes induced by knockdown of Akirin1 and Akirin2 suggest that they might have different roles during Xenopus development. By reporter gene assays in both Xenopus animal caps and human HEK-293 cells, we found that Akirin2 played a role in regulation of BMP signal. Knockdown of Akirin2 in Xenopus animal caps leads to decrease of BMP signaling activity, while overexpression of Akirin2 in HEK-293 cells increases BMP activity. Further investigations are required to verify the exact role of Akirin2 in BMP signaling regulation. Xenopus ZFP36L1 belongs to the ZFP36 family, which contains a group of RNA-binding proteins that contain two or more characteristic tandem CCCH-type zinc-finger domains. Members of this family can bind to AU-rich elements in 3’-UTR of specific mRNAs and remove the poly(A) tails, promoting turnover of the mRNA. Knockout of Zfp36l1 in mouse leads to embryonic lethal. However, the expression and function of ZFP36L1 during Xenopus embryo development were largely unknown. In Chapter 3, I report that XZfp36l1 is specifically expressed in the neural tissues. Its overexpression leads to neural tube defects in Xenopus embryos and decrease of neural marker expression. Both the zinc finger and C-terminal domains are required for its activity to induce neural tube defects (NTD) and its cytoplasmic localization. These results suggest XZFP36L1 may be involved in neural differentiation in Xenopus embryos.
语种	中文
内容类型	学位论文
源URL	[http://159.226.149.26:8080/handle/152453/10162]
专题	昆明动物研究所_发育生物学
推荐引用方式 GB/T 7714	夏英杰. Akirin及ZFP36L1在非洲爪蛙神经发育中的表达及功能研究[D]. 北京. 中国科学院研究生院. 2011.

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