【作者】 孟凡伟；

【导师】 孟安明；

【作者基本信息】 清华大学 ， 生物学， 2008， 博士

【摘要】 Dapper(Dpr)家族成员在胚胎发育过程中发挥着重要的功能,并且参与了多种信号通路的调节,主要包括TGF-β/Nodal,经典和非经典的Wnt信号通路。目前,在小鼠中已发现三种Dpr家族成员,Dpr1-Dpr3。通过对他们时空表达谱的研究发现,三种Dpr均在胚胎的各时期表达,在成年组织的表达略有差异,但是在脑中的表达量都比较高。已有研究发现斑马鱼Dpr2通过促进Nodal/TGF-β的I型受体经溶酶体途径降解来调节其信号通路,体内功能实验证明斑马鱼Dpr2抑制Nodal信号的中胚层诱导活性。虽然小鼠Dpr2在体外能够抑制TGF-β信号,并且在斑马鱼胚胎中过表达也能减少一些中胚层特异基因的表达,但是关于小鼠Dpr2体内功能的研究还没有报道。在本研究中,通过基因打靶技术制备了Dpr2基因完全敲除小鼠(Dpr2-/-)。但是却发现Dpr2-/-小鼠胚胎发育正常,并没有出现胚胎致死的表型。Dpr2-/-小鼠的囊胚同野生型的一样,可以从透明带中孵出并且拥有正常的Outgrowth。出生后的Dpr2-/-小鼠能够正常生长,雌雄均可育。对Dpr2-/-小鼠脑进行组织学分析没有发现任何异常,其神经干细胞的增殖同野生型小鼠也没有差别。本研究还发现Dpr2在成年小鼠的表皮及毛囊角质细胞中高表达,并且缺失Dpr2导致小鼠皮肤创伤愈合的再表皮化加快。进一步的研究证实,缺失Dpr2增强了角质细胞对TGF-β信号的反应性,并且TGF-β信号通过上调特定的integrin基因的表达来促进角质细胞的迁移。由此可以得出如下结论:缺失Dpr2基因对于小鼠胚胎发育、生长和脑的形态没有影响,Dpr2通过抑制TGF-β信号来抑制创伤皮肤的再表皮化。更多还原

【Abstract】 Transforming growth factor (TGF-β) signals regulate a variety of cellular events and play important roles in embryonic development. Members of the Dapper (Dpr)/Dact family play roles in regulating distinct signaling pathways, including TGF-β/Nodal as well as canonical and noncanonical Wnt pathways. Three mouse Dpr genes, Dpr1-Dpr3, are expressed in mouse embryos and in distinct adult tissues, particularly in the brain. It has been demonstrated that zebrafish Dpr2 modulates Nodal/TGF-βsignals by promoting lysosomal degradation of their receptors and inhibits mesoderm induction in zebrafish embryos. Mouse Dpr2 is able to antagonize TGF-β? signaling in vitro and ectopic expression in zebrafish embryos also results in reduction of mesoderm gene expression. However, functions of mDpr2 in vivo have not been reported.In this study, Dpr2-deficient mice were generated by gene knockout approach. Dpr2 knockout (Dpr2-/-) embryos developed normally and they were alive at birth. Like wild-type blastocysts, the isolated Dpr2-/- E3.5 blastocysts hatched from the zona pellucida, and had normal Outgrowth. Postnatal Dpr2-/- mice were able to grow up and the adults were fertile. The distribution of Dpr2 transcripts in subregions of adult brain of mice was examined in details. Dpr2 appears to be highly expressed in the cerebral cortex, hippocampus, thalamus and medulla oblongata. However, histological analyses revealed that Dpr2-/- mice had normal brain morphology; their neural stem cells showed proliferative activity similar to those of their wild-type littermates. Dpr2 was found to be highly expressed in epidermal keratinocytes and in hair follicles of adult mice, and its deficiency resulted in the accelerated re-epithelialization during cutaneous wound healing. Furthermore, loss of Dpr2 function enhanced the responses of keratinocytes to TGF-βstimulation; and TGF-βsignals promoted keratinocytes migration by regulating the expression of specific integrin genes.Taken together, these data suggest that Dpr2 is dispensable for mouse embryonic development, postnatal growth and brain formation. But, Dpr2 plays an inhibitory role in the re-epithelialization of adult skin wounds by attenuating TGF-βsignaling.更多还原