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Abstract
We have previously shown that keratinocyte-specific deletion of Smad4, a TGFp/Activin/BMP signaling mediator, results in a progressive alopecia. To further assess the molecular mechanisms of Smad4 loss-mediated alopecia, we examined expression levels of key molecules associated with hair follicle differentiation in Smad4-deleted skin. Among them, Desmoglein 4 (Dsg4) was down regulated in Smad4-deleted skin prior to the onset of hair follicle abnormalities with gradual depletion coinciding with hair follicle degeneration. Chromatin immunoprecipitation (ChIP) assay showed that Smad4, together with the BMP mediators Smadl and SmadS, but not the TGFp/Activin mediators Smad2 or Smad3, bound to the Smad Binding Element (SBE) of the Dsg4 promoter. A Dsg4 reporter assay revealed that Smad4 was required for the maximal transactivation of Dsg4 in cooperation with Smadl and SmadS. Mutating the SBE of the Dsg4 promoter abrogated Smad4 transactivation of Dsg4. Furthermore, BMP ligands, but not ligands of TGFp and Activin, induced endogenous Dsg4 expression. Our data demonstrate that in the presence of Smad4, BMP signaling participated in transcriptional regulation of Dsg4. Thus, Smad4 loss-associated Dsg4 depletion contributed, at least in part, to hair follicles degeneration in Smad4 deficient skin.
摘要
我们先前的研究显示特异性角质细胞缺失Smad4,一种TGFp /活化素/ BMP信令调停,导致进一步的脱发。 为了进一步评估Smad4缺失的分子脱发机制,我们研究与缺失Smad4的皮肤毛囊分化有关的重要分子的表达水平。 其中,在缺失Smad4皮肤中桥粒芯蛋白4(Dsg4)先于毛发逐渐的消耗和退化而畸形之前下降。染色质免疫沉淀(ChIP)实验表明,Smad4与同骨形态发生蛋白Smadl及SMADs, 促使Dsg4启动子蛋白元素(SBE法)的的结合。而不是TGFp /激活蛋白Smad2或Smad3,一个关于Dsg4的报告分析发现,Smad4在Dsg4与Smadl和SMADs的最大式激活中是必需的。变异的Dsg4启动子阻止Smad4的Dsg4反式激活。 此外,bmp配体诱导内源性Dsg4的表达,而不是TGFp和Activin配体。我们的数据表明,在Smad4的存在下,BMP信号参与Dsg4调控的转录。 因此,至少在部分Smad4变性的皮肤毛囊中,Smad4缺失相关Dsg4的功能。 |
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