Genetic mechanisms of craniofacial dermal development

描述(由申请人提供)：颅面畸形是全世界约75%的出生缺陷的组成部分(CDC，2010)。正确的颅面形态形成和组织构型需要整合来自不同组织来源的信号。患有局限性皮肤发育不全和先天性皮肤再生不全的儿童，皮肤上有斑块，缺乏真皮。先天性皮肤和真皮缺陷、慢性伤口和严重的大面积烧伤呈现出一系列令人衰弱的慢性问题。先天性皮肤缺陷的遗传基础与Wnt信号功能的丧失有关。我们发现，真皮Wnt/β-catenin信号是促进真皮成纤维细胞命运和抑制软骨命运所必需的。挑战仍然是确定连环蛋白活性如何发挥作用以抑制不同的细胞命运，以及在真皮谱系诱导和分化过程中，WNT的哪些组织来源有助于产生连环蛋白活性。我们最近发现，在颅骨真皮成纤维细胞中，β-连环蛋白活性是下调多梳抑制起始复合体(PRC2)靶基因的关键。这些基因包括Sox9和胶原2？1，它们是软骨谱系的决定因素。我们还确定了表面外胚层和颅骨间充质是Wnt的来源；表面外胚层Wnts是激活真皮连环蛋白和防止软骨形成所必需的。支持这一建议的假设是，外胚层和间充质WNT顺序地产生依赖于连环蛋白活性的PRC2抑制基因，以确保谱系限制和促进真皮发育。为了实现这一目标，我们将在Aim1中证明，连环蛋白的活性招募PRC2来抑制颅骨真皮成纤维细胞中不同的细胞命运。这些发现将为连环蛋白的功能和谱系限制提供新的机械性见解。在AIM2中，我们将确定间充质Wnts是否在外胚层Wnts下游发挥作用，以传播Wnt/？-catenin信号，从而促进颅底真皮和脑膜的形成。我们的方法是组织限制性缺失Wnless，这是贩运所有Wnt配体所必需的，将揭示Wnt来源之间对颅面发育的相互依赖。影响：通过这项工作获得的基础知识将提供一个新的框架，以了解连环蛋白激活如何与表观遗传沉默机制相互作用，以确保血统限制和促进皮肤头面部真皮的形成。这些结果不仅与其他发育中的细胞类型有关，而且 在癌症中也是如此，在癌症中，连环蛋白活性和PRC2活性都处于失调状态。我们组织特异性缺失Wnless的结果对疾病和更好地理解头面部出生缺陷的发病机制具有重要意义。

DESCRIPTION (provided by applicant): Craniofacial dysmorphologies are a component of approximately 75% of birth defects worldwide (CDC, 2010). Proper craniofacial morphogenesis and patterning of tissues requires integrating signals from distinct tissue sources. Children born with Focal Dermal Hypoplasia and Aplasia Cutis Congenita have patches of skin that lack dermis. Congenital skin and dermal defects, chronic wounds, and severe large area burns present a debilitating array of chronic problems. The genetic basis of congenital dermal defects is associated with a loss of Wnt signaling function. We found that dermal Wnt/¿- catenin signaling is required to promote dermal fibroblast fate and suppress cartilage fate. The challenge remains to define how ¿-catenin activity functions to suppress alternative cell fates and which tissue sources of Wnts contribute to generating ¿-catenin activity during dermal lineage induction and differentiation. We recently discovered that ¿-catenin activity is critical fr down-regulation of genes that are targets of Polycomb Repressive Initiation Complex (PRC2) in cranial dermal fibroblasts. These genes include Sox9 and Collagen2¿1, which are determinants of the cartilage lineage. We have also identified the surface ectoderm and cranial mesenchyme as Wnt sources; surface ectoderm Wnts are required for dermal ¿-catenin activation and prevention of cartilage formation. The hypothesis underlying this proposal is that ectodermal and mesenchymal Wnts sequentially generate ¿-catenin activity-dependent PRC2 repression of genes to ensure lineage restriction and promote dermal development. Towards this goal, in Aim1 we will demonstrate that ¿-catenin activity recruits PRC2 to suppress alternative cell fates in cranial dermal fibroblasts. These findings will provide new mechanistic insight into ¿-catenin function and lineage restriction. In Aim2, we will determine if mesenchymal Wnts function downstream of ectodermal Wnts to propagate Wnt/¿-catenin signaling for cranial dermis and meninges formation. Our approach with tissue-restricted deletion of Wntless, which is required for trafficking of all Wnt ligands, will reveal the interdependence between Wnt sources for craniofacial development. Impact: The fundamental knowledge gained through this work will provide a new framework to understand how ¿-catenin activation interacts with the epigenetic silencing machinery to ensure lineage restriction and promote the formation of craniofacial dermis of the skin. These results will be relevant not only in other cell types in development, but also in cancer, where both ¿-catenin activity and PRC2 activity are dysregulated. Our results from tissue-specific deletion of Wntless have implications in diseases and in better understanding the pathogenesis of craniofacial birth defects.