Genetic mechanisms of craniofacial dermal development

描述（由申请人提供）：颅面畸形是全球约75%出生缺陷的组成部分（CDC，2010）。正确的颅面形态发生和组织模式需要整合来自不同组织来源的信号。出生时患有局灶性皮肤发育不全和先天性皮肤发育不全的儿童有缺乏真皮的皮肤斑块。先天性皮肤和真皮缺陷、慢性创伤和严重的大面积烧伤呈现出一系列使人衰弱的慢性问题。先天性皮肤缺陷的遗传基础与Wnt信号传导功能的丧失有关。我们发现，真皮Wnt/β-连环蛋白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β-连环蛋白活性如何发挥作用以抑制替代细胞命运，以及Wnt的哪些组织来源有助于在真皮谱系诱导和分化期间产生β-连环蛋白活性。我们最近发现，β-连环蛋白活性对于颅真皮成纤维细胞中Polycomb抑制起始复合物（PRC 2）靶基因的下调至关重要。这些基因包括Sox 9和胶原蛋白2 β 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间充质为Wnt来源;表面外胚层Wnt是真皮β-连环蛋白激活和预防软骨形成所必需的。这一提议背后的假设是，外胚层和间充质Wnt依次产生β-连环蛋白活性依赖性PRC 2基因抑制，以确保谱系限制和促进真皮发育。为了实现这一目标，在Aim 1中，我们将证明β-连环蛋白活性招募PRC 2来抑制颅真皮成纤维细胞中的替代细胞命运。这些发现将为β-连环蛋白功能和谱系限制提供新的机制见解。在Aim 2中，我们将确定间充质Wnt是否在外胚层Wnt的下游起作用，以传播Wnt/β-连环蛋白信号，用于颅真皮和脑膜形成。我们的方法与Wntless的组织限制性缺失，这是需要所有Wnt配体的贩运，将揭示Wnt来源之间的相互依赖性颅面发育。影响力：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β-连环蛋白激活如何与表观遗传沉默机制相互作用，以确保谱系限制并促进皮肤颅面真皮的形成。这些结果不仅与发育中的其他细胞类型有关， 在癌症中也是如此，其中β-连环蛋白活性和PRC 2活性都失调。我们的结果从组织特异性缺失的Wntless的疾病和更好地理解颅面出生缺陷的发病机制的影响。

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.