Molecular Regulation of Embryonic Limb and Facial Cartilage Differentiation

成人身体的大多数骨骼是由胚胎发育期间形成的软骨组织模板产生的。因此，阐明胚胎内软骨形成的机制对于理解正常骨骼发育至关重要。我的研究计划主要是为了阐明控制脊椎动物胚胎四肢和单个面部区域软骨细胞（软骨细胞）分化的分子途径。我们的研究目前集中在确定各种蛋白激酶在将生长调节信号从软骨细胞祖细胞表面传递到细胞核内关键靶基因中所起的作用。我们最近发现，细胞质ERK 1/2蛋白激酶系统传递来自成纤维细胞生长因子（FGF）作用于软骨细胞表面的信号。有趣的是，FGF和ERK 1/2都具有位置依赖性作用，刺激面部下颌区域细胞中的软骨形成，但抑制发育肢体和面部额鼻区域细胞中的软骨分化。在本项目中，我们将检验以下假设：下颌、额鼻和肢体细胞群对FGF和ERK 1/2信号的不同反应是PEA 3家族核蛋白表达差异的结果（即，Er 81、Pea 3和Erm转录因子）。此外，我们将研究一个独特的蛋白激酶系统，ERK 5通路，在胚胎软骨形成的作用。最后，我们将采用一种创新的“激酶组分析”蛋白质组学技术，对调节软骨形成的多个蛋白激酶系统的相互作用进行全面分析。这些研究将揭示控制胚胎肢体和面部正常骨骼发育的新分子机制，并可能深入了解某些先天性骨畸形的原因。此外，我们的研究结果可能为软骨组织工程策略的改进提供了途径，这些策略旨在为受伤的关节制造替代组织。

Most bones of the adult body are generated from cartilage tissue templates that are formed during the period of embryonic development. Therefore, elucidating the mechanisms that govern cartilage formation within the embryo is crucial for understanding normal skeletal development. My research program is broadly aimed at clarifying the molecular pathways that control cartilage cell (chondrocyte) differentiation in the limbs and individual facial regions of the vertebrate embryo. Our research is currently focused on identifying the roles that various protein kinase enzymes play in relaying growth regulatory signals from the surface of chondrocyte progenitor cells to crucial target genes within the nucleus. We have recently shown that the cytoplasmic ERK1/2 protein kinase system relays signals from Fibroblast Growth Factor (FGFs) acting on the chondrocyte cell surface. Intriguingly, both FGFs and ERK1/2 have location-dependent effects, stimulating cartilage formation in cells from the mandibular region of the face, but inhibiting cartilage differentiation in cells from the developing limbs and the frontonasal region of the face. In the present project, we will test the hypothesis that the differential responses of mandibular, frontonasal, and limb cell populations to FGF and ERK1/2 signals are the result of differences in their expression of nuclear proteins of the PEA3 family (i.e., Er81, Pea3 and Erm transcription factors). In addition, we will investigate the role of a distinct protein kinase system, the ERK5 pathway, in embryonic cartilage formation. Finally, we will employ an innovative "kinome profiling" proteomic technique to initiate a comprehensive analysis of the multiple protein kinase systems interactions that regulate chondrogenesis. These studies will uncover novel molecular mechanisms controlling normal skeletal development in the limb and facial areas of the embryo, and may provide insight into the causes of some congenital bone malformations. In addition, our findings may suggest avenues for the refinement of cartilage tissue engineering strategies aimed at fabricating replacement tissue for injured joints.