Molecular Pathology and Embryology of HOXD Related Limb Malformations

Hox基因是控制包括肢体在内的身体许多部位的模式和形态发生的发育主控基因。Hox基因的突变会导致各种肢体畸形，Hoxd13的多ala扩增就是一个突出的例子，它会导致合指畸形（synpolypolydactyly， SPD）。在这项研究中，我们将利用体内和体外模型系统，结合人类遗传学方法和发育遗传学来研究hoxd相关肢体畸形的分子病理学。我们将研究先前在鸡细胞培养系统中发现的人类HOXD13错义突变，以确定改变的靶基因识别。基于我们之前的发现，Hoxd13突变体严重改变了骨和软骨的形成，我们将研究Hox基因在软骨细胞和成骨细胞分化中的作用。我们假设hoxd调控的Wnt基因参与了软骨细胞的极化，并将使用原位杂交筛选、基因调控试验和跖器官培养来研究这一点。基于我们的表达筛选，我们的目标是确定控制骨形成的hoxd基因周围的转录网络。Hoxd13多ala突变的显性负性将被研究。

Hox genes are master genes of development that control patterning and morphogenesis in many parts of the body including the limb. Mutations in Hox genes result in various limb malformations, a prominent example being the poly-Ala expansion in Hoxd13 which causes synpolydactyly (SPD). In this study we will investigate the molecular pathology of HOXD-related limb malformations combining a human genetic approach with developmental genetics using in vivo and in vitro model systems. We will investigate previously identified human HOXD13 missense mutations in chick cell culture systems to identify altered target gene recognition. Based on our previous findings that bone and cartilage formation is severely altered in Hoxd13 mutants we will investigate the role of Hox genes in chondrocyte and osteoblast differentiation. We hypothesize that Hoxd-regulated Wnt genes are involved in the polarization of chondrocytes and will investigate this using in situ hybridization screens, gene regulation assays and metatarsal organ culture. Based on our expression screen we aim at identifying a transcriptional network around the Hoxd-genes that controls bone formation. The dominant negative character of the Hoxd13 poly-Ala mutations will be investigated.