Role of Hox Genes in Integration of the Musculoskeletal System in Development

描述(申请人提供)：关于肌肉、骨和肌腱组织的单独形成和分化，存在着大量的数据，但对于允许这些组织相互之间进行适当连接的分子机制了解甚少。这一知识对于建立有用的治疗方法以修复因受伤或疾病而破裂的这些组织至关重要。HOX基因在骨骼图案化过程中发挥着基础作用，但新的初步数据显示，HOX基因在发育中的肢体中的表达并不局限于骨骼组织，这些基因在肌腱和肌肉组织的图案化以及所有三种组织类型的整合中似乎也扮演着预期较少的角色。最近的数据还表明，这些基因在损伤后高度上调，表明在损伤反应中发生的愈合和重塑中发挥了作用。这项研究的长期目标是了解HOX基因如何调控肌肉骨骼系统特定区域的形成和整合，以及这些信息如何被用于指导损伤或疾病后的再生治疗。这项建议的目的是了解HOX在发育中的前肢肌肉、肌腱和骨骼的发育和整合中的细胞机制，以及这些机制是如何在损伤反应中重新部署的。核心假设是，Hox11基因的功能是指导发育中的肢体的肌肉、肌腱和软骨的模式和整合，这些基因在损伤后上调，以便在体内进行适当的修复和重塑。将使用现有的零等位基因和荧光报告系来评估Hox11基因如何对发育中的肢体内肌肉群、肌腱和软骨元素的形成和模式做出贡献。在肌肉骨骼系统中，通过使用空间和时间受限的CRE删除线有条件地消融HOX功能，将检验HOX介导的模式的时空控制和肌肉骨骼系统中连通性的建立。最后，HOX基因在组织修复和骨骼重塑中的作用将通过在成年后有条件地去除HOX功能(在获得适当的肌肉骨骼模式之后)并检查HOX功能丧失对骨折修复和随后的骨骼重塑的影响来确定。这项拟议研究的贡献是重大的，因为将获得关于区域调节肌肉骨骼整合的关键新知识，将定义传递这些信息的组织(S)，以及这些因素如何在成年后重新部署以修复损伤。在这项申请中提出的研究在确定与肌肉骨骼系统的各个组成部分的整合有关的因素和细胞类型以及产生的新工具方面具有创新性，这些工具允许理解在损伤修复过程中正确构型的成人组织中HOX基因的功能。总之，从这些研究中获得的信息将提供对肌肉骨骼生物学中HOX功能的范式转换的理解。

DESCRIPTION (provided by applicant): A significant amount of data exists regarding the formation and differentiation of muscle, bone and tendon tissue individually, but little is understood regarding molecular mechanisms that allow these tissues to make appropriate connections with one another. This knowledge is critical for establishing useful therapies to repair these tissues after disruption from injury or disease. Hox genes perform fundamental roles in patterning the skeleton, but new preliminary data shows that Hox gene expression in the developing limb is not restricted to skeletal tissue, and these genes also appear to play less anticipated roles in patterning tendon and muscle tissue as well as in the integration of all three tissue types. Recent data additionally that shows that these genes are highly up-regulated following injury, suggesting a role in the healing and remodeling that occurs in response to injury. The long-term goal of this research is to understand how Hox genes regulate the region- specific formation and integration of the musculoskeletal system and how this information can be used to inform regenerative therapies following injury or disease. The objective of this proposal is to achieve an understanding of the cellular mechanisms of Hox function in the development and integration of muscle, tendon and bone in the developing forelimb and how these mechanisms are redeployed in response to injury. The central hypothesis is that Hox11 genes function to direct the patterning and the integration of the muscle, tendon and cartilage in the developing limb and that these genes are up-regulated in response to injury to allow proper repair and remodeling in vivo. How Hox11 genes contribute to the formation and patterning of muscle groups, tendons and cartilage elements within the developing limb will be assessed using existing null alleles and fluorescent reporter lines. The spatiotemporal control of Hox-mediated patterning and the establishment of connectivity in the musculoskeletal system will be examined by conditionally ablating Hox function using spatial and temporally restricted Cre deletor lines. Finally, the roles for Hox genes in tissue repair and skeletal remodeling will be determined by conditionally ablating Hox function in adulthood (after proper musculoskeletal patterning has been achieved) and examining the effects of loss of Hox function on fracture repair and subsequent skeletal remodeling. The contribution of the proposed research is significant because critical new knowledge regarding the regional regulation musculoskeletal integration will be gained, the tissue(s) from which this information is transmitted will be defined, and how these factors are redeployed in adulthood to repair injuries will be determined. The research proposed in this application is innovative in identifying factors and cell types involved in the integration of individual components of the musculoskeletal system as well as in the novel tools generated to allow an understanding of the function of Hox genes in properly patterned adult tissue during injury repair processes. Together, the information gained from these studies will provide a paradigm-shifting understanding of Hox function in musculoskeletal biology.