Molecular Genetics of Progressive Osseous Heteroplasia

描述(由申请人提供)：罕见疾病可以提供对基本细胞机制的关键洞察。其中一种名为进行性骨质疏松症(POH)的疾病是一种遗传性疾病，身体在皮肤、脂肪和骨骼肌中产生骨骼。成骨障碍，如POH，通过揭示改变多潜能前体细胞以促进成骨细胞分化的基因突变，提供了获得有关骨形成调控的有价值的信息的机会。我们发现，在POH中，GNAS基因的两个副本中的一个发生了突变，证实了失活的GNAS突变可以改变细胞的命运，在不适当的位置诱导骨形成。GNAS基因的主要产物是Gs？，这是一个G蛋白亚基，从细胞表面受体传递信号来激活cAMP。POH患者的异位(骨外)骨形成通常始于皮下脂肪，提示有共同的祖细胞，成骨和成脂之间可能存在相互作用的关系。我们的调查显示Gs？POH患者细胞的mRNA、蛋白表达和cAMP活性降低，GNAS和cAMP的表达降低与成骨增强有关，而cAMP信号的激活则抑制成骨，有利于成脂。我们的研究表明，GNAS在细胞命运决定中扮演着复杂的角色，并指导我们进一步研究GNAS对成骨和成脂调控的细胞和分子机制。为了深入了解这一非常复杂的过程，并基于我们的初步数据，我们将重点研究cAMP信号作为通过GNAS/Gs？下行信号的关键入口点。调节细胞命运的决定。我们假设，cAMP信号调节早期细胞命运的决定，从而指导成骨和成脂。我们提出了三个特定的目标：目的1.通过体外和体内实验，确定GNAS和cAMP信号在调节细胞命运决定和组织发育中的作用和阶段。目的2.研究cAMP和其他信号通路在GNAS失活反应中的相互作用，重点研究cAMP与BMP通路的串扰。目的3.通过体内谱系示踪实验，研究GNAS失活后被招募形成异位骨和脂肪组织的祖细胞的特性。这一建议将为在正常和病理条件下调节成骨和脂肪生成的分子途径提供新的见解，将描绘控制肌肉骨骼系统中的多能干细胞分化为不同谱系的因素，并将为设计针对广泛的人类骨和脂肪组织疾病的分子诊断和治疗策略提供重要基础。

DESCRIPTION (provided by applicant): Rare diseases can provide critical insight into fundamental cellular mechanisms. One such disease, progressive osseous heteroplasia (POH), is a genetic disorder in which the body produces bone in skin, fat and skeletal muscle. Disorders of osteogenesis such as POH provide the opportunity to gain valuable information about the regulation of bone formation by revealing gene mutations that alter multi-potential precursor cells to promote osteoblast differentiation. We discovered that one of two copies of the GNAS gene is mutated in POH, establishing that inactivating GNAS mutations can alter cell fate to induce bone formation in inappropriate locations. The major product of the GNAS gene is Gs?, a G protein subunit that transmits signals from cell surface receptors to activate cAMP. Heterotopic (extra-skeletal) bone formation in POH patients often initiates within subcutaneous fat, suggesting common progenitor cells and a relationship, perhaps reciprocal, between osteogenesis and adipogenesis. Our investigations have shown that Gs? mRNA and protein expression and cAMP activity are reduced in cells from patients with POH and that decreased expression of GNAS and cAMP are associated with enhanced osteogenesis, while increased activation of cAMP signaling inhibits osteogenesis and favors adipogenesis. Our studies have demonstrated that GNAS plays a complex role in cell fate decisions and have directed us to further investigate the cellular and molecular mechanisms of osteogenic and adipogenic regulation by GNAS. In order to gain insight into this very complex process and based on our preliminary data, we will focus this proposal on investigations of cAMP signaling as a critical entry point to downstream signaling through GNAS/Gs? in regulating cell fate decisions. We hypothesize that cAMP signaling regulates early stage cell fate decisions that direct osteogenesis and adipogenesis. We propose three Specific Aims: Aim 1. Identify the roles and stages of GNAS and cAMP signaling in regulating cell fate decisions and tissue development using in vitro and in vivo assays. Aim 2. Examine interactions between cAMP and other signaling pathways in response to GNAS inactivation, focusing on cAMP crosstalk with the BMP pathway. Aim 3. Investigate the identity of progenitor cells that are recruited to form heterotopic bone and adipose tissue in response to GNAS inactivation through in vivo lineage tracing experiments. This proposal will provide new insights into the molecular pathways that regulate osteogenesis and adipogenesis under normal and pathological conditions, will delineate factors that control the differentiation of pluripotent stem cells in the musculoskeletal system into different lineages, and will provide an important foundation for the design of molecular diagnostic and treatment strategies for a wide range of human disorders of bone and adipose tissue.