MOLECULAR GENETICS OF PROGRESSIVE OSSEOUS HETEROPLASIA

描述(由申请人提供)：成骨的遗传障碍为骨形成的调节提供了有价值的见解。进行性骨质疏松症(POH)是一种罕见的致残性遗传性疾病，身体在皮肤、脂肪和骨骼肌中产生骨。POH患者的基因突变使GNAS基因的两个拷贝之一失活，并改变细胞的命运，导致不适当位置的骨形成(异位骨化)。GNAS编码G(S)α蛋白，通过细胞表面受体将信号耦合到细胞内的第二信使，然而这些突变对骨细胞分化的具体影响尚不清楚。POH患者的异位骨形成通常发生在皮下脂肪中，这表明骨和脂肪细胞分化之间存在密切的、可能是相互作用的关系。除了继续研究GNAS在POH中的遗传和表达外，这项建议的一个主要目标是检查杂合子失活GNAS突变对骨(成骨细胞)和脂肪(脂肪细胞)细胞分化的影响。我们假设：(1)GNAS基因杂合失活突变改变了引导成骨细胞和/或脂肪细胞分化的细胞信号；(2)GNAS基因失活突变的复杂表型后果受GNAS的母系/父系遗传的影响。1.研究POH患者中携带GNAS突变的GNAS等位基因的亲代来源。2.检测POH基因组DNA在GNAS基因座的甲基化特征。3.检测成骨细胞和脂肪细胞分化过程中GNAS基因表达的差异。4.检测杂合子GNAS基因失活对成骨细胞和脂肪细胞分化的影响。5.研究失活GNAS基因在成骨细胞和脂肪细胞分化过程中对特异性GNAS转录本表达的影响。该项目的总体目标是确定GNAS基因在骨细胞分化调节中的作用。这项建议中描述的研究将为研究GNAS调节成骨的具体途径提供基础。这些研究将为制定诊断和治疗多种骨骼疾病的策略提供重要信息，如POH和更常见的疾病。

DESCRIPTION (provided by applicant): Genetic disorders of osteogenesis provide valuable insight into the regulation of bone formation. Progressive osseous heteroplasia (POH) is a rare and disabling genetic disorder in which the body produces bone in skin, fat and skeletal muscle. Gene mutations in POH patients inactivate one of the two copies of the GNAS gene and alter the fate of cells to cause bone formation in inappropriate locations (heterotopic ossification). GNAS encodes the G(s)alpha protein, which couples signaling via cell surface receptors to intracellular second messengers, however the specific effects of these mutations on bone cell differentiation are unknown. Ectopic bone formation in POH patients often arises within subcutaneous fat, suggesting a close, perhaps reciprocal, relationship between bone and fat cell differentiation. In addition to continuing investigations of GNAS inheritance and expression in POH, a primary goal of this proposal is to examine the effects of heterozygous inactivating GNAS mutations on bone (osteoblast) and fat (adipocyte) cell differentiation. We hypothesize that: (1) Heterozygous inactivating mutation of the GNAS gene alters cellular signaling that directs osteoblast and/or adipocyte differentiation, and (2) The complex phenotypic consequences of inactivating GNAS mutations are influenced by maternal/paternal inheritance of GNAS. The following Specific Aims will be conducted: 1. Investigate the parental origin of the GNAS allele that carries GNAS mutations in POH patients. 2. Examine POH genomic DNA for methylation characteristic of imprinting at the GNAS locus. 3. Examine the differential expression of GNAS mRNAs during osteoblast and adipocyte differentiation. 4. Examine the effects of heterozygous GNAS gene inactivation on osteoblast and adipocyte differentiation. 5. Investigate the effects of an inactive GNAS gene on expression of specific GNAS transcripts during osteoblast and adipocyte differentiation. The overall goal of this project is to characterize the role of the GNAS gene in the regulation of bone cell differentiation. The studies described in this proposal will provide the foundation to examine the specific pathways through which GNAS regulates osteogenesis. These investigations will provide important information for developing diagnostic and treatment strategies for a wide range of disorders of bone such as POH and more common conditions.