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.

Public Health Relevance

Rare genetic disorders can provide valuable insight into fundamental cellular mechanisms that impact more common conditions. POH, a disease which forms extra-skeletal bone, is caused by gene mutations that regulate pluripotent stem cell differentiation in the musculoskeletal system. Our studies will investigate specific effects of the mutated POH gene on cell differentiation as well as identify progenitor cells and signaling pathways that regulate bone and fat formation. These studies will provide new insights leading to diagnostic and treatment strategies for a wide range of human disorders of bone and adipose tissue.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
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Skeletal Biology Structure and Regeneration Study Section (SBSR)
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Sharrock, William J
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University of Pennsylvania
Schools of Medicine
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Cairns, Dana M; Pignolo, Robert J; Uchimura, Tomoya et al. (2013) Somitic disruption of GNAS in chick embryos mimics progressive osseous heteroplasia. J Clin Invest 123:3624-33
Kaplan, J; Kaplan, F S; Shore, E M (2012) Restoration of normal BMP signaling levels and osteogenic differentiation in FOP mesenchymal progenitor cells by mutant allele-specific targeting. Gene Ther 19:786-90
Shore, Eileen M (2012) Fibrodysplasia ossificans progressiva: a human genetic disorder of extraskeletal bone formation, or--how does one tissue become another? Wiley Interdiscip Rev Dev Biol 1:153-65
Liu, Jan-jan; Russell, Elizabeth; Zhang, Deyu et al. (2012) Paternally inherited gsýý mutation impairs adipogenesis and potentiates a lean phenotype in vivo. Stem Cells 30:1477-85
Shore, Eileen M; Kaplan, Frederick S (2011) Role of altered signal transduction in heterotopic ossification and fibrodysplasia ossificans progressiva. Curr Osteoporos Rep 9:83-8
Pignolo, Robert J; Xu, Meiqi; Russell, Elizabeth et al. (2011) Heterozygous inactivation of Gnas in adipose-derived mesenchymal progenitor cells enhances osteoblast differentiation and promotes heterotopic ossification. J Bone Miner Res 26:2647-55
Schimmel, R J; Pasmans, S G M A; Xu, M et al. (2010) GNAS-associated disorders of cutaneous ossification: two different clinical presentations. Bone 46:868-72
Adegbite, N S; Xu, M; Kaplan, F S et al. (2008) Diagnostic and mutational spectrum of progressive osseous heteroplasia (POH) and other forms of GNAS-based heterotopic ossification. Am J Med Genet A 146A:1788-96
Shore, Eileen M; Kaplan, Frederick S (2008) Insights from a rare genetic disorder of extra-skeletal bone formation, fibrodysplasia ossificans progressiva (FOP). Bone 43:427-33
Kaplan, Frederick S; Glaser, David L; Hebela, Nader et al. (2004) Heterotopic ossification. J Am Acad Orthop Surg 12:116-25

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