Description of Research Expertise

RESEARCH INTERESTS:
Genetic regulation of cell differentiation and tissue development through investigations of rare human genetic diseases of extra-skeletal bone formation.

KEY WORDS: 
Bone formation, cell differentiation, human genetics, molecular biology, cell biology, developmental biology, genetic diseases, rare disease, bone, cartilage, bone morphogenetic protein, BMP, ACVR1, G-proteins, GNAS, FOP, POH.


DESCRIPTION OF RESEARCH:
My longstanding interest is the genetic regulation of cell differentiation and tissue development, with specific focus on human genetic diseases of extra-skeletal bone formation (heterotopic ossification; HO), including fibrodysplasia ossificans progressiva (FOP), a disorder of ectopic endochondral ossification caused by activating mutations in the BMP receptor ACVR1/ALK2, and progressive osseous heteroplasia (POH) caused by inactivating mutations in GNAS. Having identified the genetic causes of FOP and POH, we continue to explore the cellular and molecular basis of the dysregulated stem cell fates, bone tissue formation, and effects on skeletal development. A major focus of my research program explores the cellular and molecular regulation of chondrogenesis and osteogenesis in heterotopic ossification and development and maintenance of skeletal bone. Our work develops, characterizes, and uses in vitro and in vivo models to understand the consequences of the mutations and to develop models for developing and testing therapeutic strategies.

fibrodysplasia ossificans progressiva (FOP)
Through a partnership with my long time colleague Frederick Kaplan MD, our lab investigates fibrodysplasia ossificans progressive (FOP), a rare human genetic disease of heterotopic ossification. In patients with FOP, progenitor cells in connective tissues are misdirected by their underlying mutations to aberrantly differentiate into cartilage and bone. The extra-skeletal bone formation begins during early childhood, progresses episodically, and causes severe debilitation. Genetic studies in rare disorders pose special challenges and our early efforts focused on detailed clinical characterization of FOP and identification of the underlying genetic We also identified and investigated the BMP signaling pathway as dysregulated in FOP cells. USING Genetic linkage and positional cloning, we successfully identified ACVR1, which encodes a BMP receptor, as the mutant gene and identified previously unknown functions specific to this receptor. We made the surprising discovery that nearly all (>98%) FOP patients carry the identical mutation in this highly conserved gene. Despite this common mutation, disease phenotypes in patients vary in age of onset, rate of progression, severity of HO, supporting the influence of genetic and environmental modifiers of the disease. In addition to the recurrent FOP mutation, we also identified very rare mutations in ACVR1 that cause more severe or mild forms of FOP. This work, which began when few knew of FOP or heterotopic ossification or appreciated the value of understanding rare diseases, has stimulated an active and expanding field of basic research and translational application.
Our current focus is to understand how ACVR1 mutations alter BMP signaling and lead to altered cell differentiation and ectopic cartilage and bone formation. We determined that FOP ACVR1 mutations lead to ligand dependent and independent gain of function and increased BMP signaling. Mouse and zebrafish models have been used to demonstrate the activity of the mutation in vivo and provide tools for characterizing the changes in connective tissues that lead to heterotopic ossification and for pre-clinical drug testing. A series of studies demonstrated that FOP mutations enhance differentiation to osteoblast and chondrocyte fates and that ACVR1 is critical during early cell fate commitment stages. We have defined stages of heterotopic ossification progression that include inflammation and connective tissue degradation, followed by active fibroproliferation prior to cartilage and bone tissue formation. The role of immune cells in supporting HO formation and how immune cells are altered by the FOP mutation is of ongoing interest. A recent and growing area of investigation is the interaction of biomechanical signaling pathways with ACVR1 signaling as a regulatory mechanism that alters soft connective tissues such as skeletal muscle to be conducive for the extra-skeletal bone formation.

progressive osseous heteroplasia (POH)
Clinical mis-diagnosis of patients thought to have FOP led to the identification and clinical characterization of progressive osseous heteroplasia (POH). While several features distinguish POH from FOP, both of these disorders of heterotopic ossification induce ectopic bone formation during early childhood and are progressive throughout life. Based on clinical similarity to another rare disease (PHP1a/AHO), a candidate gene approach identified inactivating gene mutations in GNAS, placing POH on a clinical phenotype spectrum with other GNAS inactivation disorders. GNAS is a complex genetic locus that synthesizes multiple transcripts from different promoters and is additionally regulated by genomic imprinting. The main protein product of GNAS is Gsalpha, a G-protein subunit that regulates downstream cAMP activity. We determined that POH is caused by mutations in the paternally-inherited GNAS allele. Recent studies have supported that POH is additionally influenced by ‘second hit’ somatic mutations.
As for FOP, our goal for POH is to understand how the underlying genetic mutations lead to ectopic osteogenesis and heterotopic ossification in order to identify potential therapeutic targets and strategies. Through a series of investigations, we demonstrated that GNAS inactivation appears to act as a regulatory cell fate ‘switch’ that leads to increased osteogenesis and decreased adipogenesis. While GNAS inactivation and decreased Gsalpha singling underlies POH, Gsalpha/cAMP is a ubiquitous signaling pathway and identification of the downstream pathways that specifically direct the aberrant osteogenic phenotype is key to identifying specific and effective targets for therapeutic intervention. Mutation-induced physical changes in the tissues where POH HO forms has implicated a role for biomechanical signaling. A recently developed strategy for inducing HO in our mouse model for POH is accelerating our investigations of the early inductive events and mechanisms that regulate POH HO.

PUBMED: Shore EM


ROTATION PROJECTS:

Rotation projects are available in most of the research areas described in the Research Summary. Specific projects will be discussed individually. Laboratory research is conducted with a translational perspective, and is closely tied to clinical observation and patient care, and students are encouraged to have patient contact.


LAB PERSONNEL: (as of Spring 2019)

Collaborators: Frederick Kaplan MD, Rob Mauck PhD, Foteini Mourkioti PhD, Mary Mullins PhD; Maurizio Pacifici PhD
Students: Alexandra Stanley (CAMB); Will Towler (CAMB); Niambi Brewer (CAMB); Robyn Allen (CAMB)
Post-doc/Research Associates: Salin Chakkalakal PhD; Vitali Lounev PhD
Research Specialists: Bob Caron; Meiqi Xu; Deyu Zhang
Recent lab members: Michael Convente (CAMB); Andria Culbert (CAMB); Julia Haupt (post-doc); Girish Ramaswamy (post-doc)

Selected Publications

Haupt, J. A. Stanley, C.M. McLeod, B.D. Cosgrove, A.L. Culbert, L. Wang, F. Mourkioti, R.L. Mauck, E.M. Shore: ACVR1 R206H FOP mutation alters mechanosensing and tissue stiffness during heterotopic ossification. Molec. Biol. Cell. 30(1) : 17-29,2019.

Convente, M.R., S.A. Chakkalakal, E. Yang, R.J. Caron, D. Zhang, T. Kambayashi, F.S. Kaplan, and E.M. Shore: Depletion of mast cells and macrophages impairs heterotopic ossification in an Acvr1R206H mouse model of fibrodysplasia ossificans progressiva. J. Bone Min. Res. 33 : 269-282,2018.

Girish Ramaswamy, Hyunsoo Kim, Deyu Zhang, Vitali Lounev, Joy Y. Wu, Yongwon Choi, Frederick S. Kaplan, Robert J. Pignolo & Eileen M. Shore.: Gsα Controls Cortical Bone Quality by Regulating Osteoclast Differentiation via cAMP/PKA and β-Catenin Pathways. Sci Rep. 7, 45140; doi: 10.1038/srep45140. : 2017.

Chakkalakal, S.A., K. Uchibe, M. Convente, D. Zhang, A. Economides, F.S. Kaplan, M. Pacifici, M. Iwamoto, E.M. Shore: Palovarotene inhibits heterotopic ossification and maintains limb mobility and growth in mice with the human ACVR1R206H FOP mutation. J. Bone Min. Res. 31 : 1666-1675,2016.

Culbert, A.L., S.A. Chakkalakal, E. Theosmy, T.A. Brennan, F.S. Kaplan, and E.M. Shore: Alk2 regulates early chondrogenic fate in FOP heterotopic endochondral ossification. Stem Cells 32 : 1289-1300,2014.

Regard, J.B., D. Malhotra, J. Gvozdenovic-Jeremic, M. Josey, M. Chen, L.S. Weinstein, E.M. Shore, F.S. Kaplan, and Y. Yang: Activation of Hedgehog signaling by loss of GNAS causes heterotopic ossification. Nature Medicine 19 : 1505-1512,2013.

Shore, E.M. and F.S. Kaplan: Inherited Human Diseases of Heterotopic Bone Formation. Nature Reviews Rheumatology 6 (9): 518-527,2010.

Medici, D., E.M. Shore, V.Y. Lounev, F.S. Kaplan, R. Kalluri, and B.R. Olsen: Conversion of vascular endothelial cells into multipotent stem-like cells. Nature Medicine 16 (12): 1400-1406,2010.

Shen, Q., S.C. Little, M. Xu, J. Haupt, C. Ast, T. Katagiri, S. Mundlos, P. Seemann, F.S. Kaplan, M.C. Mullins, E.M. Shore.: Fibrodysplasia ossifcans progressiva ACVR1 R206H mutation activates BMP-independent chondrogenesis and ventralization of zebrafish embryos. J. Clin. Invest 119 (11): 3462-3472,2009.

Shore EM., Xu M., Feldman GJ., Fenstermacher DA., FOP International Research Consortium., Brown MA., Kaplan FS.: A recurrent mutation in the BMP type I receptor ACVR1 causes inherited and sporadic fibrodysplasia ossificans progressiva Nature Genetics 38 (5): 525-527,2006.

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Academic Contact Information

McKay Orthopaedic Research Laboratory
309A Stemmler Hall
3450 Hamilton Walk
Philadelphia, PA 19104-6081
Philadelphia, PA 19104-6081
Phone: 215-898-2331