Activation of Hedgehog signaling by loss of GNAS causes heterotopic ossification



Heterotopic ossification, the pathologic formation of extraskeletal bone, occurs as a common complication of trauma or in genetic disorders and can be disabling and lethal. However, the underlying molecular mechanisms are largely unknown. Here we demonstrate that Gαs restricts bone formation to the skeleton by inhibiting Hedgehog signaling in mesenchymal progenitor cells. In progressive osseous heteroplasia, a human disease caused by null mutations in GNAS, which encodes Gαs, Hedgehog signaling is upregulated in ectopic osteoblasts and progenitor cells. In animal models, we show that genetically-mediated ectopic Hedgehog signaling is sufficient to induce heterotopic ossification, whereas inhibition of this signaling pathway by genetic or pharmacological means strongly reduces the severity of this condition. As our previous work has shown that GNAS gain-of-function mutations upregulate WNT–β-catenin signaling in osteoblast progenitor cells, resulting in their defective differentiation and fibrous dysplasia, we identify Gαs as a key regulator of proper osteoblast differentiation through its maintenance of a balance between the Wnt–β-catenin and Hedgehog pathways. Also, given the results here of the pharmacological studies in our mouse model, we propose that Hedgehog inhibitors currently used in the clinic for other conditions, such as cancer, may possibly be repurposed for treating heterotopic ossification and other diseases caused by GNAS inactivation.

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Figure 1: Loss of Gnas in limb mesenchyme leads to heterotopic ossification.
Figure 2: Loss of Gnas in adult subcutaneous tissue leads to heterotopic ossification.
Figure 3: Removal of Gnas from mesenchymal progenitor cells upregulates Hedgehog signaling in vitro and in vivo.
Figure 4: Gαs acts through cAMP and PKA to suppress Hedgehog signaling.
Figure 5: Reducing Hedgehog signaling inhibits heterotopic ossification in vivo and in vitro.
Figure 6: Hedgehog signaling is activated in ectopic bone from individuals with POH, and activation of Hedgehog signaling is sufficient to cause heterotopic ossification.

Change history

  • 18 October 2013

     In the version of this article initially published online, the gene symbol for Prrx1 was misidentified as Prdx1 in four instances. The error has been corrected for the print, PDF and HTML versions of this article.


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We thank the entire Yang lab for stimulating discussions. We thank J. Fekecs and P. Andre for helping with the data illustration. The work in the Yang and Weinstein labs was supported by the intramural research programs of NHGRI and NIDDK at the US National Institutes of Health (NIH), respectively. We thank R. Caron for his work on the POH lesion histological analyses. The rabbit anti-Gli3 antibody was provided by S. Mackem (NIH NCI), and the dnPKA adenovirus was a gift from C.-M. Fan (Carnegie Institution for Science). The work in the Kaplan and Shore lab was supported by the Progressive Osseous Heteroplasia Association, the University of Pennsylvania Center for Research in FOP and Related Disorders, the Penn Center for Musculoskeletal Disorders (NIH NIAMS P30-AR050950), the Isaac and Rose Nassau Professorship of Orthopaedic Molecular Medicine and NIH NIAMS (R01-AR046831 and R01-AR41916).

Author information

J.B.R., D.M. and Y.Y. designed the experiments and analyzed the data. J.B.R., D.M., F.S.K., E.M.S. and Y.Y. wrote the manuscript. J.B.R., D.M., J.G.-J., M.J. and J.L. carried out the actual experiments. F.S.K. saw the patients with POH. F.S.K. and E.M.S. provided the POH samples and carried out the GLI immunohistochemistry on the human samples. M.C. and L.S.W. generated and provided the Gnasfl/fl mice.

Correspondence to Jean B Regard or Yingzi Yang.

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Regard, J., Malhotra, D., Gvozdenovic-Jeremic, J. et al. Activation of Hedgehog signaling by loss of GNAS causes heterotopic ossification. Nat Med 19, 1505–1512 (2013).

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