A Recurrent Mosaic Mutation in SMO, Encoding the Hedgehog Signal Transducer Smoothened, Is the Major Cause of Curry-Jones Syndrome

Stephen R.F. Twigg, Robert B. Hufnagel, Kerry A. Miller, Yan Zhou, Simon J. McGowan, John Taylor, Jude Craft, Jenny C. Taylor, Stephanie L. Santoro, Taosheng Huang, Robert J. Hopkin, Angela F. Brady, Jill Clayton-Smith, Carol L. Clericuzio, Dorothy K. Grange, Leopold Groesser, Christian Hafner, Denise Horn, I. Karen Temple, William B. DobynsCynthia J. Curry, Marilyn C. Jones, Andrew O.M. Wilkie

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

Curry-Jones syndrome (CJS) is a multisystem disorder characterized by patchy skin lesions, polysyndactyly, diverse cerebral malformations, unicoronal craniosynostosis, iris colobomas, microphthalmia, and intestinal malrotation with myofibromas or hamartomas. Cerebellar medulloblastoma has been described in a single affected individual; in another, biopsy of skin lesions showed features of trichoblastoma. The combination of asymmetric clinical features, patchy skin manifestations, and neoplastic association previously led to the suggestion that this could be a mosaic condition, possibly involving hedgehog (Hh) signaling. Here, we show that CJS is caused by recurrent somatic mosaicism for a nonsynonymous variant in SMO (c.1234C>T [p.Leu412Phe]), encoding smoothened (SMO), a G-protein-coupled receptor that transduces Hh signaling. We identified eight mutation-positive individuals (two of whom had not been reported previously) with highly similar phenotypes and demonstrated varying amounts of the mutant allele in different tissues. We present detailed findings from brain MRI in three mutation-positive individuals. Somatic SMO mutations that result in constitutive activation have been described in several tumors, including medulloblastoma, ameloblastoma, and basal cell carcinoma. Strikingly, the most common of these mutations is the identical nonsynonymous variant encoding p.Leu412Phe. Furthermore, this substitution has been shown to activate SMO in the absence of Hh signaling, providing an explanation for tumor development in CJS. This raises therapeutic possibilities for using recently generated Hh-pathway inhibitors. In summary, our work uncovers the major genetic cause of CJS and illustrates strategies for gene discovery in the context of low-level tissue-specific somatic mosaicism.

Original languageEnglish
Pages (from-to)1256-1265
Number of pages10
JournalAmerican journal of human genetics
Volume98
Issue number6
DOIs
StatePublished - Jun 2 2016

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