Activating mutations in genes encoding phosphatidylinositol 3-kinase (PI3K)-AKT pathway components cause megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome (MPPH, OMIM 603387)1,2,3. Here we report that individuals with MPPH lacking upstream PI3K-AKT pathway mutations carry de novo mutations in CCND2 (encoding cyclin D2) that are clustered around a residue that can be phosphorylated by glycogen synthase kinase 3β (GSK-3β)4. Mutant CCND2 was resistant to proteasomal degradation in vitro compared to wild-type CCND2. The PI3K-AKT pathway modulates GSK-3β activity4, and cells from individuals with PIK3CA, PIK3R2 or AKT3 mutations showed similar CCND2 accumulation. CCND2 was expressed at higher levels in brains of mouse embryos expressing activated AKT3. In utero electroporation of mutant CCND2 into embryonic mouse brains produced more proliferating transfected progenitors and a smaller fraction of progenitors exiting the cell cycle compared to cells electroporated with wild-type CCND2. These observations suggest that cyclin D2 stabilization, caused by CCND2 mutation or PI3K-AKT activation, is a unifying mechanism in PI3K-AKT–related megalencephaly syndromes.

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We thank the study patients and their families, without whose participation this work would not be possible. We thank M. O'Driscoll (University of Sussex) for advice and help. This work was funded by the Government of Canada through Genome Canada, the Canadian Institutes of Health Research (CIHR), the Ontario Genomics Institute (OGI-049), Genome Quebec and Genome British Columbia (to K.M.B.). The work was selected for study by the FORGE Canada Steering Committee, consisting of K. Boycott (University of Ottawa), J. Friedman (University of British Columbia), J. Michaud (Université de Montreal), F. Bernier (University of Calgary), M. Brudno (University of Toronto), B. Fernandez (Memorial University), B. Knoppers (McGill University), M. Samuels (Université de Montreal) and S. Scherer (University of Toronto). Research reported in this publication was supported by the National Institute of Neurological Disorders and Stroke (NINDS) of the US National Institutes of Health under award numbers P01-NS048120 (to M.E.R.), NRSA F32 NS086173 (to K.A.G.) and R01NS058721 (to W.B.D.), by The Baily Thomas Charitable Fund (to D.T.P.) and by the Sir Jules Thorn Charitable Trust and Great Ormond Street Children's Hospital Charity (to E.G.S.).

Author information

Author notes

    • Ghayda M Mirzaa
    • , David A Parry
    • , Andrew E Fry
    •  & Kristin A Giamanco

    These authors contributed equally to this work.


  1. Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, USA.

    • Ghayda M Mirzaa
    • , Carissa Adams
    • , Rebecca D Hodge
    • , Robert F Hevner
    •  & William B Dobyns
  2. Department of Pediatrics, University of Washington, Seattle, Washington, USA.

    • Ghayda M Mirzaa
    •  & William B Dobyns
  3. Leeds Institute of Biomedical and Clinical Science, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds, UK.

    • David A Parry
    • , Clare V Logan
    • , Nicola Roberts
    • , Colin A Johnson
    • , David T Bonthron
    •  & Eamonn G Sheridan
  4. Institute of Medical Genetics, University Hospital of Wales, Cardiff, UK.

    • Andrew E Fry
    •  & Daniela T Pilz
  5. Neurogenetics and Development, Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, New York, New York, USA.

    • Kristin A Giamanco
    • , Shawn Singh
    • , Stanislav S Kholmanskikh
    •  & M Elizabeth Ross
  6. McGill University and Genome Quebec Innovation Centre, Montréal, Quebec, Canada.

    • Jeremy Schwartzentruber
    •  & Jacek Majewski
  7. Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada.

    • Megan Vanstone
    •  & Kym M Boycott
  8. Department of Neurological Surgery, University of Washington, Seattle, Washington, USA.

    • Rebecca D Hodge
    •  & Robert F Hevner
  9. Department of Pathology, University of Washington, Seattle, Washington, USA.

    • Robert F Hevner
  10. Department of Child Neurology, University Medical Center (UMC) Utrecht, Utrecht, The Netherlands.

    • Kees P J Braun
  11. Centre de Génétique et Centre de Référence Anomalies du Développement et Syndromes Malformatifs, Hôpital d'Enfants, Centre Hospitalier Universitaire (CHU) Dijon, Université de Bourgogne, Dijon, France.

    • Laurence Faivre
  12. Université de Bourgogne, Equipe Génétique des Anomalies du Développement (GAD), EA 4271, Dijon, France.

    • Jean-Baptiste Rivière
    •  & Judith St-Onge
  13. Division of Medical Genetics, A.I. duPont Hospital for Children, Wilmington, Delaware, USA.

    • Karen W Gripp
  14. Department of Clinical Genetics and Expertise Centre for Neurodevelopmental Disorders, Erasmus University Medical Center, Rotterdam, The Netherlands.

    • Grazia M S Mancini
  15. Department of Paediatric Neurology, Royal Victoria Infirmary, Newcastle upon Tyne, UK.

    • Ki Pang
  16. Department of Clinical Genetics, Liverpool Women's National Health Service (NHS) Foundation Trust, Liverpool, UK.

    • Elizabeth Sweeney
  17. Centre for Human Genetics, University Hospital Gasthuisberg, Herestraat, Leuven, Belgium.

    • Hilde van Esch
  18. Department of Medical Genetics, UMC Utrecht, Utrecht, The Netherlands.

    • Nienke Verbeek
  19. Institut fur Humangenetik, Universitatsklinikum Essen, Essen, Germany.

    • Dagmar Wieczorek
  20. Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.

    • Michelle Steinraths
  21. Department of Neurology, University of Washington, Seattle, Washington, USA.

    • William B Dobyns


  1. FORGE Canada Consortium

    Membership of the Steering Committee for the Consortium is provided in the Acknowledgments section.


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E.G.S., W.B.D., D.T.P., M.E.R., K.M.B., G.M.M., D.A.P., A.E.F. and K.A.G. designed the study and experiments. G.M.M., A.E.F., C.A., D.T.B., K.P.J.B., L.F., K.W.G., G.M.S.M., K.P., E.S., H.v.E., N.V., D.W., D.T.P., W.B.D. and E.G.S. identified, consented and recruited the study subjects and provided clinical information. J.-B.R., J.S-O. and M.S. recruited patients. G.M.M., A.E.F., D.T.P. and W.B.D. evaluated the magnetic resonance imaging. G.M.M., D.A.P., C.A.J., J.S., M.V., C.V.L. and N.R. developed the bioinformatics scripts and performed genetic data analysis and confirmation studies. R.D.H. and R.F.H. provided the AKT3 mouse mutant brain samples. D.A.P. and C.V.L. performed the protein stability experiments. K.A.G., S.S., S.S.K. and M.E.R. performed and analyzed the IUEP experiments and quantitative western blot analyses of p.Asp219Val AKT3. J.M. analyzed data. G.M.M., D.A.P., A.E.F., K.A.G., D.T.P., M.E.R., W.B.D. and E.G.S. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to M Elizabeth Ross or Eamonn G Sheridan.

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