Human Molecular Genetics Advance Access originally published online on November 7, 2008
Human Molecular Genetics 2009 18(3):440-453; doi:10.1093/hmg/ddn371
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The gene responsible for Dyggve-Melchior-Clausen syndrome encodes a novel peripheral membrane protein dynamically associated with the Golgi apparatus
1 Unité INSERM U676, Physiopathologie et Neuroprotection des Atteintes du Cerveau en Développement, Hôpital Robert Debré, 75019 Paris, France 2 Unité INSERM U781, Handicaps Génétiques de l’Enfant 3 Unité INSERM U574, Néphropathies Héréditaires et Rein en Développement, Hôpital Necker Enfants Malades, 75015 Paris, France 4 UMR CNRS 144 5 Centre de Recherches, Institut Curie, 75005 Paris, France 6 INSERM U686, Biologie des Jonctions Neuromusculaires Normales et Pathologiques, Université Paris Descartes, 75006 Paris, France
* To whom correspondence should be addressed Tel: +33 140031973; Fax: +33 140031978; Email: vincent.elghouzzi{at}inserm.fr (V.E.); INSERM U676, Hôpital Robert Debré, 48, Bd Sérurier, 75019 Paris, France; or Tel: +33 156246388; Fax: +33 156246319; Email: franck.perez{at}curie.fr (F.P.); CNRS UMR144, Institut Curie, 26, rue d’Ulm, 753248 Paris Cedex 05, France
Received October 16, 2008; Accepted November 4, 2008
Dyggve-Melchior-Clausen dysplasia (DMC) is a rare inherited dwarfism with severe mental retardation due to mutations in the DYM gene which encodes Dymeclin, a 669-amino acid protein of yet unknown function. Despite a high conservation across species and several predicted transmembrane domains, Dymeclin could not be ascribed to any family of proteins. Here we show, using in situ hybridization, that DYM is widely expressed in human embryos, especially in the cortex, the hippocampus and the cerebellum. Both the endogenous and the recombinant protein fused to green fluorescent protein co-localized with Golgi apparatus markers. Electron microscopy revealed that Dymeclin associates with the Golgi apparatus and with transitional vesicles of the reticulum–Golgi interface. Moreover, permeabilization assays revealed that Dymeclin is not a transmembrane but a peripheral protein of the Golgi apparatus as it can be completely released from the Golgi after permeabilization of the plasma membrane. Time lapse confocal microscopy experiments on living cells further showed that the protein shuttles between the cytosol and the Golgi apparatus in a highly dynamic manner and recognizes specifically a subset of mature Golgi membranes. Finally, we found that DYM mutations associated with DMC result in mis-localization and subsequent degradation of Dymeclin. These data indicate that DMC results from a loss-of-function of Dymeclin, a novel peripheral membrane protein which shuttles rapidly between the cytosol and mature Golgi membranes and point out a role of Dymeclin in cellular trafficking.
The authors wish it to be known that, in their opinion, the first two and the last two authors should be regarded as joint Authors.