Human Molecular Genetics Advance Access published online on November 7, 2008
Human Molecular Genetics, 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, Hôpital Necker Enfants Malades, 75015 Paris, France 3 UMR CNRS 144, Institut Curie, 75005 Paris, France 4 Unité INSERM U574, Néphropathies Héréditaires et Rein en Développement, Hôpital Necker Enfants Malades, 75015 Paris, France 5 INSERM U686, Biologie des Jonctions Neuromusculaires Normales et Pathologiques, Université Paris Descartes 75006 Paris France 6 Institut Curie – Centre de Recherches - 75005 Paris, France
Correspondence should be addressed to: - Vincent El Ghouzzi, INSERM U676 - Physiopathologie et Neuroprotection des Atteintes du Cerveau en Développement – Hôpital Robert Debré – 75019 Paris, France – Tel: +33 1 40 03 19 73 – Fax: +33 1 40 03 19 78 – E-mail: vincent.elghouzzi{at}inserm.fr – Franck Perez, CNRS UMR144, Institut Curie – 26, rue d'Ulm – 753248 Paris Cedex 05 – France – Tel: +33 1 56 24 63 88 – Fax: +33 1 56 24 63 19 – Email: Franck.Perez{at}curie.fr
Received October 16, 2008; Revised November 4, 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-aminoacid 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 GFP 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.
* indicate equal contributions.