Human Molecular Genetics Advance Access published online on March 25, 2009
Human Molecular Genetics, doi:10.1093/hmg/ddp148
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Loss-of-Function Mutations in ATP6V0A2 Impair Vesicular Trafficking, Tropoelastin Secretion, and Cell Survival
,
1 Department of Pediatrics, Washington University School of Medicine, St. Louis, 63110, USA 2 Department of Pediatrics, Radboud University Medical Centre Nijmegen, Nijmegen, 6525GA, The Netherlands 3 Institute for Medical Genetics, Charité Universitätsmedizin, Berlin, 13353, Germany 4 Development and Disease Research Group, Max Planck Institute for Molecular Genetics, Berlin, 14195, Germany 5 Laboratory of Pediatrics and Neurology, Radboud University Medical Centre Nijmegen, Nijmegen, 6525GA, The Netherlands 6 Department of Anatomy and Cell Biology, McGill University, Montreal, Canada, H3A 2B2 7 Department of Pediatrics, Rhode Island Hospital, Hasbro Children's Hospital and Brown University School of Medicine, Providence, 02903, USA 8 Department of Biochemistry and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, 04730, Poland 9 Princess Al Jawhara Center of Excellence in the Research of Hereditary Disorders, King Abdulaziz University, Jeddah, 21486, Saudi Arabia 10 Raphael Recanati Genetics Institute, Schneider Children's Medical Center and Rabin Medical Center, Petah Tikva, 49202, Israel 11 Medical Genetics Program, Eastern Health, St. John's, Canada, A1B 3V6 12 National College of Medicine and Medical Sciences, Arabian Gulf University, Manama, 26671, Bahrain 13 Institut für Humangenetik, Universität zu Lübeck, Lübeck, 23538, Germany 14 Department of Medical Genetics, Faculty of Medicine, University of Istanbul, Istanbul, 34390, urkey 15 Service de Génétique Médicale, CHU-Ste-Justine, Montreal, Quebec, Canada 16 Department of Pediatrics, Ankara University School of Medicine, Ankara, 06100, urkey 17 Department of Pediatric Genetics, Cerrahpasa Medical School, Istanbul University, Istanbul, 34452, urkey 18 Centre de Génétique Humaine, Centre Hospitalier Universitaire du Sart-Tilman, Université de Liège, Liège, 4000, Belgium 19 Department of Genetics, Washington University School of Medicine, St. Louis, 63110, USA 20 Department of Medicine, Washington University School of Medicine, St. Louis, 63110, USA
* To whom correspondence should be addressed at: Zsolt Urban, Ph.D. Department of Pediatrics, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8208, St. Louis, MO 63110, Phone: (314) 286-2973, Fax: (314) 286-2893, Email: urban_z{at}kids.wustl.edu
Received December 5, 2008; Revised February 27, 2009; Accepted March 23, 2009
Autosomal recessive cutis laxa type 2 (ARCL2), a syndrome of growth and developmental delay and redundant, inelastic skin, is caused by mutations in the a2 subunit of the vesicular ATPase H+-pump (ATP6V0A2). The goal of this study was to define the disease mechanisms that lead to connective tissue lesions in ARCL2. In a new cohort of 17 patients, DNA sequencing of ATP6V0A2 detected either homozygous or compound heterozygous mutations. Considerable allelic and phenotypic heterogeneity was observed, with a missense mutation of a moderately conserved residue p.P87L leading to unusually mild disease. Abnormal N- and/or mucin type O-glycosylation was observed in all patients tested. Premature stop codon mutations led to decreased ATP6V0A2 mRNA levels by destabilizing the mutant mRNA via the nonsense-mediated decay pathway. Loss of ATP6V0A2 either by siRNA knockdown or in ARCL2 cells resulted in distended Golgi cisternae, accumulation of abnormal lysosomes, and multivesicular bodies. Immunostaining of ARCL2 cells showed accumulation of tropoelastin in the Golgi and in large, abnormal intracellular and extracellular aggregates. Pulse-chase studies confirmed impaired secretion and increased intracellular retention of tropoelastin, and insoluble elastin assays showed significantly reduced extracellular deposition of mature elastin. Fibrillin-1 microfibril assembly and secreted lysyl oxidase activity were normal in ARCL2 cells. TUNEL staining demonstrated increased rates of apoptosis in ARCL2 cell cultures. We conclude that loss of function mutations in ATP6V0A2 lead to tropoelastin aggregation in the Golgi, impaired clearance of tropoelastin aggregates, and increased apoptosis of elastogenic cells.
The authors wish it to be known that, in their opinion, the first 3 authors should be regarded as joint First Authors. 
These authors belong to the ARCL Debré-type study group.