This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/humu.22728. This article is protected by copyright. All rights reserved. 1 Humu-2014-0337 Research Article Two siblings with homozygous pathogenic splice site variant in mitochondrial asparaginyl-tRNA synthetase (NARS2) Arnaud V. Vanlander 1 , Björn Menten 2 , Joél Smet 1 , Linda De Meirleir 3 , Tom Sante 2 , Boel De Paepe 1 , Sara Seneca 4 , Sarah F. Pearce 5 , Christopher A. Powell 5 , Sarah Vergult 2 , Alex Michotte 6 , Elien De Latter 1 , Lies Vantomme 2 , Michal Minczuk 5 , Rudy Van Coster 1 1 Department of Pediatric Neurology and Metabolism, Ghent University Hospital, Belgium 2 Center for Medical Genetics Ghent, Ghent University, Belgium 3 Department of Pediatric Neurology and Metabolism, Brussels University Hospital, Brussels, Belgium 4 Center for Medical Genetics, Free University of Brussel, Brussels, Belgium 5 MRC Mitochondrial Biology Unit, Cambridge, UK 6 Department of Neurology, Brussels University Hospital, Brussels, Belgium Corresponding author: R Van Coster, M.D., PhD. Universitair Ziekenhuis Gent De Pintelaan, 185 9000 Gent Belgium Phone: +32.(0)9.3323585 Fax: +32.(0)9.3323839 Email: rudy.vancoster@ugent.be