Title: Glycine decarboxylase deficiency impairs motor behaviour in zebrafish rescued by 1 counterbalancing glycine synaptic level. 2 Raphaëlle Riché 1 , Meijiang Liao 1 , Izabella A. Pena 2 , Kit-Yi Leung 3 , Nathalie Lepage 2 , Nicolas D.E. 3 Greene 3 , Kyriakie Sarafoglou 4 , Lisa A. Schimmenti 5 , Pierre Drapeau 1,6 and Éric Samarut 1,6* . 4 5 1-Research Center of the University of Montreal Hospital Center (CRCHUM), Department of 6 Neurosciences, Université de Montréal, Montréal, QC, Canada. 7 2- Children’s Hospital of Eastern Ontario Research Institute and Department of Pediatrics, 8 Faculty of Medicine, University of Ottawa, Ontario K1H 8L1, Canada 9 3- Developmental Biology & Cancer Programme, UCL Great Ormond Street Institute of Child 10 Health, University College London, London WC1N 1EH, UK 11 4- Division of Pediatric Endocrinology, Department of Pediatrics, University of Minnesota, 12 Minneapolis, Minnesota, USA 13 5- Mayo Clinic College of Medicine, Department of Otorhinolaryngology, Rochester, MN, United 14 States; Mayo Clinic College of Medicine, Department of Pediatrics, Rochester, MN, United 15 States; Mayo Clinic College of Medicine, Department of Clinical Genomics, Rochester, MN, 16 United States. 17 6-DanioDesign Inc., Montréal, QC, Canada. 18 19 corresponding author: eric.samarut@umontreal.ca 20 21 The authors have declared that no conflict of interest exists. 22