Anne-Claude Tabet, Thomas Rolland, Marie Ducloy, Jonathan Lévy, Julien Buratti, Alexandre Mathieu, Damien Haye, Laurence Perrin, Céline Dupont, Sandrine Passemard, Yline Capri, Alain Verloes, Séverine Drunat, Boris Keren, Cyril Mignot, Isabelle Marey, Aurélia Jacquette, Sandra Whalen, Eva Pipiras, Brigitte Benzacken, Sandra Chantot-Bastaraud, Alexandra Afenjar, Delphine Héron, Cédric Le Caignec, Claire Beneteau, Olivier Pichon, Bertrand Isidor, Albert David, Laila El Khattabi, Stephan Kemeny, Laetitia Gouas, Philippe Vago, Anne-Laure Mosca-Boidron, Laurence Faivre, Chantal Missirian, Nicole Philip, Damien Sanlaville, Patrick Edery, Véronique Satre, Charles Coutton, Françoise Devillard, Klaus Dieterich, Marie-Laure Vuillaume, Caroline Rooryck, Didier Lacombe, Lucile Pinson, Vincent Gatinois, Jacques Puechberty, Jean Chiesa, James Lespinasse, Christèle Dubourg, Chloé Quelin, Mélanie Fradin, Hubert Journel, Annick Toutain, Dominique Martin, Abdelamdjid Benmansour, Claire S. Leblond, Roberto Toro, Frédérique Amsellem, Richard Delorme, Thomas Bourgeron

Phelan-McDermid syndrome (PMS) is characterized by a variety of clinical symptoms with heterogeneous degrees of severity, including intellectual disability (ID), absent or delayed speech, and autism spectrum disorders (ASD). It results from a deletion of the distal part of chromosome 22q13 that in most cases includes the SHANK3 gene. SHANK3 is considered a major gene for PMS, but the factors that modulate the severity of the syndrome remain largely unknown. In this study, we investigated 85 patients with different 22q13 rearrangements (78 deletions and 7 duplications). We first explored the clinical features associated with PMS, and provide evidence for frequent corpus callosum abnormalities in 28% of 35 patients with brain imaging data. We then mapped several candidate genomic regions at the 22q13 region associated with high risk of clinical features, and suggest a second locus at 22q13 associated with absence of speech. Finally, in some cases, we identified additional clinically relevant copy-number variants (CNVs) at loci associated with ASD, such as 16p11.2 and 15q11q13, which could modulate the severity of the syndrome. We also report an inherited SHANK3 deletion transmitted to five affected daughters by a mother without ID nor ASD, suggesting that some individuals could compensate for such mutations. In summary, we shed light on the genotype-phenotype relationship of patients with PMS, a step towards the identification of compensatory mechanisms for a better prognosis and possibly treatments of patients with neurodevelopmental disorders.