Mirror extreme BMI phenotypes associated with gene dosage at the chromosome 16p11.2 locus

Sébastien Jacquemont, Alexandre Reymond, Flore Zufferey, Louise Harewood, Robin G. Walters, Zoltán Kutalik, Danielle Martinet, Yiping Shen, Armand Valsesia, Noam D. Beckmann, Gudmar Thorleifsson, Marco Belfiore, Sonia Bouquillon, Dominique Campion, Nicole de Leeuw, Bert B. A. de Vries, Tõnu Esko, Bridget A. Fernandez, Fernando Fernández-Aranda, José Manuel Fernández-Real, Mònica Gratacòs, Audrey Guilmatre, Juliane Hoyer, Marjo-Riitta Jarvelin, R. Frank Kooy, Ants Kurg, Cédric Le Caignec, Katrin Männik, Orah S. Platt, Damien Sanlaville, Mieke M. Van Haelst, Sergi Villatoro Gomez, Faida Walha, Bai-lin Wu, Yongguo Yu, Azzedine Aboura, Marie-Claude Addor, Yves Alembik, Stylianos E. Antonarakis, Benoît Arveiler, Magalie Barth, Nathalie Bednarek, Frédérique Béna, Sven Bergmann, Mylène Beri, Laura Bernardini, Bettina Blaumeiser, Dominique Bonneau, Armand Bottani, Odile Boute, Han G. Brunner, Dorothée Cailley, Patrick Callier, Jean Chiesa, Jacqueline Chrast, Lachlan Coin, Charles Coutton, Jean-Marie Cuisset, Jean-Christophe Cuvellier, Albert David, Bénédicte de Freminville, Bruno Delobel, Marie-Ange Delrue, Bénédicte Demeer, Dominique Descamps, Gérard Didelot, Klaus Dieterich, Vittoria Disciglio, Martine Doco-Fenzy, Séverine Drunat, Bénédicte Duban-Bedu, Christèle Dubourg, Julia S. El-Sayed Moustafa, Paul Elliott, Brigitte H. W. Faas, Laurence Faivre, Anne Faudet, Florence Fellmann, Alessandra Ferrarini, Richard Fisher, Elisabeth Flori, Lukas Forer, Dominique Gaillard, Marion Gerard, Christian Gieger, Stefania Gimelli, Giorgio Gimelli, Hans J. Grabe, Agnès Guichet, Olivier Guillin, Anna-Liisa Hartikainen, Délphine Heron, Loyse Hippolyte, Muriel Holder, Georg Homuth, Bertrand Isidor, Sylvie Jaillard, Zdenek Jaros, Susana Jiménez-Murcia, Géraldine Joly Helas, Philippe Jonveaux, Satu Kaksonen, Boris Keren, Anita Kloss-Brandstätter, Nine V. A. M. Knoers, David A. Koolen, Peter M. Kroisel, Florian Kronenberg, Audrey Labalme, Emilie Landais, Elisabetta Lapi, Valérie Layet, Solenn Legallic, Bruno Leheup, Barbara Leube, Suzanne Lewis, Josette Lucas, Kay D. MacDermot, Pall Magnusson, Christian Marshall, Michèle Mathieu-Dramard, Mark I. McCarthy, Thomas Meitinger, Maria Antonietta Mencarelli, Giuseppe Merla, Alexandre Moerman, Vincent Mooser, Fanny Morice-Picard, Mafalda Mucciolo, Matthias Nauck, Ndeye Coumba Ndiaye, Ann Nordgren, Laurent Pasquier, Florence Petit, Rolph Pfundt, Ghislaine Plessis, Evica Rajcan-Separovic, Gian Paolo Ramelli, Anita Rauch, Roberto Ravazzolo, Andre Reis, Alessandra Renieri, Cristobal Richart, Janina S. Ried, Claudine Rieubland, Wendy Roberts, Katharina M. Roetzer, Caroline Rooryck, Massimiliano Rossi, Evald Saemundsen, Véronique Satre, Claudia Schurmann, Engilbert Sigurdsson, Dimitri J. Stavropoulos, Hreinn Stefansson, Carola Tengström, Unnur Thorsteinsdóttir, Francisco J. Tinahones, Renaud Touraine, Louis Vallée, Ellen van Binsbergen, Nathalie Van der Aa, Catherine Vincent-Delorme, Sophie Visvikis-Siest, Peter Vollenweider, Henry Völzke, Anneke T. Vulto-van Silfhout, Gérard Waeber, Carina Wallgren-Pettersson, Robert M. Witwicki, Simon Zwolinksi, Joris Andrieux, Xavier Estivill, James F. Gusella, Omar Gustafsson, Andres Metspalu, Stephen W. Scherer, Kari Stefansson, Alexandra I. F. Blakemore, Jacques S. Beckmann, Philippe Froguel

Both obesity and being underweight have been associated with increased mortality. Underweight, defined as a body mass index (BMI) ≤ 18.5 kg per m(2) in adults and ≤ -2 standard deviations from the mean in children, is the main sign of a series of heterogeneous clinical conditions including failure to thrive, feeding and eating disorder and/or anorexia nervosa. In contrast to obesity, few genetic variants underlying these clinical conditions have been reported. We previously showed that hemizygosity of a ∼600-kilobase (kb) region on the short arm of chromosome 16 causes a highly penetrant form of obesity that is often associated with hyperphagia and intellectual disabilities. Here we show that the corresponding reciprocal duplication is associated with being underweight. We identified 138 duplication carriers (including 132 novel cases and 108 unrelated carriers) from individuals clinically referred for developmental or intellectual disabilities (DD/ID) or psychiatric disorders, or recruited from population-based cohorts. These carriers show significantly reduced postnatal weight and BMI. Half of the boys younger than five years are underweight with a probable diagnosis of failure to thrive, whereas adult duplication carriers have an 8.3-fold increased risk of being clinically underweight. We observe a trend towards increased severity in males, as well as a depletion of male carriers among non-medically ascertained cases. These features are associated with an unusually high frequency of selective and restrictive eating behaviours and a significant reduction in head circumference. Each of the observed phenotypes is the converse of one reported in carriers of deletions at this locus. The phenotypes correlate with changes in transcript levels for genes mapping within the duplication but not in flanking regions. The reciprocal impact of these 16p11.2 copy-number variants indicates that severe obesity and being underweight could have mirror aetiologies, possibly through contrasting effects on energy balance.