PIK3CA-associated developmental disorders exhibit distinct classes of mutations with variable expression and tissue distribution

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Abstract

Mosaicism is increasingly recognized as a cause of developmental disorders with the advent of next-generation sequencing (NGS). Mosaic mutations of PIK3CA have been associated with the widest spectrum of phenotypes associated with overgrowth and vascular malformations. We performed targeted NGS using 2 independent deep-coverage methods that utilize molecular inversion probes and amplicon sequencing in a cohort of 241 samples from 181 individuals with brain and/or body overgrowth. We identified PIK3CA mutations in 60 individuals. Several other individuals (n = 12) were identified separately to have mutations in PIK3CA by clinical targeted-panel testing (n = 6), whole-exome sequencing (n = 5), or Sanger sequencing (n = 1). Based on the clinical and molecular features, this cohort segregated into three distinct groups: (a) severe focal overgrowth due to low-level but highly activating (hotspot) mutations, (b) predominantly brain overgrowth and less severe somatic overgrowth due to less-activating mutations, and (c) intermediate phenotypes (capillary malformations with overgrowth) with intermediately activating mutations. Sixteen of 29 PIK3CA mutations were novel. We also identified constitutional PIK3CA mutations in 10 patients. Our molecular data, combined with review of the literature, show that PIK3CA-related overgrowth disorders comprise a discontinuous spectrum of disorders that correlate with the severity and distribution of mutations.

Authors

Ghayda Mirzaa, Andrew E. Timms, Valerio Conti, Evan August Boyle, Katta M. Girisha, Beth Martin, Martin Kircher, Carissa Olds, Jane Juusola, Sarah Collins, Kaylee Park, Melissa Carter, Ian Glass, Inge Krägeloh-Mann, David Chitayat, Aditi Shah Parikh, Rachael Bradshaw, Erin Torti, Stephen Braddock, Leah Burke, Sondhya Ghedia, Mark Stephan, Fiona Stewart, Chitra Prasad, Melanie Napier, Sulagna Saitta, Rachel Straussberg, Michael Gabbett, Bridget C. O’Connor, Catherine E. Keegan, Lim Jiin Yin, Angeline Hwei Meeng Lai, Nicole Martin, Margaret McKinnon, Marie-Claude Addor, Luigi Boccuto, Charles E. Schwartz, Agustina Lanoel, Robert L. Conway, Koenraad Devriendt, Katrina Tatton-Brown, Mary Ella Pierpont, Michael Painter, Lisa Worgan, James Reggin, Raoul Hennekam, Karen Tsuchiya, Colin C. Pritchard, Mariana Aracena, Karen W. Gripp, Maria Cordisco, Hilde Van Esch, Livia Garavelli, Cynthia Curry, Anne Goriely, Hulya Kayserilli, Jay Shendure, John Graham Jr., Renzo Guerrini, William B. Dobyns