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  • De novo germline and postzygotic mutations in AKT3, PIK3R2 and PIK3CA cause a spectrum of related megalencephaly syndromes.

De novo germline and postzygotic mutations in AKT3, PIK3R2 and PIK3CA cause a spectrum of related megalencephaly syndromes.

Nature genetics (2012-06-26)
Jean-Baptiste Rivière, Ghayda M Mirzaa, Brian J O'Roak, Margaret Beddaoui, Diana Alcantara, Robert L Conway, Judith St-Onge, Jeremy A Schwartzentruber, Karen W Gripp, Sarah M Nikkel, Thea Worthylake, Christopher T Sullivan, Thomas R Ward, Hailly E Butler, Nancy A Kramer, Beate Albrecht, Christine M Armour, Linlea Armstrong, Oana Caluseriu, Cheryl Cytrynbaum, Beth A Drolet, A Micheil Innes, Julie L Lauzon, Angela E Lin, Grazia M S Mancini, Wendy S Meschino, James D Reggin, Anand K Saggar, Tally Lerman-Sagie, Gökhan Uyanik, Rosanna Weksberg, Birgit Zirn, Chandree L Beaulieu, Jacek Majewski, Dennis E Bulman, Mark O'Driscoll, Jay Shendure, John M Graham, Kym M Boycott, William B Dobyns
PMID22729224
ABSTRACT

Megalencephaly-capillary malformation (MCAP) and megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndromes are sporadic overgrowth disorders associated with markedly enlarged brain size and other recognizable features. We performed exome sequencing in 3 families with MCAP or MPPH, and our initial observations were confirmed in exomes from 7 individuals with MCAP and 174 control individuals, as well as in 40 additional subjects with megalencephaly, using a combination of Sanger sequencing, restriction enzyme assays and targeted deep sequencing. We identified de novo germline or postzygotic mutations in three core components of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway. These include 2 mutations in AKT3, 1 recurrent mutation in PIK3R2 in 11 unrelated families with MPPH and 15 mostly postzygotic mutations in PIK3CA in 23 individuals with MCAP and 1 with MPPH. Our data highlight the central role of PI3K-AKT signaling in vascular, limb and brain development and emphasize the power of massively parallel sequencing in a challenging context of phenotypic and genetic heterogeneity combined with postzygotic mosaicism.