Brain malformations are individually rare but collectively common causes of developmental disabilities. Many forms of malformation occur sporadically and are associated with reduced reproductive fitness, pointing to a causative role for de novo mutations. Here, we report a study of Baraitser-Winter syndrome, a well-defined disorder characterized by distinct craniofacial features, ocular colobomata and neuronal migration defect. Using whole-exome sequencing of three proband-parent trios, we identified de novo missense changes in the cytoplasmic acting-encoding genes ACTB and ACTG1 in one and two probands, respectively. Sequencing of both genes in 15 additional affected individuals identified disease-causing mutations in all probands, including two recurrent de novo alterations (ACTB, encoding p.Arg196His, and ACTG1, encoding p.Ser155Phe). Our results confirm that trio-based exome sequencing is a powerful approach to discover genes causing sporadic developmental disorders, emphasize the overlapping roles of cytoplasmic actin proteins in development and suggest that Baraitser-Winter syndrome is the predominant phenotype associated with mutation of these two genes.
Bibliographical noteFunding Information:
We thank the families for their contribution to this study. We thank all members of the Northwest Genomics Center and Genomic Disorders Group Nijmegen, as well as personnel from the Microarray Facility and Sequencing Facility Nijmegen, for excellent technical assistance. This work was supported by grants from the US National Institutes of Health (NS058721 to W.B.D. and NS048120 to M.E.R.), the Netherlands Organization for Health Research and Development (ZonMW; 917-66-363 and 911-08-025 to J.A.V.), the European Union (EU)-funded TECHGENE project (Health-F5-2009-223143 to J.A.V.) and the AnEUploidy project (LSHG-CT-2006-37627 to A.H., B.W.M.v.B., H.G.B. and J.A.V.). J.-B.R. is supported by a Banting Postdoctoral Fellowship from the Canadian Institutes of Health Research. T.R. is supported by an Australian National Health and Medical Research Council (NHMRC) postdoctoral fellowship. We thank the Simons Foundation Autism Research Initiative (SFARI) that provided control exome data (191889), the National Institute of Environmental Health Services (NIEHS) Environmental Genome Project for providing support for this project (HHSN273200800010C) and the NHLBI GO Exome Sequencing Project and its ongoing studies that produced and provided exome variant calls for comparison, including the Lung GO Sequencing Project (HL-102923), the Women’s Health Initiative (WHI) Sequencing Project (HL-102924), the Broad GO Sequencing Project (HL-102925), the Seattle GO Sequencing Project (HL-102926) and the Heart GO Sequencing Project (HL-103010).