Spatially clustering de novo variants in CYFIP2, encoding the cytoplasmic FMRP interacting protein 2, cause intellectual disability and seizures.

CYFIP2, encoding the evolutionary highly conserved cytoplasmic FMRP interacting protein 2, has previously been proposed as a candidate gene for intellectual disability and autism because of its important role linking FMRP-dependent transcription regulation and actin polymerization via the WAVE regulatory complex (WRC). Recently, de novo variants affecting the amino acid p.Arg87 of CYFIP2 were reported in four individuals with epileptic encephalopathy. We here report 12 independent patients harboring a variety of de novo variants in CYFIP2 broadening the molecular and clinical spectrum of a novel CYFIP2-related neurodevelopmental disorder. Using trio whole-exome or -genome sequencing, we identified 12 independent patients carrying a total of eight distinct de novo variants in CYFIP2 with a shared phenotype of intellectual disability, seizures, and muscular hypotonia. We detected seven different missense variants, of which two occurred recurrently (p.(Arg87Cys) and p.(Ile664Met)), and a splice donor variant in the last intron for which we showed exon skipping in the transcript. The latter is expected to escape nonsense-mediated mRNA decay resulting in a truncated protein. Despite the large spacing in the primary structure, the variants spatially cluster in the tertiary structure and are all predicted to weaken the interaction with WAVE1 or NCKAP1 of the actin polymerization regulating WRC-complex. Preliminary genotype-phenotype correlation indicates a profound phenotype in p.Arg87 substitutions and a more variable phenotype in other alterations. This study evidenced a variety of de novo variants in CYFIP2 as a novel cause of mostly severe intellectual disability with seizures and muscular hypotonia.

Citation

Markus Zweier, Anaïs Begemann, Kirsty McWalter, Megan T Cho, Lucia Abela, Siddharth Banka, Bettina Behring, Andrea Berger, Chester W Brown, Maryline Carneiro, Jiani Chen, Gregory M Cooper, Deciphering Developmental Disorders (DDD) Study, Candice R Finnila, Maria J Guillen Sacoto, Alex Henderson, Ulrike Hüffmeier, Pascal Joset, Bronwyn Kerr, Gaetan Lesca, Gloria S Leszinski, John Henry McDermott, Meira R Meltzer, Kristin G Monaghan, Roya Mostafavi, Katrin Õunap, Barbara Plecko, Zöe Powis, Gabriela Purcarin, Tiia Reimand, Korbinian M Riedhammer, John M Schreiber, Deepa Sirsi, Klaas J Wierenga, Monica H Wojcik, Sorina M Papuc, Katharina Steindl, Heinrich Sticht, Anita Rauch. Spatially clustering de novo variants in CYFIP2, encoding the cytoplasmic FMRP interacting protein 2, cause intellectual disability and seizures. European journal of human genetics : EJHG. 2019 May;27(5):747-759

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PMID: 30664714

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