JOURNAL ARTICLE

The expanding clinical phenotype of Bosch-Boonstra-Schaaf optic atrophy syndrome: 20 new cases and possible genotype-phenotype correlations

Chun-An Chen, Daniëlle G M Bosch, Megan T Cho, Jill A Rosenfeld, Marwan Shinawi, Richard Alan Lewis, John Mann, Parul Jayakar, Katelyn Payne, Laurence Walsh, Timothy Moss, Allison Schreiber, Cheri Schoonveld, Kristin G Monaghan, Frances Elmslie, Ganka Douglas, F Nienke Boonstra, Francisca Millan, Frans P M Cremers, Dianalee McKnight, Gabriele Richard, Jane Juusola, Fran Kendall, Keri Ramsey, Kwame Anyane-Yeboa, Elfrida Malkin, Wendy K Chung, Dmitriy Niyazov, Juan M Pascual, Magdalena Walkiewicz, Vivekanand Veluchamy, Chumei Li, Fuki M Hisama, Bert B A de Vries, Christian Schaaf
Genetics in Medicine: Official Journal of the American College of Medical Genetics 2016, 18 (11): 1143-1150
26986877

PURPOSE: Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) is an autosomal-dominant disorder characterized by optic atrophy and intellectual disability caused by loss-of-function mutations in NR2F1. We report 20 new individuals with BBSOAS, exploring the spectrum of clinical phenotypes and assessing potential genotype-phenotype correlations.

METHODS: Clinical features of individuals with pathogenic NR2F1 variants were evaluated by review of medical records. The functional relevance of coding nonsynonymous NR2F1 variants was assessed with a luciferase assay measuring the impact on transcriptional activity. The effects of two start codon variants on protein expression were evaluated by western blot analysis.

RESULTS: We recruited 20 individuals with novel pathogenic NR2F1 variants (seven missense variants, five translation initiation variants, two frameshifting insertions/deletions, one nonframeshifting insertion/deletion, and five whole-gene deletions). All the missense variants were found to impair transcriptional activity. In addition to visual and cognitive deficits, individuals with BBSOAS manifested hypotonia (75%), seizures (40%), autism spectrum disorder (35%), oromotor dysfunction (60%), thinning of the corpus callosum (53%), and hearing defects (20%).

CONCLUSION: BBSOAS encompasses a broad range of clinical phenotypes. Functional studies help determine the severity of novel NR2F1 variants. Some genotype-phenotype correlations seem to exist, with missense mutations in the DNA-binding domain causing the most severe phenotypes.Genet Med 18 11, 1143-1150.

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