Novel Biallelic Synonymous Exonic Variant in VPS13A Affecting mRNA Splicing: Case Report.

Journal: Neurology. Genetics
Published:
Abstract

Chorea-acanthocytosis is an autosomal recessively inherited condition caused by loss-of-function pathogenic variants in VPS13A. We identified a novel synonymous exonic variant leading to abnormal mRNA splicing in a patient with chorea-acanthocytosis. A patient with focal epilepsy developed generalized chorea with orolingual dystonia, cognitive decline, and peripheral neuropathy, consistent with chorea-acanthocytosis. Her parents were first cousins, but there was otherwise no family history. Targeted gene sequencing for variants in VPS13A, mRNA splicing analysis, and Western blot for chorein were performed. A homozygous synonymous variant in exon 41 of VPS13A (NM_033305.3): c.5157C>T; p.Gly1719 = was identified; this was previously classified as a variant of uncertain significance. SpliceAI predicted a splice donor gain with a score of 0.75 2 base pairs upstream of the reported variant. RNA splicing analysis revealed the creation of a type III splice variant, resulting in a frameshift and a premature termination codon. Western blot showed absent chorein/VPS13A protein. The variant is reclassified as likely pathogenic based on the American College of Medical Genetics criteria. This is the first reported case of ChAc caused by a synonymous variant in VPS13A proven to affect splicing. Our report further expands the spectrum of variants known to cause ChAc.

Authors
Rebecca Hui Hoe, Yi Zhao, Helen Ong, Karine Su Tay, Nigel Choon Tan, Mikaelea Jia Khor, Bingwen Fan, Kevin Peikert, Andreas Hermann, Shermyn Neo, Zhiyong Chen