Novel loss-of-function mutations in VPS13A cause chorea-acanthocytosis in two families

Abstract

Introduction: Chorea-acanthocytosis (ChAc) is the most common subtype of neuroacanthocytosis (NA) caused by mutations in VPS13A (vacuole protein sorting-associated protein 13A). ChAc is characterized by the presence of spherocytes and neurological symptoms. This article reports two families with ChAc and summarizes some suggestive characteristics, providing an effective basis for clinicians to screen ChAc in the early stage and effectively reduce the misdiagnosis and missed diagnosis of this disease.

Methods: We first performed whole-exome sequencing (WES) and confirmed three NA cases in two families. Detailed clinical and peripheral blood smear analyses are presented, supplemented by molecular electron microscopy to assess erythrocyte ultrastructure. To further evaluate the functional impact of candidate variants, we additionally performed RNA splicing analysis.

Results: Three ChAc cases in two families were identified. Clinically, almost all cases presented initial movement disorders, and Elevated creatine kinase (CK) level. Besides, both peripheral blood smear and scanning electron microscopy revealed characteristic acanthocytes.

Conclusions: This study provides key clinical indicators for early ChAc screening: early movement disorders combined with persistently elevated CK levels and significant acanthocytosis on peripheral blood smear. We further identified three novel VPS13A mutations, expanding the variant spectrum and confirming clinical heterogeneity in ChAc.

Keywords: VPS13A; chorea-acanthocytosis; gene mutations; neurology; whole-exome sequencing.

Figure 1

Pedigrees, mutation analysis, RNA Splicing Analysis, and peripheral blood smear for the ChAc families. (A) Pedigrees of three cases from two ChAc families: The square represents the male, and the circle represents the female. A filled symbol indicates the proband. (B) Mutation analysis: Visualization of the mutations in our cases is shown with Chromas. (C) RNA Splicing Analysis: Agarose gel electrophoresis analysis of VPS13A fragments in the proband (II-2, lane 2) and normal controls. The proband exhibits an aberrant 474 bp fragment (F1) compared to the wild-type 517 bp band, indicating exon skipping. Mutation visualization via Chromas confirms the splicing site mutation c.145-2A>G. (D) RNA Splicing Analysis: Schematic diagram illustrating the consequence of the c.145-2A>G mutation, which disrupts the canonical splice acceptor site of intron 2, resulting in complete skipping of exon 3 during transcript processing. (E) Peripheral blood smear: acanthocytes were shown via Wright-Gimsa staining (original magnification, ×400) in proband (II-2) in F1 (a), proband (II-1) in F2 (b). Examination of peripheral blood of proband (II-2) in F1 by scanning electron microscopy (original magnification, ×2500) showing acanthocytosis (c).

Figure 2

Clinical comparison of alopecia symptoms during disease progression. (a) Photos of the patient at the age of 30, showing uniform hair distribution, normal density, and no visible exposed areas of the scalp. (b) A photo of the patient at the age of 42. It has been 10 years since then. The picture shows obvious hair thinning and increased scalp visibility, tongue muscle tone disorder, and the tongue protruding to the right.