SLC25A46 Mutations Associated with Autosomal Recessive Cerebellar Ataxia in North African Families

Abstract

Background: Autosomal recessive cerebellar ataxias (ARCA) are a complex group of neurodegenerative disorders with high clinical and genetic heterogeneity. In most cases, the cerebellar ataxia is not pure, and complicating clinical features such as pyramidal signs or extraneurological features are found.

Objective: To identify the genetic origin of the cerebellar ataxia for 3 consanguineous North African families presenting with ARCA.

Methods: Genome-wide high-density SNP genotyping and whole-exome sequencing were performed followed by Sanger sequencing for mutation confirmation.

Results: Two variants were identified in SLC25A46. Mutations in this gene have been previously associated with Charcot-Marie-Tooth type 2 and optic atrophy. While the previously reported variant p.Arg340Cys seems to be consistently associated with the same clinical features such as childhood onset, optic atrophy, gait and speech difficulties, and wasting of the lower limbs, the patient with the novel mutation p.Trp160Ser did not present with optic atrophy and his ocular abnormalities were limited to nystagmus and saccadic pursuit.

Conclusion: In this study, we report a novel variant (p.Trp160Ser) in SLC25A46 and we broaden the phenotypic spectrum associated with mutations in SLC25A46.

Keywords: Ataxia; Mutation; North Africa; SLC25A46.

Figure 1

Family pedigrees Affected family members are shaded. Males are represented by squares, females are represented by circles

Figure 2

Brain MRI of patient AAR-322-001 at age 31. Sagittal view of T1-weighted image (A) showing a very mild upper vermis atrophy of the cerebellum (arrow) and an axial FLAIR section (B) showing very subtle white matter abnormalities in the cerebellar hemisphere (arrows).

Figure 3

SLC25A46 domains and functional sites