Expansion of the Spinocerebellar ataxia type 10 (SCA10) repeat in a patient with Sioux Native American ancestry

Abstract

Spinocerebellar ataxia type 10 (SCA10), an autosomal dominant cerebellar ataxia, is caused by the expansion of the non-coding ATTCT pentanucleotide repeat in the ATAXIN 10 gene. To date, all cases of SCA10 are restricted to patients with ancestral ties to Latin American countries. Here, we report on a SCA10 patient with Sioux Native American ancestry and no reported Hispanic or Latino heritage. Neurological exam findings revealed impaired gait with mild, age-consistent cerebellar atrophy and no evidence of epileptic seizures. The age at onset for this patient, at 83 years of age, is the latest documented for SCA10 patients and is suggestive of a reduced penetrance allele in his family. Southern blot analysis showed an SCA10 expanded allele of 1400 repeats. Established SNPs surrounding the SCA10 locus showed a disease haplotype consistent with the previously described "SCA10 haplotype". This case suggests that the SCA10 expansion represents an early mutation event that possibly occurred during the initial peopling of the Americas.

Figure 1. Southern blot analysis of the SCA10 ATTCT repeat expansion in our Sioux patient with SCA10.

Lane 1: positive control, 2300 repeats (genomic DNA from SCA10 somatic cell hybrid line (SCH)) ; Lane 2: no DNA control; Lane 3: positive control, 800 repeats (genomic DNA from SCA10 SCH); Lane 4: negative control (genomic DNA from normal control SCH); Lane 5: DNA from Sioux SCA10 patient.

Figure 2. The distribution of SCA10 in the American continents and the proposed dispersal pattern of the mutation.

Possible dispersal patterns of Native American and Amerindian populations as they began entering the Americas ∼15,000 years ago are shown as solid blue lines. Asterisks indicate countries where SCA10 patients have documented ancestral ties.