SCA2 trinucleotide expansion in German SCA patients

Area of Science:

• Genetics
• Neurodegenerative Disorders
• Molecular Biology

Background:

• Autosomal dominant spinocerebellar ataxias (SCA) are a diverse group of neurodegenerative conditions.
• SCA type 2 is linked to an unstable, expanded (CAG)n trinucleotide repeat on chromosome 12.

Purpose of the Study:

• To investigate the prevalence and characteristics of SCA2 (CAG)n repeat expansions in German patients.
• To analyze the correlation between repeat length, age of onset, and transmission patterns.

Main Methods:

• Genotyping of the (CAG)n repeat in the SCA2 gene for 842 sporadic ataxia patients and 96 German families with dominant SCA.
• Analysis of repeat length variations, age of onset, and transmission history.

Main Results:

• SCA2 (CAG)n expansion identified in 71 patients from 54 families, with repeat lengths ranging from 36 to 64 units.
• Paternal transmission was more frequently associated with significant repeat expansions.
• An inverse correlation was observed between (CAG)n repeat length and age of onset.
• Alleles with 16-31 repeats were common in healthy individuals, while 34 repeats were observed in a healthy carrier.

Conclusions:

• The SCA2 (CAG)n expansion is a significant cause of autosomal dominant SCA in Germany, accounting for nearly 14% of cases.
• Defining the range between normal and disease-associated alleles is crucial due to overlapping repeat lengths.
• Genetic testing for SCA2 mutations is important for diagnosing and understanding the inheritance of spinocerebellar ataxias.