Intergenerational instability and marked anticipation in SCA-17

Area of Science:

• Genetics
• Neurology
• Molecular Biology

Background:

• Autosomal dominant ataxia presents with a spectrum of neurological and psychiatric symptoms.
• Genetic mutations are a key factor in the pathogenesis of spinocerebellar ataxias.
• TBP gene expansions are associated with certain neurodegenerative disorders.

Purpose of the Study:

• To investigate the genetic basis of autosomal dominant ataxia with dementia and extrapyramidal features in an Italian family.
• To characterize the clinical presentation and molecular findings in affected individuals, including a child with early-onset disease.
• To identify the specific genetic mutation responsible for the observed phenotype.

Main Methods:

• Clinical evaluation of affected family members, including neurological examinations and MRI.
• Molecular genetic analysis to identify repeat expansions in candidate genes.
• DNA sequencing and repeat length analysis of the TBP gene.

Main Results:

• The family exhibited autosomal dominant inheritance of ataxia, dementia, psychiatric symptoms, epilepsy, and neuropathy.
• MRI revealed cerebral and cerebellar atrophy.
• Molecular analysis identified an expanded CAG/CAA repeat in the TBP gene (SCA-17) in all affected individuals.
• The child with early-onset, severe disease had a larger repeat expansion (66 triplets) compared to other patients (53 triplets).

Conclusions:

• The study identifies a TBP gene (SCA-17) expansion as the cause of autosomal dominant ataxia, dementia, and associated features in this Italian family.
• The findings highlight the variable clinical presentation and the correlation between repeat size and disease severity, particularly in early-onset cases.
• This research contributes to understanding the genetic heterogeneity and molecular mechanisms underlying spinocerebellar ataxias.