Spinocerebellar ataxia type 28.

Area of Science:

• Genetics
• Neurology
• Molecular Biology

Background:

• Spinocerebellar ataxias (SCAs) are a group of inherited neurodegenerative disorders.
• Spinocerebellar ataxia type 28 (SCA28) has been previously mapped to chromosome 18p11.22-q11.2.
• The genetic basis for SCA28 remained largely elusive prior to this study.

Purpose of the Study:

• To identify the specific gene responsible for spinocerebellar ataxia type 28 (SCA28).
• To characterize the mutations and their segregation within affected families.
• To determine the frequency of SCA28 gene mutations in patients with autosomal dominant spinocerebellar ataxia.

Main Methods:

• Genetic linkage analysis in a large Italian family to map the SCA28 locus.
• Fine mapping of the critical region on chromosome 18p11.22-q11.2.
• Direct sequencing of candidate genes within the identified locus.
• Screening of additional SCA patients for mutations in the identified SCA28 gene.

Main Results:

• Mapping of the SCA28 locus to a 7.9 Mb region on chromosome 18p11.22-q11.2.
• Identification of a heterozygous point mutation in a candidate gene within the critical interval, segregating with the disease in the first family.
• Discovery of a distinct missense mutation in the same gene in a second Italian family.
• Both identified mutations alter evolutionarily conserved residues in the SCA28 gene product.
• SCA28 is confirmed as the sixth SCA genotype caused by point mutations.

Conclusions:

• Point mutations in the SCA28 gene are a cause of spinocerebellar ataxia type 28.
• The identified mutations lead to amino acid changes in conserved regions, suggesting a functional impact.
• This finding expands the genetic landscape of spinocerebellar ataxias and provides a molecular basis for SCA28.