Correlation between CAG repeat length and clinical features in Machado-Joseph disease
P Maciel1, C Gaspar, A L DeStefano
1Centre for Research in Neuroscience, McGill University, Montreal General Hospital Research Institute, Québec, Canada.
American Journal of Human Genetics
|July 1, 1995
Summary
Machado-Joseph disease (MJD) is caused by expanded CAG repeats in a specific gene. Repeat size strongly correlates with disease onset and symptoms, with some instability during transmission.
Area of Science:
- Genetics
- Neurology
- Molecular Biology
Background:
- Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3, is a progressive neurodegenerative disorder.
- MJD is characterized by the expansion of a CAG trinucleotide repeat within a specific gene located on chromosome 14q32.1.
Purpose of the Study:
- To investigate the genetic basis of Machado-Joseph disease.
- To analyze the CAG repeat expansion in MJD patients from diverse geographic origins.
- To determine the correlation between CAG repeat size, disease onset, and clinical presentation.
Main Methods:
- Genetic analysis of CAG trinucleotide repeat length in the MJD gene.
- Study of 156 MJD patients from 33 families across different geographic locations.
- Correlation analysis between repeat size and clinical parameters.
Main Results:
- Confirmed CAG repeat expansion in MJD patients, with normal alleles ranging from 12-37 repeats and expanded alleles from 62-84 repeats.
- Observed a strong correlation between expanded CAG repeat size and earlier age of onset, as well as disease severity.
- Identified mild instability of CAG tract length during transmission, with greater variation in male transmissions.
Conclusions:
- The CAG repeat expansion in the MJD gene is the primary genetic cause of the disease.
- CAG repeat length is a significant determinant of MJD's clinical variability.
- Further research is needed to identify other factors influencing MJD's phenotypic expression.
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