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Machado-Joseph disease gene product identified in lymphocytes and brain
1Department of Neurology, Institute for Brain Research, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Japan.
Abstract:
Machado-Joseph disease (MJD) is associated with the expansion of an unstable CAG repeat. The existence of an abnormal gene product in MJD was previously suggested with the expanded polyglutamine stretch-specific antibody. However, the product of the normal allele has not previously been identified. We generated monoclonal antibodies against the fusion protein (codon 225-310) of the MJD gene product and then identified the MJD1 gene product in normal lymphoblastoid cells as a approximately 50-kDa protein by immunoblot analysis. The electrophoretic mobility differences among the normal allele products corresponds to the molecular size difference produced by the polyglutamine stretch and the polymorphism at the C-terminus. Moreover, abnormal immunoreactive bands which were larger than the normal ones were found as a approximately 60-kDa protein exclusively in the MJD samples. The cytoplasm and the nuclei of neurons and glial cells were stained by these antibodies with immunocytochemistry. As in other CAG repeat diseases, the abnormal and normal allele products were almost equally expressed in lymphoblastoid cells and the brain of MJD patients.
Insights
Researchers identified the normal Machado-Joseph disease (MJD) gene product, a ~50-kDa protein. Abnormal MJD proteins (~60-kDa) were found exclusively in patients, aiding disease understanding.
Area of Science:
- Neurogenetics
- Molecular Biology
- Protein Biochemistry
Background:
- Machado-Joseph disease (MJD) is a neurodegenerative disorder linked to CAG repeat expansion.
- Previous studies suggested an abnormal MJD gene product but failed to identify the normal allele product.
Purpose of the Study:
- To identify and characterize the normal Machado-Joseph disease (MJD) gene product.
- To develop tools for distinguishing normal and abnormal MJD protein variants.
Main Methods:
- Generation of monoclonal antibodies against a MJD gene product fusion protein.
- Immunoblot analysis to detect MJD protein in lymphoblastoid cells and patient samples.
- Immunocytochemistry to localize MJD protein in neuronal and glial cells.
Main Results:
- Identified the normal MJD gene product as a ~50-kDa protein in lymphoblastoid cells.
- Detected abnormal, larger (~60-kDa) MJD protein variants exclusively in MJD patient samples.
- Observed protein expression in both cytoplasm and nuclei of neurons and glial cells, with equal expression of normal and abnormal alleles.
Conclusions:
- The study successfully identified the normal MJD gene product and characterized abnormal variants.
- These findings provide crucial insights into the molecular pathology of Machado-Joseph disease.
- The developed antibodies are valuable tools for MJD research and diagnostics.