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Reduced expression of DMAHP/SIX5 gene in myotonic dystrophy muscle
Abstract:
In myotonic dystrophy (DM), the expansion of CTG triplet repeats in the 3'-untranslated region of DM-protein kinase (DMPK) is a causal gene mutation. However, the pathogenic molecular mechanism of CTG repeat expansion for DM phenotypic expression is unclear. To investigate this issue, we examined the influence of CTG repeat expansion on the expression levels of DMPK gene and 3'-flanking DM locus-associated homeodomain protein (DMAHP)/SIX5 gene in the muscles of DM patients. We isolated RNA from muscle tissues of six DM patients and six controls, and performed a competitive reverse transcriptional polymerase chain reaction (RT-PCR) assay. The total mRNA level of DMAHP/SIX5 was significantly lower in DM than in controls, but the DMPK mRNA level was unchanged. Our results suggest that CTG repeat expansion influences the expression of genes other than DMPK to cause the DM phenotype.
Insights
Myotonic dystrophy (DM) involves CTG repeat expansion, but its mechanism is unclear. This study found that DM patients have lower DMAHP/SIX5 gene expression, suggesting CTG repeats affect other genes to cause DM symptoms.
Area of Science:
- Genetics
- Molecular Biology
- Neurology
Background:
- Myotonic dystrophy (DM) is caused by CTG triplet repeat expansion in the DMPK gene.
- The precise molecular mechanisms linking CTG repeat expansion to DM phenotypes remain largely unknown.
Purpose of the Study:
- To investigate the impact of CTG repeat expansion on DMPK and DMAHP/SIX5 gene expression in DM patient muscles.
- To elucidate the molecular basis of DM pathogenesis.
Main Methods:
- RNA isolation from muscle tissues of six DM patients and six healthy controls.
- Competitive reverse transcriptional polymerase chain reaction (RT-PCR) assay to quantify gene expression levels.
Main Results:
- Significantly reduced total mRNA levels of DMAHP/SIX5 in DM patients compared to controls.
- No significant change observed in DMPK mRNA levels between DM patients and controls.
Conclusions:
- CTG repeat expansion in DM may exert its pathogenic effects by influencing the expression of genes other than DMPK.
- DMAHP/SIX5 gene downregulation is a potential mechanism contributing to the DM phenotype.