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Characterization of the myotonic dystrophy region predicts multiple protein isoform-encoding mRNAs
G Jansen1, M Mahadevan, C Amemiya
1Department of Cell Biology and Histology, Faculty of Medical Sciences, University of Nijmegen, The Netherlands.
Abstract:
The mutation underlying myotonic dystrophy (DM) has been identified as an expansion of a polymorphic CTG-repeat in a gene encoding protein kinase activity. Brain and heart transcripts of the DM-kinase (DMR-B15) gene are subject to alternative RNA splicing in both human and mouse. The unstable [CTG]5-30 motif is found uniquely in humans, although the flanking nucleotides are also present in mouse. Characterization of the DM region of both species reveals another active gene (DMR-N9) in close proximity to the kinase gene. DMR-N9 transcripts, mainly expressed in brain and testis, possess a single, large open reading frame, but the function of its protein product is unknown. Clinical manifestation of DM may be caused by the expanded CTG-repeat compromising the (alternative) expression of DM-kinase or DMR-N9 proteins.
Insights
Myotonic dystrophy (DM) is linked to expanded CTG-repeats in the DM-kinase gene. This mutation may disrupt alternative RNA splicing of DM-kinase or the nearby DMR-N9 gene, causing disease symptoms.
Area of Science:
- Genetics
- Molecular Biology
- Neurology
Background:
- Myotonic dystrophy (DM) is a genetic disorder characterized by muscle weakness and wasting.
- The underlying genetic mutation involves an expanded CTG-repeat sequence.
- The DM-kinase (DMR-B15) gene, encoding protein kinase activity, is implicated in DM pathogenesis.
Purpose of the Study:
- To investigate the role of the CTG-repeat expansion in DM pathogenesis.
- To characterize the DM-kinase (DMR-B15) and a nearby gene (DMR-N9) in humans and mice.
- To explore the impact of the mutation on alternative RNA splicing.
Main Methods:
- Analysis of CTG-repeat expansion in the DM-kinase gene.
- Characterization of DM-kinase (DMR-B15) and DMR-N9 gene transcripts in human and mouse.
- Investigation of alternative RNA splicing patterns.
Main Results:
- The mutation in DM is an expansion of a polymorphic CTG-repeat in the DM-kinase gene.
- DM-kinase (DMR-B15) transcripts undergo alternative RNA splicing in both humans and mice.
- A neighboring gene, DMR-N9, is also identified and expressed in brain and testis, with unknown protein function.
Conclusions:
- The expanded CTG-repeat in DM may impair the alternative expression of DM-kinase or DMR-N9 proteins.
- Alternative RNA splicing of these genes is a key factor in DM pathology.
- Further research is needed to elucidate the function of DMR-N9 and its role in DM.