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Developmental expression of mouse muscleblind genes Mbnl1, Mbnl2 and Mbnl3
Rahul N Kanadia1, Carl R Urbinati, Valerie J Crusselle
1Department of Molecular Genetics and Microbiology, Powell Gene Therapy Center, University of Florida, College of Medicine, 1600 SW Archer Road, Gainesville, FL 32610-0267, USA.
Abstract:
The RNA-mediated pathogenesis model for the myotonic dystrophies DM1 and DM2 proposes that mutant transcripts from the affected genes sequester a family of double-stranded RNA-binding factors, the muscleblind proteins MBNL1, MBNL2 and MBNL3, in the nucleus. These proteins are homologues of the Drosophila muscleblind proteins that are required for the terminal differentiation of muscle and photoreceptor tissues, and thus nuclear sequestration of the human proteins might impair their normal function in muscle and eye development and maintenance. To examine this model further, we analyzed the expression pattern of the mouse Mbnl1, Mbnl2, and Mbnl3 genes during embryonic development and compared muscleblind gene expression to Dmpk since the RNA pathogenesis model for DM1 requires the coordinate synthesis of mutant Dmpk transcripts and muscleblind proteins. Our studies reveal a striking overlap between the expression of Dmpk and the muscleblind genes during development of the limbs, nervous system and various muscles, including the diaphragm and tongue.
Insights
Mutant RNA in myotonic dystrophies sequesters muscleblind proteins. This study finds overlapping expression of muscleblind genes and DMPK during embryonic development, supporting the RNA pathogenesis model.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- Myotonic dystrophies (DM1 and DM2) are proposed to be caused by RNA toxicity.
- This toxicity involves sequestration of muscleblind (MBNL) proteins by mutant transcripts.
- MBNL proteins are crucial for muscle and photoreceptor development.
Purpose of the Study:
- To investigate the expression patterns of Mbnl1, Mbnl2, and Mbnl3 during mouse embryonic development.
- To compare Mbnl gene expression with Dmpk expression, a key gene in DM1 pathogenesis.
- To provide further evidence for the RNA-mediated pathogenesis model of myotonic dystrophies.
Main Methods:
- Analysis of mouse Mbnl1, Mbnl2, and Mbnl3 gene expression during embryonic development.
- Comparative expression analysis of muscleblind genes and Dmpk.
Main Results:
- Identified overlapping expression patterns between Dmpk and Mbnl genes during embryonic development.
- Observed striking co-localization in developing limbs, nervous system, and various muscles (diaphragm, tongue).
Conclusions:
- The study supports the RNA-mediated pathogenesis model for DM1 and DM2.
- Coordinated expression of Dmpk and Mbnl genes during development is critical.
- Nuclear sequestration of MBNL proteins by mutant transcripts likely contributes to DM pathogenesis.