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Intergenerational stability of the myotonic dystrophy protomutation
J M Barceló1, M S Mahadevan, C Tsilfidis
1Department of Microbiology and Immunology, University of Ottawa, Ontario, Canada.
Abstract:
The amplification of the CTG trinucleotide repeat in myotonic dystrophy (DM) correlates with increasingly severe phenotypes. We designate its minimal amplification the 'protomutation' since it is the mutation itself at an early stage of intergenerational evolution and is associated with very mild clinical signs. From the study of 536 DM mutation carriers (from 158 affected families), a total of 60 DM-parent/DM-offspring pairings were identified in which the parent had the protomutation. We found a strong correlation between the protomutation length and the amplification observed in the next generation. We also observed the stable transmission of the protomutation through successive generations. This stability may explain the maintenance in the population of this autosomal dominant disease despite the low reproductive fitness of severe DM phenotypes.
Insights
The CTG repeat expansion in myotonic dystrophy (DM) shows a protomutation stage. This early-stage mutation stably transmits, correlating with next-generation amplification and explaining DM
Area of Science:
- Genetics
- Molecular Biology
- Human Disease Genetics
Background:
- Myotonic dystrophy (DM) is characterized by CTG trinucleotide repeat amplification.
- Repeat expansion correlates with disease severity and phenotype.
- The earliest stage of mutation, the 'protomutation,' presents with mild clinical signs.
Purpose of the Study:
- To investigate the intergenerational stability and amplification patterns of the DM CTG protomutation.
- To determine the relationship between protomutation length and subsequent repeat expansion in offspring.
- To elucidate the role of the protomutation in the population maintenance of DM.
Main Methods:
- Analysis of 536 DM mutation carriers from 158 families.
- Identification of 60 DM-parent/DM-offspring pairings where the parent carried the protomutation.
- Correlation analysis of protomutation length and offspring repeat amplification.
Main Results:
- A strong correlation exists between the length of the protomutation in parents and the amplified repeat size in their offspring.
- The protomutation demonstrates stable transmission across successive generations.
- Protomutation stability contributes to the persistence of DM in the population.
Conclusions:
- The protomutation is a key factor in the intergenerational amplification of CTG repeats in DM.
- Stable transmission of the protomutation facilitates the inheritance of DM.
- Understanding protomutation dynamics is crucial for comprehending DM's genetic architecture and population prevalence.