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Metastable epialleles in mammals.
Vardhman K Rakyan1, Marnie E Blewitt, Riki Druker
1School of Molecular and Microbial Biosciences, University of Sydney, NSW-2006, Sydney, Australia.
Trends in Genetics : TIG
|July 20, 2002
Summary
Some mammalian alleles show variable traits due to their epigenetic state, not genetic differences. These metastable epialleles are established during embryogenesis and influence gene expression, leading to mosaicism and variable expressivity.
Area of Science:
- Genetics
- Epigenetics
- Developmental Biology
Background:
- Some mammalian alleles exhibit variable expressivity without genetic heterogeneity.
- This phenomenon is linked to the allele's epigenetic state, which can be unstable.
Purpose of the Study:
- To introduce and define a new class of alleles termed "metastable epialleles."
- To explain the mechanisms underlying variable expressivity and phenotypic mosaicism in these alleles.
Main Methods:
- The study is primarily conceptual, proposing a new classification based on existing observations.
- It discusses the influence of epigenetic state establishment during early embryogenesis.
Main Results:
- Epigenetic state is labile, causing cellular mosaicism (variegation) and inter-individual variation (variable expressivity).
- The epigenetic state is established probabilistically during embryogenesis, influenced by parental origin (imprinting).
- The epigenetic state dictates whether these alleles are dominant.
Conclusions:
- Mammalian alleles with epigenetic-dependent, variable expressivity should be classified as metastable epialleles.
- Recognizing metastable epialleles is crucial for their future identification and understanding of their prevalence.