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Different patterns of gene silencing in position-effect variegation
Vett K Lloyd1, David Dyment, Donald A R Sinclair
1Department of Zoology, University of British Columbia, Canada. vlloyd@is.dal.ca
Genome
|December 10, 2003
Summary
Position-effect variegation (PEV) instability is caused by spontaneous mutations that suppress gene silencing. These suppressors, which can be dominant or recessive, influence variegation patterns and are influenced by the number of silenced genes.
Area of Science:
- Genetics
- Molecular Biology
- Epigenetics
Background:
- Position-effect variegation (PEV) arises when genes relocate near heterochromatin, causing variable gene silencing.
- Phenotypic instability in PEV stocks suggests the influence of genetic modifiers.
Purpose of the Study:
- To investigate if phenotypic instability in PEV is due to accumulated mutations suppressing variegation.
- To characterize spontaneous variegation suppressors and their genetic nature.
- To determine temperature sensitivity during development for different PEV strains.
Main Methods:
- Four PEV strains (wm4, wmMc, wm51b, wmJ) were outcrossed for 30 generations to remove existing modifiers.
- Variegating strains were then allowed to reaccumulate spontaneous suppressors.
- Phenotypes and temperature sensitivity were monitored throughout the experiment.
Main Results:
- Spontaneous suppressors of variegation were identified as dominant/recessive, autosomal/X-linked alleles.
- All examined variegators shared an early peak sensitivity to temperature.
- Differences in inactivation frequency and extent were observed between strains after suppressor removal.
Conclusions:
- Phenotypic instability in PEV is likely a consequence of spontaneous variegation suppressors.
- The nature of suppressors depends on the number of silenced genes in the rearrangement.
- Underlying PEV patterns may result from heterochromatin domain propagation properties during cell division.