Transposon Silencing, RNA Interference and Cosuppression in Caenorhabditis elegans

Sylvia E.J. Fischer
Hubrecht Laboratory
Uppsalalaan 8
3584 CT Utrecht, The Netherlands
telephone: +31 302121965
fax: +31 302516554
prestype: Platform
presenter: Sylvia E.J. Fischer

Sylvia E.J. Fischer, Rene F. Ketting, Femke Simmer, Marcel Tijsterman, Marieke van der Horst, Karen Thijssen, Kristy Okihara and Ronald H.A. Plasterk

All known natural isolates of the nematode C. elegans have active transposition of the Tc1 transposon in the soma. In the germ line of many strains however, Tc1 transposition is silenced. 43 mutants in which Tc1 has been activated in the germ line ("mutators") were isolated after random mutagenesis of a silenced strain. These mutants have several phenotypes in addition to the alleviation of transposon silencing: temperature sensitive sterility and high incidence of males. Half of the mutants are also resistance to RNA interference, the silencing of gene expression in response to exogenous dsRNA. One of these RNAi-resistant mutators, mut-7, was cloned, and shown to encode a protein with homology to RNaseD. This mutant is also resistant to cosuppression, a phenomenon in which introduction of transgenic copies of certain genes results in reduced expression of both the transgene and the endogenous gene. Interestingly, several RNAi-sensitive mutators are also sensitive to cosuppression. On the other hand, several mutants that are resistant to RNAi like mut-7, do not show alleviation of transposon silencing nor resistance to cosuppression. We will discuss progress in identifying more genes of the three classes of mutants: RNAi-resistant mutators, RNAi-sensitive mutators and RNAi-deficient non-mutators.

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