Transgene-mediated cosuppression in the C-elegans germ line

Functional silencing of chromosomal loci can be induced by transgenes (cosu ppression) or by introduction of double-stranded RNA (RNAi). Here, we demon strate the generality of and define rules for a transgene-mediated cosuppre ssion phenomenon in the Caenorhabditis elegans germ line. Functional repres sion is not a consequence of persistent physical association between transg enes and endogenous genes or of mutations in affected genes. The cosuppress ion mechanism likely involves an RNA mediator that defines its target speci ficity, reminiscent of RNAi. Cosuppression is strongly abrogated in rde-2 a nd mut-7 mutants, but is not blocked in an rde-1 mutant, indicating that co suppression and RNAi have overlapping but distinct genetic requirements.