Heritable and inducible genetic interference by double-stranded RNA encoded by transgenes

Double-stranded RNA interference (RNAi) is an effective method for disrupti ng expression of specific genes in Caenorhabditis elegans and other organis ms(1-5). Applications of this reverse-genetics tool, however, am somewhat r estricted in nematodes because introduced dsRNA is not stably inherited(5). Another difficulty is that RNAi disruption of late-acting genes has been g enerally less consistent than that of embryonically expressed genes, perhap s because the concentration of dsRNA becomes lower as cellular division pro ceeds or as developmental time advances(1). In particular, some neuronally expressed genes appear refractory to dsRNA-mediated interference. We sought to extend the applicability of RNAi by in vivo expression of heritable inv erted-repeat (IR) genes. We assayed the efficacy of in vivo-driven RNAi in three situations for which heritable, inducible RNAi would be advantageous: (i) production of large numbers of animals deficient for gene activities r equired for viability or reproduction; (ii) generation of large populations of phenocopy mutants for biochemical analysis; and (iii) effective gene in activation in the nervous system. We report that heritable IR genes confer potent and specific gene inactivation for each of these applications. We su ggest that a similar strategy might be used to test for dsRNA interference effects in higher organisms in which it is feasible to construct transgenic animals, but impossible to directly or transiently introduce high concentr ations of dsRNA.