RNA interference, is an efficient way to silence a gene. In C.elegans, most neuronally expressed genes are resistant to the silencing by RNAi when dsRNA is introduced by either feeding or injection. However, expression of snap-back dsRNA in neurons results in stable gene silencing, showing that neurons are capable of processing RNAi. To understand the resistance of neuronal genes to RNAi, we performed a forward genetics screen to look for genes which, when mutated, enable feeding RNAi of genes expressed in neurons. We utilized the silencing of
osm-3 gene as a marker for our screen. Expressed in sensory neurons,
osm-3 encodes a homolog of the heavy chain subunit of heteromeric anterograde motor kinesins and is required for the development of ciliated sensory neurons. Therefore,
osm-3 loss-of-function mutants fail to take up fluorescein dye DiI, which stains amphid cilia in wildtype animals. Feeding RNAi of
osm-3 gene fails to phenocopy
osm-3(lf) in both wildtype N2 and the RNAi sensitive mutant
rrf-3(
pk1426). Wildtype N2 were mutagenized using EMS (18,000 haploid genome, 15 pools). The progeny were fed with bacteria expressing dsRNA targeting
osm-3 gene. 95 mutants were picked based on the absence of DiI staining in their amphid cilia neurons. Among the 95, only 5 mutants were saved after a secondary screen to eliminate background dye filling deficient (dyf) mutants. Feeding RNAi of other genes that affect sensory ciliated neuron development (
osm-1,-2, & -6) also resulted in the loss of DiI staining in the 5 mutants, indicating that they are hypersensitive to RNAi of osm genes. One mutant, 6F, also showed enhanced sensitivity to
dpy-13 and
daf-2 RNAi, indicating that the corresponding gene might be a general but not a neuronal specific inhibitor of RNAi. We are in the process of characterizing the 5 mutants and hope that this could facilitate our understanding of RNA interference.