We are investigating the roles of RNAi-induced transcriptional gene silencing (RNAi-TGS) in the development of Caenorhabditis elegans. We have found that a RNAi-promoting chromatin factor Zinc Finger Protein 1 (ZFP-1), a dsRNA-binding protein of the Dicer complex, RDE-4 and DAF-16, a conserved FOXO family transcription factor, are involved in the control of migration, axonal outgrowth and cell fate of the hermaphrodite-specific neurons (HSNs). The hermaphrodite-specific neurons (HSNs) are a pair of bilaterally symmetric serotonergic motor neurons that innervate the vulval muscles and stimulate hermaphrodites to lay eggs. The HSNs are generated 400 minutes after fertilization in the tail of the embryo when each of two HSN/PHB precursors divides to give rise to an HSN and a PHB phasmid chemosensory neuron. Ten minutes after being born, the HSNs migrate to the center of the embryo where they flank the gonad primordium. In order to visualize the hermaphrodite-specific neurons (HSNs) in various mutant backgrounds, a
tph-1::gfp reporter, a transcriptional fusion that drives the expression of GFP in serotonergic neurons, was used to detect HSNs in young adult worms. The HSNs in the
rde-4 (
ne301) mutants fail to migrate fully out of the tail 50% of the time, whereas in the
zfp-1 (
ok554) and
daf-16 (
mu86) mutants the frequency of partial migration out of the tail is 13% and 18%, respectively. A
daf-16;
zfp-1 double mutant exhibits the most severe HSN migration defects since the majority of those HSNs that have not migrated out of the tail remain the most posterior as compared to the single mutants of
zfp-1,
daf-16 and
rde-4. In addition to HSN migration defects, the
daf-16;
zfp-1 mutant strain exhibits the most penetrant defects in HSN axonal outgrowth and HSN lineage abnormalities (extra HSNs) as compared to the single mutants
zfp-1,
rde-4, and
daf-16, which only occasionally exhibit these additional phenotypes. We predict that the chromatin factor ZFP-1 and the dsRNA binding protein RDE-4 negatively regulate neuronal genes required for proper migration during development through RNAi-TGS. The gene
daf-16 has been identified as a positive regulator of
zfp-1 and therefore may work through ZFP-1 during neuronal development and/or in parallel to negatively regulate common targets.