In C elegans , the biosynthesis of serotonin requires the tryptophane hydroxylase gene,
tph-1. In the serotonergic chemosensory neurons ADF, serotonin biosynthesis is regulated by a cell-specific mechanism that involves the OCR-2 TRPV ion channel. Beside this function in ADF, OCR-2 is also known to be required for mechanic, osmotic and olfactory sensations mediated by AWA and ASH neurons (Tobin et al, 2002). In previous studies we showed that the
ocr-2(
yz5) point mutation which substitutes the G36E dramatically down-regulates
tph-1. expression in the ADF and abolishes the osmotic sensation mediated by the chemosensory ASH neurons, however the diacetyl sensation mediated by the olfactory AWA neurons was not affected by this mutation. This suggests that the capacity of the
ocr-2 to discriminate between a variety of sensory signals arise from distinct intrinsic determinants within the channel and point to the presence of cell specific partners. In order to understand the mechanisms underlying the cell-specific regulation of
tph-1 in ADF neurons, we conducted a genetic screen, using
tph-1::gfp as reporter, for suppressors that recover
tph-1 expression in
ocr-2(
yz5) mutant animals. We mutagenized
ocr-2(
yz5) with EMS and screened 12036 genomes. Through this screen we selected 45 mutants that strongly recover
tph-1 expression in the ADF. Using snip-SNPs genotyping, we have discovered that two of them,
jy448 and
jy292, were allelic of
dyf-1 and
dyf-12.
dyf-1 and
dyf-12. are essential components of the Intraflagellar Transport (IFT) a processes that is required for the build up and maintenance of sensory ending within ciliated neurons (Pan et al, 2004). Mutations of some genes encoding IFT components lead to defect in chemosensory function, amphid ultrastructure and defect in lipophilic dye uptake into sensory neurons. OCR-2 is localized to the cilia of the chemosensory neurons (Tobin et al., 2002; Sokolchick et al., 2005), and OCR-2 localization is altered in IFT mutants (Qin et al., 2004). We will present genetic, cellular, molecular analyses of the role of IFT in regulating OCR-2 signaling and serotonin synthesis. Ongoing experiments are testing the role of this mechanism in transducing signaling events from sensory ending, to TRPV ion channel activation.