In C. elegans,
sax-1 and
sax-2 regulate neurite termination and the maintenance of neuron morphology. Specifically, in
sax-1 and
sax-2 loss-of-function mutants, the neurite of the posterior mechanosensory neuron (PLM) extends beyond its normal site of termination anterior to the ALM cell body. In addition, ectopic neurites extend from the cell soma of most if not all neurons, a mutant phenotype that worsens as the animal ages.
sax-1 and
sax-2 are likely orthologs of budding yeast RAM pathway members, CBK1 and TAO3, respectively. Additional members of this pathway include KIC1, SOG2/HYM1, and MOB2. We are taking a reverse genetic approach to determine the role that putative RAM pathway members and candidate downstream effectors play in PLM neurite termination and maintenance of neuron morphology in C. elegans. Specifically, we have used single and combinatorial RNAi to knockdown gene activity of putative MOB2 and KIC1 orthologs. Genes examined in this RNAi study include
gck-1,
gck-4,
cst-1/cst-2, T12B3.4 and F38H4.10. We are also using deletion allels to test the role that candidate downstream effectors,
rab-8 and
rab-10, play in PLM neurite termination.
rab-8 and
rab-10 are most closely related to yeast SEC4, a RAB GTPase involved in polarized secretion. Interestingly, yeast Cbk1p binds Sec2p, the guanyl-nucleotide exchange factor for Sec4p. Results will be presented.