Identifying genes affecting SAD-1 localization in Caenorhabditis elegans.

SAD-1 is a neuron-specific Serine/Threonine protein kinase that regulates several aspects of neural development in Caenorhabditis elegans. Double immunostaining using antibodies against SAD-1 and other presynaptic proteins suggests that endogenous SAD-1 localizes to regions outside active zones at presynapses. I also observed that the synaptic subcellular localization pattern of endogenous SAD-1, as well as the SAD-1::RFP marker is partially altered in mutants for UNC-104, a kinesin motor that transports synaptic vesicles, suggesting that anterograde transport of SAD-1 is partially dependent on UNC-104. In a screen for mutations affecting the distribution pattern of hpIs1/SAD-1::GFP puncta, I recovered 25 phenotypically distinct mutants. Among them, unc-41(hp293), hp314(I), hp296(IV) may represent genes that function in general presynaptic differentiation because mutations in these genes also display defective morphology of other presynaptic markers. Another mutant, hp313, affects the SAD-1::GFP marker specifically, suggesting that it either regulates the transgene expression or represents a gene specifically affecting SAD-1.