Active zones are electron dense presynaptic specializations in neurons that play a pivotal role in providing sites for neurotransmitter release and synaptic vesicle recycling. However, the mechanisms that regulate the formation and maintenance of the active zone remain to be elucidated. To address these questions, we took a genetic approach to identify genes that affect active zone development using an active zone marker, SYD-2::GFP that was developed in our laboratory (Yeh, E et al. J. Neuro. Sci. 2005). From this screen, a gene encoding innexin gap junction protein,
unc-7, has been isolated (Yeh, E. et al. (629A) and Ng, S. et al. (27) 2005 worm meeting). The innexins are functional homologs of connexins, gap junction components in vertebrates. Investigations into the biological function of innexins have been started, however, the mechanisms that regulate these channels are unknown. In the
unc-7 loss-of-function background, the active zone linear density is decreased and forms large gaps along the nerve cord. Also, UNC-7 is required to restrict the localization of another presynaptic protein, SAD-1 kinase, which is involved in synaptic vesicle pool organization and neuronal polarity, to the presynaptic site. Furthermore,
sad-1 suppressed the
unc-7 phenotypes, suggesting these genes function in same pathway to regulate synaptic development. To investigate the
unc-7 sad-1 pathway, we conducted a suppressor screen of the
unc-7 kinker uncoordinated phenotype. Here we present that
unc-7 stomatin homolog interacts with
unc-7 and
sad-1. Stomatin is a membrane associated protein, and reported as an ion channel regulator. The dominant mutations of
unc-1 showed a severe coiler unc phenotype. The
unc-1(dm)
unc-7(lf) double mutants showed mild coiler or loopy with no tendency of kinking. On the other hand,
unc-9, another innexin mutant having a kinker phenotype, strongly suppressed
unc-1(dm) coiler phenotype. In addition,
unc-1(dm) also suppressed the SAD-1 localization defect within the
unc-7 background. Also,
unc-1(lf) kinker phenotype was suppressed by
sad-1. UNC-1 and UNC-7 colocalized within the neuron and body wall muscle, suggesting that UNC-1 and UNC-7 function together to regulate SAD-1. Our data expand the previously reported genetic interactions among genes involved in the volatile anesthetics sensitivity