The regulated localization of glutamate receptors to synaptic membranes plays a critical role in synaptic plasticity, as well as learning and memory. In C. elegans, GLR-1 is an AMPA-type glutamate receptor subunit that is localized to synapses, and our lab has been identifying factors that mediate GLR-1 localization. We previously demonstrated that the PDZ-domain protein LIN-10, a shared component of the polarized protein-sorting pathways in epithelia and neurons, is required for the localization of GLR-1. In
lin-10 mutant neurons, GLR-1 is diffusely distributed throughout the neurites, and accumulates to high levels in these neurites. However, little is known about the role of LIN-10 for the correct postsynaptic GLR-1 localization; therefore, in order to gain a better understanding of the function of LIN-10 in GLR-1 localization, we decided to identify suppressors and enhancers of
lin-10 mutants with regard to GLR-1 localization. We conducted an EMS mutagenesis of
lin-10 mutants that express an integrated GLR-1::GFP. So far we have screened about 20,000 mutagenized haploid genomes by mutagenizing at a standard rate for C. elegans (1 mutation/2,000 genes). We identified 18 mutants (suppressors) that display wild-type GLR-1 localization in a
lin-10 mutant background and 2 mutants (enhancers) that display an increased accumulation of GLR-1 (compared to
lin-10 single mutants) in a
lin-10 mutant background. We are analyzing and cloning two of the mutations isolated in the screen:
od14 and
od15. An enhancer mutation, called
od14, results in mutant neurites with thicker and longer accumulations of GLR-1::GFP than in
lin-10 mutants alone. The
od14 mutants are wild-type for locomotion and show normal GLR-1::GFP localization in a wild-type background. We are currently SNP mapping to narrow the interval containing
od14. Another mutation identified in the screen,
od15, suppresses the abnormal GLR-1 localization of
lin-10 mutants. In addition to suppressing
lin-10, it has a unique dorsal coiler behavioral phenotype: mutants coil in response to touch with a platinum wire. The
od15 mutants show decreased levels of GLR-1 accumulation in neurites of wild-type animals. We are currently SNP mapping to narrow the interval containing
od15. We anticipate that studying the genes identified by these mutations will provide clues to the role of
lin-10 in postsynaptic glutamate receptor localization.