One of the largest families of adhesion molecules with a role in nervous system development is the immunoglobulin-superfamily (IgCAM-SF). IgCAM family members can be grouped according to their modular organisation. The C.elegans genome contains 28 genes encoding transmembrane or GPI-anchored proteins with extracellular IG domains. We are focusing on a core set of 17 IgCAMs, consisting of proteins with Ig domains only (5 genes) or with Ig domains and fibronectin III domains (12 genes). Out of these 17 genes 14 have not been analyzed functionally and ten genes are evolutionary conserved with orthologs in other animals. To identify IgCAM genes with a putative role in axon guidance we started to analyze their expression patterns. Transgenic animals were generated expressing promoter-GFP fusion constructs for individual IgCAMs. Expression typically is dynamic and not confined to a single tissue. Some IgCAMs (e.g. C26G2.1/Nephrin) show predominantly non-neuronal expression. Many others are expressed mainly in particular subsets of neurons. Five IgCAMs (
rig-1,
rig-2/syg-1,
rig-3,
rig-4 and
wrk-1) are expressed in motorneurons or interneurons with axons in the ventral cord. For functional analysis we generated a library of mutagenized worms to isolate deletion alleles. So far we have isolated deletions in ten different IgCAM genes. All mutants are viable and healthy. A detailed phenotypic analysis of these mutants is in progress.