IDENTIFICATION OF CAENORHABDITIS-ELEGANS GENES REQUIRED FOR NEURONAL DIFFERENTIATION AND MIGRATION

To understand the mechanisms that guide migrating cells, we have been studying the embryonic migrations of the C. elegans canal-associated n eurons (CANs). Here, we describe two screens used to identify genes in volved in CAN migration. First, we screened for mutants: that died as clear larvae (Clr) or had withered tails (Wit), phenotypes displayed b y animals lacking normal CAN function. Second, we screened directly fo r mutants with missing or misplaced CANs. We isolated and characterize d 30 mutants that defined 14 genes necessary for CAN migration. We fou nd that one of the genes, ceh-10, specifies CAN fate. ceh-10 had been defined molecularly as encoding a homeodomain protein expressed in the CANs. Mutations that reduce ceh-10 function result in Wit animals wit h CANs that are partially defective in their migrations. Mutations tha t eliminate ceh-10 function result in Clr animals with CANs that fail to migrate or express CEH-23, a CAN differentiation marker. Null mutan ts also fail to express CEH-10, suggesting that CEH-10 regulates its o wn expression. Finally we found that ceh-10 is necessary for the diffe rentiation of AIY and RMED, two additional cells that express CEH-10.