unc-40 is required with
unc-6 to guide ventral migrations on the nematode epidermis (Hedgecock et al., Neuron 4, 61-85, 1990). We have positioned
unc-40 genetically by 3-factor crosses with
dpy-5 and
bli-4 as flanking markers and we have isolated 5 new alleles of
unc-40 (2 spontaneous, 2 gamma, and 1 EMS) making a total of 12. DNAs from cosmids covering this region (obtained from Alan Coulson and John Sulston) are being used to probe DNA and RNA from the mutants and DNA from strains carrying duplications that break to either side of
unc-40 (obtained from Anne Rose's laboratory). We are also injecting cosmid DNAs into gonads to look for rescue by germline transformation. The brood sizes of various
unc-40 alleles are very small, so we have resorted to injecting the wild type in order to create a series of transformed lines, each carrying an extrachromosomal array of a different cosmid. Each array will be passed into appropriately marked
unc-40 animals to ask if any can rescue the mutant phenotype. Mosaic experiments are also underway to determine whether
unc-40 acts in migrating cells.