Worm Breeder's Gazette 14(5): 76 (February 1, 1997)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Biology Department, Johns Hopkins University, Baltimore, MD 21218
mig-15 is important in several developmental processes including epidermal development, Q neuroblast migrations, and muscle arm targeting. mig-15(rh148) mutants have an obvious body shape defect that is easily recognizable under the dissecting microscope. Adult worms are smaller in size than wild type. Most animals have protruding vulvae and give small brood sizes of about 40. The QL neuroblast migrations are reversed in mig-15(rh148) mutants, similar to that in mig-5 and mab-5 animals. Besides the above more commonly described phenotypes, mig-15(rh148) also show muscle arm targeting defects. Muscle arms are cytoplasmic extensions of muscle cells that make neuro-muscular junctions with motor neuron axons. In wild type, muscle cells in the dorsal quadrant extend arms toward the dorsal nerve cord and ventral arms extend toward the ventral nerve cord. In mig-15(rh148) mutants, however, muscle arms are occasionally seen extending from dorsal to ventral or from ventral to dorsal directions. We have cloned the mig-15 gene using the transgenic rescue method. First we mapped mig-15 between unc-115 and vab-3 on the X chromosome by three-factor crosses. A single cosmid ZC504 within the corresponding region on the physical map rescued mig-15(rh148) mutant phenotypes. Sequence data from the genome consortium predicted four genes on the cosmid. We constructed subclones that contained only one gene at a time, and tested each subclone for rescuing activity. A subclone that contains only ZC504.4 rescued mig-15(rh148) phenotypes while others failed. When coding sequence of ZC504.4 was disrupted by site directed mutagenesis, it failed to rescue. Based on the above evidence, we concluded that ZC504.4 is the mig-15 gene. ZC504.4 encodes a novel Ser/Thr protein kinase in the Ste20/p65PAK family (See Figure). The kinase domain is most homologous to GC kinases which activate SAPK pathways in response to TNF-a and IL1 (Pombo et al., Nature 377, 750, 1994); These kinases may be regulated directly by Rab8 or other G-proteins (Ren et al., PNAS 93, 5151, 1996). Near the C-terminus, there is a 40 residue motif which is shared with one other protein called citron, a presumptive Rho/Rac effector without a kinase domain (Madaule et al., FEBS Letters 377, 243, 1995). We are currently working on the Mig-15 expression pattern using the GFP tagging method. Future experiments include isolation and characterization of additional allele; sequencing mutation and epistatic analysis between mig-15(rh148) and other genes in the same pathway.