Worm Breeder's Gazette 14(5): 42 (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.
Department of Molecular Biology and Biochemistry, Rutgers University, Center for Advanced Biotechnology and Medicine, Piscataway NJ 08854
mec-4 encodes a candidate subunit of a mechanosensitive ion channel that plays a key role in touch transduction. Unusual dominant mec-4(d) alleles cause the swelling and necrotic-like death of the six touch receptor neurons. Neurodegeneration is thought to be initiated by elevated ion influx allowed by the mutant MEC-4 channel. A time course study of mec-4(d)-inducedneurodegeneration revealed that remarkable infoldings of the plasma membrane occurs, membranous whorls are internalized, vacuoles appear and the chromatin clumps (Hall et al., 1997). To learn more about mechanosensory ion channel function and about mechanisms of degenerative cell death, we are isolating suppressor mutations that block mec-4(d) mediated neurodegeneration. The mutagenesis scheme involves the expression of the green fluorescent protein in the touch receptor neurons under the control of the mec-4 promoter. ZB134, a strain in which a pmec-4GFP construct is integrated into a mec-4(+) background, exhibits 6 brightly fluorescent touch receptor neurons. When a mec-4(d) allele, mec-4(u231), is crossed into this background (strain ZB137), fluorescent touch cells are no longer evident as they have undergone cell death. We mutagenize strain ZB137 and screen for rare animals that have glowing touch cells and thus bear candidate suppressor mutations. To date we have mutagenized and screened 12,000 haploid genomes for death suppressing mutations. Our preliminary screen has resulted in seventeen non-mec-4 alleles that suppress touch cell death. Surprisingly, many of these exert dominant effects. Mapping and determination of linkage groups of the suppressors is underway. We are also testing the three recessive suppressors to determine whether they fall into distinct complementation groups. The recessive suppressors are being tested for complementation with mec-6 (mec-6 is the only known suppressor of mec-4(d)-induced degeneration) and a combinatorial matrix is being constructed to determine which alleles, if any, possess discernible epistatic or synergistic effects. We will also determine the touch sensitivity of the suppressor alleles in the absence of mec-4(d). We are further testing the suppressors for the ability to block the formation of vacuoles induced by expression of human Ab4 peptide (we thank C. Link for providing this strain) in order to help distinguish between general necrotic-like death disrupters and mec-4 channel disrupters. We are optimistic that our suppressors will identify new genes that affect channel function, cellular osmotic balance and necrotic-like cell death.