Worm Breeder's Gazette 13(1): 36 (October 1, 1993)

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.

Cold-Sensitive Uncs May Reveal Genes That Encode Channel Proteins

Mary A. Norman, William J. Jones, Ralph M. Hecht.

Department of Biochemistry, University of Houston, Houston, TX 77204-5934.

Our long-term goal is to define stringent conditions that will enable us to identify suppressors to ts mutations that gain an independent cold-sensitive (cs) phenotype. In pursuit of this goal we have obtained a set of cold-sensitive unc mutations whose map positions are in the process of being completed. Two of these cs mutations may encode components of channel membrane proteins or other proteins critical for neurotransmission.

The first cs mutation, HH53 ,is a new unc mutation which maps to the X-chromosome between dpy-3 and unc-2 .It exhibits an immediate paralytic phenotype at restrictive-temperature and recovers instantaneously from paralysis at permissive temperature during all stages of development. HH53 is also a dominant mutation and its reversible paralysis is observed in the presence of the wild-type protein which supports the hypothesis that HH53 encodes a structural protein. This property of instantaneous reversibility of paralysis has been found in the Drosophila gene para(ts) which encodes a sodium channel structural component (Suzuki et al., 1971, PNAS 68:890; Loughney et al., 1989, Cell 58:1143) and in nap(ts) and tip-E which interact with para(ts). Also, Hosono et. al. (1985, J. Exp. Zool. 235:409) isolated a temperature-sensitive allele of cha-1 (abnormal choline acetyltransferase) which exhibits reversible paralysis.

The second cs uncoordinated mutation, HH34 ,maps between dpy-8 and unc-10 on the X-chromosome and interacts with (fails to complement) unc-7 . Unc-7 encodes a transmembrane protein which is believed to be involved in the function of neuronal ion channels (Starich et al., 1993, Gen. 133:527). We have also isolated a cs allele (HH30) of unc-7 as well as five cs alleles of unc-1 and three alleles of unc-9 .

Once the mapping of all unc(cs) mutations is completed we will attempt to isolate the gene for HH53 to see if it is a channel membrane protein. Concurrently, suppressors to HH53 will be analyzed to obtain an independent ts mutation.