From owner-celegans@net.bio.net Fri Sep 23 23:00:00 1994 Path: biosci!EATWORMS.SWMED.EDU!leon From: leon@EATWORMS.SWMED.EDU ("Leon Avery") Newsgroups: bionet.celegans Subject: Postdoc opening in the Avery Lab Date: 24 Sep 1994 05:13:11 -0700 Organization: BIOSCI International Newsgroups for Molecular Biology Lines: 109 Sender: daemon@net.bio.net Distribution: world Message-ID: <9409240713.ZM2277@eatworms.swmed.edu> NNTP-Posting-Host: net.bio.net We have an opening for a postdoctoral fellow interested in the genetics and physiology of excitable cell function in Caenorhabditis elegans. Examples of the kinds of projects we're interested in are given below, but your actual project would be your own choice. If you're interested, please send a curriculum vitae, a list of publications, preprints of any papers in preparation or in press, the names and addresses of three people who can supply recommendations, and a cover letter describing your research interests to: Leon Avery Department of Biochemistry University of Texas Southwestern Medical Center 5323 Harry Hines Blvd Dallas, TX 75235-9038 Fax: (214) 648-8856 e-mail: leon@eatworms.swmed.edu RECENT PAPERS FROM THE AVERY LAB: Raizen, DM, and Avery, Leon (1994), "Electrical activity and behavior in the pharynx of Caenorhabditis elegans", Neuron 12: 483-495. Avery, Leon (1993), "Genetics of feeding in Caenorhabditis elegans", Genetics 133: 897-917. Avery, Leon (1993), "Motor neuron M3 controls pharyngeal muscle relaxation timing in Caenorhabditis elegans", J Exp Biol 175: 283-297. PROJECT EXAMPLES: 1. Motor neuron M4 function and muscle excitability The pharyngeal motor neuron M4 is usually essential: if you kill it, worms don't swallow any food, and therefore don't grow. We recently discovered conditions under which M4- worms survive. There are two tricks. First you feed the worms baby food--HB101, an E coli strain that produces a particularly liquid lawn. Second you depolarize the pharyngeal muscles. This can be done either with a drug, arecoline, or by a mutation, for instance in the worm sodium pump gene eat-6. If you use just one of these tricks, about 10% of M4- worms will become fertile adults. Using both together boosts the number to 70%. This means that a mutant in which M4 didn't function would be a conditional lethal. The worms would not grow under normal conditions, but on HB101 and arecoline they would reproduce. Furthermore, mutations that depolarize pharyngeal muscles would partially suppress the lethality of an M4- mutant. The project has two parts. The first part is to isolate M4- mutants. The mutant phenotype is very specific, so this should be a straight- forward screen. The mutations would identify genes necessary for M4 action; we know of no such genes now. The second part of the project would be to isolate suppressors. These mutations would identify genes necessary for the maintenance of pharyngeal muscle resting membrane potential. We would expect such genes to include ion pumps and ion channels. 2. Cell-cell coupling and the genetics of ivermectin-resistance Normally the posterior part of the pharynx, the terminal bulb, contracts and relaxes in precise synchrony with the anterior part, the corpus. This synchronization is probably effected by electrical coupling, since the muscles are dye-coupled, and corpus and terminal bulb remain synchronized when all pharyngeal neurons are killed. The gene eat-5 was identified by a single mutation, ad464, that uncouples corpus and terminal bulb contractions (Avery, 1993). We cloned eat-5 and found that it encodes a protein similar to the C elegans integral membrane protein UNC-7 and the fly proteins ogre and Passover. Intriguingly, unc-7 and Passover both affect gap junction connections. Todd Starrich (who cloned unc-7) has found many additional genes that belong to this family. Carl Johnson, studying the genetics of ivermectin resistance, has found another clue to the function of this gene family. He selected C elegans mutants resistant to the anthelminthic ivermectin. In order to be strongly resistant, a worm must carry two mutations. One mutation must be in the gene avr-15, which we suspect encodes a glutamate-gated chloride channel. (Such a channel has been cloned by Joseph Arena and Doris Cully at Merck.) The other mutation can be in any one of five genes: avr-14, avr-20, unc-1, unc-9, or unc-7. The simplest interpretation of this result is that ivermectin has two targets, one encoded by avr-15, and one controlled by five genes, one of which is unc-7. Either of these targets is sufficient to kill a worm. An intriguing (although completely speculative) hypothesis is that this gene family encodes a structural component of an invertebrate gap junction. One family of gap junction proteins, the connexins, has been well characterized. However, despite looking very hard, no one has been able to find an invertebrate connexin. The project would be to investigate the function of this gene family. First, the genetics of eat-5 need to be worked out. Since we have only one eat-5 mutation, we don't know the null phenotype. Second, the physiological effects of mutations in the various genes in the family in the presence and absence of ivermectin would be investi- gated. Third, specific hypotheses about gene function might be investigated by expression in Xenopus oocytes or transgenic worms. -- Leon Avery (214) 648-2420 (office) Department of Biochemistry -2768 (lab) University of Texas Southwestern Medical Center -8856 (fax) 5323 Harry Hines Blvd leon@eatworms.swmed.edu Dallas, TX 75235-9038 .