Worm Breeder's Gazette 11(4): 18
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.
unc-49 shrinks by the simultaneous contraction of the dorsal and ventral musculature when provided with mechanosensory stimulation of the head region. It also displays severe difficulties in spontaneous backward locomotion and its body length is slightly reduced. Abnormalities in the placement of the axons of the anterior mechanosensory receptors, the ALMs, have been observed (Siddiqui, abstracts of the 1989 C. elegans meeting), but the axons of the cross- inhibitor motorneurons, the DDs and VDs, display normal trajectories ( McIntyre, personal communication). Several lines of evidence suggest that abnormalities in the GABA receptor or regulation of its expression or binding ability may be the primary defect in unc-49 ( McIntyre, personal communication): a) unc-49 specimens fail to exhibit normal behavioral responses to muscimol, a GABA agonist, when both the rate of locomotion or pharyngeal pumping are monitored, b) binding assays reveal abnormal GABA binding kinetics in unc-49 when compared to N2 tissue, and c) immunocytochemical staining with antibodies against GABA suggests normal levels of GABA in ventral cord motorneurons. unc-49 is being cloned by transposon tagging. Eighty two recombinant strains were generated using unc-49 (n1324) and two flanking markers, sma-2 and vab-7. Using Southern blot analysis and probes for the 5 known C. elegans transposons, a Tc1 band that consistently segregates with the unc-49 phenotype was identified. A 4. 5 kb EcoRI fragment containing this Tc1 insertion was isolated and the 2.9 kb of flanking genomic sequences have been cloned and are being used to probe a cDNA library, probe Northern blots for the unc-49 transcript and to probe the cosmid library in Cambridge for the corresponding genomic clones. During a screen using PCR-generated probes sharing sequences with the mammalian GABA receptor, Silver and Way (personal communication) have identified a YAC clone which maps to the unc-49 region in the genetic map, further suggesting that unc-49 may encode the GABA receptor or one of its sub-units.