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.

Molecular Cloning of unc-49

Alberto Ruiz Morales and Jorge R. Mancillas

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 
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.