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Targeted Expression of tba-1 in C. elegans: Determining the Cause of the
tba-1(ju89) Neurodevelopmental and Behavioral Phenotypes The ju89 mutation in the C. elegans alpha-tubulin gene tba-1 alters an amino acid in the loop between helices 11 and 12 of the tba-1 alpha-tubulin subunit. This lesion results in an uncoordinated behavior and axon and synapse defects in the DD and VD GABAergic and the DA and DB cholinergic motor neurons. Previous work showed that intragonadal injection of a functional wild-type copy of tba-1 under the control of its endogenous promoter is sufficient to rescue the synaptic phenotypes in ju89 mutants and restore normal movement. While this treatment showed that a functional copy of tba-1 could rescue the behavioral phenotype, it lacked specificity. The treatment did not reveal if the changes in tba-1 function in cholinergic motor neurons, GABAergic motor neurons, or the body muscle, each critical for coordinated movement, were required for the developmental and behavioral phenotypes. To answer these questions, plasmids were constructed containing a wild-type copy of the tba-1 genomic coding sequence preceded by one of three tissue-specific promoters. These promoters direct tba-1 expression exclusively within a specific tissue. The promoter Punc-25 targets tba-1 expression to GABAergic cells while Punc-129 directs expression to the cholinergic motor neurons and Pmyo-3 targets tba-1 expression exclusively to the body muscle. These constructs will be used to create transgenic C. elegans strains to confirm that tba-1 is required cell-autonomously in the motor neurons and to determine which cells in the motor circuit contribute to the uncoordinated behavioral phenotype of ju89 mutants. Support provided by: National Science Foundation Grant to Prof. Baran |
