Worm Breeder's Gazette 13(3): 48 (June 1, 1994)
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.
We have recently characterized the entire alpha tubulin gene family in C. elegans, comprising four members tba-1 to tba-4 .Among these tba-3 gene encodes the only alpha tubulin isotype ( TBA-3 )that has a lysine residue at position 40 ( known to be the site of post-translational acetylation in alpha tubulins). The McAb 6-11B-1, specific for the acetylated alpha tubulins from a variety of organisms (Piperno and Fuller, JCB, 101:2085-2094), cytochemically stains in the wild type the cell bodies of six touch receptor neurons, PVR in the right lumbar ganglion, and axonal processes from several neurons located in the head, ventral cord and tail ganglia (Siddiqui et al. J. Neurosci, 9:2963-2972). Mutants in mec-12 ( u76 ),lacking the 15 (pf) microtubules normally found in the six touch cells and touch insensitive (Chalfie and Au, Science, 243:1027-1033), are also abnormal in 6-11B-1 staining, but other alleles such as the e1605 and e1607 show normal staining in the touch neurons.
Since the tba-3 locus has the same genomic position as the mec-12 locus, we have rescued the mutant mec-12 ( u76 )phenes by germline transformation, both touch sensitivity and the 6-11B-1 staining, using a phage clone of the tba-3 gene. These results are consistent with those of M. Hamelin, M. Chou and J. Culotti (WBG, 13:38), where they have used a cosmid clone C56F12 for the mec-12 rescue. We also found a RFLP in the genomic DNA of the u76 allele, which is absent in the e1605 and e1607 alleles when probed with a tba-3 specific probe, indicating that indeed, mec-12 and tba-3 is the same gene. Finally, the tba-3 ::lacZfusion gene constructs with and without the nuclear localization signal reveal that the tba-3 is expressed in the set of touch neurons, a few ventral cord neurons, and a number of neurons in the head and tail ganglia including the labial and other sensory neurons in the head, PVR and other sensory neurons in the tail. This is in contrast to the MEC-7 beta tubulin isotype (Savage et al. Gene & Dev., 3:870-881) which is primarily restricted to the set of touch neurons. Since the mec-12 mutants do not display other behavioral deficits besides the insensitivity to touch, it is interesting to investigate the function of the mec-12 encoded alpha tubulin. An even more intriguing observation of the mec-12 mutants is their ability to partially suppress the cell degeneration caused by the mec-10 mutants (Chalfie et al. Nature, 1994). Thus, the role of acetylated alpha tubulin in the nematode promises to reveal some elegant mechanisms of signal transduction. We thank M. Hamelin, M. Chou, J. Culotti, A. Fire and S. Mitani for their cooperation.