Worm Breeder's Gazette 14(3): 55 (June 1, 1996)

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.

Mutations of lev-11 in the tropomyosin gene tmy-1 of C. elegans

Kyoko Takuwa, Hiroaki Kagawa

Department of Biology, Faculty of Science, Okayama University, Okayama, JAPAN 700

      The tropomyosin gene tmy-1 spans approximately 13 kilo bases and
includes 14 exons which encodes three tissue specific isoforms.  The 5'
end promoter common to CeTMI and CeTMII expresses in the body wall
muscles, vulva, anus muscles and male tail muscles.  Two of them having
284 amino acid residues are only different in the last 27 amino acid
residues.  By the sequence comparison of the last 27 amino acid residues
to that of other animals, we assume that CeTMII could be the cytoplasmic
type.  The third isoform ceTMIII encoding 256 amino acids is expressed in
the pharyngeal muscles by the promoter in the third intron.  mRNA of
CeTMIII was transspliced with SL1.  The tmy-1 gene is locates on the C.
elegans genomic YAC grid near the right end of chromosome I, in the region
of the lev-11 gene (Kagawa et al, 1995).  Levamisol is a potent agonist of
acetylcholine in the worm and lev-11 is isolated as twitchers (Lewis et
al, 1980).  The mutant embryos of lev-11(st557) having Pat phenotype show
greatly reduced or undetectable staining with purified anti-tropomyosin
antibody (Williams and Waterston, 1994). 

      We determined the sequences of the exon parts of tmy-1 gene from
lev-11 mutations.  The lev-11(st557) mutation occurred at the splice donor
site of exon 1 (GAAG GTTT at 2373 to GAAG ATTT) and results in translation
termination at 2412 after adding twelve amino acid residues.  Nucleotide
sequence numbers follow that of the database of the tmy-1 gene D38539. 
Although small sized protein from herozygous (+/st557) animal was not
detected by Western analysis, our result could be the reason of Pat
(paralyzed, arrested elongation at two fold) phenotype of the mutation. 
The lev-11(X12) mutation occurred in exon 7 (AAG GAG at 10262 to AAG AAG)
and results in amino acid substitution at 234 from Glu to Lys.  This
substitution give a charge change from - to + at this point.  As this
region is common in three isoforms, there may be functional importance of
this region for calcium signaling from troponins to actins through
molecular interactions.  We can not detect mutation in the lev-11(X1) and
lev-11 (st536) at the moment.  

       We have determined the mutation site of levamisol sensitive but
anomalous unc mutation unc-68 in the ryanodine receptor gene ryr-1 (Sakube
et al, unpublished observation).  These results allows us to understand
not only calcium signaling from post synaptic membrane to muscle filaments
but also developmental importance of muscle formation in the worm. 

Kagawa et al, (1995) J. Mol. Biol. 251, 606-613.
Lewis et al, (1980) Genetics 95, 905-925.
Williams and Waterston, (1994) J. Ce.. Biol. 124, 457-490.