Worm Breeder's Gazette 3(2): 26

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.

Immunocytochemical Localization of Two Myosins Within the Same Muscle Cells in Caenorhabditis elegans

J.M. Mackenzie Jr., F. Schachat, H.F. Epstein

Nematodes synthesize two major classes of myosin heavy chains.  
These heavy chains associate to form only homodimeric myosin molecules,
and these myosin homodimers are antigenically different from one 
another (See Schachat, Garcea and Epstein).  The two myosins may be 
designated unc-54 myosin since this species is altered in mutants of 
the unc-54 locus and non-unc-54 myosin since this class is not 
affected in unc-54 mutants.  We present here experiments in which 
specific anti-myosin IgG and anti-unc-54 myosin IgG are used to locate 
the two myosins within the same body-wall muscle cells of 
Caenorhabditis esults are necessary for 
further evaluation of the possible functions of the two myosin 
homodimers in the thick filaments of these muscles.
Myosin can be localized using anti-myosin antibody to all body-wall 
and pharyngeal muscle cells.  The antibody-antigen complexes are 
visualized by the peroxidase-anti-peroxidase method.  In longitudinal 
sections of bodywall muscle, the staining with anti-myosin coincides 
with the birefringence of A bands that contain thick filaments.  Anti-
unc-54 myosin stains all body-wall A bands that contain thick 
filaments.  Anti-unc-54 myosin stains all body wall A bands uniformly 
but does not react with the pharynx.  This result demonstrates that 
unc-54 is located exclusively in body-wall muscle cells of the wild-
type strain N2.  Non-unc-54 myosin is localized with anti-myosin in 
all body-wall muscle cells of the unc-54 null mutant E190, however, as 
expected, unc-54 myosin could not be detected by anti-unc-54 myosin 
antibody in this mutant.
Since we can localize unc-54 myosin and non-unc-54 myosin in all 
body-wall muscle cells of wild-type and E190, respectively, we 
conclude that the two myosins must be present in the same muscle cells.
In addition, since unc-54 myosin is located in all body-wall A bands,
at least some sarcomel-ts must then contain both myosins.  This 
conclusion is consistent with our observations (See Garcea, Schachat 
and Epstein) that wild-type and E190 synthesize similar amounts of non-
unc-54 myosin.  Within the limits of resolution of our methods, unc-54 
myosin is distributed throughout body-wall A bands.  We conclude, 
therefore, that the majority of thick filaments within these A bands 
must contain unc-54 along their entire length.  We are currently 
applying the immunochemical approach to the substructure of the thick 
filaments in C.  elegans.