Worm Breeder's Gazette 10(1): 134

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.

Do C. elegans Germ Line Granules Contain a Myosin-like Protein?

K. Kususmi, D. Kiehart and D. Stinchcomb

Cytoplasmic myosins are responsible for generating the force 
required for many cell motility phenomena.  We are trying to identify 
and characterize nematode cytoplasmic myosins to determine what role 
they may play in the intra- and intercellular movements that occur 
during C.  elegans development.  Towards this end, a library of 
monoclonal antibodies raised against Acanthamoeba myosins were 
screened for cross-reactivity to C.  elegans.  Antibodies directed 
against two classes of Acanthamoeba myosin isoforms were used.  Myosin-
I is a globular protein that is implicated in organelle transport.  
Myosin-II is structurally more similar to body wall myosins.  In other 
systems, myosin-like isoforms are required for cytokinesis.
Adult hermaphrodites were bissected on polylysine-coated slides, 
frozen and then fixed in methanol and acetone.  Fixed worms were 
incubated with mouse monoclonal antibodies and binding was detected by 
indirect immunofluorescence.  All seven monoclonal antibodies directed 
against Acanthamoeba myosin-I bound to granules present in the germ 
line of C.  elegans.  The cellular distribution of the granules mimics 
that of P granules: the granules are perinuclear in the ovary, 
dispersed in the cytoplasm of mature oocytes and fertilized eggs, and 
the granules are segregated into the P cell lineage during early 
cleavages.  Antibodies harvested from ascites fluid or cell culture 
supernatants reproducibly bound germ line granules.  Secondary 
antibodies alone produced only faint background immunofluorescence.  
Myosin-I antibodies also bound to antigens present in nucleoli, in the 
spermathecae and in a thread-like structure in the developing pharynx. 
In contrast to the germ line granule immunofluorescence, these other 
structures were recognized by some antibodies but not others.  Two 
different monoclonal antibodies directed against myosin-II of 
Acanthamoeba did not bind germ line granules.  Thus, P granules may 
share a determinant with Acanthamoeba myosin-I isoforms.  We are 
presently trying to identify and biochemically characterize C.  
elegans proteins that are bound by these monoclonal antibodies.  Such 
proteins may represent components of the mechanism responsible for 
germ line granule segregation during early cell.