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.
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.