Proteins shifting from the cytoplasm into the nuclei during early embryogenesis of Drosophila melanogaster.

Monoclonal antibodies have been used to study the distribution of several proteins in cleavage and blastoderm stages of Drosophila melanogaster. These antigens are known to be associated with hnRNA-containing particles in tissue culture cells. Protein blotting shows that they are present in the embryo 1 hr after egg deposition. A redistribution from the cytoplasm into the somatic nuclei can be observed during developmental stage 12/13, one stage prior to the formation of the cellular blastoderm. Yolk nuclei become stained by these antibodies at about the same time. The shift into pole cell nuclei, however, occurs 1 1/2 hr later, during the migration of these cells into the posterior midgut rudiment.