[Centrosome morphogenesis in the early development of mice: an immunofluorescence study using antibodies to the...

The distribution of a centrosomal antigen, recognized by RN-C6 monoclonal antibody (monAB. RN-C6), was studied. The monAB. RN-C6 was directed against the common phosphoepitope in several high molecular cell proteins. In the mouse embryonal fibroblasts the monAB. RN-C6 stained discrete spots in the interphase nuclei, centrioles throughout the cell cycle and the midbody in mitosis. In the oocytes and the early mouse embryos, the monAB. RN-C6 stained only the nuclei, the staining of pronuclei in zygote being absent. In the mouse spermatozoon, the monAB. RN-C6 recognized the centriole and axoneme. Nevertheless, the stained sperm axoneme was revealed in the cytoplasm of early embryos up to the morula stage. No staining was observed in the mitotic spindle or in the midbody, or in any dots in the cytoplasm of oocytes/early embryos. On the blastocyst stage, the monAB. RN-C6 stained first the cytoplasmic dots in some cells, in the spindle poles and midbody. The appearance of stained dots and mitotic figures coincides with that of centrioles revealed at the ultrastructural level in some cells. Thus, during centrosome formation a given centriolar antigen is found only in the centriole, never being accumulated previously in the cytoplasm or in cell organelles.