EXPRESSION OF PROLIFERATING CELL NUCLEAR ANTIGEN IN THE MOUSE GERM-LINE AND SURROUNDING SOMATIC-CELLS SUGGESTS BOTH PROLIFERATION-DEPENDENTAND PROLIFERATION-INDEPENDENT MODES OF FUNCTION

The distribution of proliferating cell nuclear antigen (PCNA) in speci fic somatic and germ cells of the adult mouse ovary and testis was ass essed using immunocytochemical staining and immunoblot analysis and wa s correlated with cellular proliferation and differentiation. In the a dult ovary, immunocytochemical staining for PCNA within follicular cel ls varied depending on the stage of follicular growth. Since PCNA stai ning has proven to be a useful indicator of cells involved in DNA synt hesis and repair, the pattern of PCNA staining in the ovary was compar ed to previous studies which used tritiated thymidine labeling as a ma rker for DNA synthesis. In the testis, PCNA was detected in the mitoti cally proliferating spermatogonia, but not in spermatocytes which had just entered meiosis. PCNA staining was again observed in spermatogeni c cells in later stages of meiotic prophase, in particular zygotene an d pachytene spermatocytes. As these cells are undergoing meiotic recom bination, the presence of PCNA in these meiotic prophase cells could r eflect a second function of PCNA, that of DNA excision repair.