REGULATION OF M-PHASE PROMOTING FACTOR ACTIVITY DURING DEVELOPMENT OFMOUSE MALE GERM-CELLS

While the role of M-phase promoting factor (MPF) in controlling meiosi s in oocytes has been well documented, very little is known about its function in male germ cells. Previous studies have localized transcrip ts for cyclin B1, the regulatory subunit of MPF, in male germ cells, w ith highest levels in postmeiotic, early round spermatids and much red uced levels in the meiotically dividing pachytene spermatocytes. The p resent study describes the localization of the regulatory and the cata lytic subunits of MPF, CycB1 and Cdc2, respectively, to specific cell types within the testis. Immunoblotting revealed that both CycB1 and C dc2 were present at highest levels in pachytene spermatocytes, with lo wer levels observed in the postmeiotic compartment. To assay for MPF a ctivity, kinase complexes were isolated from lysates of testicular cel ls using p13(suc1) agarose and antibodies directed against Cdc2 and Cy cB1. Activity of these kinase complexes was analyzed using histone H1 as an exogenous substrate. Cdc2 and CycB1-associated kinase activities were localized to the meiotically dividing pachytene spermatocytes, b ut not to postmeiotic spermatids. (C) 1994 Academic Press, Inc.