CYCLIN B-1 EXPRESSION IN MEIOTICALLY COMPETENT AND INCOMPETENT GOAT OOCYTES

To start determining the nature of meiotic incompetence in goat oocyte s, we have examined the expression of one of the potential pre-MPF sub units: the cyclin B-1. We have been isolating a small DNA probe encodi ng the goat cyclin B-1 box to analyze the expression of the cyclin B-1 gene in competent and incompetent goat oocytes. This probe was easily obtained by polymerase-chain-reaction (PCR) on reverse-transcribed mR NA from granulosa cells, using cyclin B specific primers derived from a bovine cDNA. The transcript corresponding to cyclin B-1 in goat gran ulosa cells is 1.8 kb. In situ hybridization analysis indicated that c ompetent and incompetent oocytes contained cyclin B-1 mRNA, but also t hat active cyclin B-1 mRNA synthesis occured at the end of the growth phase, e.g., when oocytes progressed in the acquisition of meoitic com petence; Western blot analysis, performed with a monoclonal anticyclin B-1 antibody, revealed in competent and incompetent oocytes a polypep tide of 65kDa corresponding to the goat cyclin B-1 protein. This patte rn of cyclin B-1 expression further suggested that meiotic incompetenc e in goat oocytes could not be primarily correlated with a lack of cyc lin B-1 protein as potential pre-MPF subunit, but to a limiting amount of this protein. (C) 1997 Wiiey-iiss, inc.