Fig. 7. Exogenous GDF9 can override the impairment of proliferation in Cx43 null mutant granulosa cells (CD1 strain) that lack gap junctional coupling. The frequency of PCNA staining for each treatment group is normalized to the respective control. The error bars indicate s.e.; different letters above the bars indicate significant differences (P<0.01). The number of follicles examined is indicated in parentheses above each bar.