Follistatin has characteristics of a primary response gene in porcine granulosa cells.

To explore the regulation of follistatin gene expression, porcine granulosa cells were incubated with the translational inhibitor, cycloheximide (CHX), for periods from 6-24 h. This resulted in a 3 to 10-fold increase in follistatin mRNA accumulation compared to vehicle treated control cultures. At 20 h, CHX augmented the follicle stimulating hormone (FSH) induced stimulation of follistatin mRNA accumulation by a mean of more than sixfold. Over 6 h, CHX elevated follistatin mRNA abundance twofold, while epidermal growth factor (EGF) increased the message threefold. CHX in the presence of EGF produced an effect additive to the EGF response. Results in the longer term differed, as pretreatment of granulosa cells with CHX for 20 h suppressed the induction of follistatin gene expression by both EGF and phorbol 12-myristate-13-acetate. By blockade of transcription with Actinomyocin D, an estimate of the half-life of follistatin mRNA between 4 and 8 h was made. Half-life did not appear to be affected by the CHX suppression of protein translation. From the observations of the occurrence of follistatin gene expression independent of protein synthesis, superinduction in the presence of CHX and FSH, and the interactions between CHX and EGF, it is concluded that follistatin is a primary response gene in porcine granulosa cells.