Stage-specific regulation of stem cell factor gene expression in the rat seminiferous epithelium

To assess the regulation of stem factor factor (SCF) gene expression during spermatogenesis, we tested the effects of hormones (FSH, testosterone, and 17beta-estradiol) and some growth factors [transforming growth factor-beta (TGF beta), TGF alpha, tumor necrosis factor-alpha, and activin] on SCF gene expression by using a transillumination-assisted microdisection technique, a seminiferous tubule culture system, and Northern hybridization. Our results showed that FSH (10 ng/ml) increased steady state levels of SCF messenger RNA (mRNA) in a stage-specific and time-dependent manner. 8-Bromo-cAMP could increase the SCF mRNA level in a similar way as FSH, whereas phorbol 12-myristate 13-acetate had no effect. Actinomycin D could abolish the stimulatory effect of FSH, whereas cyclohexamide could not. The half-life of SCF mRNA was apparently prolonged after FSH stimulation (FSH-treated tubules, 15.6 +/- 1.2 h; controls, 8.6 +/- 2.7 h). Nuclear run-on assay revealed 5- and 10-fold increases in the transcription rate after FSH stimulation for 8 and 30 h, respectively. Neither testosterone nor estradiol had significant effects on SCF gene expression in our tissue culture system. Activin, TGF beta, TGF alpha, and tumor necrosis factor-alpha had no effect on SCF gene expression in vitro. In conclusion, SCF gene expression in the rat seminiferous tubule is regulated by FSH through the cAMP/protein kinase A pathway. FSH regulates SCF gene expression at both transcriptional and posttranscriptional levels involving the increase in transcription rate and prolongation of half-life of SCF mRNA, but is independent of de novo protein synthesis.