Gonadotrope-specific expression of the human follicle-stimulating hormone beta-subunit gene in pituitaries of transgenic mice.

The molecular basis for the cell-specific and hormonal regulation of the pituitary gonadotropin beta-subunit genes is unknown. To identify the essential DNA regulatory elements of the human FSH beta (hFSH beta) gene, we introduced a 10-kilobase cloned fragment encompassing the gene into the germline of transgenic mice. We showed by a combination of Northern blot hybridization, RIA, and immunofluorescence histochemistry that the hFSH beta gene was expressed exclusively in mouse pituitary gonadotropes. Human FSH beta was actively secreted, presumably as an interspecies heterodimer, with mouse alpha-subunit, and no free hFSH beta was detected in serum. Male transgenic mice consistently had higher basal pituitary expression and secretion of hFSH beta than the female transgenic mice. Castration combined with testosterone replacement caused a marked reduction in hFSH beta gene expression in transgenic males, but had no effect on the pituitary levels of FSH in normal male mice. These experiments demonstrate that the essential DNA regulatory elements and gonadotrope transcription factors required for cell-specific expression of the FSH beta gene must be conserved between human and mouse. There appear to be important differences in the hormonal regulation of the gene between species, however.