FIG 7.

SRp20 and Homer1 regulate gonadotropin β-subunit gene expression (schematic). Upon activation by its ligand, the GnRH receptor (GnRHR) activates the phosphorylation of SRp20, which in turn increases the Homer1a-to-Homer1b/c splice variant ratio, resulting in the repression of Homer1b/c. Homer1b/c has an inhibitory effect on FSHβ and LHβ gene transcription. The finding that both SRp20 knockdown and Homer1b/c knockdown increase FSHβ suggests the presence of an inhibitory pathway downstream of SRp20, as indicated by the dotted line.