MicroRNA-133b stimulates ovarian estradiol synthesis by targeting Foxl2

Abstract

Forkhead L2 (Foxl2) is expressed in ovarian granulosa cells and participates in steroidogenesis by transcriptionally regulating target genes such as steroidogenic acute regulatory protein (StAR) and CYP19A1. In this study, a direct link between microRNA-133b (miR-133b) and Foxl2-mediated estradiol release in granulosa cells was established. miR-133b was involved in follicle-stimulating hormone (FSH)-induced estrogen production. Luciferase assays confirmed that miR-133b was bound to the 3' untranslated region (3'UTR) of Foxl2 mRNA. Consistent with this finding, miR-133b overexpression reduced the Foxl2 levels. Furthermore, miR-133b inhibited Foxl2 binding to the StAR and CYP19A1 promoter sequences. These results demonstrate that miR-133b down-regulates Foxl2 expression in granulosa cells by directly targeting the 3'UTR, thus inhibiting the Foxl2-mediated transcriptional repression of StAR and CYP19A1to promote estradiol production.

Keywords: 3′ untranslated region; 3′UTR; ACVRIB; ACVRIIA; CREB; CYP; CYP19A1; ChIP; ERK; Estrogen; FSH; Foxl2; Granulosa cell; LH; MAPK; PI3K; PKA; POF; RBMS1; RNA binding motif, single stranded interacting protein 1; StAR; activin receptor typeIB; activin receptor typeIIA; adenosine-3′:5′-monophosphate; cAMP; cAMP response element binding protein; chromatin immunoprecipitation; cytochrome P450; extracellular regulated kinase; follicle-stimulating hormone; forkhead L2; luteinizing hormone; mGCs; miR-133b; microRNA-133b; mitogen-activated protein kinase; mouse granulosa cells; phosphoinositide 3-kinase; premature ovarian failure; protein kinase A; steroidogenic acute regulatory protein.