Mouse forkhead L2 maintains repression of FSH-dependent genes in the granulosa cell

Abstract

The forkhead transcription factor forkhead box L2 (FOXL2) is expressed in granulosa cells of small and medium follicles in the mouse ovary. Foxl2 female knockout mice exhibit primordial follicle depletion and primary ovarian failure, but evidence from adult female conditional Foxl2 knockout mice suggests that FOXL2 may also play a significant role in maintenance of ovarian differentiation at stages beyond the primordial follicle and initial wave of folliculogenesis. We previously showed that human FOXL2 functions as a transcriptional repressor of several key genes involved in granulosa cell proliferation and differentiation, including steroidogenic acute regulatory protein (STAR), P450aromatase (CYP19A1 (CYP19)), P450scc (CYP11A1 (CYP11A)), and cyclin D2 (CCND2). To elucidate the role of mouse FOXL2, we determined its role in transcriptional regulation in Chinese hamster ovary (CHO) cells and then confirmed our findings in mouse granulosa cells. We found that mouse FOXL2 represses the activities of the mouse Star, Cyp19a1, Cyp11a1 promoters in CHO cells, but may not repress the Ccnd2 promoter, and identified the minimal mouse Star, Cyp19a1, and Cyp11a1 promoter regions responsive to FOXL2 regulation. We then knocked down Foxl2 in mouse granulosa cells using siRNA, which resulted in significantly increased expression levels of mouse Star, Cyp19a1, and Cyp11a1 but not Ccnd2. To increase Foxl2 expression levels, we generated a mouse Foxl2 lentiviral construct and used it to infect mouse granulosa cells. Following lentiviral infection, the expression levels of mouse Star, Cyp19a1, and Cyp11a1, but not Ccnd2, decreased significantly. These data confirm that mouse FOXL2 functions as a transcriptional repressor of key granulosa cell genes that influence ovarian development.

MicroRNA‐133b stimulates ovarian estradiol synthesis by targeting Foxl2

“…The high conservation of Foxl2 sequences and mammalian expression suggests a key role in ovarian development and function [30,31]. Either human or mouse Foxl2 can function as a transcriptional repressor of StAR and CYP19A1, likely by binding to specific sites in the gene promoters [25,26,32], consistent with our results from the ChIP assay. Foxl2 is responsible for POF, and is involved in inflammation, apoptosis, reactive oxygen species metabolism, and granulosa cell tumors [3,5,33].…”

Granulosa cell tumor mutant FOXL2C134W suppresses GDF-9 and activin A-induced follistatin transcription in primary granulosa cells

“…5A and inset). As StAR is an established target of FOXL2, with FOXL2 shown to inhibit StAR transcription and gene expression in other cell types [6,58], we measured StAR mRNA expression and confirmed that the reduction in FOXL2 lead to increased StAR expression in GCs (Fig. 5A).…”

Pituitary Gland Development and Disease

“…FOXL2 is important for ovarian development and function 104, 105 , and it promotes female sex determination 100, 106, 107 . Mutations in the human FOXL2 gene result in an autosomal dominant, loss of function disease called blepharophimosis, ptosis, and epicanthus inversus syndrome (BEPS), which causes eyelid abnormalities and premature ovarian failure 108 .…”