WNT5a is required for normal ovarian follicle development and antagonizes gonadotropin responsiveness in granulosa cells by suppressing canonical WNT signaling

Abstract

Whereas the roles of the canonical winglesstype MMTV (mouse mammary tumor virus) integration site family (WNT) signaling pathway in the regulation of ovarian follicle growth and steroidogenesis are now established, noncanonical WNT signaling in the ovary has been largely overlooked. Noncanonical WNTs, including WNT5a and WNT11, are expressed in granulosa cells (GCs) and are differentially regulated throughout follicle development, but their physiologic roles remain unknown. Using conditional gene targeting, we found that GC-specific inactivation of Wnt5a (but not Wnt11) results in the female subfertility associated with increased follicular atresia and decreased rates of ovulation. Microarray analyses have revealed that WNT5a acts to down-regulate the expression of FSH-responsive genes in vitro, and corresponding increases in the expression of these genes have been found in the GCs of conditional knockout mice. Unexpectedly, we found that WNT5a regulates its target genes not by signaling via the WNT/Ca 2+ or planar cell polarity pathways, but rather by inhibiting the canonical pathway, causing both b-catenin (CTNNB1) and cAMP responsive element binding (CREB) protein levels to decrease via a glycogen synthase kinase-3b-dependent mechanism. We further found that WNT5a prevents follicle-stimulating hormone and luteinizing protein from up-regulating the CTNNB1 and CREB proteins and their target genes, indicating that WNT5a functions as a physiologic inhibitor of gonadotropin signaling. Together, these findings identify WNT5a as a key regulator of follicle development and gonadotropin responsiveness.-Abedini, A., Zamberlam, G., Lapointe, E., Tourigny, C., Boyer, A., Paquet, M., Hayashi, K., Honda, H., Kikuchi, A., Price, C., Boerboom, D. WNT5a is required for normal ovarian follicle development and antagonizes gonadotropin responsiveness in granulosa cells by suppressing canonical WNT signaling. FASEB J. 30, 1534-1547 (2016 The pituitary gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) represent the major endocrine regulators of ovarian function and are essential for follicle development beyond the secondary stage (1, 2). In addition to the endocrine level of control, follicle development is regulated by several paracrine and autocrine factors produced within the ovary itself. These factors notably include IGF-1, steroid hormones, prostaglandins, epidermal growth factor-like molecules and several TGF-b superfamily members, all of which are indispensable for normal ovarian function and female fertility. The gonadotropins can affect the expression and function of these intraovarian factors; conversely, these factors can modulate follicular responses to the gonadotropins (1-3).Recent studies have established the wingless-type MMTV (mouse mammary tumor virus) integration site (WNT) family of secreted glycoproteins as yet another class of signaling molecules that act to modulate and coordinate follicular responses to the gonadotropins and whose activities are indispensable for ovarian...

APC2 is Critical for Ovarian WNT Signalling Control, Fertility and Tumour Suppression

“…We have shown that reduced ovulation observed in APC2-deficient mice is not caused by defects in ovulation and terminal differentiation of granulosa cells (which happen when WNT signalling is activated in antral follicles), but rather caused by restricted follicular growth and failure to reach the preovulatory stage. This phenotype is similar to previous phenotypes published when WNT Mohamed et al APC2 in ovarian homeostasis and tumourigenesis 13 signalling was activated in pre-antral follicles (16,17), implying that APC2 activity is required in growing follicles as early as the pre-antral stage.…”

“…The current findings also extend our knowledge of deleterious effects of WNT signalling activation on ovarian homeostasis and fertility (10,(15)(16)(17). We have shown that reduced ovulation observed in APC2-deficient mice is not caused by defects in ovulation and terminal differentiation of granulosa cells (which happen when WNT signalling is activated in antral follicles), but rather caused by restricted follicular growth and failure to reach the preovulatory stage.…”

“…Over-activation of canonical WNT signalling also has deleterious effects on ovarian homeostasis. Ovarian amplification of Rspo1 (15), deletion of Wnt5a (antagonist of canonical WNT signalling) (16) or expression of dominant stable β -catenin (10,17) all resulted in up-regulated ovarian WNT signalling and ovarian subfertility caused by disruption of follicle growth (16,17), ovulation and luteinisation (10,15). Taken together, these findings indicate the importance of tight regulation of canonical WNT signalling in growing follicles.…”

“…On activation of AKT, FOXO proteins are inactivated by phosphorylation and translocated from nucleus to cytoplasm(47). In addition, the crosstalk between activated WNT signalling and PTEN, causing the over-expression of the latter, is well established(16,17,48). IHC analysis of PTEN, p-AKT and p-FOXO 1,3,4 in Apc2 +/+ and Apc2 -/ovaries revealed that PTEN expression was stronger in theca and granulosa cells of Apc2 -/follicles(Figure 4e).…”

Insights into granulosa cell tumors using spontaneous or genetically engineered mouse models

“…The PI3K/AKT signaling pathway can also activate the WNT/CTNNB1 pathway through inactivation of GSK3β [ 50 ]. Both Wnt4 flox/- ;Amhr2 tm3(cre)Bhr/+ and Wnt5a flox/- ;Amh2 cre/+ mice are subfertile and have small ovaries, follicle atresia, and a decreased ovulation rate, indicating that the WNT signaling pathway is important in ovarian follicle growth/survival and steroidogenesis [ 51 52 53 54 55 ]. Catnb flox(ex3)/+ ;Amhr2 Cre/+ mice, which express stable nuclear β-catenin driven by the Amhr2 promoter, develop GCTs, suggesting the importance of the misregulated Wnt/β-catenin pathway in GCT development [ 56 ].…”