The WNT signaling cascade is involved in regulation of cytoskeletal rearrangements, apoptosis, and
proliferation. WNT-mediated simulation of 'frizzled' receptors (e.g., FZD2; OMIM 600667) can activate the beta-catenin
(CTNNB1; OMIM 116806) pathway, mitogen-activated protein kinase (MAPK) cascades, and G protein-dependent pathways. The
signaling function of the WNT/frizzled pathway is antagonized by secreted frizzled-related proteins ,
which bind to either WNTs or frizzled receptors. Frizzled-related proteins contain a
cysteine-rich domain of approximately 110 residues that is 30 to 40% identical to the putative ligand-binding domain
of FZ proteins, but lacks the 7-transmembrane motif that anchors FZ proteins to the plasma membrane.
NCBI Summary:
Secreted frizzled-related protein 4 (SFRP4) is a member of the SFRP family that contains a cysteine-rich domain homologous to the putative Wnt-binding site of Frizzled proteins. SFRPs act as soluble modulators of Wnt signaling. The expression of SFRP4 in ventricular myocardium correlates with apoptosis related gene expression. [provided by RefSeq, Jul 2008]
Exogenous Secreted Frizzled-Related Protein-4 Modulates Steroidogenesis of Rat Granulosa Cells through Wnt/β-catenin and PI3K/AKT Signaling Pathways. Hossein G et al. (2016) It has been reported that secreted frizzled-related protein-4 known as an antagonist of Wnt signaling pathway plays a role in luteinization process of rodent granulosa cells. The purpose of this study was twofold: 1) to determine whether recombinant human secreted frizzled-related protein-4 (rhSFRP-4) could directly induce terminal differentiation of rat Granulosa Cells (GCs) and 2) to understand how the modulation of β-catenin and Protein Kinase B (PKB)/AKT activity by exogenous SFRP-4 could be involved in steroidogenesis. GCs were firstly stimulated with Follicle-Stimulating Hormone (FSH) named as FSH-primed cells then were treated with luteinizing hormone (LH). Then estradiol (E2) and progesterone (P4) production levels were assessed in the absence or presence of rhSFRP-4 treatment. The expression levels of activated β-catenin, pAKTser (473) , pGSK3βser (9) were assessed by western blot or immunofluoresence. In the presence of rhSFRP-4, there was 38% decreased E2 levels compared to untreated FSH-primed cells (p<0.05), and P4 production subsequently decreased. However, in GCs pre-treated with rhSFRP-4 prior to addition of FSH, P4 levels increased 2-fold compared with untreated cells (p<0.05). Unexpectedly, treatment with rhSFRP-4 prior to LH stimulation inhibited LH-induced P4 secretion. Treatment with low (0.5 ng/ml) but not high (50 ng/ml) concentrations of rhSFRP-4 led to significantly increased levels of pGSK3βser (9) (1.6-fold) and nuclear active β-catenin (2.8-fold) in GCs compared with untreated cells. Interestingly, pre-treating GCs with rhsFPR4 prior to LH stimulation resulted in a 38% decrease in pAKTser (473) levels compared with those in LH-treated cells (p<0.05). Taken together, our results showed that rhSFRP-4 could directly induce terminal differentiation in GCs via the modulation of β-catenin and PKB/AKT pathways and that it does so in a dose-dependent manner.//////////////////
Differences in the transcriptional profiles of human cumulus cells isolated from MI and MII oocytes of patients with polycystic ovary syndrome (PCOS). Huang X et al. Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disorder in women. Abnormalities of endocrine and intra-ovarian paracrine interactions may change the microenvironment for oocyte development during the folliculogenesis process and reduced oocyte development competence in PCOS patients who are sufferring from anovulatory infertility and pregnancy loss. In this microenvironment, the cross talk between the oocyte and surrounding cumulus cells (CCs) is critical for obtaining oocyte competence. The aim of our study was to investigate gene expression profile of CCs from PCOS patients undergoing IVF cycles in terms of oocyte maturity by using human Genome U133 Plus 2.0 microarrays. A total of 59 genes were differentially expressed between the two CC categories. Most of these genes were identified to be involved in one or more of the following pathways: receptor interactions, calcium signaling, metabolism and biosynthesis, focal adhesion, melanogenesis, leukocyte transendothelial migration, Wnt signaling pathway, and Type II diabetes mellitus. According to the different expression levels in the microarray and their putative functions, six differentially expressed genes (LHCGR, ANGPTL1, TNIK, GRIN2A, SFRP4 and SOCS3) were selected and analyzed by quantitative RT-PCR. The qRT-PCR results were consistent with the microarray data. Moreover, the molecular signatures (LHCGR, TNIK and SOCS3) were associated with developmental potential from embryo to blastocyst stage and were proposed as biomarkers for embryo viability in PCOS patients. Our results may have important clinically useful by offering a new potential strategy for competent oocyte/embryo selection in PCOS patients.
Expression and Regulation of sFRP Family Members in Human Granulosa Cells. Maman E et al. Follicular development and ovulation are major processes in the reproductive system. Understanding their complexity is important to female fertility treatments and the control of reproductive processes. Wnt signaling pathway components were shown to be involved in reproduction in animal models. The secreted frizzled-related protein-4 (sFRP4), a potential modulator of Wnt4 signaling pathway, was shown to be induced by luteinizing hormone (LH) in rodents. and expressed in the corpus lutea, but the pattern of its expression in human ovaries remains unknown. We evaluated the expression pattern of sFRP4 and other sFRP family members in human mural and cumulus granulosa cells (GCs), as well as their regulation by LH and human-chorionic-gonadotrophin (LH/hCG). GCs were obtained from follicles aspirated during in vitro maturation (IVM) and in vitro fertilization (IVF) procedures. GCs were also plated and grown in culture. We showed that the human sFRP4 expression decreases as follicles grows to the preovulatory stage and its expression was higher in cumulus GCs than in mural GCs. Interestingly, LH/hCG stimulation of GCs in vivo and in culture resulted in decreased expression of sFRP4. Of the other sFRP family members, sFRP5 expression was found in mural and cumulus GC in vivo and was shown to be induced by LH/hCG in vitro and in vivo . In summary, sFRP4 is expressed in human GCs and its expression declines during late antral follicular growth. sFRP4 expression is also inhibited by LH/hCG, unlike its rodent homolog. In human GC, sFRP5 may substitute the role of sFRP4 in mouse GC.
Jabara S, et al 2003 reported stromal cells of the human postmenopausal ovary display a
distinctive biochemical and molecular phenotype.
Changes in mouse granulosa cell gene expression during early luteinization. McRae RS et al. Changes in gene expression during granulosa cell luteinization have been measured using serial analysis of gene expression (SAGE). Immature normal mice were treated with pregnant mare serum gonadotropin (PMSG) or PMSG followed, 48 h later, by human chorionic gonadotropin (hCG). Granulosa cells were collected from preovulatory follicles after PMSG injection or PMSG/hCG injection and SAGE libraries generated from the isolated mRNA. The combined libraries contained 105,224 tags representing 40,248 unique transcripts. Overall, 715 transcripts showed a significant difference in abundance between the two libraries of which 216 were significantly down-regulated by hCG and 499 were significantly up-regulated. Among transcripts differentially regulated, there were clear and expected changes in genes involved in steroidogenesis as well as clusters of genes involved in modeling of the extracellular matrix, regulation of the cytoskeleton and intra and intercellular signaling. The SAGE libraries described here provide a base for functional investigation of the regulation of granulosa cell luteinization.
The stroma of the human postmenopausal ovary is postulated to produce androgens,
but evidence for and against this idea exits in the literature. The purpose of this study
was to determine whether key steroidogenic enzymes involved in androgen synthesis
are expressed in the postmenopausal ovarian stroma. Stromal cells were isolated
from postmenopausal ovaries and expression for genes involved in steroidogenesis,including
steroidogenic acute regulatory protein (StAR), P450scc, 3beta-hydroxysteroid
dehydrogenase (3beta-HSD) P450c17, and P450c27 as well as for several growth
factor binding proteins including gremlin, IGF binding protein-4, follistatin, and secreted
frizzled-related protein (sFRP)-1 and -4, were compared with cultured human theca
cells and dermal fibroblasts. Follistatin, gremlin, IGF
binding protein-4, and sFRP-1 and -4 transcripts were detected in the stromal cells in
relative amounts significantly higher than theca cells, but not significantly different
from fibroblasts, except for sFRP-1, which was significantly higher in stromal cells.
Many apoptosis related genes have been identified in the ovary. Secreted Frizzled Related Protein 4 (sFRP4) is a protein that appears to antagonize a molecular pathway for cell survival. sFRP4 gene expression is known to be upregulated with apoptosis in the ovarian corpus luteum. In this study by Drake JM, et al
, ovulation was hormonally induced in immature Wistar rats and their ovaries collected for analysis of apoptosis and sFRP4. TUNEL staining identified a greater amount of dying cells in the thecal layer of treated rat ovaries compared to controls. The results of 3'-end labelling revealed a significant increase (p < 0.01) in apoptosis at 12 hours following treatment compared to other time points and control. In situ hybridization exhibited a visible increase in amounts of sFRP4 mRNA expression in the thecal layers of follicles from treated rats compared to controls. Quantitative RT-PCR revealed no significant difference in sFRP4 expression levels between treated and control tissues although a clear trend towards an increase was observed in the treated group. This study demonstrates an association between sFRP4 and apoptosis in rat ovulation.
Gene expression profiles of cumulus cell oocyte complexes (COCs) during ovulation reveal cumulus cells express neuronal and immune-related genes: Does this expand their role in the ovulation process
Hernandez-Gonzalez I, et al ?
Ovulation is a complex process initiated by the preovulatory LH surge, characterized by cumulus oocyte complex (COC) expansion and completed by the release of a mature oocyte. Although many ovarian genes that impact ovulation have been identified, we hypothesized that genes selectively expressed in COCs would be overlooked by approaches using whole ovary or granulosa cell samples. RNA isolated from COCs collected from preovulatory follicles of eCG-primed mice and at selected times following hCG treatment was subjected to microarray analyses and results confirmed by RT-PCR analyses, Western blotting and immunofluorescent studies. A remarkable number of genes was up-regulated in COCs including Areg, Ereg, and Btc. Several genes selectively expressed in cumulus cells compared with granulosa cells were related to neuronal (Mbp, Tnc, Nts) or immune (Alcam, Pdcd1, Cd34, Cd52 and Cxcr4) cell function. In addition to Sfrp2, other members of the Wnt/Fzd family (Sfrp4, Fdz1 and Fdz2) were expressed in COCs. Thus, there is a cumulus cell-specific, terminal differentiation process. Furthermore, immunofluorescent analyses documented that cumulus cells are highly mitotic for 4-8 h after hCG and then cease dividing in association with reduced levels of Ccnd2 mRNA. Other down-regulated genes included: Cyp19a1, Fshr, Inhb, and the oocyte factors Zp1-3 and Gja4. In summary, the vast number of matrix, neuronal and especially immune cell-related genes identified by the gene profiling data of COCs constitutes strong and novel evidence that cumulus cells possess a repertoire of immune functions that could be far greater than simply mediating an inflammatory-like response.
Follicle stages
Corpus luteum
Comment
Using differential display, Lacher MD, et al isolated DDC-4, a secreted frizzled-related protein (sFRP), which is induced in the physiological apoptosis of hormonally regulated, reproductive tissues such as mammary gland, prostate, corpus luteum and uterus. The role of this gene in apoptosis was studied in animals overexpressing ectopic DDC-4/sFRP-4. Transgenic mice bearing the DDC-4/sFRP-4 cDNA under the control of the MMTV-LTR promoter showed lactational insufficiency and many apoptotic cells in the alveoli between day 19 of pregnancy and day 4 of lactation as demonstrated by TUNEL reaction and the presence of activated caspase-3. Hsieh M, et al 2003 reported the expression and Localization of Secreted Frizzled-Related Protein-4 (sFRP-4) in the Rodent Ovary and Evidence for Selective Upregulation in Luteinized Granulosa Cells.
Secreted frizzled-related protein-4 (sFRP-4) belongs to a family of soluble proteins that have a Frizzled-like cysteine-rich domain and function as modulators of Wnt-Fz signals. Since several Wnts and Frizzleds (Fz) are expressed at defined stages of follicular development in rodent ovaries, these studies were undertaken to evaluate the hormone-regulated expression and localization of sFRP-4. In the mouse ovary, expression of sFRP-4 mRNA was upregulated in granulosa cells of large antral follicles after hCG administration, and was also elevated in corpora lutea as determined by RT-PCR and in situ hybridization analyses. In hypophysectomized rat ovaries, sFRP-4 expression was similarly induced by hCG and further upregulated by prolactin (PRL). PRL also stimulated secretion of sFRP-4 protein from luteinized rat granulosa cells in culture. Therefore, regulation of sFRP-4 by LH and PRL may be important for modulating Fz-1 known to be expressed in periovulatory follicles, and Wnt-4/Fz-4 expressed in corpora lutea.
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: type: null mutation fertility: fertile Comment: SFRP4 is a negative regulator of ovarian follicle development and female fertility. Zamberlam G et al. (2019) WNT signaling regulates a variety of ovarian processes including follicle development, granulosa cell (GC) proliferation and differentiation, steroidogenesis and ovulation. The secreted frizzled-related proteins (SFRPs) comprise a family of WNT signaling antagonists. Sfrp4 expression was previously reported to be induced in ovarian GCs and cumulus cells in vivo following hCG treatment, suggesting that it may play key roles in cumulus expansion, ovulation/luteinization and corpus luteum (CL) function. Here, we aimed to define the physiological roles of Sfrp4 in the ovary by gene targeting. Sfrp4-null female mice were found to produce larger litters than their wild-type littermates. Although previous studies had suggested roles of Sfrp4 in luteal cell survival, no differences in CL formation, morphology, steroidogenesis, involution or luteal cell apoptosis were found in Sfrp4-null mice. Likewise, cumulus expansion occurred normally in Sfrp4-null mice, with minimal changes in cumulus cell gene expression. Hyperfertility in the Sfrp4-null model was ultimately attributed to decreased antral follicle atresia, leading to an enhanced ovulatory rate. Increased expression of FSH- and LH-responsive genes was found in GCs from Sfrp4-null mice, and GCs isolated from Sfrp4-null mice were found to be hyper-responsive to FSH and LH in vitro. Although Sfrp2 was found to be overexpressed in the GCs of Sfrp4-null mice (suggesting a compensatory mechanism), Sfrp2-null mice had normal fertility and ovulatory rates, and Sfrp2/4 double knockout mice did not differ from Sfrp4-null mice. Together, our results suggest that SFRP4 acts to attenuate GC responsiveness to gonadotropins, thereby decreasing follicle survival, ovulatory rate and fertility.//////////////////