Epiregulin is a member of the epidermal growth factor (EGF) family. Epiregulin functions as a tumor growth-inhibitory factor inducing morphologic changes in HeLa cells. Purified mouse
epiregulin contains 46 amino acid residues with 24 to 50% sequence identity with other members of the EGF family and
exhibits low affinity for the EGF receptor.
NCBI Summary:
Epiregulin is a member of the epidermal growth factor family. Epiregulin can function as a ligand of EGFR (epidermal growth factor receptor), as well as a ligand of most members of the ERBB (v-erb-b2 oncogene homolog) family of tyrosine-kinase receptors.
General function
Ligand, Growth factor
Comment
Cellular localization
Secreted, Plasma membrane
Comment
Ovarian function
Antral follicle growth, Cumulus expansion, Ovulation, Follicle rupture, Luteinization, Oocyte maturation, Early embryo development
, First polar body extrusion
Comment
Claude Robert et al used differential display and suppressive subtractive hybridization to identify
granulosa cell messenger RNA associated with bovine oocyte developmental
competence.
The main objective of this study was to identify mRNA expressed in the granulosa cells
characterizing differentiated follicles bearing developmentally competent bovine oocytes.
Analytical comparisons were made on mRNA pools of granulosa cells using differential display
reverse transcription polymerase chain reaction (DDRT) analysis and suppressive subtractive
hybridization (SSH). With the SSH analysis, four clones specific to
the presence of an incompetent oocyte were sequenced and none were identified, whereas 49
clones specific to the presence of a competent oocyte were sequenced and 18 were identified.
Among these clones, early growth response 1, sprouty 2, cytochrome C oxidase, matrix
metalloproteinase inducer, matrix metalloproteinase, epiregulin, prostaglandin receptor, and
progesterone receptor were the most relevant to the ovarian physiology being examined.
EGF-like growth factors: endogenous mediators of the ovulatory response?
Ashkenazi H, et al .
Previous studies showed that EGF and TGFalpha mimic the action of LH on the resumption of oocyte maturation. We tested whether EGF-like agents, such as amphiregulin (AR), epiregulin (ER) and betacellulin (BTC) also mediate the LH stimulation of the ovulatory response in the rat. LH induced transient follicular expression of AR, ER and BTC mRNA reaching a maximum after 3 h incubation. Furthermore, the addition of ER, AR and BTC to the culture medium could mimic some of LH actions. AR and ER fully simulated LH-induced resumption of meiosis in vitro, whereas BTC was less effective. To study the putative involvement of EGF-like factors in mediation of LH signal, the effect of EGFR kinase inhibitor AG1478 was tested. When added with LH, AG1478, but not its inactive analog AG43, reduced EGFR phosphorylation and oocyte maturation compared with follicles treated with LH only. In addition to the inhibition of resumption of meiosis, AG1478 administration into the bursa (3 micro g/bursa) resulted in 51% (P < 0.0005) inhibition of ovulation in the treated ovaries, compared with the untreated contralateral ones, as well as to the vehicle treated ovaries (P < 0.02). LH, as well as ER, induced the expression of genes associated with the ovulatory response like rCOX-2, rHAS-2 and rTSG-6 mRNA, whereas AG1478 inhibited this effect of LH. Release of EGF-like factors from the membrane is dependent on activated metalloproteases. Indeed, Galardin, a broad-spectrum metalloprotease inhibitor, but not a specific matrix metalloprotease 2 and 9 (MMP 2 and 9) inhibitor, suppressed meiotic maturation induced by LH. Conversely, meiotic maturation induced by ER was not affected by Galardin. Thus, supporting the notion that LH releases follicular membrane bound EGF-like agents. In summary, EGF-like factors such as ER, AR and BTC seem to mediate, at least partially, the LH stimulation of oocyte maturation, ovulatory enzyme expression and ovulation.
EGF receptor kinase activity is required for gap junction closure and for part of the decrease in ovarian follicle cGMP in response to luteinizing hormone. Norris RP et al. The meiotic cell cycle in mouse oocytes is arrested in prophase, and then restarted when luteinizing hormone (LH) acts on the surrounding granulosa cells. The granulosa cells keep meiosis arrested by providing a source of cGMP that diffuses into the oocyte through gap junctions, and LH restarts the cell cycle by closing the junctions and by decreasing granulosa cell cGMP, thus lowering oocyte cGMP. Epidermal growth factor receptor (EGFR) activation is an essential step in triggering LH-induced meiotic resumption, but its relationship to the cGMP decrease in the follicle is incompletely understood, and its possible function in causing gap junction closure has not been investigated. Here we use EGFR agonists (epiregulin and amphiregulin), and an EGFR kinase inhibitor (AG1478) to study the function of the EGFR in the signaling pathways leading to the release of oocytes from prophase arrest. Our results indicate that the EGFR kinase contributes to LH-induced meiotic resumption in two different ways. First, it is required for gap junction closure. Second, it is required for an essential component of the decrease in follicle cGMP. Our data show that the EGFR kinase-dependent component of the cGMP decrease is required for LH-induced meiotic resumption, but they also indicate that an as yet unidentified pathway accounts for a large part of the cGMP decrease.
In vitro maturation of human germinal vesicle-stage oocytes: role of epidermal growth factor-like growth factors in the culture medium. Ben-Ami I et al. BACKGROUND In vitro maturation (IVM) of oocytes is a promising technique to reduce the costs and avert the side effects of gonadotrophin stimulation for IVF. The pregnancy rates from oocytes matured in vitro are still lower than those of in vivo stimulation cycles, indicating that optimization of IVM remains a challenge. Recently, it was demonstrated that LH exerts its action on ovulation, at least in part, through stimulation of the production of the epidermal growth factor family members amphiregulin (Areg) and epiregulin (Ereg) in pre-ovulatory follicles, and they, in turn, serve as paracrine mediators of LH. We aimed to investigate the effect of supplementation of the medium with Areg and Ereg on the maturation rate of immature oocytes. METHODS A total of 105 sibling human germinal vesicle (GV) oocytes obtained after gonadotrophin stimulation were cultured in a complex defined medium either with or without supplemented recombinant human Areg (75 ng/ml) and Ereg (75 ng/ml) for 24 h. RESULTS Significantly more oocytes reached the metaphase II stage at 24 h in media supplemented with Areg and Ereg (75.5 versus 36.5%, P < 0.001). In vitro matured oocytes retrieved from the two subgroups had no statistically significant difference in fertilization and cleavage rates or morphology scores. Overall, a significantly higher number of Day 2 (52.8 versus 26.9% P < 0.01) and Day 3 (45.2 versus 23%, P < 0.05) embryos originated from GV oocytes cultured in the Areg- and Ereg-enriched medium. CONCLUSIONS Supplementation of the maturation medium with Areg and Ereg improves the maturation of human GV oocytes in vitro.
Expression regulated by
FSH, LH, Eicosanoids
Comment
Park JY, et al reported EGF-like Growth Factors as Mediators of LH Action in the Ovulatory Follicle.
Prior to ovulation in mammals, a cascade of events resembling an inflammatory/tissue remodeling process is triggered by luteinizing hormone (LH) in the ovarian follicle. Many LH effects, however, are thought to be indirect because of the restricted expression of its receptor. Here we demonstrate that LH stimulation induces the transient and sequential expression of the epidermal growth factor (EGF) family members amphiregulin, epiregulin, and betacellulin. Incubation of follicles with these growth factors recapitulates the morphological and biochemical events triggered by LH, including cumulus expansion and oocyte maturation. Thus, these EGF-related growth factors are paracrine mediators that propagate the LH signal throughout the follicle.
PGE2 up-regulates EGF-like growth factors biosynthesis in human granulosa cells: new insights into the coordination between PGE2 and LH in ovulation. Ben-Ami I et al. LH and prostaglandin E2 (PGE2) share many similar effects on the pre-ovulatory follicle. They can induce independently cumulus expansion, the resumption of meiosis and progesterone production. However, cyclooxygenase-2 (COX-2) inhibitors were found to hinder most of the LH-induced effects. Recently, EGF-like growth factors amphiregulin (Ar) and epiregulin (Ep) were found to be produced in response to LH stimulation and to induce cumulus expansion and oocyte maturation. We aimed at evaluating whether PGE2 induces Ar and Ep syntheses in human granulosa cells and whether the inhibition of PGE2 production by selective COX-2 inhibitor, nimesulide, affects LH-induced Ar and Ep biosynthesis. Ar and Ep mRNA levels increased following PGE2 stimulation, in a dose- and time-dependent manner, which resembled those of LH. The blockade of protein kinase A (PKA) (by H89) and mitogen-activated protein kinase (MAPK) (by UO126) reduced the expression of PGE2-induced Ar and Ep biosynthesis. Although the stimulation of the cells with LH in the presence of nimesulide did not change the progesterone levels, it resulted in a significant reduction of Ar and Ep biosynthesis. In conclusion, PGE2 may mimic LH action, at least in part, by the induction of Ar and Ep biosynthesis, which involves cAMP/PKA and MAPK pathways. The negative effect of nimesulide on the ovulatory process may be due to the reduction of Ar and Ep biosynthesis, which implies a possible collaborative role between PGE2 and LH on their induction.
Ovarian localization
Granulosa, Ovarian tumor
Comment
Toshio Sekiguchi, et al 2002 reported the transcriptional Regulation of the Epiregulin Gene in the Rat Ovary.
The authors demonstrated that a growth factor of epidermal growth factor (EGF) family epiregulin was rapidly induced in the primary culture of rat ovarian granulosa cells by FSH within 1 h. Epiregulin gene expression was also observed in granulosa cells of antral ovarian follicles from pregnant mare?s serum gonadotropin-primed rats in vivo. By using a luciferase reporter system, deletion and mutation analyses of rat epiregulin gene promoter region revealed that 125 bp upstream of transcriptional start site was essential, and that two CT boxes and one GT box within this region were important for the gene expression. The authors demonstrated by EMSAs that Sp1/Sp3 proteins were involved in the epiregulin gene expression via the upstream sequence. Involvement of Sp1/Sp3 was also demonstrated that transfection of Sp1 or Sp3 expression plasmids dramatically increased the epiregulin gene promoter activities about 90- or 7.9-fold, respectively, in Drosophila SL2 cells that lack endogenous Sp family proteins. Such an increase in the promoter activity was also observed in mammalian cells when NIH-3T3 cells were used.
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.
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.
Epiregulin as a marker for the initial steps of ovarian cancer development. Amsterdam A et al. Epiregulin (Ep) was found to be produced in non-cancer ovarian cells in response to gonadotropin stimulation as well in ovarian cancer cells in an autonomous manner. However, there were no systematic follow-up studies of Ep expression in the development of different stages of ovarian cancer. Using specific antibodies to Ep and the indirect immunocytochemistry methods, we found that in normal ovary the staining for Ep was mainly confined to the epithelial cells, while the stromal cells were only occasionally and moderately stained. In contrast in benign serous and mucinous tumors most of the tumor cells showed a clear staining in the cytoplasm. In borderline serous and mucinous tumors the staining was much more intensive, and appear occasionally in aggregated form. In serous, mucinous and endometrioid carcinomas labeling remain high, with more frequent aggregated form. It is suggested that follow-up of the expression of Ep can serve as a reliable early indication of the development of ovarian cancer. Moreover, the cytoplasmic aggregation of Ep may suggest a specific mechanism of the release of this growth factor to the extracellular space in order to exert its autocrine and paracrine effect on the family of the EGF receptors.
Follicle stages
Secondary, Antral, Preovulatory, Corpus luteum
Comment
EGF-like growth factors as LH mediators in the human corpus luteum. Ben-Ami I et al. BACKGROUND This study aims to investigate the role of epidermal growth factor-like ligands, amphiregulin (Ar) and epiregulin (Ep), in regulation of apoptosis in luteinized human granulosa cells. METHODS Luteinized human granulosa cells were obtained from women undergoing IVF treatment. Ar and Ep mRNA levels were measured by real-time RT-PCR. The rate of apoptosis was measured by TUNEL. Progesterone levels were measured using radioimmunoassay. Ar- and Ep-induced activation of signaling cascades and Ar protein levels were detected by western blotting. RESULTS LH stimulation of luteinized human granulosa cells induced biosynthesis of Ar and Ep mRNA in a time-dependent manner. The blockade of MEK (by U0126) reduced the expression of LH-induced Ar and Ep biosynthesis. Incubation of the cells with Ar and Ep completely abolished the increase in apoptosis rate induced by serum starvation, and concomitantly caused a pronounced increase in progesterone production. Stimulation of the cells with Ar and Ep also activated the ERK and AKT signaling cascades. Finally, we demonstrated that the pro-survival effect of Ar and Ep is partially dependent on their ability to induce progesterone production. CONCLUSIONS Ar and Ep serve as pro-survival LH mediators in the human corpus luteum.
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: subfertile Comment: LH-Dependent Activation of the EGF Network is Essential for Ovulation. Hsieh M et al. In the preovulatory ovarian follicle, mammalian oocytes are maintained in prophase meiotic arrest until the luteinizing hormone (LH) surge induces reentry into the first meiotic division. Dramatic changes in the somatic cells surrounding the oocytes and in the follicular wall also are induced by LH and are necessary for ovulation. Here, we provide genetic evidence that LH-dependent transactivation of the EGF receptor (EGFR) is indispensable for oocyte reentry into the meiotic cell cycle, for the synthesis of the extracellular matrix surrounding the oocyte that causes cumulus expansion, and for follicle rupture in vivo. Mice deficient in either of two EGFR ligands, amphiregulin or epiregulin, display delayed or reduced oocyte maturation and cumulus expansion. In compound mutant mice where loss of one EGFR ligand is associated with decreased signaling from a hypomorphic allele of the EGFR, LH no longer signals oocyte meiotic resumption. Moreover, induction of genes involved in cumulus expansion and follicle rupture is compromised in these mice, resulting in impaired ovulation. Thus, these studies demonstrate that LH induction of EGF-like growth factors and EGFR transactivation are essential for the regulation of a critical physiological process such as ovulation, and provide new strategies for manipulation of fertility.