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natriuretic peptide receptor 2 OKDB#: 359
 Symbols: NPR2 Species: human
 Synonyms: GCB, AMDM, ANPb, ECDM, GC-B, NPRB, SNSK, ANPRB, GUC2B, NPRBi, GUCY2B  Locus: 9p13.3 in Homo sapiens
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General Comment Natriuretic peptides comprise a family of 3 structurally related molecules: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (NPPC). The physiological activities of NPs are mediated by two specific plasma membrane receptors, guanylyl cyclase-type receptors GC-A and GC-B Chang et al. (1989) . The molecular structures of GC-A and GC-B receptors are similar. Their cytosolic region contains a guanylyl cyclase and a kinase-like domain. The extracellular parts of these receptors exhibit higher affinity either to ANP (GC-A) or to CNP (GC-B). The activation of the receptors by NPs results in cGMP production. The natural ligand of GC-A is ANP, whereas that of GC-B is CNP. It is thought that these pairs represent two distinct natriuretic peptide regulatory systems. The third receptor, ANP-Rc, binds all three natriuretic peptides. Its messenger RNA lacks the guanylyl cyclase sequence present in the mRNA of the other natriuretic peptide receptors, suggesting that this receptor functions to remove natriuretic peptides from the circulation and regulate plasma levels of the natriuretic peptides. Jamison et al. (1992)

NCBI Summary: This gene encodes natriuretic peptide receptor B, one of two integral membrane receptors for natriuretic peptides. Both NPR1 and NPR2 contain five functional domains: an extracellular ligand-binding domain, a single membrane-spanning region, and intracellularly a protein kinase homology domain, a helical hinge region involved in oligomerization, and a carboxyl-terminal guanylyl cyclase catalytic domain. The protein is the primary receptor for C-type natriuretic peptide (CNP), which upon ligand binding exhibits greatly increased guanylyl cyclase activity. Mutations in this gene are the cause of acromesomelic dysplasia Maroteaux type. [provided by RefSeq, Jul 2008]
General function Receptor
Comment ANP and BNP act mainly as cardiac hormones, produced primarily by the atrium and ventricle, respectively. C-type natriuretic peptide occurs in a wide variety of tissues, where it acts as a local regulator. Natriuretic peptides stimulate natriuretic, diuretic, and vasorelaxant activity in vivo, through the activation of two known cell surface receptor guanylyl cyclases (ANPR-A and ANPR-B).
Cellular localization Plasma membrane
Comment
Ovarian function Follicle development, Preantral follicle growth, Ovulation, Oocyte maturation
Comment MicroRNA-127-5p impairs function of granulosa cells via HMGB2 gene in premature ovarian insufficiency. Zhang X et al. (2020) Distinct microRNA (miRNA) profiles have been reported in premature ovarian insufficiency (POI), but their functional relevance in POI is not yet clearly stated. In this study, aberrant expressions of miR-127-5p and high mobility group box 2 (HMGB2) were observed by microarrays in granulosa cells (GCs) from biochemical POI (bPOI) women and further confirmed by a quantitative reverse-transcription polymerase chain reaction. Immortalized human granulosa cell line and mouse primary ovarian GCs were used for functional validation. Orthotopic mouse model was established to examine the role of miR-127-5p in vivo. Finally, the expression of miR-127-5p was measured in the plasma of bPOI women. The receiver operating characteristic curve analysis was performed to determine the indicative role of miR-127-5p for ovarian reserve. Results showed the upregulation of miR-127-5p was identified in GCs from bPOI patients. It inhibited GCs proliferation and impaired DNA damage repair capacity through targeting HMGB2, which was significantly downregulated in GCs from the same cohort of cases. miR-127-5p was confirmed to attenuate DNA repair capability via HMGB2 in mouse ovary in vivo. Intriguingly, the upexpression of miR-127-5p was also detected in plasma of bPOI individuals, suggesting that miR-127-5p could be a promising indicator for bPOI. Taken together, our results discovered the deleterious effects of miR-127-5p on GCs function and its predictive value in POI process. The target gene HMGB2 could be considered as a new candidate for POI. This study highlights the importance of DNA repair capacity for ovarian function and sheds light on the epigenetic mechanism in the pathogenicity of POI.////////////////// Macrophage colony-stimulating factor (M-CSF) is an intermediate in the process of luteinizing hormone-induced decrease in natriuretic peptide receptor 2 (NPR2) and resumption of oocyte meiosis. Sun W et al. (2017) Luteinizing hormone (LH) regulation of the ligand, natriuretic peptide precursor type C, and its receptor, natriuretic peptide receptor 2 (NPR2), is critical for oocyte maturation; however, the mechanism is not fully understood. Macrophage colony-stimulating factor (M-CSF) has recently been shown to be involved in oocyte maturation and ovulation. In the present study we determined whether or not M-CSF plays a role in the intermediate signal that mediates LH regulation of NPR2 in resumption of oocyte meiosis. Immature female C57BL/6 mice were injected i.p. with 5 IU of equine chorionic gonadotropin (eCG) to stimulate follicle development. After 44-48 h, the eCG-stimulated mice were injected i.p. with an ovulatory dose of 5 IU of human chorionic gonadotropin (hCG). The ovaries were excised at selected times. Pre-ovulatory follicles (POFs) and cumulus-oocyte complexes were cultured in different media. Immunohistochemical and quantitative real-time PCR analyses were used to assess the expression of M-CSF, M-CSF receptor (M-CSF-R), and NPR2. The presence of germinal vesicle breakdown (GVBD) was examined under a stereomicroscope to morphologically evaluate resumption of oocyte meiosis. NPR2 was mainly expressed in cumulus cells of pre-ovulatory follicles, while M-CSF and M-CSF-R were expressed in both mural granulosa and cumulus cells. The levels of M-CSF/M-CSF-R and NPR2 decreased within 4 h after treatment of hCG. M-CSF not only reduced the expression of NPR2 mRNA via its receptor (M-CSF-R), but also increased the proportion of GVBD in oocytes. M-CSF serves as an intermediate signal, thus inducing a vital decrease in the NPR2 levels in cumulus cells, and regulates the process of LH-induced resumption of meiosis.////////////////// NPR2 is involved in FSH-mediated mouse oocyte meiotic resumption. Yang L et al. (2016) Previous studies have reported that follicle-stimulating hormone (FSH) is often added to culture media to induce oocyte meiotic resumption and maturation and to improve subsequent embryonic development during in vitro maturation (IVM). However, the underlying mechanisms remain unclear. Cumulus-oocyte complexes (COCs) were collected from ovaries 46-48 h after the female mice were intraperitoneally injected with 8 IU equine chorionic gonadotropin (eCG) and then the COCs were cultured in different medium. qRT-PCR analysis was used to assess mRNA expression of EGF-like factors and natriuretic peptide receptor 2 (NPR2). Western Blot analysis was used to assess phosphorylation of mitogen-activated protein kinase 3/1 (MAPK3/1). The oocytes were morphologically assessed for meiotic resumption. FSH stimulated the expression of EGF-like factors, the activation of MAPK3/1, a decrease in NPR2 mRNA and oocyte meiotic resumption. Moreover, the FSH-induced decrease in NPR2 and oocyte meiotic resumption occurred via the MAPK3/1 singling pathway, which was activated by the epidermal growth factor receptor (EGFR) pathway. NPR2 is involved in FSH-mediated oocyte meiotic resumption, and this process is associated with the EGFR and MAPK3/1 signaling pathways.////////////////// Dephosphorylation of juxtamembrane serines and threonines of the NPR2 guanylyl cyclase is required for rapid resumption of oocyte meiosis in response to luteinizing hormone. Shuhaibar LC et al. (2015) The meiotic cell cycle of mammalian oocytes starts during embryogenesis and then pauses until luteinizing hormone (LH) acts on the granulosa cells of the follicle surrounding the oocyte to restart the cell cycle. An essential event in this process is a decrease in cyclic GMP in the granulosa cells, and part of the cGMP decrease results from dephosphorylation and inactivation of the natriuretic peptide receptor 2 (NPR2) guanylyl cyclase, also known as guanylyl cyclase B. However, it is unknown whether NPR2 dephosphorylation is essential for LH-induced meiotic resumption. Here, we prevented NPR2 dephosphorylation by generating a mouse line in which the seven regulatory serines and threonines of NPR2 were changed to the phosphomimetic amino acid glutamate (Npr2-7E). Npr2-7E/7E follicles failed to show a decrease in enzyme activity in response to LH, and the cGMP decrease was attenuated; correspondingly, LH-induced meiotic resumption was delayed. Meiotic resumption in response to EGF receptor activation was likewise delayed, indicating that NPR2 dephosphorylation is a component of the pathway by which EGF receptor activation mediates LH signaling. We also found that most of the NPR2 protein in the follicle was present in the mural granulosa cells. These findings indicate that NPR2 dephosphorylation in the mural granulosa cells is essential for the normal progression of meiosis in response to LH and EGF receptor activation. In addition, these studies provide the first demonstration that a change in phosphorylation of a transmembrane guanylyl cyclase regulates a physiological process, a mechanism that may also control other developmental events.////////////////// Granulosa cell ligand NPPC and its receptor NPR2 maintain meiotic arrest in mouse oocytes. Zhang M et al. Granulosa cells of mammalian Graafian follicles maintain oocytes in meiotic arrest, which prevents their precocious maturation. We show that mouse mural granulosa cells, which line the follicle wall, express natriuretic peptide precursor type C (Nppc) messenger RNA (mRNA), whereas cumulus cells surrounding oocytes express mRNA of the NPPC receptor NPR2, a guanylyl cyclase. NPPC increased cGMP levels in cumulus cells and oocytes and inhibited meiotic resumption in vitro. Meiotic arrest was not sustained in most Graafian follicles of Nppc or Npr2 mutant mice, and meiosis resumed precociously. Oocyte-derived paracrine factors promoted cumulus cell expression of Npr2 mRNA. Therefore, the granulosa cell ligand NPPC and its receptor NPR2 in cumulus cells prevent precocious meiotic maturation, which is critical for maturation and ovulation synchrony and for normal female fertility. Since C-type natriuretic peptide (CNP) and the guanylyl cyclase receptors A and B (GC-A and GC-B) showed coordinate estrous cycle-dependent variation with maximal expression at proestrus, it was concluded that the natriuretic peptides may play an important role in either the development of ovulatory follicles or in the ovulatory process Jankowski et al. (1997) . Furthermore, Gutkowska?s study Gutkowska et al. (1999) of the hormonal regulation of natriuretic peptide system during induced ovarian follicular development showed a coordinated hormonal stimulation of the NPs and their receptors in the rat ovary. CNP in the ovary is most likely due to local synthesis since CNP is not detected or circulates in very low concentrations. Together with the presence of guanylyl cyclase B receptor subtypes in the ovary and the responsiveness to hormonal regulation, CNP and GC-B receptors emerge as specific regulators of ovarian functions./C-type natriuretic peptide stimulates ovarian follicle development. Sato Y et al. (2012) C-type natriuretic peptide (CNP) encoded by the NPPC (Natriuretic Peptide Precursor C) gene expressed in ovarian granulosa cells inhibits oocyte maturation by activating the natriuretic peptide receptor (NPR)B (NPRB) in cumulus cells. RT-PCR analyses indicated increased NPPC and NPRB expression during ovarian development and follicle growth, associated with increases in ovarian CNP peptides in mice. In cultured somatic cells from infantile ovaries and granulosa cells from prepubertal animals, treatment with CNP stimulated cGMP production. Also, treatment of cultured preantral follicles with CNP stimulated follicle growth whereas treatment of cultured ovarian explants from infantile mice with CNP, similar to FSH, increased ovarian weight gain that was associated with the development of primary and early secondary follicles to the late secondary stage. Of interest, treatment with FSH increased levels of NPPC, but not NPRB, transcripts in ovarian explants. In vivo studies further indicated that daily injections of infantile mice with CNP for 4 d promoted ovarian growth, allowing successful ovulation induction by gonadotropins. In prepubertal mice, CNP treatment alone also promoted early antral follicle growth to the preovulatory stage, leading to efficient ovulation induction by LH/human chorionic gonadotropin. Mature oocytes retrieved after CNP treatment could be fertilized in vitro and developed into blastocysts, allowing the delivery of viable offspring. Thus, CNP secreted by growing follicles is capable of stimulating preantral and antral follicle growth. In place of FSH, CNP treatment could provide an alternative therapy for female infertility.//////////////////
Expression regulated by FSH, LH, Steroids, Growth Factors/ cytokines, EGF
Comment Epidermal Growth Factor-Mobilized Intracellular Calcium of Cumulus Cells Decreases Natriuretic Peptide Receptor 2 Affinity for Natriuretic Peptide Type C and Induces Oocyte Meiotic Resumption in the Mouse. Hao X et al. (2016) Natriuretic peptide type C (NPPC) activation of the guanylyl cyclase-linked natriuretic peptide receptor 2 (NPR2) maintains oocyte meiotic arrest. Luteinizing hormone (LH)-dependent epidermal growth factor (EGF) receptor signaling elevates calcium of cumulus cells to inactivate NPR2, resulting in meiotic resumption. This study investigated the regulatory mechanism of calcium on NPR2 inactivation. In mouse ovarian follicles, LH, through the activation of EGF receptor, significantly elevated calcium levels in cumulus cells, but decreased the binding affinity of NPR2 for NPPC. In cultured cumulus-oocyte complexes (COCs), the activation of EGF receptor by EGF mobilized intracellular calcium of cumulus cells to decrease NPR2 affinity and cyclic guanosine monophosphate (cGMP) levels, resulting in meiotic resumption. However, hormone treatments had not changed NPR2 protein levels. In addition, the removal of magnesium ions from the medium decreased the binding affinity of NPR2 for NPPC, resulting in cGMP levels decrease and meiotic resumption. It is concluded that magnesium ions are required to maintain functional NPR2, and LH-dependent EGF receptor signaling mobilizes intracellular calcium of cumulus cells to reduce NPPC-NPR2 interaction that is required for meiotic resumption.////////////////// Multiple pathways mediate luteinizing hormone regulation of cGMP signaling in the mouse ovarian follicle. Liu X et al. (2014) Luteinizing hormone (LH) regulation of the epidermal growth factor (EGF) network is critical for oocyte maturation and the ovulatory process. Recent studies have indicated that C-type natriuretic peptide (CNP) and its receptor natriuretic peptide receptor B (NPR2) play an important role in the control of meiotic arrest. Here, we investigated the involvement of the EGF network in the LH-dependent regulation of the CNP/NPR2 axis and cGMP accumulation. LH/hCG treatment causes a major decrease in both cGMP and the CNP precursor (natriuretic peptide precursor C,Npp]) mRNA accumulation in vivo and in vitro. However, the cGMP downregulation precedes the decrease in Nppc mRNA by more than 1 h. Amphiregulin, an EGF-like factor, suppresses Nppc mRNA levels in cultured follicles to the same extent as LH, and this effect is completely prevented by the EGF receptor (EGFR) kinase inhibitor AG1478. However, the LH-dependent suppression of Nppc is insensitive to AG1478. Similarly, Nppc suppression by LH occurs in follicles from EGFR null mice. These findings document that EGFR signaling is sufficient to downregulate CNP, but is not necessary for LH action. When cGMP concentration in the follicle is measured, the short-term, but not long-term, LH effects on cGMP are prevented by AG1478, suggesting that ligand availability may be responsible for the late response. Human CG decreases the CNP-dependent cGMP synthesis in wild-type and EGFR knockdown cumulus-oocyte complexes. These findings demonstrate that redundant pathways are involved in the regulation of cGMP. EGFR-dependent events are involved in the short-term regulation of cGMP, whereas the long-term effects may involve regulation of the CNP.////////////////// Dephosphorylation and inactivation of NPR2 guanylyl cyclase in granulosa cells contributes to the LH-induced decrease in cGMP that causes resumption of meiosis in rat oocytes. Egbert JR 2014 et al. In mammals, the meiotic cell cycle of oocytes starts during embryogenesis and then pauses. Much later, in preparation for fertilization, oocytes within preovulatory follicles resume meiosis in response to luteinizing hormone (LH). Before LH stimulation, the arrest is maintained by diffusion of cyclic (c)GMP into the oocyte from the surrounding granulosa cells, where it is produced by the guanylyl cyclase natriuretic peptide receptor 2 (NPR2). LH rapidly reduces the production of cGMP, but how this occurs is unknown. Here, using rat follicles, we show that within 10 min, LH signaling causes dephosphorylation and inactivation of NPR2 through a process that requires the activity of phosphoprotein phosphatase (PPP)-family members. The rapid dephosphorylation of NPR2 is accompanied by a rapid phosphorylation of the cGMP phosphodiesterase PDE5, an enzyme whose activity is increased upon phosphorylation. Later, levels of the NPR2 agonist C-type natriuretic peptide decrease in the follicle, and these sequential events contribute to the decrease in cGMP that causes meiosis to resume in the oocyte. ///////////////////////// Poster presentation Cyclic GMP-mediated intercellular communication in mammalian ovarian follicles Laurinda A Jaffe1*, Jeremy R Egbert1, Leia C Shuhaibar1, Lai Wen2, Martin Thunemann2, Robert Feil2, Viacheslav Nikolaev3, Jerid W Robinson4 and Lincoln R Potter4 Conclusion LH signaling rapidly reduces cGMP synthesis in the granulosa cells of the ovarian follicle, by dephosphorylating the NPR2 guanylyl cyclase. The resulting decrease in cGMP propagates through gap junctions to reduce cGMP in the oocyte, where it promotes the resumption of meiosis.////// Epidermal Growth Factor Receptor Signaling-dependent Calcium Elevation in Cumulus Cells Is Required for NPR2 Inhibition and Meiotic Resumption in Mouse Oocytes. Wang Y et al. In preovulatory ovarian follicles, oocyte is maintained in meiotic prophase arrest by natriuretic peptide precursor C (NPPC) and its receptor natriuretic peptide receptor 2 (NPR2). LH treatment results the decrease of NPR2 guanylyl cyclase activity that promotes resumption of meiosis. We investigated the regulatory mechanism of LH-activated epidermal growth factor (EGF) receptor signaling on NPR2 function. Cumulus cell-oocyte complex (COC) is cultured in the medium with 30 nM NPPC to prevent oocyte spontaneous maturation. In this system, EGF could stimulate oocyte meiotic resumption after 4 h of incubation. Further study showed that EGF elevated intracellular calcium concentrations of cumulus cells and decreased cGMP levels in cumulus cells and oocytes, and calcium elevating reagents ionomycin and sphingosine-1-phosphate (S1P) mimicked the effects of EGF on oocyte maturation and cGMP levels. EGF-mediated cGMP levels and meiotic resumption could be reversed by EGF receptor inhibitor AG1478 and the calcium chelator BAPTA/AM. EGF also decreased the expression of Npr2 mRNA in cumulus cells, which may be not involved in meiotic resumption, since the block of NPR2 protein de novo synthesis by cycloheximide had no effect on NPPC and EGF-mediated oocyte maturation. However, EGF had no effect on oocyte maturation when meiotic arrest was maintained in the present of cGMP analog 8-Br-cGMP. These results suggest that EGF receptor signaling induces meiotic resumption by elevating calcium concentrations of cumulus cells to decrease NPR2 guanylyl cyclase activity. ////Luteinizing hormone reduces the activity of the NPR2 guanylyl cyclase in mouse ovarian follicles, contributing to the cyclic GMP decrease that promotes resumption of meiosis in oocytes. Robinson JW et al. In preovulatory ovarian follicles of mice, meiotic prophase arrest in the oocyte is maintained by cyclic GMP from the surrounding granulosa cells that diffuses into the oocyte through gap junctions. The cGMP is synthesized in the granulosa cells by the transmembrane guanylyl cyclase natriuretic peptide receptor 2 (NPR2) in response to the agonist C-type natriuretic peptide (CNP). In response to luteinizing hormone (LH), cGMP in the granulosa cells decreases, and as a consequence, oocyte cGMP decreases and meiosis resumes. Here we report that within 20min, LH treatment results in decreased guanylyl cyclase activity of NPR2, as determined in the presence of a maximally activating concentration of CNP. This occurs by a process that does not reduce the amount of NPR2 protein. We also show that by a slower process, first detected at 2h, LH decreases the amount of CNP available to bind to the receptor. Both of these LH actions contribute to decreasing cGMP in the follicle, thus signaling meiotic resumption in the oocyte. Estradiol Promotes and Maintains Cumulus Cell Expression of Natriuretic Peptide Receptor 2 (NPR2) and Meiotic Arrest in Mouse Oocytes In Vitro. Zhang M et al. Natriuretic peptide type C (NPPC) and its cognate receptor natriuretic peptide receptor 2 (NPR2) are essential for maintaining meiotic arrest in mouse oocytes residing in Graafian follicles. Cumulus cells, which are associated with the oocyte, express the receptor NPR2, a guanylyl cyclase, whereas mural granulosa cells express ligand NPPC. This study determined the temporal expression of Npr2 and the hormonal factors that participate in regulating its expression and, thereby, in oocyte meiotic arrest. Stimulation of follicular development in vivo with equine chorionic gonadotropin (eCG) promoted expression of Npr2 mRNA by cumulus cells and some periantral mural granulosa cells. However, FSH did not elevate the levels of Npr2 mRNA in cultured cumulus-oocyte complexes (COCs) isolated from mice not stimulated in vivo with eCG. Nevertheless, estradiol elevated expression of this transcript in vitro to the same steady-state level found in COCs isolated from eCG-stimulated follicles in vivo. Expression of Npr2 mRNA was rapidly reduced in COCs in vitro after isolation from eCG-primed mice unless maintained in culture with estradiol. The ability of NPPC to maintain meiotic arrest in cultured COCs was transient unless culture was in estradiol-containing medium. Ability of cumulus cells to produce cyclic GMP, which is required for the maintenance of meiotic arrest, was also lost in the absence of estradiol, indicating that estradiol is required to maintain functional NPR2 receptors on cumulus cells in vitro. It is concluded that estradiol promotes and maintains expression of NPR2 in cumulus cells and participates in NPPC-mediated maintenance of oocyte meiotic arrest in vitro. Gutkowska et al. 1999 studied the hormonal regulation of the NP system during follicular growth and ovulation induced by gonadotropins eCG (a glycoprotein hormone that possesses primarily FSH activity) and hCG in the rat. After treatment, the expression level of both receptors (GC-A and GC-B) increased, and ovarian ANP and C-type natriuretic peptide (CNP) gene expression was also activated.
Ovarian localization Oocyte, Cumulus, Granulosa, Theca
Comment C-type natriuretic peptide signaling in human follicular environment and its relation with oocyte maturation. Casalechi M et al. (2019) Studies in mice have shown that C-type natriuretic peptide (CNP) is produced by granulosa cells and contributes to ovarian follicle growth and oocyte meiotic arrest until the preovulatory LH surge. In humans, the relationship between intraovarian CNP levels and oocyte meiotic resumption is unknown. The aim of this study was to investigate whether CNP and its receptor NPR2 are expressed in human ovarian follicles and if their levels change according to the meiotic phase of oocytes. We collected follicular fluid (FF) and luteinized granulosa cells (LGC) from follicle pools (n = 47), and FF, LGC and cumulus cells (CC) from individual follicles (n = 96) during oocyte pickup for in vitro fertilization. There was a positive linear correlation between CNP levels in FF pools and basal antral follicle counting (rs = 0.458; p = 0.002), number of preovulatory follicles >16 mm (rs = 0.361; p = 0.016) and number of oocytes retrieved (rs = 0,378; p = 0.011) and a negative correlation between CNP levels in FF pools and the percentage of mature (MII) oocytes retrieved (rs = -0.39; p = 0.033). FF CNP levels in follicles containing MII oocytes were significantly lower than in follicles containing immature (MI) oocytes (median = 0.44 vs. 0.57 ng/ml, p < 0.05). Accordingly, the CNP precursor gene NPPC was 50% less expressed in LGC from follicles containing MII oocytes than in follicles containing MI oocytes (p < 0.01). In addition, NPR2 mRNA was down-regulated in CC surrounding MII oocytes (60% reduction, p < 0.01). CNP signaling is downregulated in human ovarian follicles containing mature oocytes. Further studies should clarify whether CNP signaling is essential to keep oocyte meiotic arrest in humans.////////////////// Expression and localization of Npr2 in mouse oocytes and pre-implantation embryos. Xi H et al. (2019) We investigated the expression and localization of natriuretic peptide receptor 2 (Npr2) in mouse oocytes and pre-implantation embryos. Immunocytochemistry and quantitative real-time polymerase chain reaction (qRT-PCR) were performed on mouse oocytes and embryos at different developmental stages. Npr2 was expressed in all oocyte and pre-implantation embryo stages analyzed. Germinal vesicle oocytes exhibited greater Npr2 expression than metaphase II oocytes. In pre-implantation embryos, Npr2 expression was significantly greater from the 2-cell stage to the blastocyst stage than for the zygote. Npr2 expression at the blastocyst stage was significantly less than at the morula stage. We found that Npr2 is expressed not only in mouse oocytes, but also in mouse embryos. Npr2 may play an important role in early embryonic development and embryo implantation.////////////////// Brain natriuretic peptide and C-type natriuretic peptide maintain porcine oocyte meiotic arrest. Zhang W 2014 et al. Recent studies have shown that C-type natriuretic peptide (CNP) serves as a key control system during mouse oocyte maturation. We used pig models (in vitro and in vivo) to explore the role played by the natriuretic peptide family in porcine oocyte maturation. We reported the expression and location of natriuretic peptide system in different stages of porcine antral follicles. Atrial natriuretic peptide (ANP) and CNP were expressed primarily in granulosa cells, whereas brain natriuretic peptide (BNP) and natriuretic peptide receptor-B (NPRB) receptor were expressed in granulosa cells (both cumulus and mural granulosa cells) and thecal internal cells, and the natriuretic peptide receptor-A (NPRA) receptor predominantly in thecal cells. Upon in vitro culture, BNP and CNP maintained meiotic arrest of oocytes associated with cumulus cells. The expression levels of BNP, CNP, and the NPRB receptor increased upon treatment of prepubertal gilts with pregnant mare's serum gonadotropin and decreased upon subsequent human chorionic gonadotropin injection. Such dynamic changes in the expression of natriuretic peptides and their receptor paralleled the proportions of oocytes exhibiting nuclear maturation in vivo. These data indicated that BNP and CNP co-contributed to maintaining porcine meiotic arrest under physiological condition and lutenizing hormone (LH) relieved this inhibitory effect by decreasing the expression levels of BNP and CNP in vivo. Our present work, combined with previous data, improved the understanding of the oocyte meiotic arrest mechanisms and further revealed that natriuretic peptides serve as oocyte maturation inhibitor (OMI) to inhibit oocyte maturation in mammals. ? 2014 Wiley Periodicals, Inc. /////////////////////////
Follicle stages
Comment Natriuretic peptides stimulate oocyte meiotic resumption in bovine. Cesaro MP et al. (2015) The aim of the present study was to evaluate the expression of mRNA encoding natriuretic peptides (NPs) and their receptors in the cumulus-oocyte complex in cattle, a monovular mammalian species, and also to investigate the role of NPs in oocyte meiotic resumption in vitro. mRNA was observed for the NP precursor type-A (NPPA), type-C (NPPC), NP receptor-1 (NPR-1), receptor-2 (NPR-2) and receptor-3 (NPR-3) in bovine cumulus cells, and NPR-2 mRNA was observed in oocytes. These results are different from those obtained in mouse and pig models. The effects of NPPA, NP precursor type-B (NPPB) and NPPC on the resumption of arrested meiosis maintained by forskolin were studied at three different doses (10, 100 and 1000nM) with a 12h culture system. The germinal vesicle breakdown rates were greater (P≤0.05) in oocytes that were cultured in the presence of one or a combination of NPs (from 44% to 73%) than the negative control (from 24% to 27%). Additionally, it was demonstrated that the concentration of cyclic guanosine 3',5'-monophosphate (cGMP) is increased by NPPA and NPPC in oocytes and cumulus cells after 3h of in vitro maturation. However, in both groups, the concentration of cyclic adenosine 3',5'-monophosphate (cAMP) in the oocyte did not increase between 3 and 6h of culture, even when forskolin was used. In summary, we observed the presence of mRNA for NPs and their receptors in the bovine cumulus-oocyte complex and demonstrated that, in vitro, NPPA, NPPB and NPPC stimulate oocyte meiotic resumption in a monovular species.////////////////// Epidermal growth factor-network signaling mediates luteinizing hormone regulation of BNP and CNP and their receptor NPR2 during porcine oocyte meiotic resumption. Zhang W et al. (2014) The epidermal growth factor (EGF) network, induced by luteinizing hormone (LH), plays an essential role during the regulation of oocyte maturation, cumulus expansion, and ovulation. Binding of brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) to natriuretic receptor 2 (NPR2) generates cyclic guanosine monophosphate (cGMP), a key inhibitor that sustains porcine oocyte meiotic arrest. This correlation suggests that LH interacts with natriuretic-peptide signaling, possibly via the EGF network, to promote porcine meiotic resumption. In testing this hypothesis, we found that the majority of porcine oocytes remain arrested in the germinal-vesicle stage after 44 hr of co-culturing cumulus-oocyte complexes with 10(7) granulosa cells, which secreted active BNP and CNP; these natriuretic peptides associate with NPR2 on cumulus cells, thereby inhibiting porcine oocyte maturation. This inhibitory effect of BNP and CNP was relieved by EGF-like growth factors, whose expression naturally increases in granulosa cells 18 hr after human chorionic gonadotropin injection. LH and the EGF-like peptide amphiregulin (AREG) decreased BNP and CNP production in granulosa cells and down-regulated NPR2 expression in cumulus cells, which together decreased oocyte cGMP to levels that permit meiotic resumption. The effects of AREG on the gene expression of natriuretic-peptide signaling components and on oocyte maturation were completely blocked by the EGF receptor kinase inhibitor AG1478; the effect of LH, however, was only partially reversed by AG1478. Based on these results, LH regulates natriuretic-peptide signaling, although other pathways also cooperate with the EGF network to induce porcine oocyte maturation.//////////////////
Phenotypes
Mutations 5 mutations

Species: mouse
Mutation name: None
type: null mutation
fertility: infertile - ovarian defect
Comment: Critical roles of the guanylyl cyclase B receptor in endochondral ossification and development of female reproductive organs. Tamura N et al. Guanylyl cyclase B is the receptor for a small peptide (C-type natriuretic peptide) produced locally in many different tissues. To unravel the functions of the receptor, we generated mice lacking guanylyl cyclase B through gene targeting. Expression of the receptor mRNA in tissues such as bone and female reproductive organs was evident, and significant phenotypes associated with each of these tissues were apparent in null mice. A dramatic impairment of endochondral ossification and an attenuation of longitudinal vertebra or limb-bone growth were seen in null animals. C-type natriuretic peptide-dependent increases of guanylyl cyclase B activity, but not basal enzyme activity, appeared to be required for the progression of endochondral ossification. Female mice were infertile, but male mice were not. This result was due to the failure of the female reproductive tract to develop. Thus, the guanylyl cyclase B receptor is critical for the development of both bone and female reproductive organs. Well developed corpora lutea were present in WT mice, whereas only primordial through secondary antral follicles existed in Npr2 ?/? ovaries (Fig. 6 e and f ). No estrus cycles were apparent, based on the cytology of vaginal smear.

Species: mouse
Mutation name: None
type: null mutation
fertility: infertile - ovarian defect
Comment: NPPC/NPR2 signaling is essential for oocyte meiotic arrest and cumulus oophorus formation during follicular development in the mouse ovary. Kiyosu C 2012 et al. Natriuretic peptide type C (NPPC) and its high affinity receptor, natriuretic peptide receptor 2 (NPR2), have been assumed to be involved in female reproduction and have recently been shown to play an essential role in maintaining meiotic arrest of oocytes. However, the overall role of NPPC/NPR2 signaling in female reproduction and ovarian function is still less clear. Here we report the defects observed in oocytes and follicles of mice homozygous for Nppc(lbab) or Npr2(cn), mutant alleles of Nppc or Npr2 respectively to clarify the exact consequences of lack of NPPC/NPR2 signaling in female reproductive systems. We found that: i) Npr2(cn)/Npr2(cn) female mice ovulated a comparable number of oocytes as normal mice but never produced a litter; ii) all ovulated oocytes of Npr2(cn)/Npr2(cn) and Nppc(lbab)/Nppc(lbab) mice exhibited abnormalities, such as fragmented or degenerated ooplasm and never developed to the two-cell stage after fertilization; iii) histological examination of the ovaries of Npr2(cn)/Npr2(cn) and Nppc(lbab)/Nppc(lbab) mice showed that oocytes in antral follicles prematurely resumed meiosis and that immediately before ovulation, oocytes showed disorganized chromosomes or fragmented ooplasm; and iv) ovulated oocytes and oocytes in the periovulatory follicles of the mutant mice were devoid of cumulus cells. These findings demonstrate that NPPC/NPR2 signaling is essential for oocyte meiotic arrest and cumulus oophorus formation, which affects female fertility through the production of oocytes with developmental capacity. /////////////////////////

Species: mouse
Mutation name: None
type: naturally occurring
fertility: infertile - ovarian defect
Comment: A Novel Loss-of-Function Mutation in Npr2 Clarifies Primary Role in Female Reproduction and Reveals a Potential Therapy for Acromesomelic Dysplasia, Maroteaux Type. Geister KA et al. We discovered a new spontaneous mutant allele of Npr2 named peewee (pwe) that exhibits severe disproportionate dwarfism and female infertility. The pwe phenotype is caused by a 4 base-pair deletion in exon three that generates a premature stop codon at codon 313 (L313X). The Npr2(pwe/pwe) mouse is a model for the human skeletal dysplasia acromesomelic dysplasia, Maroteaux type (AMDM). We conducted a thorough analysis of the female reproductive tract and report that the primary cause of Npr2(pwe/pwe) female infertility is premature oocyte meiotic resumption, while the pituitary and uterus appear normal. Npr2 is expressed in chondrocytes and osteoblasts. We determined that loss of Npr2 causes a reduction in the hypertrophic and proliferative zones of the growth plate but mineralization of skeletal elements is normal. Mutant tibiae have increased levels of the activated form of ERK1/2, consistent with the idea that NPR2 signaling inhibits the activation of the MEK/ERK MAPK pathway. Treatment of fetal tibiae explants with MEK1/2 inhibitors U0126 and PD325901 rescues the Npr2(pwe/pwe) growth defect, providing a promising foundation for skeletal dysplasia therapeutics.

Species: human
Mutation name: None
type: targeted overexpression
fertility: fertile
Comment: An activating mutation in the kinase homology domain of the natriuretic Peptide receptor-2 causes extremely tall stature without skeletal deformities. Hannema SE 2013 et al. Background: C-type natriuretic peptide (CNP)/natriuretic peptide receptor 2 (NPR2) signaling is essential for long bone growth. Enhanced CNP production caused by chromosomal translocations results in tall stature, a Marfanoid phenotype, and skeletal abnormalities. A similar phenotype was described in a family with an activating NPR2 mutation within the guanylyl cyclase domain. Case: Here we describe an extremely tall male without skeletal deformities, with a novel NPR2 mutation (p.Arg655Cys) located in the kinase homology domain. Objectives: The objective of the study was to investigate the functional and structural effects of the NPR2 mutation. Methods: Guanylyl cyclase activities of wild-type vs mutant NPR2 were analyzed in transfected human embryonic kidney 293 cells and in skin fibroblasts. The former were also used to study possible interactions between both isoforms. Homology modeling was performed to understand the molecular impact of the mutation. Results: CNP-stimulated cGMP production by the mutant NPR2 was markedly increased in patient skin fibroblasts and transfected human embryonic kidney 293 cells. The stimulatory effects of ATP on CNP-dependent guanylyl cyclase activity were augmented, suggesting that this novel mutation enhances both the responsiveness of NPR2 to CNP and its allosteric modulation/stabilization by ATP. Coimmunoprecipitation showed that wild-type and mutant NPR2 can form stable heterodimers, suggesting a dominant-positive effect. In accordance with augmented endogenous receptor activity, plasma N-terminal pro-CNP (a marker of CNP production in tissues) was reduced in the proband. Conclusions: We report the first activating mutation within the kinase homology domain of NPR2, resulting in extremely tall stature. Our observations emphasize the important role of this domain in the regulation of guanylyl cyclase activity and bone growth in response to CNP. /////////////////////////

Species: human
Mutation name: None
type: naturally occurring
fertility: unknown
Comment: Identification and functional characterization of two novel NPR2 mutations in Japanese patients with short stature. Amano N 2014 et al. CONTEXT C-type natriuretic peptide-natriuretic peptide receptor B (NPR-B) signaling is critical for endochondral ossification, which is responsible for longitudinal growth in limbs and vertebrae. Biallelic NPR2 mutations cause acromesomelic dysplasia, type Maroteaux, which is bone dysplasia characterized by severe short stature and short limbs. A monoallelic NPR2 mutation has been suggested to mildly impair long bone growth. OBJECTIVE The goal of this study was to identify and characterize NPR2 mutations among Japanese patients with short stature. SUBJECTS AND METHODS We enrolled 101 unrelated Japanese patients with short stature. NPR2 and NPPC were sequenced, and the identified variants were characterized in vitro. RESULTS In two subjects, we identified two novel heterozygous NPR2 mutations (R110C and Q417E) causing a loss of C-type natriuretic peptide-dependent cGMP generation capacities and having dominant-negative effects. R110C was defective in trafficking from the endoplasmic reticulum to the Golgi apparatus. In contrast, Q417E showed clear cell surface expression. CONCLUSIONS We identified heterozygous NPR2 mutations in 2% of Japanese patients with short stature. Our in vitro findings indicate that NPR2 mutations have a dominant negative effect, and their dominant-negative mechanisms vary corresponding to the molecular pathogenesis of the mutations. /////////////////////////

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