| R-spondin 1 | OKDB#: 3660 |
| Symbols: | RSPO1 | Species: | human | ||
| Synonyms: | RSPO, CRISTIN3 | Locus: | 1p34.3 in Homo sapiens |
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| General Comment |
Mitogenic influence of human R-spondin1 on the intestinal epithelium. Kim KA et al.. Several described growth factors influence the proliferation and regeneration of the intestinal epithelium. Using a transgenic mouse model, we identified a human gene, R-spondin1, with potent and specific proliferative effects on intestinal crypt cells. Human R-spondin1 (hRSpo1) is a thrombospondin domain-containing protein expressed in enteroendocrine cells as well as in epithelial cells in various tissues. Upon injection into mice, the protein induced rapid onset of crypt cell proliferation involving beta-catenin stabilization, possibly by a process that is distinct from the canonical Wnt-mediated signaling pathway. The protein also displayed efficacy in a model of chemotherapy-induced intestinal mucositis and may have therapeutic application in gastrointestinal diseases.
Lgr5 homologues associate with Wnt receptors and mediate R-spondin signalling. de Lau W et al. The adult stem cell marker Lgr5 and its relative Lgr4 are often co-expressed in Wnt-driven proliferative compartments. We find that conditional deletion of both genes in the mouse gut impairs Wnt target gene expression and results in the rapid demise of intestinal crypts, thus phenocopying Wnt pathway inhibition. Mass spectrometry demonstrates that Lgr4 and Lgr5 associate with the Frizzled/Lrp Wnt receptor complex. Each of the four R-spondins, secreted Wnt pathway agonists, can bind to Lgr4, -5 and -6. In HEK293 cells, RSPO1 enhances canonical WNT signals initiated by WNT3A. Removal of LGR4 does not affect WNT3A signalling, but abrogates the RSPO1-mediated signal enhancement, a phenomenon rescued by re-expression of LGR4, -5 or -6. Genetic deletion of Lgr4/5 in mouse intestinal crypt cultures phenocopies withdrawal of Rspo1 and can be rescued by Wnt pathway activation. Lgr5 homologues are facultative Wnt receptor components that mediate Wnt signal enhancement by soluble R-spondin proteins. These results will guide future studies towards the application of R-spondins for regenerative purposes of tissues expressing Lgr5 homologues.
NCBI Summary: This gene encodes a secreted activator protein with two cysteine-rich, furin-like domains and one thrombospondin type 1 domain. The encoded protein is a ligand for leucine-rich repeat-containing G-protein coupled receptors (LGR proteins) and positively regulates the Wnt signaling pathway. In mice, the protein induces the rapid onset of crypt cell proliferation and increases intestinal epithelial healing, providing a protective effect against chemotherapy-induced adverse effects. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Apr 2014] |
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| General function | Ligand, Cytokine | ||||
| Comment | |||||
| Cellular localization | Secreted | ||||
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| Ovarian function | Germ cell development | ||||
| Comment | Involvement of FOXL2 and RSPO1 in Ovarian Determination, Development, and Maintenance in Mammals. Pannetier M et al. (2016) In mammals, sex determination is a process through which the gonad is committed to differentiate into a testis or an ovary. This process relies on a delicate balance between genetic pathways that promote one fate and inhibit the other. Once the gonad is committed to the female pathway, ovarian differentiation begins and, depending on the species, is completed during gestation or shortly after birth. During this step, granulosa cell precursors, steroidogenic cells, and primordial germ cells start to express female-specific markers in a sex-dimorphic manner. The germ cells then arrest at prophase I of meiosis and, together with somatic cells, assemble into functional structures. This organization gives the ovary its definitive morphology and functionality during folliculogenesis. Until now, 2 main genetic cascades have been shown to be involved in female sex differentiation. The first is driven by FOXL2, a transcription factor that also plays a crucial role in folliculogenesis and ovarian fate maintenance in adults. The other operates through the WNT/CTNNB1 canonical pathway and is regulated primarily by R-spondin1. Here, we discuss the roles of FOXL2 and RSPO1/WNT/ CTNNB1 during ovarian development and homeostasis in different models, such as humans, goats, and rodents.////////////////// R-spondin1, WNT4 and the CTNNB1 signaling pathway: tight control over ovarian differentiation. Chassot AA 2014 et al. Sex differentiation is a unique developmental process. Starting from a bipotential gonad, it gives rise to the ovary and the testis, two highly specialized organs which differ morphologically and physiologically despite sharing common reproductive and endocrine functions. This highlights the specific plasticity of the gonadal precursors and the existence of complex antagonistic genetic regulation. Mammalian sex determination is controlled by paternal transmission of the Y-linked gene, SRY. Using mouse models, it has been shown that the main role of SRY is to activate the expression of the transcription factor Sox9; either one of these two genes is necessary and sufficient to allow testicular development through Sertoli cell differentiation. Thus, defects in SRY/Sry and/or SOX9/Sox9 expression result in male-to-female sex reversal of XY individuals. Molecular mechanisms governing ovarian differentiation remained unknown for a long time, until the discovery of the roles of R-spondin1 and WNT4. In XX individuals, activation of the -catenin signaling pathway by the secreted proteins RSPO1 and WNT4 is required to allow granulosa cell differentiation and, in turn, ovarian differentiation. Thus, mutations in RSPO1 result in female-to-male sex reversal of XX patients, and mouse models have allowed the identification of genetic cascades activated by RSPO1 and WNT4 to regulate ovarian development. In this review, we will discuss the respective roles of RSPO1, WNT4 and the -catenin signaling pathway during ovarian differentiation in mice. ///////////////////////// RSPO1/?Catenin Signaling Pathway Regulates Oogonia Differentiation and Entry into Meiosis in the Mouse Fetal Ovary. Chassot AA et al. Differentiation of germ cells into male gonocytes or female oocytes is a central event in sexual reproduction. Proliferation and differentiation of fetal germ cells depend on the sex of the embryo. In male mouse embryos, germ cell proliferation is regulated by the RNA helicase Mouse Vasa homolog gene and factors synthesized by the somatic Sertoli cells promote gonocyte differentiation. In the female, ovarian differentiation requires activation of the WNT/?catenin signaling pathway in the somatic cells by the secreted protein RSPO1. Using mouse models, we now show that Rspo1 also activates the WNT/?catenin signaling pathway in germ cells. In XX Rspo1(-/-) gonads, germ cell proliferation, expression of the early meiotic marker Stra8, and entry into meiosis are all impaired. In these gonads, impaired entry into meiosis and germ cell sex reversal occur prior to detectable Sertoli cell differentiation, suggesting that ?catenin signaling acts within the germ cells to promote oogonial differentiation and entry into meiosis. Our results demonstrate that RSPO1/?catenin signaling is involved in meiosis in fetal germ cells and contributes to the cellular decision of germ cells to differentiate into oocyte or sperm. Cloning and expression of R-Spondin1 in different vertebrates suggests a conserved role in ovarian development. Smith CA et al. ABSTRACT: BACKGROUND: R-Spondin1 (Rspo1) is a novel regulator of the Wnt/beta-catenin signalling pathway. Loss-of-function mutations in human RSPO1 cause testicular differentiation in 46, XX females, pointing to a role in ovarian development. Here we report the cloning and comparative expression analysis of R-SPONDIN1 orthologues in the mouse, chicken and red-eared slider turtle, three species with different sex-determining mechanisms. Evidence is presented that this gene is an ancient component of the vertebrate ovary-determining pathway. RESULTS: Gonadal RSPO1 gene expression is female up-regulated in the embryonic gonads in each species at the onset of sexual differentiation. In the mouse gonad, Rspo1 mRNA is expressed in the somatic cell lineage at the time of ovarian differentiation (E12.5- E15.5), with little expression in germ cells. However, the protein is localised in the cytoplasm and at the cell surface of both somatic (pre-follicular) and germ cells. In the chicken embryo, RSPO1 expression becomes elevated in females at the time of ovarian differentiation, coinciding with female-specific activation of the FOXL2 gene and estrogen synthesis. RSPO1 protein in chicken is localised in the outer cortical zone of the developing ovary, the site of primordial follicle formation and germ cell differentiation. Inhibition of estrogen synthesis with a specific aromatase inhibitor results in a decline in chicken RSPO1 expression, indicating that RSPO1 is influenced by estrogen. In the red-eared slider turtle, which exhibits temperature-dependent sex determination, up-regulation of RSPO1 occurs during the temperature-sensitive period, when gonadal development is responsive to temperature. Accordingly, RSPO1 expression is temperature-responsive, and is down-regulated in embryos shifted from female- to male-producing incubation temperatures. CONCLUSIONS: These results indicate that RSPO1 is up-regulated in the embryonic gonads of female vertebrates with different sex-determining mechanisms. In all instances, RSPO1 is expressed in the incipient ovary. These findings suggest that R-SPONDIN1 is an ancient, conserved part of the vertebrate ovary-determining pathway. Goat RSPO1 over-expression rescues sex-reversal in Rspo1-knockout XX mice but does not perturb testis differentiation in XY or sex-reversed XX mice. Buscara L et al. RSPO1 is a newly discovered gene involved in sex differentiation. Two goat BAC clones encompassing the RSPO1 gene (gRSPO1) were injected into mouse oocytes and several transgenic lines derived. Both clones induced gRSPO1 over-expression in various tissues, including male and female gonads, with no obvious phenotype and normal sex-ratios. Introgression of the gRSPO1 transgene into a mouse RSPO1 knockout genotype resulted in the rescue of the fertility and the disappearance of the masculinized gonadic features of the females, demonstrating the functionality of the goat protein in a mouse context. On the contrary, over-expression of gRSPO1 within a mSRY or a gSRY-XX genotypes did not interfere with the SRY-induced male phenotype. The human and mouse sex-determining SRY genes repress the Rspol/beta-catenin signaling. Lau YF et al. The sex-determining region Y (SRY) is the gene on the Y chromosome responsible for switching on male sex determination during mammalian embryogenesis. In its absence, ovaries develop in the embryo. Hence, ovarian determination and differentiation is considered to be a default, or passive, developmental pathway. Recently this classical paradigm of sex determination has been challenged with the discovery of the R-spondin 1 (RSPO1) as an active ovarian determinant. Mutations of RSPO1 cause a female-to-male sex reversal. RSPO1 synergizes with WNT4 in activating an ovarian development in the bipotential gonad via the canonical Wnt signaling. Early studies showed that SRY represses such Wnt signaling, but also generated discrepancies on whether only mouse Sry is capable of inhibiting such Wnt signaling and whether both human and mouse SRY proteins are able to interact with beta-catenin, the intracellular messenger responsible for executing the Wnt signals. Our studies show that both human SRY and mouse Sry are capable of repressing the Rspo1/Wnt/beta-catenin signaling. However, the repression activities vary among different SRY/Sry proteins and paradoxically related to the presence and/or size of an acidic/glutamine-rich domain. The HMG box of human SRY could bind directly to beta-catenin while the mouse Sry binds to beta-catenin via its HMG box and glutamine-rich domain. The results clarify some of the initial discrepancies, and raise the possibility that SRY interacts with beta-catenin in the nucleus and represses the transcriptional activation of the Rspo1/Wnt target genes involved in ovarian determination, thereby switching on testis determination. | ||||
| Expression regulated by | |||||
| Comment | Wnt Signaling in Ovarian Development Inhibits Sf1 Activation of Sox9 via the Tesco Enhancer. Bernard P et al. Genome analysis of patients with disorders of sex development, and gain- and loss-of-function studies in mice indicate that gonadal development is regulated by opposing signals. In females, the Wnt/?catenin canonical pathway blocks testicular differentiation by repressing the expression of the Sertoli cell-specific gene Sox9 by an unknown mechanism. Using cell and embryonic gonad culture models, we show that activation of the Wnt/?catenin pathway inhibits the expression of Sox9 and Amh, whereas mRNA and protein levels of Sry and steroidogenic factor 1 (Sf1), two key transcriptional regulators of Sox9, are not altered. Ectopic activation of Wnt/?catenin signaling in male gonads led to a loss of Sf1 binding to the Tesco enhancer and absent Sox9 expression that we also observed in wild-type ovaries. Moreover, ectopic Wnt/?catenin signaling induced the expression of the female somatic cell markers, Bmp2 and Rspo1, as a likely consequence of Sox9 loss. Wnt/?catenin signaling in XY gonads did not, however, affect gene expression of the steroidogenic Leydig cell Sf1 target gene, Cyp11a1, or Sf1 binding to the Cyp11a1 promoter. Our data support a model in ovary development whereby activation of ?catenin prevents Sf1 binding to the Sox9 enhancer, thereby inhibiting Sox9 expression and Sertoli cell differentiation. | ||||
| Ovarian localization | Primordial Germ Cell, Oocyte, Granulosa | ||||
| Comment | Human RSPO1/R-spondin1 Is Expressed during Early Ovary Development and Augments ?Catenin Signaling. Tomaselli S et al. Human testis development starts from around 42 days post conception with a transient wave of SRY expression followed by up-regulation of testis specific genes and a distinct set of morphological, paracrine and endocrine events. Although anatomical changes in the ovary are less marked, a distinct sub-set of ovary specific genes are also expressed during this time. The furin-domain containing peptide R-spondin1 (RSPO1) has recently emerged as an important regulator of ovary development through up-regulation of the WNT/?catenin pathway to oppose testis formation. Here, we show that RSPO1 is upregulated in the ovary but not in the testis during critical early stages of gonad development in humans (between 6-9 weeks post conception), whereas the expression of the related genes WNT4 and CTNNB1 (encoding ?catenin) is not significantly different between these tissues. Furthermore, reduced R-spondin1 function in the ovotestis of an individual (46,XX) with a RSPO1 mutation leads to reduced ?catenin protein and WNT4 mRNA levels, consistent with down regulation of ovarian pathways. Transfection of wild-type RSPO1 cDNA resulted in weak dose-dependent activation of a ?catenin responsive TOPFLASH reporter (1.8 fold maximum), whereas co-transfection of CTNNB1 (encoding ?catenin) with RSPO1 resulted in dose-dependent synergistic augmentation of this reporter (approximately 10 fold). Furthermore, R-spondin1 showed strong nuclear localization in several different cell lines. Taken together, these data show that R-spondin1 is upregulated during critical stages of early human ovary development and may function as a tissue-specific amplifier of ?catenin signaling to oppose testis determination. SRY and the Standoff in Sex Determination. Dinapoli L et al. SRY was identified as the mammalian sex-determining gene more than 15 years ago and has been extensively studied since. Although many of the pathways regulating sexual differentiation have been elucidated, direct downstream targets of SRY are still unclear, making a 'top down' approach difficult. However, recent work has demonstrated that the fate of the gonad is actively contested by both male-promoting and female-promoting signals. Sox9 and Fgf9 push gonads towards testis differentiation. These two genes are opposed by Wnt4, and possibly RSPO1, which push gonads towards ovary differentiation. In this review, we will discuss the history of the field, current findings, and exciting new directions in vertebrate sex-determination. X, Y, and the Gonad. | ||||
| Follicle stages | |||||
| Comment | Molecular analysis shows differential expression of R-spondin1 in zebrafish (Danio rerio) gonads. Zhang Y et al. R-spondin1 (RSPO1) is a potential female-determining gene in human (Homo sapiens) and mouse (Mus musculus). Its differential expression in these mammals is correlated with signaling for sex determination. As a way of studying sex determination in fish we cloned and analyzed a RSPO1 gene in zebrafish (Danio rerio). Using real-time PCR, we observed that RSPO1 is expressed more strongly in ovaries than in testes, suggesting that RSPO1 may have a role in gonad differentiation. High RSPO1 expression was detected in some non-gonadal organs like muscle and kidneys. In situ hybridization results demonstrate that RSPO1 is expressed in premature germ cells, in oogonia and primary oocytes in ovaries and in spermatogonia and spermatocytes in testes. It is also expressed in gonad somatic cells during gonadal development: in granulosa cells and theca cells of early and late cortical-alveolar stage follicles in ovaries, and in Leydig cells in testes. This differential expression may indicate that RSPO1 has a role(s) in zebrafish gonad development and differentiation. By fusing zebrafish RSPO1 with a green fluorescent protein gene, we found that RSPO1 is located in the cytosol and Golgi apparatus but not the nucleus of fish epithelioma papulosum cyprinid (EPC) cells. These preliminary findings suggest some aspects of RSPO1 like differential expression linked to sex determination may be conserved in fish while other aspects like subcellular localization differ from the mammalian RSPO1. | ||||
| Phenotypes | |||||
| Mutations |
4 mutations
Species: mouse
Species: human
Species: mouse
Species: mouse
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| Genomic Region | show genomic region | ||||
| Phenotypes and GWAS | show phenotypes and GWAS | ||||
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| created: | Nov. 24, 2006, 8:15 a.m. | by: |
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| last update: | Sept. 21, 2016, 10:16 a.m. | by: | hsueh email: |
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