RSPO1 Research Articles

Sox8 and Sox9 act redundantly for ovarian-to-testicular fate reprogramming in the absence of R-spondin1 in mouse sex reversals.

In mammals, testicular differentiation is initiated by transcription factors SRY and SOX9 in XY gonads, and ovarian differentiation involves R-spondin1 (RSPO1) mediated activation of WNT/β-catenin signaling in XX gonads. Accordingly, the absence of RSPO1/Rspo1 in XX humans and mice leads to testicular differentiation and female-to-male sex reversal in a manner that does not requireSry or Sox9 in mice. Here we show that an alternate testis-differentiating factor exists and that this factor is Sox8. Specifically, genetic ablation of Sox8 and Sox9 prevents ovarian-to-testicular reprogramming observed in XX Rspo1 loss-of-function mice. Consequently, Rspo1 Sox8 Sox9 triple mutant gonads developed as atrophied ovaries. Thus, SOX8 alone can compensate for the loss of SOX9 for Sertoli cell differentiation during female-to-male sex reversal.

R-spondin2 signaling is required for oocyte-driven intercellular communication and follicular growth

R-spondin2 (RSPO2) is a member of the R-spondin family, which are secreted activators of the WNT/β-catenin (CTNNB1) signaling pathway. In the mouse postnatal ovary, WNT/CTNNB1 signaling is active in the oocyte and in the neighboring supporting cells, the granulosa cells. Although the role of Rspo2 has been previously studied using in vitro experiments, the results are conflicting and the in vivo ovarian function of Rspo2 remains unclear. In the present study, we found that RSPO2/Rspo2 expression is restricted to the oocyte of developing follicles in both human and mouse ovaries from the beginning of the follicular growth. In mice, genetic deletion of Rspo2 does not impair oocyte growth, but instead prevents cell cycle progression of neighboring granulosa cells, thus resulting in an arrest of follicular growth. We further show this cell cycle arrest to be independent of growth promoting GDF9 signaling, but rather associated with a downregulation of WNT/CTNNB1 signaling in granulosa cells. To confirm the contribution of WNT/CTNNB1 signaling in granulosa cell proliferation, we induced cell type specific deletion of Ctnnb1 postnatally. Strikingly, follicles lacking Ctnnb1 failed to develop beyond the primary stage. These results show that RSPO2 acts in a paracrine manner to sustain granulosa cell proliferation in early developing follicles. Taken together, our data demonstrate that the activation of WNT/CTNNB1 signaling by RSPO2 is essential for oocyte-granulosa cell interactions that drive maturation of the ovarian follicles and eventually female fertility.

Unveiling synapse pathology in spinal bulbar muscular atrophy by genome-wide transcriptome analysis of purified motor neurons derived from disease specific iPSCs

Spinal bulbar muscular atrophy (SBMA) is an adult-onset, slowly progressive motor neuron disease caused by abnormal CAG repeat expansion in the androgen receptor (AR) gene. Although ligand (testosterone)-dependent mutant AR aggregation has been shown to play important roles in motor neuronal degeneration by the analyses of transgenic mice models and in vitro cell culture models, the underlying disease mechanisms remain to be fully elucidated because of the discrepancy between model mice and SBMA patients. Thus, novel human disease models that recapitulate SBMA patients’ pathology more accurately are required for more precise pathophysiological analysis and the development of novel therapeutics. Here, we established disease specific iPSCs from four SBMA patients, and differentiated them into spinal motor neurons. To investigate motor neuron specific pathology, we purified iPSC-derived motor neurons using flow cytometry and cell sorting based on the motor neuron specific reporter, HB9e438::Venus, and proceeded to the genome-wide transcriptome analysis by RNA sequences. The results revealed the involvement of the pathology associated with synapses, epigenetics, and endoplasmic reticulum (ER) in SBMA. Notably, we demonstrated the involvement of the neuromuscular synapse via significant upregulation of Synaptotagmin, R-Spondin2 (RSPO2), and WNT ligands in motor neurons derived from SBMA patients, which are known to be associated with neuromuscular junction (NMJ) formation and acetylcholine receptor (AChR) clustering. These aberrant gene expression in neuromuscular synapses might represent a novel therapeutic target for SBMA.

Production, purification and characterization of recombinant human R-spondin1 (RSPO1) protein stably expressed in human HEK293 cells

BackgroundThe R-Spondin proteins comprise a family of secreted proteins, known for their important roles in cell proliferation, differentiation and death, by inducing the Wnt pathway. Several studies have demonstrated the importance of RSPOs in regulation of a number of tissue-specific processes, namely: bone formation, skeletal muscle tissue development, proliferation of pancreatic β-cells and intestinal stem cells and even cancer. RSPO1 stands out among RSPOs molecules with respect to its potential therapeutic use, especially in the Regenerative Medicine field, due to its mitogenic activity in stem cells. Here, we generated a recombinant human RSPO1 (rhRSPO1) using the HEK293 cell line, obtaining a purified, characterized and biologically active protein product to be used in Cell Therapy. The hRSPO1 coding sequence was synthesized and subcloned into a mammalian cell expression vector. HEK293 cells were stably co-transfected with the recombinant expression vector containing the hRSPO1 coding sequence and a hygromycin resistance plasmid, selected for hygror and subjected to cell clones isolation.ResultsrhRSPO1 was obtained, in the absence of serum, from culture supernatants of transfected HEK293 cells and purified using a novel purification strategy, involving two sequential chromatographic steps, namely: heparin affinity chromatography, followed by a molecular exclusion chromatography, designed to yield a high purity product. The purified protein was characterized by Western blotting, mass spectrometry and in vitro (C2C12 cells) and in vivo (BALB/c mice) biological activity assays, confirming the structural integrity and biological efficacy of this human cell expression system. Furthermore, rhRSPO1 glycosylation analysis allowed us to describe, for the first time, the glycan composition of this oligosaccharide chain, confirming the presence of an N-glycosylation in residue Asn137 of the polypeptide chain, as previously described. In addition, this analysis revealing the presence of glycan structures such as terminal sialic acid, N-acetylglucosamine and/or galactose.ConclusionTherefore, a stable platform for the production and purification of recombinant hRSPO1 from HEK293 cells was generated, leading to the production of a purified, fully characterized and biologically active protein product to be applied in Tissue Engineering.

Expression of FOXL2 and RSPO1 in Hen Ovarian Follicles and Implication of Exogenous Leptin in Modulating Their mRNA Expression in In Vitro Cultured Granulosa Cells.

Simple SummaryIn highly efficient laying hens, such as in commercial layer lines, the development of follicles is mainly characterized by an organized follicular hierarchy. Leptin has been implicated in the modulation of female reproduction in vertebrate animals. Forkhead box L2 (FOXL2) and R-spondin1 (RSPO1) have also been implicated in the regulation of ovarian functions and the development of follicles. In this study, using a laying hen model, we observed abundant mRNA expression of FOXL2 and RSPO1 in small (prehierarchical) and large (hierarchical) follicles, respectively. FOXL2 mRNA expression was stable in granulosa cells harvested from 3–5 mm to F4 follicles, and exhibited a significantly higher expression in large hierarchical follicles. However, theca cells exhibited a significantly higher mRNA expression of RSPO1 in F4 to F1 follicles. In subsequent experiment, we observed that 100 ng/mL leptin significantly modulated FOXL2 and RSPO1 expression in cultured granulosa cells harvested from large hierarchical and small prehierarchical follicles. These findings reasonably suggest that FOXL2 and RSPO1 genes may have a role in modulating the ovarian mechanisms, possibly affecting follicle growth and selection in laying hens. In addition, we demonstrated that leptin administration to granulosa cells in vitro modulated FOXL2 and RSPO1 expression, suggesting an implication of leptin in the follicular development and steroidogenesis in laying hens. However, further focused studies are warranted to improve our understanding of the exact roles played by these genes in follicle development and selection in laying hens.In this study, using a laying hen model, we determined the expression of FOXL2 and RSPO1 in different central and peripheral tissue and ovarian follicles at different stages of development. At the same time, mRNA expression of both genes in granulosa and theca cells harvested from follicles at different stages of folliculogenesis was also evaluated. Finally, we assessed the effect of leptin treatment on expression of FOXL2 and RSPO1 in in vitro cultured granulosa cells harvested from 1–5 mm to F3–F1 follicles. Our RT-qPCR results revealed that a comparatively higher expression of FOXL2 and RSPO1 was observed in ovary, hypothalamus, and pituitary. Abundant mRNA expression of FOXL2 was observed in small prehierarchical follicles (1–1.9 and 2–2.9 mm follicles; p < 0.05), whereas mRNA expression of RSPO1 showed an increasing trend in large hierarchical follicles (F5–F1), and its abundant expression was observed in post-ovulatory follicles. FOXL2 mRNA expression was stable in granulosa cells harvested from 3–5 mm to F4 follicles, and exhibited a significantly higher expression in large hierarchical follicles. Conversely, relatively low mRNA expression of FOXL2 was observed in theca cells. RSPO1 mRNA expression was relatively lower in granulosa cells; however, theca cells exhibited a significantly higher mRNA expression of RSPO1 in F4 to F1 follicles. In the next experiment, we treated the in vitro cultured granulosa cells with different concentrations (1, 10, 100, and 1000 ng/mL) of exogenous leptin. Compared to the control group, a significant increase in the expression of FOXL2 was observed in groups treated with 1, 10, and 100 ng/mL leptin, whereas expression of RSPO1 was increased in all leptin-treated groups. When treated with 100 ng/mL leptin, FOXL2 and RSPO1 expression was upregulated in cultured granulosa cells harvested from both large hierarchical (F3–F1) and small prehierarchical follicles (1–5 mm). Based on these findings and evidence from mainstream literature, we envisage that FOXL2 and RSPO1 genes (in connection with hypothalamic-hypophysis axis) and leptin (via modulation of FOXL2 and RSPO1 expression) might have significant physiological roles, at least in part, in modulating the ovarian mechanisms, such as follicle development, selection, and steroidogenesis in laying hens.

Ectonucleotide pyrophosphatase 2 (ENPP2) plays a crucial role in myogenic differentiation through the regulation by WNT/β-Catenin signaling.

Ectonucleotide pyrophosphate phosphodiesterase type II (ENPP2), also known as Autotaxin (ATX), is an enzyme present in blood circulation that converts lysophosphatidyl choline (LPC) to lysophosphatidic acid (LPA). While LPA has been demonstrated to play diverse roles in skeletal myogenesis, mainly through in vitro studies, the role of ENPP2 in skeletal myogenesis has not been determined. We previously found that Enpp2 is induced by a positive WNT/β-Catenin signaling regulator, R-spondin2 (RSPO2), in C2C12 myoblast cells. As RSPO2 promotes myogenic differentiation via the WNT/β-Catenin signaling pathway, we hypothesized that ENPP2 may act as a key mediator for the crosstalk between WNT and LPA signaling during myogenic differentiation. Herein, we found that ENPP2 function is essential for myogenic differentiation in C2C12 cells. Pharmacological ENPP2 inhibitors or RNAi-mediated Enpp2 gene knockdown severely impaired the myogenic differentiation, including the cell fusion process, whereas administration of the recombinant ENPP2 protein enhanced myogenic differentiation. Consistent with the in vitro results, mice lacking the Enpp2 gene showed a disrupted muscle regeneration after acute muscle injury. The size of newly regenerated myofibers in Enpp2 mutant muscle was significantly reduced compared with wild-type regenerated muscle. Modified expression patterns of myogenic markers in Enpp2 mutant muscle further emphasized the impaired muscle regeneration process. Finally, we convincingly demonstrate that the Enpp2 gene is a direct transcriptional target for WNT/β-Catenin signaling. Functional TCF/LEF1 binding sites within the upstream region of Enpp2 gene were identified by chromatin immunoprecipitation using anti-β-Catenin antibodies and reporter assay. Our study reveals that ENPP2 is regulated by WNT/β-Catenin signaling and plays a key positive role in myogenic differentiation.

Rapid chromosomal evolution in enigmatic mammal with XX in both sexes, the Alay mole vole Ellobiusalaicus Vorontsov et al., 1969 (Mammalia, Rodentia).

Evolutionary history and taxonomic position for cryptic species may be clarified by using molecular and cytogenetic methods. The subterranean rodent, the Alay mole vole Ellobiusalaicus Vorontsov et al., 1969 is one of three sibling species constituting the subgenus Ellobius Fischer, 1814, all of which lost the Y chromosome and obtained isomorphic XX sex chromosomes in both males and females. E.alaicus is evaluated by IUCN as a data deficient species because their distribution, biology, and genetics are almost unknown. We revealed specific karyotypic variability (2n = 52–48) in E.alaicus due to different Robertsonian translocations (Rbs). Two variants of hybrids (2n = 53, different Rbs) with E.tancrei Blasius, 1884 were found at the Northern slopes of the Alay Ridge and in the Naryn district, Kyrgyzstan. We described the sudden change in chromosome numbers from 2n = 50 to 48 and specific karyotype structure for mole voles, which inhabit the entrance to the Alay Valley (Tajikistan), and revealed their affiliation as E.alaicus by cytochrome b and fragments of nuclear XIST and Rspo1 genes sequencing. To date, it is possible to expand the range of E.alaicus from the Alay Valley (South Kyrgyzstan) up to the Ferghana Ridge and the Naryn Basin, Tien Shan at the north-east and to the Pamir-Alay Mountains (Tajikistan) at the west. The closeness of E.tancrei and E.alaicus is supported, whereas specific chromosome and molecular changes, as well as geographic distribution, verified the species status for E.alaicus. The case of Ellobius species accented an unevenness in rates of chromosome and nucleotide changes along with morphological similarity, which is emblematic for cryptic species.

Apoptosis of mesenchymal stem cells is regulated by Rspo1 via the Wnt/β-catenin signaling pathway

ObjectiveThe aim of this study was to investigate the effect and possible mechanism of action of roof plate-specific spondin1 (Rspo1) in the apoptosis of rat bone marrow mesenchymal stem cells (BMSCs). MethodsOsteogenic and adipogenic differentiation of BMSCs was identified by Alizarin Red and Oil Red O staining, respectively. BMSC surface markers (cluster of differentiation 29 [CD29], CD90, and CD45) were detected using flow cytometry. BMSCs were transfected with an adenoviral vector encoding Rspo1 (BMSCs-Rspo1 group). The expression levels of Rspo1 gene and Rspo1 protein in the BMSCs-Rspo1 group and the two control groups (untransfected BMSCs group and BMSCs-green fluorescent protein [GFP] group) were analyzed and compared by quantitative polymerase chain reaction and Western blot. The occurrence of apoptosis in the three groups was detected by flow cytometry and acridine orange-ethidium bromide (AO-EB) double dyeing. The activity of the Wnt/β-catenin signaling pathway was evaluated by measuring the expression levels of the key proteins of the pathway (β-catenin, c-Jun N-terminal kinase [JNK], and phospho-JNK). ResultsOsteogenic and adipogenic differentiation was confirmed in cultured BMSCs by the positive expression of CD29 and CD90 and the negative expression of CD45. Significantly increased expression levels of Rspo1 protein in the BMSCs-Rspo1 group compared to those in the BMSCs (0.60 ± 0.05 vs. 0.13 ± 0.02; t=95.007, P=0.001) and BMSCs-GFP groups (0.60 ± 0.05 vs. 0.10 ± 0.02; t=104.842, P=0.001) were observed. The apoptotic rate was significantly lower in the BMSCs-Rspo1 group compared with those in the BMSCs group ([24.06 ± 2.37]% vs. [40.87 ± 2.82]%; t = 49.872, P = 0.002) and the BMSCs-GFP group ([24.06 ± 2.37]% vs. [42.34 ± 0.26]%; t = 62.358, P = 0.001). In addition, compared to the BMSCs group, the protein expression levels of β-catenin (2.67 ± 0.19 vs. 1.14 ± 0.14; t = −9.217, P = 0.000) and JNK (1.87 ± 0.17 vs. 0.61 ± 0.07; t = −22.289, P = 0.000) were increased in the BMSCs-Rspo1 group. Compared to the BMSCs-GFP group, the protein expression levels of β-catenin (2.67 ± 0.19 vs. 1.44 ± 0.14; t = −5.692, P = 0.000) and JNK (1.87 ± 0.17 vs. 0.53 ± 0.06; t = −10.589, P = 0.000) were also upregulated in the BMSCs-Rspo1 group. Moreover, the protein expression levels of phospho-JNK were increased in the BMSCs-Rspo1 group compared to those in the BMSCs group (1.89 ± 0.10 vs. 0.63 ± 0.09; t = −8.975, P = 0.001) and the BMSCs-GFP group (1.89 ± 0.10 vs. 0.69 ± 0.08; t = −9.483, P = 0.001). ConclusionThe Wnt/β-catenin pathway could play a vital role in the Rspo1-mediated inhibition of apoptosis in BMSCs.

Altered R-spondin 1/CART neurocircuit in the hypothalamus contributes to hyperphagia in diabetes.

Hyperphagia is common in diabetes and may worsen hyperglycemia and diabetic complications. The responsible mechanisms are not well understood. The hypothalamus is a key center for the control of appetite and energy homeostasis. The ventromedial nucleus (VMH) and arcuate nucleus (ARC) are two critical nuclei involved in these processes. We have reported that R-spondin 1 (Rspo1) and its receptor leucin-rich repeat and G protein-coupled receptor 4 (LGR4) in the VMH and ARC suppressed appetite, but the downstream neuronal pathways are unclear. Here we show that neurons containing cocaine and amphetamine-regulated transcript (CART) in ARC express both LGR4 and insulin receptor; intracerebroventricular injection of Rspo1 induced c-Fos expression in CART neurons of ARC; and silencing CART in ARC attenuated the anorexigenic actions of Rspo1. In diabetic and obese fa/fa rats, Rspo1 mRNA in VMH and CART mRNA in ARC were reduced; this was accompanied by increased food consumption. Insulin treatment restored Rspo1 and CART gene expressions and normalized eating behavior. Chronic intracerebroventricular injection of Rspo1 inhibited food intake and normalized diabetic hyperphagia; intracerebroventricular injection of Rspo1 or insulin increased CART mRNA in ARC. In the CART neuron cell line, Rspo1 and insulin potentiated each other on pERK and β-catenin, and in rats, they acted synergistically to inhibit food intake. Silencing Rspo1 in VMH reduced CART expression in ARC and attenuated the inhibitory effect of insulin on food intake. In conclusion, our data indicated that CART works downstream of Rspo1 and Rspo1 mediated the action of insulin centrally. The altered Rspo1/CART neurocircuit in the hypothalamus contributes to hyperphagia in diabetes. NEW & NOTEWORTHY This study reports that cocaine and amphetamine-regulated transcript (CART) neurons in the arcuate nucleus (ARC) of hypothalamus acted downstream of R-spondin 1 (Rspo1) to inhibit food intake. The Rspo1 mRNA level in ventromedial nucleus (VMH) and CART mRNA level in ARC were reduced in type 1 diabetic rat and obese fa/fa rat. Rspo1 and insulin acted synergistically on phospho-ERK and β-catenin signal pathways and in suppressing food intake. The current results proposed that altered Rspo1/CART neurocircuit in the hypothalamus contributes to hyperphagia in diabetes.

Effect of exogenous hormones on R-spondin 1 (RSPO1) gene expression and embryo development in Pelodiscus sinensis.

Little is known about sex determination and differentiation in the Chinese soft-shelled turtle Pelodiscus sinensis. R-Spondin 1 (RSPO1), a candidate sex-determining gene, is an important regulator of ovarian differentiation in animals. Exogenous drugs can affect sex differentiation. In this study we cloned the RSPO1 gene from P. sinensis (psRSPO1) and analysed its expression profile. The psRSPO1 gene exhibited sequence identity with RSPO1 genes from other species. RSPO1 protein-based phylogenetic analysis showed that psRSPO1 in P. sinensis is closely related to RSPO1 proteins from other turtles. psRSPO1 showed abundant expression in adult brain and gonads, with higher levels in females than males. We also evaluated the effects of three finaconcentration of 2.5, 5.0 and 10mgmL-1 exogenous oestradiol (E2) and aromatase inhibitor (letrozole) on the expression of psRSPO1, external embryo morphology, growth status of embryos and the sex ratio when the drugs were injected to eggs during incubation. The expression of psRSPO1 was upregulated and downregulated by exogenous oestradiol and letrozole respectively, despite inconsistent expression trends at different embryo development times. External embryo morphology, growth status and sex ratio were affected by both exogenous oestradiol and the aromatase inhibitor. Feminisation was induced by oestradiol, but inhibited by letrozole. These results will contribute to studies of the potential molecular mechanisms underlying sex differentiation and sex control in the Chinese soft-shelled turtle.

RSPO2 enhances cell invasion and migration via the WNT/β-catenin pathway in human gastric cancer.

R-spondins comprise a group of secreted WNT agonists. R-spondin2 (RSPO2) plays a crucial role in the activation of the WNT/β-catenin pathway and oncogenesis, though its specific role in human gastric cancer (GC) remains unclear. In the current study, RSPO2 expression levels were upregulated in cancer specimens and cell lines (AGS and BGC-823). Inhibition of RSPO2 expression levels had distinct effects on cell invasion, migration, and epithelial-mesenchymal transition (EMT) in AGS and BGC-823 cells in vitro. Furthermore, RSPO2 positively correlated with leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), the receptor of RSPO2. Silencing RSPO2 reduced the expression of LGR5 and WNT/β-catenin effector molecule β-catenin together with downstream targets TCF-4 and Cyclin-D1. These observations demonstrate that upregulation of RSPO2 in GC specimens and cell lines is closely related to tumor invasion and migration and that RSPO2 promotes EMT in gastric cancer cells by activating WNT/β-catenin signaling.

Serum R-Spondin 1 Is a New Surrogate Marker for Obesity and Insulin Resistance.

BackgroundRecent in vivo studies indicated that R-spondin 1 (RSPO1) regulates food intake and increases insulin secretion, but its role in humans remains unknown. This study investigated the association between serum levels of RSPO1 and diverse metabolic parameters in humans.MethodsThe study population consisted of 43 subjects with newly diagnosed diabetes mellitus, and 79 non-diabetic participants. Serum levels of RSPO1 were measured using the enzyme-linked immunosorbent assay. The relationships between circulating RSPO1 and diverse metabolic parameters were analyzed.ResultsCirculating RSPO1 levels increased to a greater extent in the obese group than in the lean group. Moreover, serum levels of RSPO1 were higher in the insulin-resistant group than in the insulin-sensitive group. Serum levels of RSPO1 were significantly correlated with a range of metabolic parameters including body mass index, fasting C-peptide, homeostasis model assessment of insulin resistance index, and lipid profile. Moreover, levels were significantly associated with insulin resistance and obesity in non-diabetic subjects.ConclusionThis study demonstrated the association between serum levels of RSPO1 and a range of metabolic parameters in humans. Serum levels of RSPO1 are significantly related to obesity and insulin resistance, although the precise mechanisms remain unknown.

R-spondin 2 promotes osteoblastic differentiation of immature human periodontal ligament cells through the Wnt/β-catenin signaling pathway.

In this study, we measured the expression of R-spondin 2 (RSPO2) in periodontal ligament (PDL) tissue and cells. Further, we examined the effects of RSPO2 on osteoblastic differentiation of immature human PDL cells (HPDLCs). R-spondin (RSPO) family proteins are secreted glycoproteins that play important roles in embryonic development and tissue homeostasis through activation of the Wnt/β-catenin signaling pathway. RSPO2, a member of the RSPO family, has been reported to enhance osteogenesis in mice. However, little is known regarding the roles of RSPO2 in PDL tissues. Expression of RSPO2 in rat PDL tissue and primary HPDLCs was examined by immunohistochemical and immunofluorescence staining, as well as by semiquantitative RT-PCR. The effects of stretch loading on the expression of RSPO2 and Dickkopf-related protein 1 (DKK1) were assessed by quantitative RT-PCR. Expression of receptors for RSPOs, such as Leucine-rich repeat-containing G-protein-coupled receptors (LGRs) 4, 5, and 6 in immature human PDL cells (cell line 2-14, or 2-14 cells), was investigated by semiquantitative RT-PCR. Mineralized nodule formation in 2-14 cells treated with RSPO2 under osteoblastic inductive condition was examined by Alizarin Red S and von Kossa stainings. Nuclear translocation of β-catenin and expression of active β-catenin in 2-14 cells treated with RSPO2 were assessed by immunofluorescence staining and Western blotting analysis, respectively. In addition, the effect of Dickkopf-related protein 1 (DKK1), an inhibitor of Wnt/β-catenin signaling, was also examined. Rat PDL tissue and HPDLCs expressed RSPO2, and HPDLCs also expressed RSPO2, while little was found in 2-14 cells. Expression of RSPO2 as well as DKK1 in HPDLCs was significantly upregulated by exposure to stretch loading. LGR4 was predominantly expressed in 2-14 cells, which expressed low levels of LGR5 and LGR6. RSPO2 enhanced the Alizarin Red S and von Kossa-positive reactions in 2-14 cells. In addition, DKK1 suppressed nuclear translocation of β-catenin, activation of β-catenin, and increases of Alizarin Red S and von Kossa-positive reactions in 2-14 cells, all of which were induced by RSPO2 treatment. RSPO2, which is expressed in PDL tissue and cells, might play an important role in regulating the osteoblastic differentiation of immature human PDL cells through the Wnt/β-catenin signaling pathway.

Identification of RSPO2 Fusion Mutations and Target Therapy Using a Porcupine Inhibitor

Cancers are driven by a variety of somatic gene mutations and identifying these mutations enables the development of novel target drugs. We have sought to identify abnormalities in Wnt pathway-related genes that are sensitive to Wnt inhibitor treatment. We examined Patient Derived Xenograft (PDX) RNA samples and found new R-Spondin 2 (RSPO2) transcript fusions with the EMC2, PVT1 or HNF4G genes. These fusion events were identified in about 1.4% of the digestive system cancer samples. We then examined the oncogenic effects of the RSPO2-EMC2 fusion gene and confirmed that it can drive oncogenesis, sustain tumor growth and promote metastasis. Finally, we used a Wnt pathway Porcupine inhibitor CGX1321 to treat PDX mouse models containing RSPO2 fusion genes. All the RSPO2 fusion tumors responded to the treatment and stopped progression. Our data show that Wnt pathway inhibition could provide an effective treatment for cancers containing RSPO2 fusion. The RSPO2 fusion will serve as a good biomarker for screening patients to support clinical treatment of digestive system cancers using Wnt pathway inhibitors.

Abstract A055: RSPO3 overexpression is a characteristic feature of signet ring gastrointestinal malignancies

Abstract Introduction: The Wnt/β-catenin pathway is critical in the pathogenesis of many gastrointestinal malignancies, and, when disrupted, promotes aberrant cell proliferation and loss of cell stemness. Mutations in APC are the most common etiology of Wnt/β-catenin signaling dysfunction in colorectal (CRC) cancers. However, in the approximately 20% of CRCs that are APC wild-type, abnormalities in cell-surface genes like RNF43 and RSPO drive pathologic Wnt/β-catenin activity. We sought to characterize further gastrointestinal tumors harboring RSPO alterations. Methods: Under an IRB-approved protocol at MD Anderson, tumors from 665 patients with metastatic CRC at MD Anderson were evaluated by next-generation sequencing for APC mutations and for the presence of signet ring cells. Mutation profiling and gene expression data from the TCGA (www.cbioportal.org) were analyzed in 223 patients with CRC for APC mutations and for RSPO overexpression for a correlation using a Fisher’s exact test. RNA extracted from 19 separate frozen tumors from patients with confirmed signet ring metastatic CRC was next analyzed by RNA-seq for the presence for RSPO fusions and for RSPO gene expression levels. In a validation set of FFPE samples derived from patients with signet ring metastatic CRC or signet ring gastric adenocarcinomas, RSPO3 gene expression was analyzed using RT-PCR in a CLIA-validated setting (Oncomed Pharmaceuticals). Results: APC mutations were detected less frequently in signet ring CRC tumors relative to non-signet ring counterparts (18% vs. 56%, P&amp;lt; .001). RSPO overexpression was also observed more commonly in APC wild-type CRC tumors (16% vs. 7%, P= .04). Given these associations, we investigated further a correlation between signet ring adenocarcinomas and RSPO overexpression. Gene expression analysis of signet ring CRC tumors revealed high RSPO3 expression in 13 of 19 cases (68%). Here, a trend towards higher RSPO3 expression was observed in tumors with &amp;gt; 50% signet ring cells present (P=.20). In a validation cohort of patients with signet ring adenocarcinomas, RSPO3 overexpression was noted in 20/38 (52%) CRCs and 21/22 (96%) gastric adenocarcinomas. RSPO fusions were detected in 0 of 19 patients with signet ring CRC analyzed by RNA-seq. Conclusions: In molecularly specified populations of patients with colorectal and gastric malignancies, RSPO3 overexpression is detected in high frequencies in signet ring adenocarcinomas. Given the cell surface localization of RSPO3 and the importance of Wnt/β-catenin signaling in the tumorigenesis of gastrointestinal malignancies, our findings warrant further evaluation for anti-RSPO3 therapies as novel treatment options for patients with signet ring adenocarcinomas. Citation Format: Van Morris, Alexey Sorokin, Mariela Blum, Krittiya Korphaisarn, Jeannelyn Estrella, Leonardo Faoro, Min Wang, Stanley Hamilton, Ann M. Kapoun, Scott Kopetz. RSPO3 overexpression is a characteristic feature of signet ring gastrointestinal malignancies [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A055.

The RSPO3 gene as genetic markers for bone mass assessed by quantitative ultrasound in a population of young adults.

Ultrasound bone mass measurement has been postulated as a valuable bone-health assessment tool for primary care. The aim of this study was to analyse the possible relationship between the SPTBN1, RSPO3, CCDC170, DKK1, GPATCH1, and TMEM135 genes, with calcaneal quantitative ultrasound (QUS) in a population of young adults. These genes were first associated with broadband ultrasound attenuation (BUA) in the GEFOS/GENOMOS study. A cross-sectional study was conducted on 575 individuals (mean age 20.41 ± 2.69). Bone mass at the right calcaneus was estimated by QUS. Six single-nucleotide polymorphisms (SNPs) in SPTBN1 (rs11898505), RSPO3 (rs7741021), CCDC170 (rs4869739), DKK1 (rs7902708), TMEM135 (rs597319), and GPATCH1 (rs10416265) were selected as genetic markers based on their previous association with calcaneal QUS. After adjusting for multiple confounding factors, the only significant association with QUS in our population was found for the rs7741021 SNP in the RSPO3 gene (P=0.006) using the dominant model of inheritance. This suggests the possible implication of the RSPO3 gene in bone mass acquisition during early adulthood.

R-Spondin1/LGR5 Activates TGFβ Signaling and Suppresses Colon Cancer Metastasis.

Leucine-rich repeat containing G-protein-coupled receptor 5 (LGR5), an intestinal stem cell marker, is known to exhibit tumor suppressor activity in colon cancer, the mechanism of which is not understood. Here we show that R-spondin 1 (RSPO1)/LGR5 directly activates TGFβ signaling cooperatively with TGFβ type II receptor in colon cancer cells, enhancing TGFβ-mediated growth inhibition and stress-induced apoptosis. Knockdown of LGR5 attenuated downstream TGFβ signaling and increased cell proliferation, survival, and metastasis in an orthotopic model of colon cancer in vivo Upon RSPO1 stimulation, LGR5 formed complexes with TGFβ receptors. Studies of patient specimens indicate that LGR5 expression was reduced in advanced stages and positively correlated with markers of TGFβ activation in colon cancer. Our study uncovers a novel cross-talk between LGR5 and TGFβ signaling in colon cancer and identifies LGR5 as a new modulator of TGFβ signaling able to suppress colon cancer metastasis. Cancer Res; 77(23); 6589-602. ©2017 AACR.

Expression pattern and functional analysis of R-spondin1 in tongue sole Cynoglossus semilaevis

R-spondin 1 (Rspo1) is a potential female-determining gene in mammals that could regulate the Wnt/β-catenin signaling pathway. The deletion of Rspo1 causes sex reversal in females. To investigate sexual determination and differentiation, we cloned and analyzed the Rspo1 gene in Cynoglossus semilaevis. Phylogenetic and gene structure analyses revealed that Rspo1 gene exhibited high sequence conservation and contained an N-terminal signal peptide, two furin-like cysteine-rich domains (FU1 and FU2), a thrombospondin type 1 repeat, and a C-terminal region enriched with basic charged amino acids. qRT-PCR revealed that Rspo1 expressed sexual dimorphism in gonad, with higher expression levels in the ovary than in the testis, thus, suggesting the involvement of Rspo1 in gonad differentiation. In situ hybridization results demonstrated that Rspo1 was expressed in premature germ cells, including spermatogonia and spermatocytes in the testis and stage II and stage III oocytes in the ovary. The methylation levels in two CpG sites of Rspo1 promoter significantly differed among females, males, and pseudomales. After 30days of exposure to high temperature, the expression of Rspo1 significantly decreased in female individuals, some of which were prone to males. However, no difference of Rspo1 gene expression was observed between the control group and high-temperature group in males. These preliminary findings suggested that Rspo1 played a crucial role in sex determination and development. This study laid the groundwork for further sex control breeding techniques in C. semilaevis.

RSPO3 antagonism inhibits growth and tumorigenicity in colorectal tumors harboring common Wnt pathway mutations

Activating mutations in the Wnt pathway are a characteristic feature of colorectal cancer (CRC). The R-spondin (RSPO) family is a group of secreted proteins that enhance Wnt signaling and RSPO2 and RSPO3 gene fusions have been reported in CRC. We have previously shown that Wnt pathway blockers exhibit potent combinatorial activity with taxanes to inhibit tumor growth. Here we show that RSPO3 antagonism synergizes with paclitaxel based chemotherapies in patient-derived xenograft models (PDX) with RSPO3 fusions and in tumors with common CRC mutations such as APC, β-catenin, or RNF43. In these latter types of tumors that represent over 90% of CRC, RSPO3 is produced by stromal cells in the tumor microenvironment and the activating mutations appear to sensitize the tumors to Wnt-Rspo synergy. The combination of RSPO3 inhibition and taxane treatment provides an approach to effectively target oncogenic WNT signaling in a significant number of patients with colorectal and other intestinal cancers.

Search for Genetic Modifiers of PSC: Time to Increase the Number of Needles in the Haystack

Primary sclerosing cholangitis (PSC) belongs to the most obscure liver diseases. Patients with progressive PSC require liver transplantation as only therapeutic option. Previously several HLA- and non-HLA-associated PSC risk variants have been discovered, however their involvement in the development of PSC seems to be minor in comparison to environmental determinants. Lately, variant rs853974 at the RSPO3 gene locus has been shown to modulate the course of PSC. Here we briefly discuss the phenotypes related to this polymorphism and propose alternative directions of research that might help to identify new genetic modifiers of PSC progression.