Publications by authors named "Gunsmaa Nyamsuren"

8 Publications

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Perturbed differentiation of murine embryonic stem cells upon Pelota deletion due to dysregulated FOXO1/β-catenin signaling.

FEBS J 2020 Nov 27. Epub 2020 Nov 27.

Institute of Human Genetics, University Medical Centre, Göttingen, Germany.

Differentiation of the embryonic stem cells (ESCs) is regulated by a variety of different signaling pathways. Genetic depletion of murine Pelota gene (Pelo) leads to early embryonic lethality. Here, we aimed at determining the embryonic stage and deciphering the dysregulated signaling pathways affected upon Pelo deletion. We found that development of PELO-null embryos is perturbed between the embryonic day E4.5 and E5.5, at which first differentiation process of ESCs takes place. Molecular analysis revealed enhanced activity of phosphoinositide 3-kinase-protein kinase B/ AKT (PI3K-PKB/AKT) signaling, but nuclear accumulation of forkhead box O1 (FOXO1), and upregulation of the pluripotency-related gene, Oct4, in mutant ESCs cultured under differentiation condition. Despite increased levels of nuclear β-catenin in PELO-null ESCs as a result of decreased activity of glycogen synthase kinase-3β, the activity of the canonical Wingless (Wnt)/β-catenin/T cell factor (TCF) was significantly attenuated as judged by the promoter reporter assay, downregulated Wnt/β-catenin target genes, and impaired cell proliferation. Interestingly, we demonstrated an increased binding of β-catenin to FOXO1 in PELO-mutant ESCs cultured under differentiation condition that could explain, on one side, the nuclear accumulation of FOXO1 protein and hence persistent pluripotency of PELO-mutant ESCs, and on the other side, the dysregulated transcriptional activity of β-catenin/TCF and therefore attenuated PELO-null ESCs self-renewal. Taken together, our results strongly suggest that PELO deletion averts ESCs differentiation through promoting FOXO1/β-catenin binding with subsequent dysregulation of FOXO1 and canonical β-catenin/TCF signaling pathways.
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http://dx.doi.org/10.1111/febs.15643DOI Listing
November 2020

Modulation of NCAM/FGFR1 signaling suppresses EMT program in human proximal tubular epithelial cells.

PLoS One 2018 1;13(11):e0206786. Epub 2018 Nov 1.

Institute of Pathology, University of Belgrade-Faculty of Medicine, Belgrade, Serbia.

Neural cell adhesion molecule (NCAM) and fibroblast growth factor receptor 1 (FGFR1) cross-talk have been involved in epithelial-to-mesenchymal transition (EMT) process during carcinogenesis. Since EMT also contributes to maladaptive repair and parenchymal damage during renal fibrosis, we became encouraged to explore the role of NCAM/FGFR1 signaling as initiating or driving forces of EMT program in cultured human proximal tubular epithelial cells (TECs). TECs stimulated with TGF-β1 (10ng/mL) was used as an established in vitro EMT model. TGF-β1 downstream effectors were detected in vitro, as well as in 50 biopsies of different human kidney diseases to explore their in vivo correlation. NCAM/FGFR1 signaling and its modulation by FGFR1 inhibitor PD173074 (100nM) were analyzed by light microscopy, immunolabeling, qRT-PCR and scratch assays. Morphological changes associated with EMT appeared 48h after TGF-ß1 treatment and was clearly apparent after 72 hours, followed by loss of CDH1 (encoding E-Cadherin) and transcriptional induction of SNAI1 (SNAIL), SNAI2 (SLUG), TWIST1, MMP2, MMP9, CDH2 (N-Cadherin), ITGA5 (integrin-α5), ITGB1 (integrin-β1), ACTA2 (α-SMA) and S100A4 (FSP1). Moreover, at the early stage of EMT program (24 hours upon TGF-β1 exposure), transcriptional induction of several NCAM isoforms along with FGFR1 was observed, implicating a mechanistic link between NCAM/FGFR1 signaling and induction of EMT. These assumptions were further supported by the inhibition of the EMT program after specific blocking of FGFR1 signaling by PD173074. Finally, there was evidence for an in vivo TGF-β1 pathway activation in diseased human kidneys and correlation with impaired renal excretory functions. Collectively, NCAM/FGFR1 signaling appears to be involved in the initial phase of TGF-ß1 initiated EMT which can be effectively suppressed by application of FGFR inhibitor.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0206786PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6211750PMC
April 2019

Pharmacological induction of hypoxia-inducible transcription factor ARNT attenuates chronic kidney failure.

J Clin Invest 2018 07 11;128(7):3053-3070. Epub 2018 Jun 11.

Department of Nephrology and Rheumatology.

Progression of chronic kidney disease associated with progressive fibrosis and impaired tubular epithelial regeneration is still an unmet biomedical challenge because, once chronic lesions have manifested, no effective therapies are available as of yet for clinical use. Prompted by various studies across multiple organs demonstrating that preconditioning regimens to induce endogenous regenerative mechanisms protect various organs from later incurring acute injuries, we here aimed to gain insights into the molecular mechanisms underlying successful protection and to explore whether such pathways could be utilized to inhibit progression of chronic organ injury. We identified a protective mechanism controlled by the transcription factor ARNT that effectively inhibits progression of chronic kidney injury by transcriptional induction of ALK3, the principal mediator of antifibrotic and proregenerative bone morphogenetic protein-signaling (BMP-signaling) responses. We further report that ARNT expression itself is controlled by the FKBP12/YY1 transcriptional repressor complex and that disruption of such FKBP12/YY1 complexes by picomolar FK506 at subimmunosuppressive doses increases ARNT expression, subsequently leading to homodimeric ARNT-induced ALK3 transcription. Direct targeting of FKBP12/YY1 with in vivo morpholino approaches or small molecule inhibitors, including GPI-1046, was equally effective for inducing ARNT expression, with subsequent activation of ALK3-dependent canonical BMP-signaling responses and attenuated chronic organ failure in models of chronic kidney disease, and also cardiac and liver injuries. In summary, we report an organ-protective mechanism that can be pharmacologically modulated by immunophilin ligands FK506 and GPI-1046 or therapeutically targeted by in vivo morpholino approaches.
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http://dx.doi.org/10.1172/JCI89632DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6025987PMC
July 2018

Pelota Regulates Epidermal Differentiation by Modulating BMP and PI3K/AKT Signaling Pathways.

J Invest Dermatol 2016 08 7;136(8):1664-1671. Epub 2016 May 7.

Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany. Electronic address:

The depletion of evolutionarily conserved pelota protein causes impaired differentiation of embryonic and spermatogonial stem cells. In this study, we show that temporal deletion of pelota protein before epidermal barrier acquisition leads to neonatal lethality due to perturbations in permeability barrier formation. Further analysis indicated that this phenotype is a result of failed processing of profilaggrin into filaggrin monomers, which promotes the formation of a protective epidermal layer. Molecular analyses showed that pelota protein negatively regulates the activities of bone morphogenetic protein and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathways in the epidermis. To address whether elevated activities of bone morphogenetic protein and PI3K/AKT signaling pathways were the cause for the perturbed epidermal barrier in Pelo-deficient mice, we made use of organotypic cultures of skin explants from control and mutant embryos at embryonic day 15.5. Inhibition of PI3K/AKT signaling did not significantly affect the bone morphogenetic protein activity. However, inhibition of bone morphogenetic protein signaling caused a significant attenuation of PI3K/AKT activity in mutant skin and, more interestingly, the restoration of profilaggrin processing and normal epidermal barrier function. Therefore, increased activity of the PI3K/AKT signaling pathway in Pelo-deficient skin might conflict with the dephosphorylation of profilaggrin and thereby affect its proper processing into filaggrin monomers and ultimately the epidermal differentiation.
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http://dx.doi.org/10.1016/j.jid.2016.04.020DOI Listing
August 2016

Pelota mediates gonocyte maturation and maintenance of spermatogonial stem cells in mouse testes.

Reproduction 2015 Mar 2;149(3):213-21. Epub 2014 Dec 2.

Institute of Human GeneticsUniversity Medical Center of Göttingen, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany

Pelota (Pelo) is an evolutionarily conserved gene, and its deficiency in Drosophila affects both male and female fertility. In mice, genetic ablation of Pelo leads to embryonic lethality at the early implantation stage as a result of the impaired development of extra-embryonic endoderm (ExEn). To define the consequences of Pelo deletion on male germ cells, we temporally induced deletion of the gene at both embryonic and postnatal stages. Deletion of Pelo in adult mice resulted in a complete loss of whole-germ cell lineages after 45 days of deletion. The absence of newly emerging spermatogenic cycles in mutants confirmed that spermatogonial stem cells (SSCs) were unable to maintain spermatogenesis in the absence of PELO protein. However, germ cells beyond the undifferentiated SSC stage were capable of completing spermatogenesis and producing spermatozoa, even in the absence of PELO. Following the deletion of Pelo during embryonic development, we found that although PELO is dispensable for maintaining gonocytes, it is necessary for the transition of gonocytes to SSCs. Immunohistological and protein analyses revealed the attenuation of FOXO1 transcriptional activity, which induces the expression of many SSC self-renewal genes. The decreased transcriptional activity of FOXO1 in mutant testes was due to enhanced activity of the PI3K/AKT signaling pathway, which led to phosphorylation and cytoplasmic sequestration of FOXO1. These results suggest that PELO negatively regulates the PI3K/AKT pathway and that the enhanced activity of PI3K/AKT and subsequent FOXO1 inhibition are responsible for the impaired development of SSCs in mutant testes.
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http://dx.doi.org/10.1530/REP-14-0391DOI Listing
March 2015

Epigenetic balance of aberrant Rasal1 promoter methylation and hydroxymethylation regulates cardiac fibrosis.

Cardiovasc Res 2015 Mar 23;105(3):279-91. Epub 2015 Jan 23.

Department of Cardiology and Pneumology, University Medical Center of Göttingen, Georg-August University, Robert-Koch-Str. 40, 37075 Göttingen, Germany German Center for Cardiovascular Research (DZHK), Partner Site Göttingen, Göttingen, Germany

Aims: Methylation of CpG island promoters is a prototypical epigenetic mechanism to stably control gene expression. The aim of this study was to elucidate the contribution of aberrant promoter DNA methylation in pathological endothelial to mesenchymal transition (EndMT) and subsequent cardiac fibrosis.

Methods And Results: In human coronary endothelial cells, TGFβ1 causes aberrant methylation of RASAL1 promoter, increased Ras-GTP activity, and EndMT. In end-stage failing vs. non-failing human myocardium, increased fibrosis was associated with significantly increased RASAL1 promoter methylation, decreased RASAL1 expression, increased Ras-GTP activity, and increased expression of markers of EndMT. In mice with pressure overload due to ascending aortic constriction, BMP7 significantly reduced RASAL1 promoter methylation, increased RASAL1 expression, and decreased EndMT markers as well as decreased cardiac fibrosis. The ten eleven translocation (TET) family enzyme TET3, which demethylates through hydroxymethylation, was significantly decreased in fibrotic mouse hearts, restored with BMP7, and BMP7 effects were absent in coronary endothelial cells with siRNA knockdown of TET3.

Conclusion: Our study provides proof-in-principle evidence that transcriptional suppression of RASAL1 through aberrant promoter methylation contributes to EndMT and ultimately to progression of cardiac fibrosis. Such aberrant methylation can be reversed through Tet3-mediated hydroxymethylation, which can be specifically induced by BMP7. This may reflect a new treatment strategy to stop cardiac fibrosis.
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http://dx.doi.org/10.1093/cvr/cvv015DOI Listing
March 2015

Pelota regulates the development of extraembryonic endoderm through activation of bone morphogenetic protein (BMP) signaling.

Stem Cell Res 2014 Jul 26;13(1):61-74. Epub 2014 Apr 26.

Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany. Electronic address:

Pelota (Pelo) is ubiquitously expressed, and its genetic deletion in mice leads to embryonic lethality at an early post-implantation stage. In the present study, we conditionally deleted Pelo and showed that PELO deficiency did not markedly affect the self-renewal of embryonic stem cells (ESCs) or their capacity to differentiate in teratoma assays. However, their differentiation into extraembryonic endoderm (ExEn) in embryoid bodies (EBs) was severely compromised. Conversely, forced expression of Pelo in ESCs resulted in spontaneous differentiation toward the ExEn lineage. Failure of Pelo-deficient ESCs to differentiate into ExEn was accompanied by the retained expression of pluripotency-related genes and alterations in expression of components of the bone morphogenetic protein (BMP) signaling pathway. Further experiments have also revealed that attenuated activity of BMP signaling is responsible for the impaired development of ExEn. The recovery of ExEn and down-regulation of pluripotent genes in BMP4-treated Pelo-null EBs indicate that the failure of mutant cells to down-regulate pluripotency-related genes in EBs is not a result of autonomous defect, but rather to failed signals from surrounding ExEn lineage that induce the differentiation program. In vivo studies showed the presence of ExEn in Pelo-null embryos at E6.5, yet embryonic lethality at E7.5, suggesting that PELO is not required for the induction of ExEn development, but rather for ExEn maintenance or for terminal differentiation toward functional visceral endoderm which provides the embryos with growth factors required for further development. Moreover, Pelo-null fibroblasts failed to reprogram toward induced pluripotent stem cells (iPSCs) due to inactivation of BMP signaling and impaired mesenchymal-to-epithelial transition. Thus, our results indicate that PELO plays an important role in the establishment of pluripotency and differentiation of ESCs into ExEn lineage through activation of BMP signaling.
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http://dx.doi.org/10.1016/j.scr.2014.04.011DOI Listing
July 2014

Adhesion protein VSIG1 is required for the proper differentiation of glandular gastric epithelia.

PLoS One 2011 4;6(10):e25908. Epub 2011 Oct 4.

Institute of Human Genetics, University of Göttingen, Göttingen, Germany.

VSIG1, a cell adhesion protein of the immunoglobulin superfamily, is preferentially expressed in stomach, testis, and certain gastric, esophageal and ovarian cancers. Here, we describe the expression patterns of three alternatively spliced isoforms of mouse Vsig1 during pre- and postnatal development of stomach and potential function of Vsig1 in differentiation of gastric epithelia. We show that isoforms Vsig1A and Vsig1B, which differ in the 3'untranslated region, are expressed in the early stages of stomach development. Immunohistochemical analysis revealed that VSIG1 is restricted to the adherens junction of the glandular epithelium. The shorter transcript Vsig1C is restricted to the testis, encodes an N-terminal truncated protein and is presumably regulated by an internal promoter, which is located upstream of exon 1b. To determine whether the 5' flanking region of exon 1a specifically targets the expression of Vsig1 to stomach epithelia, we generated and analyzed transgenic mice. The 4.8-kb fragment located upstream of exon 1a was sufficient to direct the expression of the reporter gene to the glandular epithelia of transgenic stomach. To determine the role of VSIG1 during the development of stomach epithelia, an X-linked Vsig1 was inactivated in embryonic stem cells (ESCs). Although Vsig1(-/Y) ESCs were only able to generate low coat color chimeric mice, no male chimeras transmitted the targeted allele to their progeny suggesting that the high contribution of Vsig1(-/Y) cells leads to the lethality of chimeric embryos. Analysis of chimeric stomachs revealed the differentiation of VSIG1-null cells into squamous epithelia inside the glandular region. These results suggest that VSIG1 is required for the establishment of glandular versus squamous epithelia in the stomach.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0025908PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3186807PMC
February 2012