| 1. |
- Fischer, Yvonne, et al.
(författare)
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NANOG reporter cell lines generated by gene targeting in human embryonic stem cells.
- 2010
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:9
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Pluripotency and self-renewal of human embryonic stem cells (hESCs) is mediated by a complex interplay between extra- and intracellular signaling pathways, which regulate the expression of pluripotency-specific transcription factors. The homeodomain transcription factor NANOG plays a central role in maintaining hESC pluripotency, but the precise role and regulation of NANOG are not well defined. METHODOLOGY/PRINCIPAL FINDINGS: To facilitate the study of NANOG expression and regulation in viable hESC cultures, we generated fluorescent NANOG reporter cell lines by gene targeting in hESCs. In these reporter lines, the fluorescent reporter gene was co-expressed with endogenous NANOG and responded to experimental induction or repression of the NANOG promoter with appropriate changes in expression levels. Furthermore, NANOG reporter lines facilitated the separation of hESC populations based on NANOG expression levels and their subsequent characterization. Gene expression arrays on isolated hESC subpopulations revealed genes with differential expression in NANOG(high) and NANOG(low) hESCs, providing candidates for NANOG downstream targets hESCs. CONCLUSION/SIGNIFICANCE: The newly derived NANOG reporter hESC lines present novel tools to visualize NANOG expression in viable hESCs. In future applications, these reporter lines can be used to elucidate the function and regulation of NANOG in pluripotent hESCs.
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| 2. |
- Håkansson, Joakim, 1975, et al.
(författare)
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Neural cell adhesion molecule-deficient beta-cell tumorigenesis results in diminished extracellular matrix molecule expression and tumour cell-matrix adhesion
- 2005
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Ingår i: Tumour Biology. - : Springer Science and Business Media LLC. - 1010-4283 .- 1423-0380. ; 26:2, s. 103-112
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Tidskriftsartikel (refereegranskat)abstract
- To understand by which mechanism neural cell adhesion molecule (N-CAM) limits beta tumour cell disaggregation and dissemination, we searched for potential downstream genes of N-CAM during beta tumour cell progression by gene expression profiling. Here, we show that N-CAM-deficient beta-cell tumorigenesis is associated with changes in the expression of genes involved in cell-matrix adhesion and cytoskeletal dynamics, biological processes known to affect the invasive and metastatic behaviour of tumour cells. The extracellular matrix (ECM) molecules emerged as the primary target, i.e. N-CAM deficiency resulted in down-regulated mRNA expression of a broad range of ECM molecules. Consistent with this result, deficient deposition of major ECM stromal components, such as fibronectin, laminin 1 and collagen IV, was observed. Moreover, N-CAM-deficient tumour cells displayed defective matrix adhesion. These results offer a potential mechanism for tumour cell disaggregation during N-CAM-deficient beta tumour cell progression. Prospective consequences of these findings for the role of N-CAM in beta tumour cell dissemination are discussed.
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| 3. |
- Li, Hongzhe, et al.
(författare)
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Early growth response 1 regulates hematopoietic support and proliferation in human primary bone marrow stromal cells
- 2020
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Ingår i: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 1592-8721 .- 0390-6078. ; 105:5, s. 1206-1215
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Tidskriftsartikel (refereegranskat)abstract
- Human bone marrow stromal cells are key elements of the hematopoietic environment and they play a central role in bone and bone marrow physiology. However, how key stromal cell functions are regulated is largely unknown. We analyzed the role of the immediate early response transcription factor EGR1 as key stromal cell regulator and found that EGR1 was highly expressed in prospectively-isolated primary bone marrow stromal cells, downregulated upon culture, and low in non-colony-forming CD45neg stromal cells. Furthermore, EGR1 expression was lower in proliferative regenerating adult and fetal primary cells compared to adult steady-state bone marrow stromal cells. Overexpression of EGR1 in stromal cells induced potent hematopoietic stroma support as indicated by an increased production of transplantable CD34+CD90+ hematopoietic stem cells in expansion co-cultures. The improvement of bone marrow stroma support function was mediated by increased expression of hematopoietic supporting genes, such as VCAM1 and CCL28. Furthermore, EGR1 overexpression markedly decreased stromal cell proliferation whereas EGR1 knockdown caused the opposite effects. These findings thus show that EGR1 is a key stromal transcription factor with a dual role in regulating proliferation and hematopoietic stroma support function that is controlling a genetic program to coordinate the specific functions of bone marrow stromal cells in their different biological contexts.
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| 4. |
- Olofsson, Charlotta S, 1971, et al.
(författare)
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Impaired insulin exocytosis in neural cell adhesion molecule-/- mice due to defective reorganization of the submembrane F-actin network.
- 2009
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Ingår i: Endocrinology. - : The Endocrine Society. - 1945-7170 .- 0013-7227. ; 150:7, s. 3067-75
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Tidskriftsartikel (refereegranskat)abstract
- The neural cell adhesion molecule (NCAM) is required for cell type segregation during pancreatic islet organogenesis. We have investigated the functional consequences of ablating NCAM on pancreatic beta-cell function. In vivo, NCAM(-/-) mice exhibit impaired glucose tolerance and basal hyperinsulinemia. Insulin secretion from isolated NCAM(-/-) islets is enhanced at glucose concentrations below 15 mM but inhibited at higher concentrations. Glucagon secretion from pancreatic alpha-cells evoked by low glucose was also severely impaired in NCAM(-/-) islets. The diminution of insulin secretion is not attributable to defective glucose metabolism or glucose sensing (documented as glucose-induced changes in intracellular Ca(2+) and K(ATP)-channel activity). Resting K(ATP) conductance was lower in NCAM(-/-) beta-cells than wild-type cells, and this difference was abolished when F-actin was disrupted by cytochalasin D (1 muM). In wild-type beta-cells, the submembrane actin network disassembles within 10 min during glucose stimulation (30 mM), an effect not seen in NCAM(-/-) beta-cells. Cytochalasin D eliminated this difference and normalized insulin and glucagon secretion in NCAM(-/-) islets. Capacitance measurements of exocytosis indicate that replenishment of the readily releasable granule pool is suppressed in NCAM(-/-) alpha- and beta-cells. Our data suggest that remodeling of the submembrane actin network is critical to normal glucose regulation of both insulin and glucagon secretion.
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| 5. |
- Pontén, Annica, et al.
(författare)
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FACS-Based Isolation, Propagation and Characterization of Mouse Embryonic Cardiomyocytes Based on VCAM-1 Surface Marker Expression.
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:12
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Tidskriftsartikel (refereegranskat)abstract
- Purification of cardiomyocytes from the embryonic mouse heart, embryonic stem (ES) or induced pluripotent stem cells (iPS) is a challenging task and will require specific isolation procedures. Lately the significance of surface markers for the isolation of cardiac cell populations with fluorescence activated cell sorting (FACS) has been acknowledged, and the hunt for cardiac specific markers has intensified. As cardiomyocytes have traditionally been characterized by their expression of specific transcription factors and structural proteins, and not by specific surface markers, this constitutes a significant bottleneck. Lately, Flk-1, c-kit and the cellular prion protein have been reported to specify cardiac progenitors, however, no surface markers have so far been reported to specify a committed cardiomyocyte. Herein show for the first time, that embryonic cardiomyocytes can be isolated with 98% purity, based on their expression of vascular cell adhesion molecule-1 (VCAM-1). The FACS-isolated cells express phenotypic markers for embryonic committed cardiomyocytes but not cardiac progenitors. An important aspect of FACS is to provide viable cells with retention of functionality. We show that VCAM-1 positive cardiomyocytes can be isolated with 95% viability suitable for in vitro culture, functional assays or expression analysis. In patch-clamp experiments we provide evidence of functionally intact cardiomyocytes of both atrial and ventricular subtypes. This work establishes that cardiomyocytes can be isolated with a high degree of purity and viability through FACS, based on specific surface marker expression as has been done in the hematopoietic field for decades. Our FACS protocol represents a significant advance in which purified populations of cardiomyocytes may be isolated and utilized for downstream applications, such as purification of ES-cell derived cardiomyocytes.
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| 6. |
- Ståhlberg, Anders, 1975, et al.
(författare)
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Properties of the reverse transcription reaction in mRNA quantification.
- 2004
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Ingår i: Clinical chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 50:3, s. 509-15
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In most measurements of gene expression, mRNA is first reverse-transcribed into cDNA. We studied the reverse transcription reaction and its consequences for quantitative measurements of gene expression. METHODS: We used SYBR green I-based quantitative real-time PCR (QPCR) to measure the properties of reverse transcription reaction for the beta-tubulin, glyceraldehyde-3-phosphate dehydrogenase, Glut2, CaV1D, and insulin II genes, using random hexamers, oligo(dT), and gene-specific reverse transcription primers. RESULTS: Experimental variation in reverse transcription-QPCR (RT-QPCR) was mainly attributable to the reverse transcription step. Reverse transcription efficiency depended on priming strategy, and the dependence was different for the five genes studied. Reverse transcription yields also depended on total RNA concentration. CONCLUSIONS: RT-QPCR gene expression measurements are comparable only when the same priming strategy and reaction conditions are used in all experiments and the samples contain the same total amount of RNA. Experimental accuracy is improved by running samples in (at least) duplicate starting with the reverse transcription reaction.
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| 7. |
- Tarnawski, Laura, et al.
(författare)
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Integrin Based Isolation Enables Purification of Murine Lineage Committed Cardiomyocytes
- 2015
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:8
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Tidskriftsartikel (refereegranskat)abstract
- In contrast to mature cardiomyocytes which have limited regenerative capacity, pluripotent stem cells represent a promising source for the generation of new cardiomyocytes. The tendency of pluripotent stem cells to form teratomas and the heterogeneity fromvarious differentiation stages and cardiomyocyte cell sub-types, however, are major obstacles to overcome before this type of therapy could be applied in a clinical setting. Thus, the identification of extracellularmarkers for specific cardiomyocyte progenitors and mature subpopulations is of particular importance. The delineation of cardiomyocyte surfacemarker patterns not only serves as a means to derive homogeneous cell populations by FACS, but is also an essential tool to understand cardiac development. By using single-cell expression profiling in early mouse embryonic hearts, we found that a combination of integrin alpha-1, alpha-5, alpha-6 and N-cadherin enables isolation of lineage committed murine cardiomyocytes. Additionally, we were able to separate trabecular cardiomyocytes from solid ventricular myocardium and atrial murine cells. These cells exhibit expected subtype specific phenotype confirmed by electrophysiological analysis. We show that integrin expression can be used for the isolation of living, functional and lineage-specific murine cardiomyocytes.
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| 8. |
- Xian, Xiaojie, 1971
(författare)
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Functional role of neural cell adhesion molecule in tumorigenesis and beta-cell function
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cancer metastasis is the main lethal cause for cancer patients today. It has been demonstrated that angiogenesis is crucial for growth of both primary tumors and metastasis. In Rip1Tag2 (RT) mice expression of SV40 large T antigen under the control of the rat insulin 1 promoter results in beta-cell specific tumors in the pancreatic islets of Langerhans. RT tumor progression involves hyperplasia, angiogenesis, adenoma and carcinoma formation, but no metastasis. The angiogenic switch, which occurs between 7-9 weeks of age, is instrumental in the transition from hyperplasia to tumors. The neural cell adhesion molecule (N-CAM) is a member of the immunoglobulin superfamily that mediates Ca2+-independent homophilic and heterophilic cell adhesion. By studying tumor progression in N-CAM-deficient (loss-of-function) Rip1Tag2 (RTNC/KO) mice, we recently showed that 50% of the animals developed metastases mainly to local lymph nodes but also to distant organs. Strikingly, re-expression of N-CAM 120 in beta tumor cells totally prevented metastases, indicating that N-CAM within beta tumor cells limits tumor cell dissemination. Here, we have addressed the underlying mechanism for N-CAM s role in tumor cell metastasis. We showed that RTNC/KO islets/tumors prematurely develop disturbed micro-vessel phenotypes, such as impaired pericyte--endothelial cell interaction, and that this phenotype correlated with increased blood vessel leakiness. Moreover, the continuity between blood filled cavities containing isolated cell clusters and the circulation in RTNC/KO provides a potential metastatic route for tumor cells. To further test the role of N-CAM in regulating the integration of perivascular cells into the vessel wall, we showed that ectopic expression of N-CAM (gain-of-function) in a skin fibrosarcoma (T241) tumor model resulted in improved pericyte recruitment and coverage in a tumor cell-autonomous manner. To test if pericyte dysfunction is causally involved in tumor cell dissemination, we intercrossed RT with a genetic mouse model for defective pericyte recruitment and investment into the micro-vessel wall (pdgf-bret/ret mice). Remarkably, RTpdgf-bret/ret mice developed metastasis into local lymph node and distant organ, providing the first evidence for a causal role of pericyte dysfunction in both haematogenous and lymphatic tumor cell dissemination. We also provide data which suggests that the way N-CAM influences pericyte-endothelial cell interactions is by regulating the perivascular distribution/composition of extracellular matrix components.Insulin is exclusively secreted by beta-cell in islets of Langerhans, loss of N-CAM function in islets led to impaired systemic glucose tolerance and insulin secretion. Our studies showed that exocytosis was significantly reduced in N-CAM-/- mice, and that this observation was associated with an unusually compact submembrane actin network. These results indicate that N-CAM plays a crucial role in insulin secretion by affecting the status of the submembrane actin network.
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| 9. |
- Xian, Xiaojie, et al.
(författare)
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Generation of gene-corrected functional osteoclasts from osteopetrotic induced pluripotent stem cells
- 2020
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Ingår i: Stem Cell Research & Therapy. - : Springer Science and Business Media LLC. - 1757-6512. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Infantile malignant osteopetrosis (IMO) is an autosomal recessive disorder characterized by non-functional osteoclasts and a fatal outcome early in childhood. About 50% of patients have mutations in the TCIRG1 gene. Methods IMO iPSCs were generated from a patient carrying a homozygous c.11279G>A (IVS18+1) mutation in TCIRG1 and transduced with a lentiviral vector expressing human TCIRG1. Embryoid bodies were generated and differentiated into monocytes. Non-adherent cells were harvested and further differentiated into osteoclasts on bovine bone slices. Results Release of the bone resorption biomarker CTX-I into the media of gene-corrected osteoclasts was 5-fold higher than that of the uncorrected osteoclasts and 35% of that of control osteoclasts. Bone resorption potential was confirmed by the presence of pits on the bones cultured with gene-corrected osteoclasts, absent in the uncorrected IMO osteoclasts. Conclusions The disease phenotype was partially corrected in vitro, providing a valuable resource for therapy development for this form of severe osteopetrosis.
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| 10. |
- Xian, Xiaojie, 1971, et al.
(författare)
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Pericytes limit tumor cell metastasis.
- 2006
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Ingår i: The Journal of clinical investigation. - 0021-9738. ; 116:3, s. 642-51
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Tidskriftsartikel (refereegranskat)abstract
- Previously we observed that neural cell adhesion molecule (NCAM) deficiency in beta tumor cells facilitates metastasis into distant organs and local lymph nodes. Here, we show that NCAM-deficient beta cell tumors grew leaky blood vessels with perturbed pericyte-endothelial cell-cell interactions and deficient perivascular deposition of ECM components. Conversely, tumor cell expression of NCAM in a fibrosarcoma model (T241) improved pericyte recruitment and increased perivascular deposition of ECM molecules. Together, these findings suggest that NCAM may limit tumor cell metastasis by stabilizing the microvessel wall. To directly address whether pericyte dysfunction increases the metastatic potential of solid tumors, we studied beta cell tumorigenesis in primary pericyte-deficient Pdgfb(ret/ret) mice. This resulted in beta tumor cell metastases in distant organs and local lymph nodes, demonstrating a role for pericytes in limiting tumor cell metastasis. These data support a new model for how tumor cells trigger metastasis by perturbing pericyte-endothelial cell-cell interactions.
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