Papers by Simeon Santourlidis
Stem Cells and Development, 2015
empirically supported treatments for stress reduction on diurnal variations in salivary cortisol ... more empirically supported treatments for stress reduction on diurnal variations in salivary cortisol and other indices of physiological stress.
Cancer biomarkers : section A of Disease markers, 2014
Urinary DNA is increasingly gaining importance in diagnosis of urological malignancies. Especiall... more Urinary DNA is increasingly gaining importance in diagnosis of urological malignancies. Especially cell-free DNA originating from apoptotic and necrotic cells of the early tumor could become a key target for early stage tumor diagnosis. Aberrant DNA methylation forms tumor cell characteristic epigenetic profiles which are covalently established before any tumor related aberration at transcriptional or protein level has occurred. In addition, these epigenetic signatures are alterably adapted to and accompanying the individual stages of multistep, progressive tumorigenesis. Hence, they seem very promising for diagnosis as well as for monitoring the patient's follow-up care and even for decisions regarding personalized therapeutic options. The essential prerequisite at this approach will be a reliable methodological handling of the biological material of interest. In this study we present detailed analyses of LINE-1 DNA methylation profiles and demonstrate the sensitive detection o...
Journal of immunology (Baltimore, Md. : 1950), 2008
The clonal distribution and stable expression of killer cell Ig-like receptor (KIR) genes is epig... more The clonal distribution and stable expression of killer cell Ig-like receptor (KIR) genes is epigenetically regulated. To assess the epigenetic changes that occur during hemopoietic development we examined DNA methylation and chromatin structure of the KIR locus in early hemopoietic progenitor cells and major lymphocyte lineages. In hemopoietic progenitor cells, KIR genes exhibited the major hallmarks of epigenetic repression, which are dense DNA methylation, inaccessibility of chromatin to Micrococcus nuclease digest, and a repressive histone signature, characterized by strong H3K9 dimethylation and reduced H4K8 acetylation. In contrast, KIR genes of NK cells showed active histone signatures characterized by absence of H3K9 dimethylation and presence of H4K8 acetylation. Histone modifications correlated well with the competence of different lymphocyte lineages to express KIR; whereas H4K8 acetylation was high in NK and CD8+ T cells, it was almost absent in CD4+ T cells and B cells ...
Cellular Signalling, 2014
Stem Cell Research, 2010
Mesenchymal stem cells (MSC) have been isolated from almost every adult tissue. In cord blood (CB... more Mesenchymal stem cells (MSC) have been isolated from almost every adult tissue. In cord blood (CB), different non-hematopoietic CD45-, CD34- adherent cell populations can be generated: the cord blood derived MSC (CB-MSC), that behave almost like MSC from bone marrow (BM-MSC), and unrestricted somatic stem cells (USSC) which show a distinct differentiation potential into all three germ layers. However, distinguishing these populations easily by molecular markers is still a concern. In this study we were able to present the HOX expression pattern of USSC, CB-MSC and BM-MSC, which in fact allows a discrimination of these populations. Briefly, RT-PCR analysis of the HOX code revealed a high similarity between BM-MSC and CB-MSC, which are both HOX-positive, whereas USSC resembled H9 embryonic stem cells HOX-negative.Especially HOXA9, HOXB7, HOXC10 and HOXD8 are good candidate markers to discriminate MSC from USSC. Thus, our data suggest that the "biological fingerprint" based on the HOX code can be used to distinguish functionally distinct MSC populations derived from bone marrow and cord blood.
The Journal of Immunology, 2002
Human NK cells are characterized by the expression of surface receptors of the killer cell Ig-lik... more Human NK cells are characterized by the expression of surface receptors of the killer cell Ig-like receptor (KIR) family, which are involved in the specific recognition of pathogenic target cells. Each NK cell expresses and maintains an individual subset of inhibitory and stimulatory KIR and in this way contributes to a diversified NK cell repertoire. To date, the molecular basis for generation of clonally distributed KIR expression patterns has been elusive. Here, analyses of DNA methylation patterns of KIR genes in NK cell lines as well as in NK cells, freshly isolated from peripheral blood, demonstrated that a small CpG island surrounding the transcriptional start site of each KIR gene is consistently demethylated in expressed KIR and methylated in unexpressed KIR. DNA-demethylating treatment resulted in a rapid and stable induction of transcription and cell surface expression of all formerly unexpressed KIR in NK cell lines, NK cell clones, and freshly isolated NK cells, but not in other cell types. In vitro methylation of KIR CpG islands repressed reporter gene expression in NK cells. We conclude that clonal patterns of KIR expression are mainly epigenetically determined and maintained through DNA methylation.
Journal of Biological Chemistry, 2007
CD34 glycoprotein in human hematopoiesis is expressed on a subset of progenitor cells capable of ... more CD34 glycoprotein in human hematopoiesis is expressed on a subset of progenitor cells capable of self-renewal, multilineage differentiation, and hematopoietic reconstitution. Nucleolin is an abundant multifunctional phosphoprotein of growing eukaryotic cells, involved in regulation of gene transcription, chromatin remodeling, and RNA metabolism, whose transcripts are enriched in murine hematopoietic stem cells, as opposed to differentiated tissue. Here we show that, in human CD34-positive hematopoietic cells, nucleolin activates endogenous CD34 and Bcl-2 gene expression, and cell surface CD34 protein expression is thereby enhanced by nucleolin. Nucleolin-mediated activation of CD34 gene transcription results from direct sequence-specific interactions with the CD34 promoter region. Nucleolin expression prevails in CD34-positive cells mobilized into peripheral blood (PB), as opposed to CD34-negative peripheral blood mononuclear cells (PBMCs). Therefore, in intact CD34-positive mobilized PB cells, a recruitment of nucleolin to the CD34 promoter region takes place, accompanied by nucleosomal determinants of gene activity, which are absent from the CD34 promoter region in CD34-negative PBMCs. Our data show that nucleolin acts as a component of the gene regulation program of CD34-positive hematopoietic cells and provide further insights into processes by which human CD34-positive hematopoietic stem/progenitor cells are maintained.
Immunogenetics, 2006
Killer-cell immunoglobulin-like receptors (KIRs) are a structurally and functionally diverse fami... more Killer-cell immunoglobulin-like receptors (KIRs) are a structurally and functionally diverse family of molecules expressed by natural killer (NK) cells and T-cell subsets. The most centromeric gene in the human KIR cluster is KIR3DL3, a framework gene that is present in all haplotypes. KIR3DL3 has only one immunoreceptor tyrosine-based inhibitory motif and lacks the exon encoding the stem between the Immunoglobulin domains and the transmembrane region. We have investigated expression of KIR3DL3 in blood and decidual NK cells by reverse transcriptase polymerase chain reaction (RT-PCR) and protein analysis using a KIR3DL3-specific monoclonal antibody, CH21. KIR3DL3 mRNA was only detected in the CD56 bright subset in cells from peripheral blood and in CD56 bright decidual NK cells. The CD56 bright NK92 cell line was also positive. Quantitative RT-PCR indicated a trend for higher expression of KIR3DL3 in female peripheral blood mononuclear cells compared to that in male. Using a bisulphite conversion method, we found that the promoter of KIR3DL3 was strongly methylated. Surface protein expression was detectable after demethylation. Like other KIRs, KIR3DL3 is highly polymorphic, and we detected 14 variants in 25 unrelated individuals. Nucleotide substitutions were scattered throughout the sequence, with a cluster of alleles at the start of the transmembrane region at the site where the remnant of the linking stem present in other KIR is found. We conclude that the KIR3DL3 gene is not a pseudogene but encodes a protein that is not expressed in healthy individuals. Protein expression might be induced under certain developmental or pathological situations.
Stem cell research, 2011
Unrestricted somatic stem cells (USSC) from human cord blood display a broad differentiation pote... more Unrestricted somatic stem cells (USSC) from human cord blood display a broad differentiation potential for ectodermal, mesodermal, and endodermal cell types. The molecular basis for these stem cell properties is unclear and unlike embryonic stem cells (ESC) none of the major stem cell factors OCT4, SOX2, and NANOG exhibits significant expression in USSC. Here, we report that these key stem cell genes hold an epigenetic state in between that of an ESC and a terminally differentiated cell type. DNA methylation analysis exhibits partial demethylation of the regulatory region of OCT4 and a demethylated state of the NANOG and SOX2 promoter/enhancer regions. Further genome-wide DNA methylation profiling identified a partially demethylated state of the telomerase gene hTERT. Moreover, none of the pluripotency factors exhibited a repressive histone signature. Notably, SOX2 exhibits a bivalent histone signature consisting of the opposing histone marks dimeH3K4 and trimeH3K27, which is typica...
Experimental Hematology, 2010
Objective. Generation of induced pluripotent stem (iPS) cells from human cord blood (CB)Lderived ... more Objective. Generation of induced pluripotent stem (iPS) cells from human cord blood (CB)Lderived unrestricted somatic stem cells and evaluation of their molecular signature and differentiation potential in comparison to human embryonic stem cells. Materials and Methods. Unrestricted somatic stem cells isolated from human CB were reprogrammed to iPS cells using retroviral expression of the transcription factors OCT4, SOX2, KLF4, and C-MYC. The reprogrammed cells were analyzed morphologically, by quantitative reverse transcription polymerase chain reaction, genome-wide microRNA and methylation profiling, and gene expression microarrays, as well as in their pluripotency potential by in vivo teratoma formation in severe combined immunodeficient mice and in vitro differentiation. Results. CB iPS cells are very similar to human embryonic stem cells morphologically, at their molecular signature, and in their differentiation potential. Conclusions. Human CB-derived unrestricted somatic stem cells offer an attractive source of cells for generation of iPS cells. Our findings open novel perspectives to generate human leukocyte antigenLmatched pluripotent stem cell banks based on existing CB banks. Besides the obvious relevance of a second-generation CB iPS cell bank for pharmacological and toxicological testing, its application for autologous or allogenic regenerative cell transplantation appears feasible. Ó
Cellular Signalling, 2011
BMC Research Notes, 2010
Background: The miR-200c/141 cluster has recently been implicated in the epithelial to mesenchyma... more Background: The miR-200c/141 cluster has recently been implicated in the epithelial to mesenchymal transition (EMT) process. The expression of these two miRNAs is inversely correlated with tumorigenicity and invasiveness in several human cancers. The role of these miRNAs in cancer progression is based in part on their capacity to target the EMT activators ZEB1 and ZEB2, two transcription factors, which in turn repress expression of E-cadherin. Little is known about the regulation of the mir200c/141 cluster, whose targeting has been proposed as a promising new therapy for the most aggressive tumors. Findings: We show that the miR-200c/141 cluster is repressed by DNA methylation of a CpG island located in the promoter region of these miRNAs. Whereas in vitro methylation of the miR-200c/141 promoter led to shutdown of promoter activity, treatment with a demethylating agent caused transcriptional reactivation in breast cancer cells formerly lacking expression of miR-200c and miR-141. More importantly, we observed that DNA methylation of the identified miR-200c/141 promoter was tightly correlated with phenotype and the invasive capacity in a panel of 8 human breast cancer cell lines. In line with this, in vitro induction of EMT by ectopic expression of the EMT transcription factor Twist in human immortalized mammary epithelial cells (HMLE) was accompanied by increased DNA methylation and concomitant repression of the miR-200c/141 locus.
Analytical Biochemistry, 2006
Chromatin structure has a major impact on gene transcription . Currently, structural analyses of ... more Chromatin structure has a major impact on gene transcription . Currently, structural analyses of chromatin are mainly performed by chromatin immunoprecipitation (ChIP) 1 assays, which assess histone modifications with specific antibodies. Less frequently, nuclease digest is used for direct analysis of chromatin accessibility. However, quantitative statements are difficult to make due to lack of a reliable normalization procedure. The purpose of this study was to establish a direct and quantitative technique to investigate chromatin structure at distinct loci. Therefore, we established the novel assay termed MIRECAL (Micrococcus nuclease/real-time PCR chromatin accessibility assay with locus specificity) based on a Micrococcus nuclease (Mnase) digest of histone-associated DNA with subsequent normalization of real-time PCR results.
Cell Reports, 2014
Highlights Human iPSCs demonstrate origin-dependent expression profiles after neural induction NP... more Highlights Human iPSCs demonstrate origin-dependent expression profiles after neural induction NPCs from neuroectoderm-derived iPSCs share reprogramming memory with fetal NSCs
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Papers by Simeon Santourlidis