scholarly journals ROOT PATTERNING AND REGENERATION ARE MEDIATED BY THE QUIESCENT CENTER AND INVOLVE BLUEJAY, JACKDAW AND SCARECROW REGULATION OF VASCULATURE FACTORS

2019 ◽  
Author(s):  
Alvaro Sanchez-Corrionero ◽  
Pablo Perez-Garcia ◽  
Javier Cabrera ◽  
Javier Silva-Navas ◽  
Juan Perianez-Rodriguez ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Transcription Factors ◽  
Postembryonic Development ◽  
Quiescent Center ◽  
Ground Tissue ◽  
Short Root ◽  
Cell Lineages ◽  
Radial Patterning ◽  
Severe Impairment

ABSTRACTStem cells are central to plant development. During root postembryonic development stem cells generating tissues are patterned in layers around a stem cell organizer or quiescent center (QC). How stem cell lineages are initially patterned is unclear. Here, we describe a role for BLUEJAY (BLJ), JACKDAW (JKD) and SCARECROW (SCR) transcription factors in patterning of cell lineages during growth and in patterning reestablishment during regeneration through regulation of number of QC cells and their regenerative capacities. In blj jkd scr mutants, QC cells are progressively lost which results in loss of tissue layers. Upon laser ablation blj jkd scr is impaired in QC division and specification resulting in severe impairment in pattern regeneration. Beyond direct regulation of QC activity by these transcription factors, reduced levels of SHORT-ROOT (SHR) and of PIN auxin transporters were observed in the vasculature of blj jkd scr, leading to strong reduction in the auxin response in the QC. We narrowed down non-cell-autonomous regulation of vascularly expressed genes in blj jkd scr to C-REPEAT BINDING FACTOR 3 (CBF3). cbf3 mutant shows reduced levels of SHR in the vasculature, and in addition QC disorganization and downregulation of the QC regulator WUSCHEL-RELATED HOMEODOMAIN 5 (WOX5). CBF3 gene is primarily expressed in the ground tissue downstream of BLJ, JKD and SCR, while CBF3 protein may move. Targeted-expression of CBF3 to the ground tissue of blj jkd scr recovers radial patterning and regeneration. We propose that BLJ, JKD and SCR regulate QC-mediated patterning, and that part of this regulation involves CBF3.

scholarly journals Patterns of Cell Division and the Risk of Cancer

Genetics ◽  
2003 ◽  
Vol 163 (4) ◽  
pp. 1527-1532 ◽  
Author(s):  
Steven A Frank ◽  
Yoh Iwasa ◽  
Martin A Nowak
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Basal Layer ◽  
Mutation Rates ◽  
Tissue Architecture ◽  
Cell Lineages ◽  
Cell Mutation ◽  
Long Stem ◽  
Risk Of Cancer ◽  
Transit Cell

Abstract Epidermal and intestinal tissues divide throughout life to replace lost surface cells. These renewing tissues have long-lived basal stem cell lineages that divide many times, each division producing one stem cell and one transit cell. The transit cell divides a limited number of times, producing cells that move up from the basal layer and eventually slough off from the surface. If mutation rates are the same in stem and transit divisions, we show that minimal cancer risk is obtained by using the fewest possible stem divisions subject to the constraints imposed by the need to renew the tissue. In this case, stem cells are a necessary risk imposed by the constraints of tissue architecture. Cairns suggested that stem cells may have lower mutation rates than transit cells do. We develop a mathematical model to study the consequences of different stem and transit mutation rates. Our model shows that stem cell mutation rates two or three orders of magnitude less than transit mutation rates may favor relatively more stem divisions and fewer transit divisions, perhaps explaining how renewing tissues allocate cell divisions between long stem and short transit lineages.

scholarly journals Regulation of sarcomagenesis by the empty spiracles homeobox genes EMX1 and EMX2

2021 ◽  
Vol 12 (6) ◽  
Author(s):  
Manuel Pedro Jimenez-García ◽  
Antonio Lucena-Cacace ◽  
Daniel Otero-Albiol ◽  
Amancio Carnero
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Transcription Factors ◽  
Neural Crest ◽  
Tumor Suppressors ◽  
Homeobox Genes ◽  
Neuronal Cell ◽  
Cell Gene Expression

AbstractThe EMX (Empty Spiracles Homeobox) genes EMX1 and EMX2 are two homeodomain gene members of the EMX family of transcription factors involved in the regulation of various biological processes, such as cell proliferation, migration, and differentiation, during brain development and neural crest migration. They play a role in the specification of positional identity, the proliferation of neural stem cells, and the differentiation of certain neuronal cell phenotypes. In general, they act as transcription factors in early embryogenesis and neuroembryogenesis from metazoans to higher vertebrates. The EMX1 and EMX2’s potential as tumor suppressor genes has been suggested in some cancers. Our work showed that EMX1/EMX2 act as tumor suppressors in sarcomas by repressing the activity of stem cell regulatory genes (OCT4, SOX2, KLF4, MYC, NANOG, NES, and PROM1). EMX protein downregulation, therefore, induced the malignance and stemness of cells both in vitro and in vivo. In murine knockout (KO) models lacking Emx genes, 3MC-induced sarcomas were more aggressive and infiltrative, had a greater capacity for tumor self-renewal, and had higher stem cell gene expression and nestin expression than those in wild-type models. These results showing that EMX genes acted as stemness regulators were reproduced in different subtypes of sarcoma. Therefore, it is possible that the EMX genes could have a generalized behavior regulating proliferation of neural crest-derived progenitors. Together, these results indicate that the EMX1 and EMX2 genes negatively regulate these tumor-altering populations or cancer stem cells, acting as tumor suppressors in sarcoma.

Molecular analysis of SCARECROW function reveals a radial patterning mechanism common to root and shoot

Development ◽  
2000 ◽  
Vol 127 (3) ◽  
pp. 595-603 ◽  
Author(s):  
J.W. Wysocka-Diller ◽  
Y. Helariutta ◽  
H. Fukaki ◽  
J.E. Malamy ◽  
P.N. Benfey
Keyword(s):  
Bundle Sheath ◽  
Quiescent Center ◽  
Ground Tissue ◽  
Tissue Layer ◽  
Radial Pattern ◽  
Radial Patterning ◽  
Bundle Sheath Cells ◽  
Root Analysis ◽  
Tight Correlation ◽  
Embryonic Root

Mutation of the SCARECROW (SCR) gene results in a radial pattern defect, loss of a ground tissue layer, in the root. Analysis of the shoot phenotype of scr mutants revealed that both hypocotyl and shoot inflorescence also have a radial pattern defect, loss of a normal starch sheath layer, and consequently are unable to sense gravity in the shoot. Analogous to its expression in the endodermis of the root, SCR is expressed in the starch sheath of the hypocotyl and inflorescence stem. The SCR expression pattern in leaf bundle sheath cells and root quiescent center cells led to the identification of additional phenotypic defects in these tissues. SCR expression in a pin-formed mutant background suggested the possible origins of the starch sheath in the shoot inflorescence. Analysis of SCR expression and the mutant phenotype from the earliest stages of embryogenesis revealed a tight correlation between defective cell divisions and SCR expression in cells that contribute to ground tissue radial patterning in both embryonic root and shoot. Our data provides evidence that the same molecular mechanism regulates the radial patterning of ground tissue in both root and shoot during embryogenesis as well as postembryonically.

218 DONOR-MATCHED FUNCTIONAL AND MOLECULAR CHARACTERIZATION OF CANINE MESENCHYMAL STEM CELLS DERIVED FROM DIFFERENT ORIGINS

2012 ◽  
Vol 24 (1) ◽  
pp. 221
Author(s):  
S. A. Ock ◽  
G. H. Maeng ◽  
Y. M. Lee ◽  
T. H. Kim ◽  
B. M. Kumar ◽  
...  
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Stem Cell ◽  
Transcription Factors ◽  
Telomere Length ◽  
Telomerase Activity ◽  
Rt Pcr ◽  
Cytochemical Staining ◽  
Single Donor ◽  
Cell Capacity

Canine mesenchymal stem cells (cMSC) have been successfully isolated from several adult tissue sources. However, differences in the biological properties of MSC have been shown to be associated with donor variability. Further, the stem cell capacity of cMSC of various tissues isolated from a single donor is currently unclear. Therefore, this study investigated the functional and molecular characteristics of cMSC derived from bone marrow (cBM-MSC), adipose tissue (cA-MSC) and dermal skin (cDS-MSC) of a single donor. Three kinds of cMSC were isolated by following previously published protocols. AP activity was assessed with a chromogen kit (Abcam Inc., Cambridge, MA, USA). Expression of CD markers (CD45, 90 and 105) and stem cell transcription factors (Oct3/4, Nanog and Sox2) was analysed by immunocytochemical staining. All cells were induced into osteogenesis and adipogenesis by following protocols described earlier and confirmed by cytochemical staining and the detection of lineage specific genes by RT-PCR. Chromosomal stability was assessed by a method described earlier (Ock and Rho 2008 J. Vet. Med. Sci. 70, 1165–1172) and cell cycle status was determined by a flow cytometry. Telomere length was analysed by Telo TAGGG Telomere Length Assay kit (Roche, Mannheim, Germany) and telomerase activity was evaluated by semiquantitative nested RT-PCR. Statistical analysis was performed by ANOVA using SPSS 12.0 and significance was tested when P < 0.05. Expressions of AP activity and the transcription factors, such as Oct3/4, Nanog and Sox2 were absent in all cMSC. All 3 types of cMSC positively expressed the surface markers CD90 and 105 but not CD45. Exposure of all cell lines to osteogenic and adipogenic induction medium resulted in the calcium deposition evidenced by Alizarin red S staining and the accumulation of fat globules indicated by Oil red O staining, respectively. Differentiation was further confirmed by the detection of marker genes, such as Runx2 and Pparγ. However, the degree of osteogenic or adipogenic differentiation among the 3 kinds of cMSC was different and particularly, cA-MSC had enhanced cytochemical staining associated with expression of specific genes, Runx2 and Pparγ. Ploidy analysis showed that the diploid rate was high with over 90% in all cMSC and indicated no noticeable chromosomal abnormalities. Further, less than 52% of cells were found at G1 phase in all cMSC, with lowest percentage observed in cDS-MSC (33.3%). Regardless of varied tissue sources, cMSC from a single donor showed no differences in telomere lengths (∼18–19 kbp), but the telomerase activity was different with significantly higher levels found in cBM-MSC. In conclusion, the above results suggest that tissue specific cMSC derived from a single donor possess differences in stem cell capacity and support the consideration of tissue source before judging the suitability of cells for therapeutic applications. This work was supported by grant from Basic Science Research Program through NRF funded by the Ministry of Education, Science and Technology (2009-0064229).

Essential Role of Jun Family Transcription Factors in PU.1-Induced Leukemic Stem Cell Transformation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 463-463 ◽  
Author(s):  
Ulrich Steidl ◽  
Frank Rosenbauer ◽  
Roel G.W Verhaak ◽  
Xuesong Gu ◽  
Hasan H. Otu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Transcription Factors ◽  
Malignant Transformation ◽  
Molecular Mechanisms ◽  
Target Cells ◽  
Leukemic Stem Cell ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Transcriptional Pattern

Abstract Knockdown of the expression of the myeloid master regulator PU.1 leads to the development of an immature acute myeloid leukemia (AML) in mice. Recent reports suggest that functional inactivation of PU.1 might also play a role in human AML. However, the molecular mechanisms underlying PU.1-mediated malignant transformation are unknown. We examined leukemic PU.1 knockdown mice and found a 3-fold expansion of lin-, c-kit+, Sca1+ (KLS) hematopoietic stem cells (HSC) as compared to wildtype controls, which was not observed during the preleukemic phase. When we transplanted double-sorted leukemic KLS-HSC into NOD-SCID mice the recipients developed AML after 9–12 weeks indicating that the leukemic stem cells derive from the HSC compartment. This finding prompted us to examine the transcriptome of PU.1 knockdown preleukemic HSC to identify early transcriptional changes underlying their malignant transformation. After lineage-depletion and FACS sorting of preleukemic KLS-HSC we performed linear amplification of RNA by 2 cycles of RT-IVT and hybridized the cRNA with Affymetrix Mouse Genome 430 2.0 arrays. Principal component analysis as well as hierarchical cluster analysis clearly distinguished PU.1 knockdown and wildtype HSC. Several in-vitro targets of PU.1 such as c-Fes, BTK, TFEC, CSF2R, and Ebi3 were downregulated demonstrating that those are also affected in HSC in vivo. Differential expression of 16 genes was corroborated by qRT-PCR. Strikingly, several Jun family transcription factors including c-Jun and JunB were downregulated. Retroviral restoration of c-Jun expression in bone marrow cells of preleukemic mice rescued the PU.1-initiated myelomonocytic differentiation block in this early phase. To target cells in the leukemic stage we applied lentiviral vectors expressing c-Jun or JunB. While c-Jun did not affect leukemic proliferation, lentiviral restoration of JunB led to an 80% reduction of clonogenic growth and a loss of leukemic self-renewal capacity in serial replating assays. Expression analysis of 285 patients with AML confirmed the correlation between PU.1 and JunB downregulation and suggests its relevance in human disease. These results delineate a transcriptional pattern that precedes leukemic transformation in PU.1 knockdown HSC and demonstrate that downregulation of c-Jun and JunB contribute to the development of PU.1-induced AML by blocking differentiation (c-Jun) and increasing self-renewal (JunB). Therefore, examination of disturbed gene expression in preleukemic HSC can identify genes whose dysregulation is essential for leukemic stem cell function and are potential targets for therapeutic interventions.

scholarly journals Symplastic communication spatially directs local auxin biosynthesis to maintain root stem cell niche in Arabidopsis

2017 ◽  
Vol 114 (15) ◽  
pp. 4005-4010 ◽  
Author(s):  
Yuting Liu ◽  
Meizhi Xu ◽  
Nengsong Liang ◽  
Yanghang Zheng ◽  
Qiaozhi Yu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Stem Cell Niche ◽  
Cell Communication ◽  
Positional Information ◽  
Auxin Biosynthesis ◽  
Root Tip ◽  
Quiescent Center ◽  
Stem Cell Maintenance ◽  
Cell Niche

Stem cells serve as the source of new cells for plant development. A group of stem cells form a stem cell niche (SCN) at the root tip and in the center of the SCN are slowly dividing cells called the quiescent center (QC). QC is thought to function as a signaling hub that inhibits differentiation of surrounding stem cells. Although it has been generally assumed that cell-to-cell communication provides positional information for QC and SCN maintenance, the tools for testing this hypothesis have long been lacking. Here we exploit a system that effectively blocks plasmodesmata (PD)-mediated signaling to explore how cell-to-cell communication functions in the SCN. We showed that the symplastic signaling between the QC and adjacent cells directs the formation of local auxin maxima and establishment of AP2-domain transcription factors, PLETHORA gradients. Interestingly we found symplastic signaling is essential for local auxin biosynthesis, which acts together with auxin polar transport to provide the guidance for local auxin enrichment. Therefore, we demonstrate the crucial role of cell-to-cell communication in the SCN maintenance and further uncover a mechanism by which symplastic signaling initiates and reinforces the positional information during stem cell maintenance via auxin regulation.

Epigenetic regulation in stem cell development, cell fate conversion, and reprogramming

2015 ◽  
Vol 6 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Kazuyuki Ohbo ◽  
Shin-ichi Tomizawa
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Transcription Factors ◽  
Cell Fate ◽  
Cell Lines ◽  
Cell Fate Decisions ◽  
Micro Rnas ◽  
Stem Cell Lines ◽  
Cell Fate Conversion

AbstractStem cells are identified classically by an in vivo transplantation assay plus additional characterization, such as marker analysis, linage-tracing and in vitro/ex vivo differentiation assays. Stem cell lines have been derived, in vitro, from adult tissues, the inner cell mass (ICM), epiblast, and male germ stem cells, providing intriguing insight into stem cell biology, plasticity, heterogeneity, metastable state, and the pivotal point at which stem cells irreversibly differentiate to non-stem cells. During the past decade, strategies for manipulating cell fate have revolutionized our understanding about the basic concept of cell differentiation: stem cell lines can be established by introducing transcription factors, as with the case for iPSCs, revealing some of the molecular interplay of key factors during the course of phenotypic changes. In addition to de-differentiation approaches for establishing stem cells, another method has been developed whereby induced expression of certain transcription factors and/or micro RNAs artificially converts differentiated cells from one committed lineage to another; notably, these cells need not transit through a stem/progenitor state. The molecular cues guiding such cell fate conversion and reprogramming remain largely unknown. As differentiation and de-differentiation are directly linked to epigenetic changes, we overview cell fate decisions, and associated gene and epigenetic regulations.

scholarly journals PLETHORA and WOX5 interaction and subnuclear localisation regulates Arabidopsis root stem cell maintenance

2019 ◽  
Author(s):  
Rebecca C. Burkart ◽  
Vivien I. Strotmann ◽  
Gwendolyn K. Kirschner ◽  
Abdullah Akinci ◽  
Laura Czempik ◽  
...  
Keyword(s):  
Stem Cell ◽  
Transcription Factors ◽  
Feedback Regulation ◽  
Cell Types ◽  
Nuclear Bodies ◽  
Quiescent Center ◽  
Expression Domain ◽  
Negative Feedback Regulation ◽  
Arabidopsis Root ◽  
Intrinsically Disordered

Maintenance and homeostasis of the stem cell niche (SCN) in the Arabidopsis root is essential for growth and development of all root cell types. The SCN is organized around a quiescent center (QC) that maintains the stemness of the cells in direct contact. The transcription factors WUSCHEL-RELATED HOMEOBOX 5 (WOX5) and the PLETHORAs (PLTs) are both expressed in the SCN where they maintain the QC and regulate the fate of the distal columella stem cells (CSCs). Although WOX5 and PLTs are known as important players in SCN maintenance, much of the necessary regulation of quiescence and division in the Arabidopsis root is not understood on a molecular level. Here, we describe the concerted mutual regulation of the key transcription factors WOX5 and PLTs on a transcriptional and protein interaction level, leading to a confinement of the WOX5 expression domain to the QC cells by negative feedback regulation. Additionally, by applying a novel SCN staining method, we demonstrate that both WOX5 and PLTs are necessary for root meristem maintenance as they regulate QC quiescence and CSC fate and show that QC divisions and CSC differentiation correlate. Moreover, we uncover that PLTs, especially PLT3, contains intrinsically disordered prion-like domains (PrDs) that are necessary for complex formation with WOX5 and its recruitment to subnuclear microdomains/nuclear bodies (NBs) in the CSCs. We propose that the partitioning of the PLT-WOX5 complexes to NBs, possibly by liquid-liquid phase separation, plays an important role during determination of CSC fate.

scholarly journals CDK6 Antagonizes TP53-Induced Responses during Tumorigenesis

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. SCI-15-SCI-15
Author(s):  
Veronika Sexl ◽  
Karoline Kollmann ◽  
Florian Bellutti
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Stem Cell ◽  
Transcription Factors ◽  
Conflicts Of Interest ◽  
Induced Responses ◽  
Hematopoietic Stem ◽  
Hematopoietic Malignancies ◽  
Independent Functions ◽  
Oncogenic Stress

Inhibitors directed against cyclin dependent kinases (CDKs) have raised much interest as anti-cancer therapeutics over the last years. In particular, inhibitors directed against CDK4/6 have been declared as a major breakthrough in cancer therapy by the FDA. CDK4 and CDK6 bind to D-type cyclins and subsequently phosphorylate the RB protein to allow cells to progress through the G1 phase of the cell cycle. The effectiveness of CDK4/6 inhibitors was primarily assigned to their ability to block cell cycle progression. In hematopoietic malignancies high levels of CDK6, but not CDK4, are frequently found. Over the last years we have assigned a novel and unexpected role for CDK6 as global transcriptional regulator. ChIP-Seq experiments identified more than 20.000 specific CDK6 binding sites in leukemic cells with the majority located in the promoter regions. CDK6 binding to chromatin does not require kinase activity whereas transcriptional control is regulated in a kinase- dependent as well as kinase-independent manner. Overlaying ChIP-Seq and RNA-Seq experiments showed that CDK6 contributes to the induction or repression of genes. Target genes of CDK6 which are important for leukemia progression include PIM1, c-MYC, AURKA, AURKB, AKT and VEGF-A. Murine leukemia models verified the importance of CDK6 for myeloid and lymphoid tumor formation downstream of a variety of oncogenes including FLT3-ITD, NPM/ALK, MLL/AF9, BCR/ABL or JAK2V617F. CDK6 contributes to disease development by regulating proliferation, cell survival, angiogenesis and cytokine production. In hematopoietic stem cells and leukemic stem cells kinase-independent functions dominate and CDK6 controls a network of transcription factors regulating stem cell quiescence and activation. The importance of kinase-dependent transcriptional effects is pronounced under conditions of stress and transformation. Upon oncogenic stress, CDK6 induces a set of genes that counteract pro-apoptotic TP53 responses including MDM4, PRMT5, PPM1D and BCL2. This response is induced by a CDK6 - dependent phosphorylation of the transcription factors SP1 and NFYA as verified by phospho-chromatome analysis. Murine Cdk6-deficient cells only survive oncogenic stress by mutating Tp53. The link between CDK6 and TP53 is conserved in human hematopoietic malignancies. Kollmann K, Heller G, Schneckenleithner C, et al. A kinase-independent function of CDK6 links the cell cycle to tumor angiogenesis. Cancer Cell. 2013;24(2):167-181.Scheicher R, Hoelbl-Kovacic A, Bellutti F, et al. CDK6 as a key regulator of hematopoietic and leukemic stem cell activation. Blood. 2015;125(1):90-101.Uras IZ, Walter GJ, Scheicher R, et al. Palbociclib treatment of FLT3-ITD+ AML cells uncovers a kinase-dependent transcriptional regulation of FLT3 and PIM1 by CDK6. Blood. 2016;127(23):2890-2902.Bellutti F, Tigan AS, Nebenfuehr S, et al. CDK6 antagonizes P53-induced responses during tumorigenesis. Cancer Discov. 2018;8(7):884-897.Uras IZ, Maurer B, Nivarthi H, et al. CDK6 coordinates JAK2V617F mutant MPN via NF-kB and apoptotic networks. Blood. 2019;133(15):1677-1690. Disclosures No relevant conflicts of interest to declare.

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