Abstract P457: Systems Analysis To Understand The Impact Of The CDK Module On Cardiomyocyte Proliferation

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Bryana N Harris ◽  
Laura Woo ◽  
Jeffrey J Saucerman
Keyword(s):  
Experimental Data ◽  
Cell Cycle ◽  
Transcription Factor ◽  
Dna Synthesis ◽  
Current Knowledge ◽  
Cycle Phase ◽  
Cyclin D ◽  
Cardiomyocyte Proliferation ◽  
The Core ◽  
The Impact

Rationale: Heart failure is caused by the inability of adult mammalian hearts to overcome the loss of cardiomyocytes (CMs). This is due partly to the limited proliferative capacity of CMs, which exit the cell cycle and do not undergo cell division. Current knowledge in cardiac regeneration lacks an understanding of the molecular regulatory networks that determine whether CMs will progress through the cell cycle to proliferate. Our goal is to use computational modeling to understand the expression and activation levels of the core cell cycle network, specifically cyclins and cyclin-cyclin-dependent kinase (CDK) complexes. Methods: A model of core cell cycle dynamics was curated using previously published studies of CM proliferation regulators. This model incorporates those regulators known to stimulate G1/S and G2/M transitions through the core CDKs. The activity of each of the 22 network nodes (22 reactions) was predicted using a logic-based differential equation approach. The CDK model was then coupled with a minimal ODE model of cell cycle phase distributions and validated based on descriptions and experimental data from the literature. To prioritize key nodes for experimental validation, we performed a sensitivity analysis by stimulating individual knockdown for every node in the network, measuring the fractional activity of all nodes. Results: Our model confirmed that the knockdown of p21 and Rb protein and the overexpression of E2F transcription factor and cyclinD-cdk4 showed an increase in cells going through DNA synthesis and entering mitosis. A combined knockdown of p21 and p27 showed an increase of cells entering mitosis. Cyclin D-cdk4 and p21 overexpression showed a decrease and increase of Rb expression, respectively. Of the 14 model predictions, 12 agreed with experimental data in the literature. A comprehensive knockdown of the model nodes suggests that E2F (a key transcription factor driving DNA synthesis) is positively regulated by cyclin D while negatively regulated by GSK3B, SMAD3, and pRB. Conclusion: This model enables us to predict how cardiomyocytes respond to stimuli in the CDK network and identify potential therapeutic regulators that induce cardiomyocyte proliferation.

scholarly journals High-intensity Raf signal causes cell cycle arrest mediated by p21Cip1.

1997 ◽  
Vol 17 (9) ◽  
pp. 5588-5597 ◽  
Author(s):  
A Sewing ◽  
B Wiseman ◽  
A C Lloyd ◽  
H Land
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Cycle Arrest ◽  
Expression Patterns ◽  
Cellular Responses ◽  
Specific Cell ◽  
Cyclin D ◽  
Inhibition Of Proliferation ◽  
Cycle Arrest ◽  
Signal Specificity

Activated Raf has been linked to such opposing cellular responses as the induction of DNA synthesis and the inhibition of proliferation. However, it remains unclear how such a switch in signal specificity is regulated. We have addressed this question with a regulatable Raf-androgen receptor fusion protein in murine fibroblasts. We show that Raf can cause a G1-specific cell cycle arrest through induction of p21Cip1. This in turn leads to inhibition of cyclin D- and cyclin E-dependent kinases and an accumulation of hypophosphorylated Rb. Importantly, this behavior can be observed only in response to a strong Raf signal. In contrast, moderate Raf activity induces DNA synthesis and is sufficient to induce cyclin D expression. Therefore, Raf signal specificity can be determined by modulation of signal strength presumably through the induction of distinct protein expression patterns. Similar to induction of Raf, a strong induction of activated Ras via a tetracycline-dependent promoter also causes inhibition of proliferation and p21Cip1 induction at high expression levels. Thus, p21Cip1 plays a key role in determining cellular responses to Ras and Raf signalling. As predicted by this finding we show that Ras and loss of p21 cooperate to confer a proliferative advantage to mouse embryo fibroblasts.

Abstract 396: Regulation of Cardiomyocyte Proliferation by the Hippo Pathway and Dystrophin Complex

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Yuka Morikawa ◽  
John Leach ◽  
Todd Heallen ◽  
Ge Tao ◽  
James F Martin
Keyword(s):  
Cell Cycle ◽  
Muscular Dystrophy ◽  
Dna Synthesis ◽  
De Novo ◽  
Hippo Pathway ◽  
Myocardial Damage ◽  
Heart Regeneration ◽  
Cardiomyocyte Proliferation ◽  
Heart Repair ◽  
The Hippo Pathway

Regeneration in mammalian hearts is limited due to the extremely low renewal rate of cardiomyocytes and their inability to reenter the cell cycle. In rodent hearts, endogenous regenerative capacity exists during development but is rapidly repressed after birth, at which time growth is by hypertrophy. During the developmental and neonatal periods, heart regeneration occurs through proliferation of pre-existing cardiomyocytes. Our approach of activating heart regeneration is to uncover the mechanisms responsible for repression of cardiomyocyte proliferation. The Hippo pathway controls heart size by repressing cardiomyocyte proliferation during development. By deleting Salv , a modulator of the Hippo pathway, we found that myocardial damage in postnatal and adult hearts was repaired both anatomically and functionally. This heart repair occurred primary through proliferation of preexisting cardiomyocytes. During repair, cardiomyocytes reenter the cell cycle; de novo DNA synthesis, karyokinesis, and cytokinesis all take place. The dystrophin glycoprotein complex (DGC) is essential for muscle maintenance by anchoring the cytoskeleton and extracellular matrix. Disruption of the DGC results in muscular dystrophies, including Duchenne muscular dystrophy, resulting in both skeletal and cardiac myopathies. Recently the DGC was shown to regulate cardiomyocyte proliferation and we found that the DGC and the Hippo pathway components directly interact. To address if the DGC and the Hippo pathway coordinately regulate cardiomyocyte proliferation, we conditionally deleted Salv in the mouse model of muscular dystrophy, the mdx line. We found that simultaneous disruption of both the DGC and Hippo pathway leads an increased de novo DNA synthesis and cytokinesis in cardiomyocytes after heart damage. Our findings provide new insights into the mechanisms leading to heart repair through proliferation of endogenous cardiomyocytes.

scholarly journals Role for a YY1-Binding Element in Replication-Dependent Mouse Histone Gene Expression

1998 ◽  
Vol 18 (12) ◽  
pp. 7106-7118 ◽  
Author(s):  
Katherine A. Eliassen ◽  
Amy Baldwin ◽  
Eric M. Sikorski ◽  
Myra M. Hurt
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Transcription Factor ◽  
Protein Interaction ◽  
Histone Gene ◽  
Cycle Phase ◽  
Histone Gene Expression ◽  
Dna Protein Interaction

ABSTRACT Expression of the highly conserved replication-dependent histone gene family increases dramatically as a cell enters the S phase of the eukaryotic cell cycle. Requirements for normal histone gene expression in vivo include an element, designated α, located within the protein-encoding sequence of nucleosomal histone genes. Mutation of 5 of 7 nucleotides of the mouse H3.2 α element to yield the sequence found in an H3.3 replication-independent variant abolishes the DNA-protein interaction in vitro and reduces expression fourfold in vivo. A yeast one-hybrid screen of a HeLa cell cDNA library identified the protein responsible for recognition of the histone H3.2 α sequence as the transcription factor Yin Yang 1 (YY1). YY1 is a ubiquitous and highly conserved transcription factor reported to be involved in both activation and repression of gene expression. Here we report that the in vitro histone α DNA-protein interaction depends on YY1 and that mutation of the nucleotides required for the in vitro histone α DNA-YY1 interaction alters the cell cycle phase-specific up-regulation of the mouse H3.2 gene in vivo. Because all mutations or deletions of the histone α sequence both abolish interactions in vitro and cause an in vivo decrease in histone gene expression, the recognition of the histone α element by YY1 is implicated in the correct temporal regulation of replication-dependent histone gene expression in vivo.

scholarly journals Evidence that the cell cycle is a series of uncoupled, memoryless phases

2018 ◽  
Author(s):  
Hui Xiao Chao ◽  
Randy I. Fakhreddin ◽  
Hristo K. Shimerov ◽  
Rashmi J. Kumar ◽  
Gaorav P. Gupta ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Cycle Progression ◽  
Phase 1 ◽  
Cell Cycle Phase ◽  
Cell Cycle Checkpoints ◽  
Cycle Phase ◽  
Erlang Distribution ◽  
Cycle Progression ◽  
Gap Phase

The cell cycle is canonically described as a series of 4 phases: G1 (gap phase 1), S (DNA synthesis), G2 (gap phase 2), and M (mitosis). Various models have been proposed to describe the durations of each phase, including a two-state model with fixed S-G2-M duration and random G1 duration1,2; a “stretched” model in which phase durations are proportional3; and an inheritance model in which sister cells show correlated phase durations2,4. A fundamental challenge is to understand the quantitative laws that govern cell-cycle progression and to reconcile the evidence supporting these different models. Here, we used time-lapse fluorescence microscopy to quantify the durations of G1, S, G2, and M phases for thousands of individual cells from three human cell lines. We found no evidence of correlation between any pair of phase durations. Instead, each phase followed an Erlang distribution with a characteristic rate and number of steps. These observations suggest that each cell cycle phase is memoryless with respect to previous phase durations. We challenged this model by perturbing the durations of specific phases through oncogene activation, inhibition of DNA synthesis, reduced temperature, and DNA damage. Phase durations remained uncoupled in individual cells despite large changes in durations in cell populations. To explain this behavior, we propose a mathematical model in which the independence of cell-cycle phase durations arises from a large number of molecular factors that each exerts a minor influence on the rate of cell-cycle progression. The model predicts that it is possible to force correlations between phases by making large perturbations to a single factor that contributes to more than one phase duration, which we confirmed experimentally by inhibiting cyclin-dependent kinase 2 (CDK2). We further report that phases can show coupling under certain dysfunctional states such as in a transformed cell line with defective cell cycle checkpoints. This quantitative model of cell cycle progression explains the paradoxical observation that phase durations are both inherited and independent and suggests how cell cycle progression may be altered in disease states.

Calculation of self-broadened widths of rotational Raman lines in H2 and N2

1977 ◽  
Vol 55 (6) ◽  
pp. 542-548 ◽  
Author(s):  
R. P. Srivastava ◽  
H. R. Zaidi
Keyword(s):  
Experimental Data ◽  
Core Potential ◽  
The Core ◽  
Classical Path ◽  
Path Approximation ◽  
The Impact ◽  
Potential Parameters ◽  
Comparison With Experimental Data

Self-broadened widths of rotational Raman lines of S-branch in H2 and N2 are calculated in the impact and straight classical path approximation. A core potential of the form r−n is considered along with the quadrupole–quadrapole interaction. It is found that the results are sensitive to the core potential parameters. Comparison with experimental data yields values for these parameters.

scholarly journals A DNA-structured mathematical model of cell-cycle progression in cyclic hypoxia

2021 ◽  
Author(s):  
Giulia Laura Celora ◽  
Philip K Maini ◽  
Helen M Byrne ◽  
Ester M Hammond ◽  
Samuel B Bader ◽  
...  
Keyword(s):  
Experimental Data ◽  
Cell Cycle ◽  
Dna Synthesis ◽  
S Phase ◽  
Low Oxygen ◽  
Oxygen Levels ◽  
Wide Range ◽  
Model Predictions ◽  
Periodic Exposure

New experimental data have shown how the periodic exposure of cells to low oxygen levels (i.e., cyclic hypoxia) impacts their progress through the cell-cycle. Cyclic hypoxia has been detected in tumours and linked to poor prognosis and treatment failure. While fluctuating oxygen environments can be reproduced in vitro, the range of oxygen cycles that can be tested is limited. By contrast, mathematical models can be used to predict the response to a wide range of cyclic dynamics. Accordingly, in this paper we develop a mechanistic model of the cell-cycle that can be combined with in vitro experiments, to better understand the link between cyclic hypoxia and cell-cycle dysregulation. A distinguishing feature of our model is the inclusion of impaired DNA synthesis and cell-cycle arrest due to periodic exposure to severely low oxygen levels. Our model decomposes the cell population into four compartments and a time-dependent delay accounts for the variability in the duration of the S phase which increases in severe hypoxia due to reduced rates of DNA synthesis. We calibrate our model against experimental data and show that it recapitulates the observed cell-cycle dynamics. We use the calibrated model to investigate the response of cells to oxygen cycles not yet tested experimentally. When the re-oxygenation phase is sufficiently long, our model predicts that cyclic hypoxia simply slows cell proliferation since cells spend more time in the S phase. On the contrary, cycles with short periods of re-oxygenation are predicted to lead to inhibition of proliferation, with cells arresting from the cell-cycle when they exit the S phase. While model predictions on short time scales (about a day) are fairly accurate (i.e, confidence intervals are small), the predictions become more uncertain over longer periods. Hence, we use our model to inform experimental design that can lead to improved model parameter estimates and validate model predictions.

scholarly journals 8Cl-cAMP modifies the balance between PKAR1 and PKAR2 and modulates the cell cycle, growth and apoptosis in human adrenocortical H295R cells

2010 ◽  
Vol 44 (6) ◽  
pp. 331-347 ◽  
Author(s):  
Zhor Bouizar ◽  
Bruno Ragazzon ◽  
Lucie Viou ◽  
Mariuccia Hortane ◽  
Jerôme Bertherat ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Cycle Progression ◽  
Transforming Growth Factor ◽  
Adrenal Adenoma ◽  
Transforming Growth Factor Β ◽  
Nuclear Antigen ◽  
Adrenocortical Cells ◽  
Protein Levels ◽  
The Impact

Various types of protein kinase A (PKA) alterations have been observed in adrenocortical tumours and Carney complex (CNC). PKA is a heterotetramer of two regulatory and two catalytic subunits. The R1A and R2B proteins are the most abundant regulatory subunits in endocrine tissues. A decrease in R2B protein levels has been observed in adrenal adenoma, whereas tumours from patients with CNC display a decrease in R1A protein levels. Dysregulation of the balance between R1A and R2B may thus be involved in adrenal tumourigenesis. We investigated the impact of the differences in the balance of PKA subunits on cell growth using specific cAMP analogues. We assessed the effects of 8-chloroadenosine-cAMP (8Cl-cAMP), a site-selective activator of PKA R2B, in H295R adrenocortical cells. 8Cl-cAMP stimulated PKA activity, decreased R1A levels and increased R2B levels. It had no cytotoxic effects, initially stimulating DNA synthesis and then inducing apoptosis by disrupting G2/M progression. We observed an initial accumulation of cells in the S phase, translocation of cyclin A to the nucleus, CDK2 activation, sustained DNA synthesis and proliferating cell nuclear antigen accumulation. Cell cycle arrest in the G2 phase was parallel with the accumulation of cyclin B and the inactivation of CDC2 kinase. The 8CPT-cAMP, which activates the R2B subunit, had similar effects. R2B silencing reduced the apoptosis induced by tumour necrosis factor α and transforming growth factor β. Thus, R2B is a key regulator of proliferation/differentiation in H295R cell line along with the complex balance between the PKA subunits. Activation of PKA R2B and dysregulation of the R1A/R2B balance regulate cell cycle progression and apoptosis in adrenocortical cells by modulating cyclin production and cyclin-dependent kinase activities.

Negative Regulation of Cell Cycle Kinetics of Human Hematopoietic Cells by the Transcription Factor Dmtf1.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3359-3359
Author(s):  
Michihiro Kobayashi ◽  
Edward F. Srour
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Cord Blood ◽  
Hematopoietic Cells ◽  
Dominant Negative ◽  
Cell Cycle Kinetics ◽  
Cd34 Cells ◽  
The Impact ◽  
Kinetics Of ◽  
Time Point

Abstract Hematopoietic stem cells (HSCs) are predominantly quiescent with only a small number entering active phases of cell cycle at any time point. With such tightly regulated cell cycle kinetics, HSCs ensure preservation of the stem cell pool. Many cell cycle-related proteins, mainly tumor suppressor genes, are involved in maintenance of HSCs quiescence. Dmtf1 (Cyclin D-binding Myb-like Protein1) is a transcription factor that negatively regulates cell cycle by inducing Arf expression, and its deletion has been reported in some leukemias (Bodner SM et al, 1999). As there is no information regarding the role of Dmtf1 in hematopoiesis, we examined the impact of Dmtf1 on regulating cell cycle kinetics of hematopoietic progenitor cells. Dmtf1 mRNA was expressed in human granulocytes, lymphocytes, CD34+ cells, and in murine Sca1+lin-CD117+ (KSL) cells. Using retroviral vectors (MIEG3/IRES-GFP), we first investigated cell cycle progression in 293 cells transduced with four different constructs; GFP only control vector (−), wild type Dmtf1 (WT), and two dominant negative mutants expressing a point mutation (K319E) or a deleted myb-like repeat box (dMHR). A total of 36.0% of sorted and cultured GFP+ control (−) cells were in S/G2+M 24hr after initiation of culture. Whereas 30.8% of cells expressing (WT) were in S/G2+M at the same time point, expression of the two dominant negative mutants K319E and dMHR induced 46.6% and 45.5% of the cells into S/G2+M, respectively suggesting that loss of Dmtf1 activity results in rapid cell proliferation. Interestingly, a 2.5-fold increase in the ecxpression of Arf and p21 mesured by qPCR was detected in cells transduced with WT only whereas other transduced cells did not show any change in expression of both Arf and p21. The impact of these constructs was then evaluated in cord blood cells using CFU assays. Cord blood CD34+ cells were transduced with the four vectors mentioned above and GFP+ cells were subsequently sorted and cultured. Both K319E and dMHR induced a 25% increase in the number of clonogenic progenitors relative to (−) while a modest decrease of 10% in colony numbers was detected in the WT group. Cells cycle analysis of these cells is currently under investigation. These results demonstrate that Dmtf1 acts as a negative regulator of cell cycle control in hematopoietic cells and suggests that it may play a role in the maintenance of HSC quiescence.

scholarly journals Flavin Oxidase-Induced ROS Generation Modulates PKC Biphasic Effect of Resveratrol on Endothelial Cell Survival

Biomolecules ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 209 ◽  
Author(s):  
Anna Maria Posadino ◽  
Roberta Giordo ◽  
Annalisa Cossu ◽  
Gheyath K. Nasrallah ◽  
Abdullah Shaito ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Dna Synthesis ◽  
Cell Survival ◽  
Cellular Response ◽  
Cell Cycle Progression ◽  
Natural Antioxidants ◽  
Cycle Progression ◽  
Protein Levels ◽  
The Impact

Background: Dietary intake of natural antioxidants is thought to impart protection against oxidative-associated cardiovascular diseases. Despite many in vivo studies and clinical trials, this issue has not been conclusively resolved. Resveratrol (RES) is one of the most extensively studied dietary polyphenolic antioxidants. Paradoxically, we have previously demonstrated that high RES concentrations exert a pro-oxidant effect eventually elevating ROS levels leading to cell death. Here, we further elucidate the molecular determinants underpinning RES-induced oxidative cell death. Methods: Using human umbilical vein endothelial cells (HUVECs), the effect of increasing concentrations of RES on DNA synthesis and apoptosis was studied. In addition, mRNA and protein levels of cell survival or apoptosis genes, as well as protein kinase C (PKC) activity were determined. Results: While high concentrations of RES reduce PKC activity, inhibit DNA synthesis and induce apoptosis, low RES concentrations elicit an opposite effect. This biphasic concentration-dependent effect (BCDE) of RES on PKC activity is mirrored at the molecular level. Indeed, high RES concentrations upregulate the proapoptotic Bax, while downregulating the antiapoptotic Bcl-2, at both mRNA and protein levels. Similarly, high RES concentrations downregulate the cell cycle progression genes, c-myc, ornithine decarboxylase (ODC) and cyclin D1 protein levels, while low RES concentrations display an increasing trend. The BCDE of RES on PKC activity is abrogated by the ROS scavenger Tempol, indicating that this enzyme acts downstream of the RES-elicited ROS signaling. The RES-induced BCDE on HUVEC cell cycle machinery was also blunted by the flavin inhibitor diphenyleneiodonium (DPI), implicating flavin oxidase-generated ROS as the mechanistic link in the cellular response to different RES concentrations. Finally, PKC inhibition abrogates the BCDE elicited by RES on both cell cycle progression and pro-apoptotic gene expression in HUVECs, mechanistically implicating PKC in the cellular response to different RES concentrations. Conclusions: Our results provide new molecular insight into the impact of RES on endothelial function/dysfunction, further confirming that obtaining an optimal benefit of RES is concentration-dependent. Importantly, the BCDE of RES could explain why other studies failed to establish the cardio-protective effects mediated by natural antioxidants, thus providing a guide for future investigation looking at cardio-protection by natural antioxidants.

Control of p21Cip by BRCA1-associated protein is critical for cardiomyocyte cell cycle progression and survival

2019 ◽  
Vol 116 (3) ◽  
pp. 592-604 ◽  
Author(s):  
Cornelia Volland ◽  
Peter Schott ◽  
Michael Didié ◽  
Jörg Männer ◽  
Bernhard Unsöld ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Cycle Regulation ◽  
Cell Cycle Progression ◽  
Kinase Inhibitor ◽  
Ki 67 ◽  
Cycle Progression ◽  
Developmental Arrest ◽  
Cycle Regulation ◽  
The Impact

Abstract Aims Identifying the key components in cardiomyocyte cell cycle regulation is of relevance for the understanding of cardiac development and adaptive and maladaptive processes in the adult myocardium. BRCA1-associated protein (BRAP) has been suggested as a cytoplasmic retention factor for several proteins including Cyclin-dependent-kinase inhibitor p21Cip. We observed profound expressional changes of BRAP in early postnatal myocardium and investigated the impact of BRAP on cardiomyocyte cell cycle regulation. Methods and results General knockout of Brap in mice evoked embryonic lethality associated with reduced myocardial wall thickness and lethal cardiac congestion suggesting a prominent role for BRAP in cardiomyocyte proliferation. αMHC-Cre driven cardiomyocyte-specific knockout of Brap also evoked lethal cardiac failure shortly after birth. Likewise, conditional cardiomyocyte-specific Brap deletion using tamoxifen-induced knockout in adult mice resulted in marked ventricular dilatation and heart failure 3 weeks after induction. Several lines of evidence suggest that Brap deletion evoked marked inhibition of DNA synthesis and cell cycle progression. In cardiomyocytes with proliferative capacity, this causes developmental arrest, whereas in adult hearts loss of BRAP-induced apoptosis. This is explained by altered signalling through p21Cip which we identify as the link between BRAP and cell cycle/apoptosis. BRAP deletion enhanced p21Cip expression, while BRAP overexpression in cardiomyocyte-specific transgenic mice impeded p21Cip expression. That was paralleled by enhanced nuclear Ki-67 expression and DNA synthesis. Conclusion By controlling p21Cip activity BRAP expression controls cell cycle activity and prevents developmental arrest in developing cardiomyocytes and apoptosis in adult cardiomyocytes.

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