Defects In Cell Cycle Progression Research Articles

Loss of mitochondrial DNA is associated with reduced DNA content variability in Saccharomyces cerevisiae.

DNA content measurement by fluorescence-assisted cell sorting (FACS) provides information on cell cycle progression and DNA content variability. Saccharomyces cerevisiae mutants with DNA content variability that was reduced relative to wild-type strains had defects in mitochondrial DNA (mtDNA) maintenance and mitochondrial gene expression and were correlated with strains found to lack mtDNA ([ rho 0 ] cells) by genome sequencing and fluorescence microscopy. In contrast, mutants with increased variability had defects in cell cycle progression, which may indicate a loss of coordination between mtDNA and nuclear DNA replication. Thus, FACS measurement of DNA content variability can provide insight into cell-to-cell heterogeneity in mtDNA copy number.

Targeting the loss of cGAS/STING signaling in cancer.

The cGAS/STING pathway provides a key host defense mechanism by detecting the accumulation of cytoplasmic double-stranded DNA (dsDNA) and mediating innate and adaptive immune signaling. In addition to detecting pathogen-derived dsDNA, cGAS senses intrinsic dsDNA, such as those associated with defective cell cycle progression and mitophagy that has leaked from the nucleus or mitochondria, and subsequently evokes host immunity to eliminate pathogenic cells. In cancer cells, dysregulation of DNA repair and cell cycle caused at the DNA replication checkpoint and spindle assembly checkpoint results in aberrant cytoplasmic dsDNA accumulation, stimulating anti-tumor immunity. Therefore, the suppression of cGAS/STING signaling is beneficial for survival and frequently observed in cancer cells as a way to evade detection by the immune system, and is likely to be related to immune checkpoint blockade (ICB) resistance. Indeed, the mechanisms of ICB resistance overlap with those acquired in cancers during immunoediting to evade immune surveillance. This review highlights the current understanding of cGAS/STING suppression in cancer cells and discusses how to establish effective strategies to regenerate effective anti-tumor immunity through reactivation of the cGAS/STING pathway.

Characterization of RACK1-depleted mammalian cells by a palette of microscopy approaches reveals defects in cell cycle progression and polarity establishment

The Receptor for Activated C Kinase 1 (RACK1) is an evolutionarily conserved scaffold protein involved in the regulation of numerous cellular processes. Here, we used CRISPR/Cas9 and siRNA to reduce the expression of RACK1 in Madin-Darby Canine Kidney (MDCK) epithelial cells and Rat2 fibroblasts, respectively. RACK1-depleted cells were examined using coherence-controlled holographic microscopy, immunofluorescence, and electron microscopy. RACK1 depletion resulted in decreased cell proliferation, increased cell area and perimeter, and in the appearance of large binucleated cells suggesting a defect in the cell cycle progression. Our results show that the depletion of RACK1 has a pleiotropic effect on both epithelial and mesenchymal cell lines and support its essential role in mammalian cells.

Hdac1-deficiency affects the cell cycle axis Cdc25-Cdk1 causing impaired G2/M phase progression and reduced cardiomyocyte proliferation in zebrafish

Zebrafish have the ability to fully regenerate their hearts after injury since cardiomyocytes subsequently dedifferentiate, re-enter cell cycle, and proliferate to replace damaged myocardial tissue. Recent research identified the reactivation of dormant developmental pathways during cardiac regeneration in adult zebrafish, suggesting pro-proliferative pathways important for developmental heart growth to be also critical for regenerative heart growth after injury.Histone deacetylase 1 (Hdac1) was recently shown to control both, embryonic as well as adult regenerative cardiomyocyte proliferation in the zebrafish model. Nevertheless, regulatory pathways controlled by Hdac1 are not defined yet. By analyzing RNA-seq-derived transcriptional profiles of the Hdac1-deficient zebrafish mutant baldrian, we here identified DNA damage response (DDR) pathways activated in baldrian mutant embryos. Surprisingly, although the DDR signaling pathway was transcriptionally activated, we found the complete loss of protein expression of the known DDR effector and cell cycle inhibitor p21. Consequently, we observed an upregulation of the p21-downstream target Cdk2, implying elevated G1/S phase transition in Hdac1-deficient zebrafish hearts. Remarkably, Cdk1, another p21-but also Cdc25-downstream target was downregulated. Here, we found the significant downregulation of Cdc25 protein expression, explaining reduced Cdk1 levels and suggesting impaired G2/M phase progression in Hdac1-deficient zebrafish embryos. To finally prove defective cell cycle progression due to Hdac1 loss, we conducted Cytometer-based cell cycle analyses in HDAC1-deficient murine HL-1 cardiomyocytes and indeed found impaired G2/M phase transition resulting in defective cardiomyocyte proliferation.In conclusion, our results suggest a critical role of Hdac1 in maintaining both, regular G1/S and G2/M phase transition in cardiomyocytes by controlling the expression of essential cell cycle regulators such as p21 and Cdc25.

Conventional and Spectral Karyotyping of Murine Cerebellar Granule Neuron Progenitors.

Karyotyping remains an invaluable tool to researchers exploring the cause and consequence of genomic instability in biologic systems. It allows investigators to survey the entire chromosome complement in individual cells and in a single experiment, visualize, and measure different forms or features of instability such as aneuploidy, ongoing chromosomal instability, DNA damage/mis-repair, telomere erosion, chromosome mis-segregation, or defects in cell cycle progression. This chapter describes the combined use of conventional (DAPI-banding) and spectral karyotyping (SKY) to characterize genomic instability in murine cerebellar granule neuron progenitors (CGNPs), using CGNPs with conditional deletion of Atr as a positive control for chromosomal rearrangements. Protocols for preparing slides (metaphase spreads) from fixed cell suspension, DAPI-banding, and spectral karyotyping (SKY) are included. Pertinent aspects of image acquisition and analysis are detailed. These protocols can likely be adapted to other tissue types (murine or human).

Regulation of Iron Transport Is Required for Terminal Erythroid Differentiation Even Under Iron-Replete Conditions Sufficient for Hemoglobinization

Developing erythroid cells are the main consumer of iron in vertebrates, as their main function is to oxygenate tissues via hemoglobin. Iron metabolism is a key driver of erythroid development and hemoglobin synthesis. When iron deficient, or when iron metabolism is dysregulated, erythroid cells are both lacking in hemoglobin and exhibit differentiation defects. Currently, the efficacy of iron supplementation in patients is monitored by quantitating hemoglobin levels. However, the effect of iron supplementation on erythroid differentiation is less clear. As hemoglobinization and erythroid differentiation are inextricably intertwined with erythroid function, we sought to understand whether and how iron supplementation functions to restore erythroid differentiation during iron deficiency. Tackling this problem in vivo has been fraught with technical challenges as vertebrates with mutations in iron metabolism genes often die from anemia in utero. To circumvent this problem, we used zebrafish with genetic iron metabolism defects to determine if iron supplementation could rescue erythropoietic defects at both the cellular and systemic level. Zebrafish are tractable in vivo models for such studies as they develop externally and can easily be treated by exogenous iron in their water. To carry out this study, we designed a system to sort Tg(globin lcr:eGFP) erythrocytes from single zebrafish embryos onto slides for imaging, while keeping sufficient numbers of cells for genotyping of the same embryo. We used two zebrafish lines which carry loss of function mutations in the mfrn1 (carrying a mitochondrial iron trafficking defect) and fpn1 (carrying a defect in iron export from intestinal and yolk syncytial epithelium-a model of dietary iron deficiency). Both lines had decreased erythroid cell numbers. In addition, the erythroid cells were hemoglobin deficient and had erythroid differentiation defects which included enlarge nuclei. We showed that exogenous iron supplementation (labeled as "rescue) in mfrn1 mutant zebrafish restored hemoglobinization (benzidine staining) but not erythroid cell number (% lcr:eGFP) or terminal differentiation. However, iron supplementation in fpn1 mutant zebrafish, restored erythroid cell number but not terminal differentiation defects. The main difference in the 2 mutants is that the mfrn1 mutant has a defect in intracellular iron trafficking leading to defective iron metabolism, while the fpn1 mutant has defective iron export to erythroid cells but their erythroid cells have intact intracellular iron trafficking. mfrn1 mutants had defects in cell cycle progression and increased apoptosis in their erythroid cells which likely is a cause for decreased erythroid cell numbers. Our data suggests that in addition to adequate iron levels, correct regulation of iron trafficking is required for optimal erythroid iron utilization, terminal erythropoiesis and potentially, proliferation and differentiation of erythroid progenitors. This may indicate a role for iron transporters in directing iron fate, as well as signaling to developmental pathways. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Genome-scale RNA interference profiling of Trypanosoma brucei cell cycle progression defects

Trypanosomatids, which include major pathogens of humans and livestock, are flagellated protozoa for which cell cycle controls and the underlying mechanisms are not completely understood. Here, we describe a genome-wide RNA-interference library screen for cell cycle defects in Trypanosoma brucei. We induced massive parallel knockdown, sorted the perturbed population using high-throughput flow cytometry, deep-sequenced RNAi-targets from each stage and digitally reconstructed cell cycle profiles at a genomic scale; also enabling data visualisation using an online tool (https://tryp-cycle.pages.dev/). Analysis of several hundred genes that impact cell cycle progression reveals >100 flagellar component knockdowns linked to genome endoreduplication, evidence for metabolic control of the G1-S transition, surface antigen regulatory mRNA-binding protein knockdowns linked to G2M accumulation, and a putative nucleoredoxin required for both mitochondrial genome segregation and for mitosis. The outputs provide comprehensive functional genomic evidence for the known and novel machineries, pathways and regulators that coordinate trypanosome cell cycle progression.

Abstract GS104: Stress-induced Uhrf1 Epigenetically Modulates Angiogenesis And Cardiac Function In Ventricular Hypertrophy

Heart failure (HF) is accompanied by cardiac hypertrophy (CH) and myocardial tissue remodeling. Epigenetic mechanisms regulate cardiomyocyte (CM) gene expression during CH: the DNA methylation profile and several histone modification marks are profoundly modulated in mouse models of HF and in the human disease. UHRF1 is an epigenetic cofactor connecting DNA methylation to histone methylation. By screening for epigenetic genes upregulated during the early phase of HF, Uhrf1 emerged as a “hit”. We found that UHRF1 is highly expressed in the endothelial cell (EC) compartment under basal conditions in comparison to other myocardial cellular components, and its expression surges in the acute phase of CH induced through transverse aortic constriction (TAC). In vitro studies on HUVECs and H5V cells revealed that silencing of Uhrf1 is associated with defects in cell cycle progression, migration and tube formation. To gain further insight on the role of UHRF1, we generated an EC-specific conditional knockout (cKO) mouse line, Cdh5-CreERT2; Uhrf 1 fl/fl . Compared to control, Uhrf1 -cKO mice subjected to TAC exhibit a worsening of cardiac function associated with increased left ventricular dimension, suggesting a more rapid transition toward HF. Transcriptomic analysis of ECs revealed a robust correlation between UHRF1 depletion and alteration of cell cycle and angiogenesis, in agreement with in vitro results. These results were further corroborated in vivo through EdU injection, matrigel plug and retinal angiogenesis assays, and provided robust evidence for a key role for UHRF1 in the EC response to stress, linking the latter to neo-angiogenesis. We then defined whether the crosstalk between CMs and ECs during stress was altered by the absence of UHRF1. We found that, among other angiocrines, neuregulin-1 (Nrg-1) was strongly downregulated in ECs of Uhrf1 fl/fl mice subjected to TAC. In line with this evidence, ErbB2 and ERK pathways were significantly downregulated in the left ventricle of Uhrf1 fl/fl TAC mice, leading to increased tissue apoptosis.Our study identifies UHRF1 as a critical epigenetic regulator of stress-induced angiogenesis and, more broadly, underlines the relevance of epigenetics in modulating EC gene expression during myocardial stress.

Impaired Cell Cycle Progression and Self-Renewal of Fetal Neural Stem and Progenitor Cells in a Murine Model of Intrauterine Growth Restriction

Individuals with intrauterine growth restriction (IUGR) are at an increased risk for neurodevelopmental impairment. Fetal cortical neurogenesis is a time-sensitive process in which fetal neural stem cells (NSCs) follow a distinct pattern of layer-specific neuron generation to populate the cerebral cortex. Here, we used a murine maternal hypoxia-induced IUGR model to study the impact of IUGR on fetal NSC development. In this model, timed-pregnant mice were exposed to hypoxia during the active stage of neurogenesis, followed by fetal brain collection and analysis. In the IUGR fetal brains, we found a significant reduction in cerebral cortical thickness accompanied by decreases in layer-specific neurons. Using EdU labeling, we demonstrated that cell cycle progression of fetal NSCs was delayed, primarily observed in the G2/M phase during inward interkinetic nuclear migration. Following relief from maternal hypoxia exposure, the remaining fetal NSCs re-established their neurogenic ability and resumed production of layer-specific neurons. Surprisingly, the newly generated neurons matched their control counterparts in layer-specific marker expression, suggesting preservation of the fetal NSC temporal identity despite IUGR effects. As expected, the absolute number of neurons generated in the IUGR group remained lower compared to that in the control group due to a reduced fetal NSC pool size as a result of cell cycle defect. Transcriptome analysis identified genes related to energy expenditure and G2/M cell cycle progression being affected by maternal hypoxia-induced IUGR. Taken together, maternal hypoxia-induced IUGR is associated with a defect in cell cycle progression of fetal NSCs, and has a long-term impact on offspring cognitive development.

Intrinsic neural stem cell properties define brain hypersensitivity to genotoxic stress

SummaryImpaired replication has been previously linked to growth retardation and microcephaly; however, why the brain is critically affected compared with other organs remains elusive. Here, we report the differential response between early neural progenitors (neuroepithelial cells [NECs]) and fate-committed neural progenitors (NPs) to replication licensing defects. Our results show that, while NPs can tolerate altered expression of licensing factors, NECs undergo excessive replication stress, identified by impaired replication, increased DNA damage, and defective cell-cycle progression, leading eventually to NEC attrition and microcephaly. NECs that possess a short G1 phase license and activate more origins than NPs, by acquiring higher levels of DNA-bound MCMs. In vivo G1 shortening in NPs induces DNA damage upon impaired licensing, suggesting that G1 length correlates with replication stress hypersensitivity. Our findings propose that NECs possess distinct cell-cycle characteristics to ensure fast proliferation, although these inherent features render them susceptible to genotoxic stress.

Palmitic acid-induced defects in cell cycle progression and cytokinesis in Neuro-2a cells

ABSTRACT Obesity is associated with elevated levels of free fatty acids (FFAs). Excessive saturated fatty acids (SFAs) exhibit significant deleterious cytotoxic effects in many types of cells. However, the effects of palmitic acid (PA), the most common circulating SFA, on cell cycle progression in neuronal cells have not been well-examined. The aim of this study was to examine whether PA affects the proliferation and cell cycle progression in mouse neuroblastoma Neuro-2a (N2a) cells. Our studies found that 200 µM PA significantly decreased DNA synthesis and mitotic index in N2a cells as early as 4 h following treatment. 24 h treatment with 200 µM PA significantly decreased the percentage of diploid (2 N) cells while dramatically increasing the percentage of tetraploid (4 N) cells as compared to the BSA control. Moreover, our studies found that 24 h treatment with 200 µM PA increased the percentage of binucleate cells as compared to the BSA control. Our studies also found that unsaturated fatty acids (UFAs), including linoleic acid, oleic acid, α-linolenic acid, and docosahexaenoic acid, were able to abolish PA-induced decrease of 2 N cells, increase of 4 N cells, and accumulation of binucleate cells. Taken together, these results suggest that PA may affect multiple aspects of the cell cycle progression in N2a cells, including decreased DNA synthesis, G2/M arrest, and cytokinetic failure, which could be abolished by UFAs. Abbreviations: 4-PBA, 4-Phenylbutyric Acid; ALA, α-linolenic acid; BrdU, 5-bromo-2’-deoxyuridine; DAPI, 4′,6-diamidino-2-phenylindole; ER, endoplasmic reticulum; FFA, free fatty acids; FITC, fluorescein isothiocyanate; LA, linoleic acid; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; N2a, Neuro-2a; NAC, N-acetyl cysteine; OA, oleic acid; PA, palmitic acid; pHH3, Phosphorylation of histone H3; PI, propidium iodide; SFA, saturated fatty acids; PUFA, polyunsaturated fatty acids; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; UFA, unsaturated fatty acids

Bur1 functions with TORC1 for vacuole-mediated cell cycle progression.

The vacuole/lysosome plays essential roles in the growth and proliferation of many eukaryotic cells via the activation of target of rapamycin complex 1 (TORC1). Moreover, the yeast vacuole/lysosome is necessary for progression of the cell division cycle, in part via signaling through the TORC1 pathway. Here, we show that an essential cyclin-dependent kinase, Bur1, plays a critical role in cell cycle progression in cooperation with TORC1. A mutation in BUR1 combined with a defect in vacuole inheritance shows a synthetic growth defect. Importantly, the double mutant, as well as a bur1-267 mutant on its own, has a severe defect in cell cycle progression from G1 phase. In further support that BUR1 functions with TORC1, mutation of bur1 alone results in high sensitivity to rapamycin, a TORC1 inhibitor. Mechanistic insight for Bur1 function comes from the findings that Bur1 directly phosphorylates Sch9, a target of TORC1, and that both Bur1 and TORC1 are required for the activation of Sch9. Together, these discoveries suggest that multiple signals converge on Sch9 to promote cell cycle progression.

Cell Cycle Progression Defects and Impaired DNA Damage Signaling Drive Enlarged Cells into Senescence

Cell Cycle Progression Defects and Impaired DNA Damage Signaling Drive Enlarged Cells into Senescence

IGluK-Deep: computational identification of lysine glutarylation sites using deep neural networks with general pseudo amino acid compositions

Lysine glutarylation is a post-translation modification which plays an important regulatory role in a variety of physiological and enzymatic processes including mitochondrial functions and metabolic processes both in eukaryotic and prokaryotic cells. This post-translational modification influences chromatin structure and thereby results in global regulation of transcription, defects in cell-cycle progression, DNA damage repair, and telomere silencing. To better understand the mechanism of lysine glutarylation, its identification in a protein is necessary, however, experimental methods are time-consuming and labor-intensive. Herein, we propose a new computational prediction approach to supplement experimental methods for identification of lysine glutarylation site prediction by deep neural networks and Chou’s Pseudo Amino Acid Composition (PseAAC). We employed well-known deep neural networks for feature representation learning and classification of peptide sequences. Our approach opts raw pseudo amino acid compositions and obsoletes the need to separately perform costly and cumbersome feature extraction and selection. Among the developed deep learning-based predictors, the standard neural network-based predictor demonstrated highest scores in terms of accuracy and all other performance evaluation measures and outperforms majority of previously reported predictors without requiring expensive feature extraction process. iGluK-Deep:Computational Identification of lysine glutarylationsites using deep neural networks with general Pseudo Amino Acid Compositions Sheraz Naseer, Rao Faizan Ali, Yaser Daanial Khan, P.D.D Dominic Communicated by Ramaswamy H. Sarma

Knockdown of RpL36 in testes impairs spermatogenesis in Drosophila melanogaster.

Many ribosomal proteins (RPs) not only play essential roles in ribosome biogenesis, but also have "extraribosomal" functions in various cellular processes. RpL36 encodes ribosomal protein L36, a component of the 60S subunit of ribosomes in Drosophila melanogaster. We report here that RpL36 is required for spermatogenesis in D. melanogaster. After showing the evolutionary conservation of RpL36 sequences in animals, we revealed that the RpL36 expression level in fly testes was significantly higher than in ovaries. Knockdown RpL36 in fly testes resulted in a significantly decreased egg hatch rate when these males mated with wild-type females. Furthermore, 76.67% of the RpL36 knockdown fly testes were much smaller in comparison to controls. Immunofluorescence staining exhibited that in the RpL36 knockdown testis hub cell cluster was enlarged, while the number of germ cells, including germ stem cells, was reduced. Knockdown of RpL36 in fly testis caused much fewer or no mature sperms in seminal vesicles. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) signal was stronger in RpL36 knockdown fly testes than in the control testes, but the TUNEL-positive cells could not be stained by Vasa antibody, indicating that apoptotic cells are not germ cells. The percentage of pH3-positive cells among the Vasa-positive cells was significantly reduced. The expression of genes involved in cell death, cell cycle progression, and JAK/STAT signaling pathway was significantly changed by RpL36 knockdown in fly testes. These results suggest that RpL36 plays an important role in spermatogenesis, likely through JAK/STAT pathway, thus resulting in defects in cell-cycle progression and cell death in D. melanogaster testes.

Shared aspects of mRNA expression associated with oocyte maturation failure in humans and rhesus monkeys indicating compromised oocyte quality.

Oocyte maturation failure observed in assisted reproduction technology (ART) cycles can limit the number of quality oocytes obtained and present a pronounced barrier for some patients. The potential exists to use unmatured oocytes for ART through in vitro maturation. Understanding the molecular basis of oocyte maturation failure is pertinent to minimizing this loss of oocytes and considerations of whether such oocytes can be used safely for ART. We identified shared transcriptome abnormalities for rhesus monkey and human failed-to-mature (FTM) oocytes relative to healthy matured MII stage oocytes. We discovered that, although the number of shared affected genes was comparatively small, FTM oocytes in both species shared effects for several pathways and functions, including predicted activation of oxidative phosphorylation (OxPhos) with additional effects on mitochondrial function, lipid metabolism, transcription, nucleotide excision repair, endoplasmic reticulum stress, unfolded protein response, and cell viability. RICTOR emerged as a prominent upstream regulator with predicted inhibition across all analyses. Alterations in KDM5A, MTOR, MTORC1, INSR, CAB39L, and STK11 activities were implicated along with RICTOR in modulating mitochondrial activity and OxPhos. Defects in cell cycle progression were not a prominent feature of FTM oocytes. These results identify a common set of transcriptome abnormalities associated with oocyte maturation failure. While our results do not demonstrate causality, they indicate that fundamental aspects of cellular function are abnormal in FTM oocytes and raise significant concerns about the potential risks of using FTM oocytes for ART.

Transcription Factor AP4 Mediates Cell Fate Decisions: To Divide, Age, or Die.

Simple SummaryHere, we review the literature on Activating Enhancer-Binding Protein 4 (AP4)/transcription factor AP4 (TFAP4) function and regulation and its role in cancer. Elevated expression of AP4 was detected in tumors of various organs and is associated with poor patient survival. AP4 is encoded by a Myc target gene and mediates cell fate decisions by regulating multiple processes, such as cell proliferation, epithelial-mesenchymal transition, stemness, apoptosis, and cellular senescence. Thereby, AP4 may be critical for tumor initiation and progression. In this review article, we summarize published evidence showing how AP4 functions as a transcriptional activator and repressor of a plethora of direct target genes in various physiological and pathological conditions. We also highlight the complex interactions of AP4 with c-Myc, N-Myc, p53, lncRNAs, and miRNAs in feed-back loops, which control AP4 levels and mediate AP4 functions. In the future, a better understanding of AP4 may contribute to improved prognosis and therapy of cancer.Activating Enhancer-Binding Protein 4 (AP4)/transcription factor AP4 (TFAP4) is a basic-helix-loop-helix-leucine-zipper transcription factor that was first identified as a protein bound to SV40 promoters more than 30 years ago. Almost 15 years later, AP4 was characterized as a target of the c-Myc transcription factor, which is the product of a prototypic oncogene that is activated in the majority of tumors. Interestingly, AP4 seems to represent a central hub downstream of c-Myc and N-Myc that mediates some of their functions, such as proliferation and epithelial-mesenchymal transition (EMT). Elevated AP4 expression is associated with progression of cancer and poor patient prognosis in multiple tumor types. Deletion of AP4 in mice points to roles of AP4 in the control of stemness, tumor initiation and adaptive immunity. Interestingly, ex vivo AP4 inactivation results in increased DNA damage, senescence, and apoptosis, which may be caused by defective cell cycle progression. Here, we will summarize the roles of AP4 as a transcriptional repressor and activator of target genes and the contribution of protein and non-coding RNAs encoded by these genes, in regulating the above mentioned processes. In addition, proteins interacting with or regulating AP4 and the cellular signaling pathways altered after AP4 dysregulation in tumor cells will be discussed.

Ctdp1 deficiency leads to early embryonic lethality in mice and defects in cell cycle progression in MEFs

ABSTRACTRNA polymerase II subunit A Carboxy-Terminal Domain Phosphatase 1 (CTDP1), a member of the haloacid dehalogenase superfamily phosphatases, has a defined role in transcriptional regulation, but emerging evidence suggests an expanded functional repertoire in the cell cycle and DNA damage response. In humans, a splice site mutation in CTDP1 gives rise to the rare Congenital Cataracts Facial Dysmorphism and Neuropathy syndrome, and recent evidence from our lab indicates CTDP1 is required for breast cancer growth and proliferation. To explore the physiological function of CTDP1 in a mammalian system, we generated a conditional Ctdp1 knockout mouse model by insertion of loxP sites upstream of exon 3 and downstream of exon 4. Biallelic deletion of Ctdp1 results in lethality before embryonic day 7.5, with morphological features indicating embryo cell death and resorption. However, Ctdp1+/− mice are haplosufficient for phenotypic traits including body weight, hematological parameters, exploratory and locomotive functions. To investigate the potential mechanisms of the embryonic death caused by biallelic Ctdp1 knockout, mouse embryonic fibroblasts (MEFs) were established from Ctdp1+/+ and Ctdp1flox/flox mice. Lentivirus delivered Cre-mediated biallelic deletion of Ctdp1 in MEFs results in cell death preceded by impaired proliferation characterized by an increase in G1- and G2-phase populations and a reduction in the S-phase population. These cell cycle alterations caused by deletion of Ctdp1 are associated with an increase in p27 protein expression and a decrease in phosphorylated RB, phosphorylated Histone H3, and Cyclin B expression. Together, these results reveal that Ctdp1 plays an essential role in early mouse embryo development and cell growth and survival in part by regulating the cell cycle.

In This Issue

In This Issue

CGAS-STING pathway in oncogenesis and cancer therapeutics.

The host innate immunity offers the first line of defense against infection. However, recent evidence shows that the host innate immunity is also critical in sensing the presence of cytoplasmic DNA derived from genomic instability events, such as DNA damage and defective cell cycle progression. This is achieved through the cyclic GMP-AMP synthase (cGAS)/Stimulator of interferon (IFN) genes (STING) pathway. Here we discuss recent insights into the regulation of this pathway in cancer immunosurveillance, and the downstream signaling cascades that coordinate immune cell recruitment to the tumor microenvironment to destroy transformed cells through cellular senescence or cell death programs. Its central role in immunosurveillance positions the cGAS-STING pathway as an attractive anti-cancer immunotherapeutic drug target for chemical agonists or vaccine adjuvants and suggests a key node to be targeted in a synthetic lethal approach. We also discuss adaptive mechanisms used by cancer cells to circumvent cGAS-STING signaling and present evidence linking chronic cGAS-STING activation to inflammation-induced carcinogenesis, cautioning against the use of activating the cGAS-STING pathway as an anti-tumor immunotherapy. A deeper mechanistic understanding of the cGAS-STING pathway will aid in the identification of potentially efficacious anti-cancer therapeutic targets.