bims-pimaco Biomed News
on PI3K and MAPK signalling in colorectal cancer
Issue of 2020‒10‒25
fifteen papers selected by
Lucas B. Zeiger
Beatson Institute for Cancer Research
  1. Age-associated mitochondrial DNA mutations cause metabolic remodelling that contributes to accelerated intestinal tumorigenesis.
  2. Oncogenic mutant RAS signaling activity is rescaled by the ERK/MAPK pathway.
  3. FOXM1 drives HPV+ HNSCC sensitivity to WEE1 inhibition.
  4. The Janus-like role of proline metabolism in cancer.
  5. Glutaminase inhibitors induce thiol-mediated oxidative stress and radio-sensitization in treatment resistant cervical cancers.
  6. The Loss of Nuclear PTEN Increases Tumorigenesis in a Preclinical Mouse Model for Hepatocellular Carcinoma.
  7. Approaches to Investigating the Protein Interactome of PTEN.
  8. Reprogramming of nucleotide metabolism mediates synergy between epigenetic therapy and MAP Kinase inhibition.
  9. Statins decrease the expression of c-Myc protein in cancer cell lines.
  10. MCART1/SLC25A51 is required for mitochondrial NAD transport.
  11. PtdIns(3,4,5)P3-dependent Rac exchanger 1 (P-Rex1) promotes mammary tumor initiation and metastasis.
  12. The role of AMPK in metabolism and its influence on DNA damage repair.
  13. Gremlin-1 activates Akt/STAT3 signaling, which increases the glycolysis rate in breast cancer cells.
  14. Cytosolic pH regulates proliferation and tumour growth by promoting expression of cyclin D1.
  15. Cell-Cycle-Dependent ERK Signaling Dynamics Direct Fate Specification in the Mammalian Preimplantation Embryo.
  1. Nat Cancer. 2020 Oct;1(10): 976-989
    Age-associated mitochondrial DNA mutations cause metabolic remodelling that contributes to accelerated intestinal tumorigenesis.
    Anna Lm Smith, Julia C Whitehall, Carla Bradshaw, David Gay, Fiona Robertson, Alasdair P Blain, Gavin Hudson, Angela Pyle, David Houghton, Matthew Hunt, James N Sampson, Craig Stamp, Grace Mallett, Shoba Amarnath, Jack Leslie, Fiona Oakley, Laura Wilson, Angela Baker, Oliver M Russell, Riem Johnson, Claire A Richardson, Bhavana Gupta, Iain McCallum, Stuart Ac McDonald, Seamus Kelly, John C Mathers, Rakesh Heer, Robert W Taylor, Neil D Perkins, Doug M Turnbull, Owen J Sansom, Laura C Greaves.
      Oxidative phosphorylation (OXPHOS) defects caused by somatic mitochondrial DNA (mtDNA) mutations increase with age in human colorectal epithelium and are prevalent in colorectal tumours, but whether they actively contribute to tumorigenesis remains unknown. Here we demonstrate that mtDNA mutations causing OXPHOS defects are enriched during the human adenoma/carcinoma sequence, suggesting they may confer a metabolic advantage. To test this we deleted the tumour suppressor Apc in OXPHOS deficient intestinal stem cells in mice. The resulting tumours were larger than in control mice due to accelerated cell proliferation and reduced apoptosis. We show that both normal crypts and tumours undergo metabolic remodelling in response to OXPHOS deficiency by upregulating the de novo serine synthesis pathway (SSP). Moreover, normal human colonic crypts upregulate the SSP in response to OXPHOS deficiency prior to tumorigenesis. Our data show that age-associated OXPHOS deficiency causes metabolic remodelling that can functionally contribute to accelerated intestinal cancer development.
    DOI:  https://doi.org/10.1038/s43018-020-00112-5
  2. Mol Syst Biol. 2020 Oct;16(10): e9518
    Oncogenic mutant RAS signaling activity is rescaled by the ERK/MAPK pathway.
    Taryn E Gillies, Michael Pargett, Jillian M Silva, Carolyn K Teragawa, Frank McCormick, John G Albeck.
      Activating mutations in RAS are present in ~ 30% of human tumors, and the resulting aberrations in ERK/MAPK signaling play a central role in oncogenesis. However, the form of these signaling changes is uncertain, with activating RAS mutants linked to both increased and decreased ERK activation in vivo. Rationally targeting the kinase activity of this pathway requires clarification of the quantitative effects of RAS mutations. Here, we use live-cell imaging in cells expressing only one RAS isoform to quantify ERK activity with a new level of accuracy. We find that despite large differences in their biochemical activity, mutant KRAS isoforms within cells have similar ranges of ERK output. We identify roles for pathway-level effects, including variation in feedback strength and feedforward modulation of phosphatase activity, that act to rescale pathway sensitivity, ultimately resisting changes in the dynamic range of ERK activity while preserving responsiveness to growth factor stimuli. Our results reconcile seemingly inconsistent reports within the literature and imply that the signaling changes induced by RAS mutations early in oncogenesis are subtle.
    Keywords:  FRET biosensor; RAS disease; computational modeling; epidermal growth factor; single-cell kinetics
    DOI:  https://doi.org/10.15252/msb.20209518
  3. Proc Natl Acad Sci U S A. 2020 Oct 22. pii: 202013921. [Epub ahead of print]
    FOXM1 drives HPV+ HNSCC sensitivity to WEE1 inhibition.
    Ahmed Diab, Hakan Gem, Jherek Swanger, Hee Yeon Kim, Kaleb Smith, Grace Zou, Sharat Raju, Michael Kao, Matthew Fitzgibbon, Keith R Loeb, Cristina P Rodriguez, Eduardo Méndez, Denise A Galloway, Julia M Sidorova, Bruce E Clurman.
      Head and neck squamous cell carcinoma (HNSCC) associated with high-risk human papilloma virus (HPV) infection is a growing clinical problem. The WEE1 kinase inhibitor AZD1775 (WEE1i) overrides cell cycle checkpoints and is being studied in HNSCC regimens. We show that the HPV16 E6/E7 oncoproteins sensitize HNSCC cells to single-agent WEE1i treatment through activation of a FOXM1-CDK1 circuit that drives mitotic gene expression and DNA damage. An isogenic cell system indicated that E6 largely accounts for these phenotypes in ways that extend beyond p53 inactivation. A targeted genomic analysis implicated FOXM1 signaling downstream of E6/E7 expression and analyses of primary tumors and The Cancer Genome Atlas (TCGA) data revealed an activated FOXM1-directed promitotic transcriptional signature in HPV+ versus HPV- HNSCCs. Finally, we demonstrate the causality of FOXM1 in driving WEE1i sensitivity. These data suggest that elevated basal FOXM1 activity predisposes HPV+ HNSCC to WEE1i-induced toxicity and provide mechanistic insights into WEE1i and HPV+ HNSCC therapies.
    Keywords:  AZD1775; FOXM1; HPV16; WEE1; head and neck cancer
    DOI:  https://doi.org/10.1073/pnas.2013921117
  4. Cell Death Discov. 2020 ;6 104
    The Janus-like role of proline metabolism in cancer.
    Lynsey Burke, Inna Guterman, Raquel Palacios Gallego, Robert G Britton, Daniel Burschowsky, Cristina Tufarelli, Alessandro Rufini.
      The metabolism of the non-essential amino acid L-proline is emerging as a key pathway in the metabolic rewiring that sustains cancer cells proliferation, survival and metastatic spread. Pyrroline-5-carboxylate reductase (PYCR) and proline dehydrogenase (PRODH) enzymes, which catalyze the last step in proline biosynthesis and the first step of its catabolism, respectively, have been extensively associated with the progression of several malignancies, and have been exposed as potential targets for anticancer drug development. As investigations into the links between proline metabolism and cancer accumulate, the complexity, and sometimes contradictory nature of this interaction emerge. It is clear that the role of proline metabolism enzymes in cancer depends on tumor type, with different cancers and cancer-related phenotypes displaying different dependencies on these enzymes. Unexpectedly, the outcome of rewiring proline metabolism also differs between conditions of nutrient and oxygen limitation. Here, we provide a comprehensive review of proline metabolism in cancer; we collate the experimental evidence that links proline metabolism with the different aspects of cancer progression and critically discuss the potential mechanisms involved.
    Keywords:  Cancer; Cancer metabolism
    DOI:  https://doi.org/10.1038/s41420-020-00341-8
  5. Mol Cancer Ther. 2020 Oct 21. pii: molcanther.0271.2020. [Epub ahead of print]
    Glutaminase inhibitors induce thiol-mediated oxidative stress and radio-sensitization in treatment resistant cervical cancers.
    Ramachandran Rashmi, Kay Jayachandran, Jin Zhang, Vishnu Menon, Naoshad Muhammad, Michael Zahner, Fiona Ruiz, Sisi Zhang, Kevin Cho, Yuting Wang, Xiaojing Huang, Yi Huang, Michael L McCormick, Buck E Rogers, Douglas R Spitz, Gary J Patti, Julie K Schwarz.
      The purpose of the study was to determine if radiation resistant cervical cancers are dependent upon glutamine metabolism driven by activation of the PI3K pathway and test whether PI3K pathway mutation predicts radio-sensitization by inhibition of glutamine metabolism. Cervical cancer cell lines with and without PI3K pathway mutations, including SiHa and SiHa PTEN-/- cells engineered by CRISPR/Cas9, were used for mechanistic studies performed in vitro in the presence and absence of glutamine starvation and the glutaminase inhibitor, telaglenastat (CB-839). These studies included cell survival, proliferation, quantification of oxidative stress parameters, metabolic tracing with stable isotope labeled substrates, metabolic rescue and combination studies with L-buthionine sulfoximine (BSO), auranofin (AUR), and radiation (RT). In vivo studies of telaglenastat ± RT were performed using CaSki and SiHa xenografts grown in immune compromised mice. PI3K activated cervical cancer cells were selectively sensitive to glutamine deprivation through a mechanism that included thiol-mediated oxidative stress. Telaglenastat treatment decreased total glutathione pools, increased the percent glutathione disulfide, and caused clonogenic cell killing that was reversed by treatment with the thiol antioxidant, N-acetylcysteine. Telaglenastat also sensitized cells to killing by glutathione depletion with BSO, thioredoxin reductase inhibition with AUR, and RT. Glutamine dependent PI3K activated cervical cancer xenografts were sensitive to telaglenastat monotherapy, and telaglenastat selectively radio-sensitized cervical cancer cells in vitro and in vivo. These novel preclinical data support the utility of telaglenastat for glutamine dependent radio-resistant cervical cancers and demonstrate that PI3K pathway mutations may be used as a predictive biomarker for telaglenastat sensitivity.
    DOI:  https://doi.org/10.1158/1535-7163.MCT-20-0271
  6. iScience. 2020 Oct 23. 23(10): 101548
    The Loss of Nuclear PTEN Increases Tumorigenesis in a Preclinical Mouse Model for Hepatocellular Carcinoma.
    Takashi Kato, Tatsuya Yamada, Hideki Nakamura, Atsushi Igarashi, Robert A Anders, Hiromi Sesaki, Miho Iijima.
      The PTEN gene is highly mutated in many cancers, including hepatocellular carcinoma. The PTEN protein is located at different subcellular regions-PTEN at the plasma membrane suppresses PI3-kinase signaling in cell growth, whereas PTEN in the nucleus maintains genome integrity. Here, using nuclear PTEN-deficient mice, we analyzed the role of PTEN in the nucleus in hepatocellular carcinoma that is induced by carcinogen and oxidative stress-producing hepatotoxin. Upon oxidative stress, PTEN was accumulated in the nucleus of the liver, and this accumulation promoted repair of DNA damage in wild-type mice. In contrast, nuclear PTEN-deficient mice had increased DNA damage and accelerated hepatocellular carcinoma formation. Both basal and oxidative stress-induced localization of PTEN in the nucleus require ubiquitination of lysine 13 in PTEN. Taken together, these data suggest the critical role of nuclear PTEN in the protection from DNA damage and tumorigenesis in vivo.
    Keywords:  Cancer; Cell Biology
    DOI:  https://doi.org/10.1016/j.isci.2020.101548
  7. J Proteome Res. 2020 Oct 19.
    Approaches to Investigating the Protein Interactome of PTEN.
    Sarah L Smith, Andrew R Pitt, Corinne M Spickett.
      The tumor suppressor phosphatase and tensin homologue (PTEN) is a redox-sensitive dual specificity phosphatase with an essential role in the negative regulation of the PI3K-AKT signaling pathway, affecting metabolic and cell survival processes. PTEN is commonly mutated in cancer, and dysregulation in the metabolism of PIP3 is implicated in other diseases such as diabetes. PTEN interactors are responsible for some functional roles of PTEN beyond the negative regulation of the PI3K pathway and are thus of great importance in cell biology. Both high-data content proteomics-based approaches and low-data content PPI approaches have been used to investigate the interactome of PTEN and elucidate further functions of PTEN. While low-data content approaches rely on co-immunoprecipitation and Western blotting, and as such require previously generated hypotheses, high-data content approaches such as affinity pull-down proteomic assays or the yeast 2-hybrid system are hypothesis generating. This review provides an overview of the PTEN interactome, including redox effects, and critically appraises the methods and results of high-data content investigations into the global interactome of PTEN. The biological significance of findings from recent studies is discussed and illustrates the breadth of cellular functions of PTEN that can be discovered by these approaches.
    Keywords:  affinity pull-down; global interactome; high-data content; protein−protein interactions; redox regulation; yeast 2-hybrid
    DOI:  https://doi.org/10.1021/acs.jproteome.0c00570
  8. Mol Cancer Ther. 2020 Oct 21. pii: molcanther.0259.2020. [Epub ahead of print]
    Reprogramming of nucleotide metabolism mediates synergy between epigenetic therapy and MAP Kinase inhibition.
    Tatiana Shorstova, Jie Su, Tiejun Zhao, Michael Dahabieh, Matthew Leibovitch, Mariana De Sa Tavares Russo, Daina Avizonis, Shivshankari Rajkumar, Ian R Watson, Sonia V Del Rincón, Wilson H Miller, William D Foulkes, Michael Witcher.
      Small Cell Carcinoma of the Ovary, Hypercalcemic Type is a rare but often lethal cancer which is diagnosed at a median age of 24 years. Optimal management of patients is not well defined and current treatment remains challenging, necessitating the discovery of novel therapeutic approaches. The identification of SMARCA4-inactivating mutations invariably characterizing this type of cancer provided insights facilitating diagnostic and therapeutic measures against this disease. We show here that the BET inhibitor OTX015 acts in synergy with the MEK inhibitor cobimetinib to repress the proliferation of SCCOHT in vivo. Notably, this synergy is also observed in some SMARCA4-expressing ovarian adenocarcinoma models intrinsically resistant to BETi. Mass Spectrometry, coupled with knockdown of newly-found targets including thymidylate synthetase, revealed that the repression of a panel of proteins involved in nucleotide synthesis, underlies this synergy both in vitro and in vivo, resulting in reduced pools of nucleotide metabolites and subsequent cell cycle arrest. Overall, our data indicate that dual treatment with BETi and MEKi represents a rational combination therapy against SCCOHT and potentially additional ovarian cancer subtypes.
    DOI:  https://doi.org/10.1158/1535-7163.MCT-20-0259
  9. Mol Cell Biochem. 2020 Oct 17.
    Statins decrease the expression of c-Myc protein in cancer cell lines.
    Prema S Rao, U Subrahmanyeswara Rao.
      Statins are potent inhibitors of the mevalonate/cholesterol biosynthetic pathway and are widely prescribed for the prevention of cardiovascular diseases. Here, we carried out a comprehensive analysis of the effects of three statins, simvastatin, atorvastatin, and lovastatin, on six different cancer cell lines that include a P-glycoprotein-expressing, multidrug resistant variant of an ovarian cancer cell line. Incubation of all cancer cell lines with statins resulted in suppression of cell proliferation without inducing apoptotic cell death. The cell proliferation arrest could be reversed upon transfer of cells to statin-free growth media as well as by the supplementation of the growth media with mevalonate. Further analysis suggested that statins induced cell cycle arrest at G0/G1 phase in four cancer cell lines and the loss of c-Myc protein in three cancer cell lines. The c-Myc expression and the progression of cell division cycle were restored upon the addition of mevalonate to the culture media containing statins. Finally, cells incubated with statins contained an increased level of phosphorylated histone H2AX, an observation previously correlated to cellular senescence. Together, these data demonstrate that statins inhibit the mevalonate pathway which is tightly coupled to oxidative branch of the pentose phosphate pathway, c-Myc expression, cell division cycle progression, and cellular senescence. Implications of these observations in the application of statins as cancer therapeutics are discussed.
    Keywords:  Cell cycle; HMG CoA reductase; Mevalonate pathway; Statins; c-Myc
    DOI:  https://doi.org/10.1007/s11010-020-03940-2
  10. Sci Adv. 2020 Oct;pii: eabe5310. [Epub ahead of print]6(43):
    MCART1/SLC25A51 is required for mitochondrial NAD transport.
    Nora Kory, Jelmi Uit de Bos, Sanne van der Rijt, Nevena Jankovic, Miriam Güra, Nicholas Arp, Izabella A Pena, Gyan Prakash, Sze Ham Chan, Tenzin Kunchok, Caroline A Lewis, David M Sabatini.
      The nicotinamide adenine dinucleotide (NAD+/NADH) pair is a cofactor in redox reactions and is particularly critical in mitochondria as it connects substrate oxidation by the tricarboxylic acid (TCA) cycle to adenosine triphosphate generation by the electron transport chain (ETC) and oxidative phosphorylation. While a mitochondrial NAD+ transporter has been identified in yeast, how NAD enters mitochondria in metazoans is unknown. Here, we mine gene essentiality data from human cell lines to identify MCART1 (SLC25A51) as coessential with ETC components. MCART1-null cells have large decreases in TCA cycle flux, mitochondrial respiration, ETC complex I activity, and mitochondrial levels of NAD+ and NADH. Isolated mitochondria from cells lacking or overexpressing MCART1 have greatly decreased or increased NAD uptake in vitro, respectively. Moreover, MCART1 and NDT1, a yeast mitochondrial NAD+ transporter, can functionally complement for each other. Thus, we propose that MCART1 is the long sought mitochondrial transporter for NAD in human cells.
    DOI:  https://doi.org/10.1126/sciadv.abe5310
  11. Proc Natl Acad Sci U S A. 2020 Oct 23. pii: 202006445. [Epub ahead of print]
    PtdIns(3,4,5)P3-dependent Rac exchanger 1 (P-Rex1) promotes mammary tumor initiation and metastasis.
    Nuthasuda Srijakotre, Heng-Jia Liu, Max Nobis, Joey Man, Hon Yan Kelvin Yip, Antonella Papa, Helen E Abud, Kurt I Anderson, Heidi C E Welch, Tony Tiganis, Paul Timpson, Catriona A McLean, Lisa M Ooms, Christina A Mitchell.
      The Rac-GEF, P-Rex1, activates Rac1 signaling downstream of G protein-coupled receptors and PI3K. Increased P-Rex1 expression promotes melanoma progression; however, its role in breast cancer is complex, with differing reports of the effect of its expression on disease outcome. To address this we analyzed human databases, undertook gene array expression analysis, and generated unique murine models of P-Rex1 gain or loss of function. Analysis of PREX1 mRNA expression in breast cancer cDNA arrays and a METABRIC cohort revealed that higher PREX1 mRNA in ER+ve/luminal tumors was associated with poor outcome in luminal B cancers. Prex1 deletion in MMTV-neu or MMTV-PyMT mice reduced Rac1 activation in vivo and improved survival. High level MMTV-driven transgenic PREX1 expression resulted in apicobasal polarity defects and increased mammary epithelial cell proliferation associated with hyperplasia and development of de novo mammary tumors. MMTV-PREX1 expression in MMTV-neu mice increased tumor initiation and enhanced metastasis in vivo, but had no effect on primary tumor growth. Pharmacological inhibition of Rac1 or MEK1/2 reduced P-Rex1-driven tumoroid formation and cell invasion. Therefore, P-Rex1 can act as an oncogene and cooperate with HER2/neu to enhance breast cancer initiation and metastasis, despite having no effect on primary tumor growth.
    Keywords:  breast cancer; cell polarity; guanine nucleotide exchange factor (GEF); metastasis; transgenic mouse
    DOI:  https://doi.org/10.1073/pnas.2006445117
  12. Mol Biol Rep. 2020 Oct 18.
    The role of AMPK in metabolism and its influence on DNA damage repair.
    Michał Szewczuk, Karolina Boguszewska, Julia Kaźmierczak-Barańska, Bolesław T Karwowski.
      One of the most complex health disproportions in the human body is the metabolic syndrome (MetS). It can result in serious health consequences such as type 2 diabetes mellitus, atherosclerosis or insulin resistance. The center of energy regulation in human is AMP-activated protein kinase (AMPK), which modulates cells' metabolic pathways and protects them against negative effects of metabolic stress, e.g. reactive oxygen species. Moreover, recent studies show the relationship between the AMPK activity and the regulation of DNA damage repair such as base excision repair (BER) system, which is presented in relation to the influence of MetS on human genome. Hence, AMPK is studied not only in the field of counteracting MetS but also prevention of genetic alterations and cancer development. Through understanding AMPK pathways and its role in cells with damaged DNA it might be possible to improve cell's repair processes and develop new therapies. This review presents AMPK role in eukaryotic cells and focuses on the relationship between AMPK activity and the regulation of BER system through its main component-8-oxoguanine glycosylase (OGG1).
    Keywords:  8-oxoguanine glycosylase; AMPK; DNA damage; DNA repair
    DOI:  https://doi.org/10.1007/s11033-020-05900-x
  13. Biochem Biophys Res Commun. 2020 Oct 20. pii: S0006-291X(20)31934-3. [Epub ahead of print]
    Gremlin-1 activates Akt/STAT3 signaling, which increases the glycolysis rate in breast cancer cells.
    Na Hui Kim, Nam Ji Sung, Hyung-Sun Youn, Sin-Aye Park.
      Gremlin-1 (GREM1), one of the antagonists of bone morphogenetic proteins (BMPs), has recently been reported to be overexpressed in a variety of cancers including breast cancer. GREM1 is involved in tumor promotion, but little is known about its role in the glycolysis of cancer cells. In this study, we investigated the role of GREM1 in glycolysis of breast cancer cells and its underlying molecular mechanisms. We first observed that glucose uptake and lactate production were increased in GREM1-overexpressing breast cancer cells. GREM1 increased the expression of hexokinase-2 (HK2), which catalyzes the phosphorylation of glucose, the first step in glycolysis. In addition, GREM1 activated STAT3 transcription factor through the ROS-Akt signaling pathway. The ROS-Akt-STAT3 axis activated by GREM1 was involved in promoting glucose uptake by increasing the expression of HK2 in breast cancer cells. Therefore, our study suggested a new mechanism by which GREM1 is involved in breast cancer promotion by increasing glycolysis in breast cancer cells.
    Keywords:  Breast cancer; GREM1; Glycolysis; HK2; STAT3
    DOI:  https://doi.org/10.1016/j.bbrc.2020.10.025
  14. Nat Metab. 2020 Oct 19.
    Cytosolic pH regulates proliferation and tumour growth by promoting expression of cyclin D1.
    Lisa Maria Koch, Eivind Salmorin Birkeland, Stefania Battaglioni, Xiao Helle, Mayura Meerang, Stefanie Hiltbrunner, Alfredo J Ibáñez, Matthias Peter, Alessandra Curioni-Fontecedro, Isabelle Opitz, Reinhard Dechant.
      Enhanced growth and proliferation of cancer cells are accompanied by profound changes in cellular metabolism. These metabolic changes are also common under physiological conditions, and include increased glucose fermentation accompanied by elevated cytosolic pH (pHc)1,2. However, how these changes contribute to enhanced cell growth and proliferation is unclear. Here, we show that elevated pHc specifically orchestrates an E2F-dependent transcriptional programme to drive cell proliferation by promoting cyclin D1 expression. pHc-dependent transcription of cyclin D1 requires the transcription factors CREB1, ATF1 and ETS1, and the histone acetyltransferases p300 and CBP. Biochemical characterization revealed that the CREB1-p300/CBP interaction acts as a pH sensor and coincidence detector, integrating different mitotic signals to regulate cyclin D1 transcription. We also show that elevated pHc contributes to increased cyclin D1 expression in malignant pleural mesotheliomas (MPMs), and renders these cells hypersensitive to pharmacological reduction of pHc. Taken together, these data demonstrate that elevated pHc is a critical cellular signal regulating G1 progression, and provide a mechanism linking elevated pHc to oncogenic activation of cyclin D1 in MPMs, and possibly other cyclin D1~dependent tumours. Thus, an increase of pHc may represent a functionally important, early event in the aetiology of cancer that is amenable to therapeutic intervention.
    DOI:  https://doi.org/10.1038/s42255-020-00297-0
  15. Dev Cell. 2020 Oct 16. pii: S1534-5807(20)30715-2. [Epub ahead of print]
    Cell-Cycle-Dependent ERK Signaling Dynamics Direct Fate Specification in the Mammalian Preimplantation Embryo.
    Michael J Pokrass, Kathleen A Ryan, Tianchi Xin, Brittany Pielstick, Winston Timp, Valentina Greco, Sergi Regot.
      Despite the noisy nature of single cells, multicellular organisms robustly generate different cell types from one zygote. This process involves dynamic cross regulation between signaling and gene expression that is difficult to capture with fixed-cell approaches. To study signaling dynamics and fate specification during preimplantation development, we generated a transgenic mouse expressing the ERK kinase translocation reporter and measured ERK activity in single cells of live embryos. Our results show primarily active ERK in both the inner cell mass and trophectoderm cells due to fibroblast growth factor (FGF) signaling. Strikingly, a subset of mitotic events results in a short pulse of ERK inactivity in both daughter cells that correlates with elevated endpoint NANOG levels. Moreover, endogenous tagging of Nanog in embryonic stem cells reveals that ERK inhibition promotes enhanced stabilization of NANOG protein after mitosis. Our data show that cell cycle, signaling, and differentiation are coordinated during preimplantation development.
    Keywords:  ERK; NANOG; blastocyst; cell cycle; embryonic stem cells; preimplantation development; signaling dynamics
    DOI:  https://doi.org/10.1016/j.devcel.2020.09.013
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