scholarly journals Dimerization partners determine the activity of the Twist bHLH protein during Drosophila mesoderm development

Development ◽  
2001 ◽  
Vol 128 (16) ◽  
pp. 3145-3159 ◽  
Author(s):  
Irinka Castanon ◽  
Stephen Von Stetina ◽  
Jason Kass ◽  
Mary K. Baylies
Keyword(s):  
Cell Fate ◽  
Muscle Development ◽  
Bhlh Protein ◽  
Mesoderm Induction ◽  
Loss Of Function ◽  
Somatic Muscle ◽  
Cell Fate Decisions ◽  
Sequence Of Events

The basic helix-loop-helix transcription factor Twist regulates a series of distinct cell fate decisions within the Drosophila mesodermal lineage. These twist functions are reflected in its dynamic pattern of expression, which is characterized by initial uniform expression during mesoderm induction, followed by modulated expression at high and low levels in each mesodermal segment, and finally restricted expression in adult muscle progenitors. We show two distinct partner-dependent functions for Twist that are crucial for cell fate choice. We find that Twist can form homodimers and heterodimers with the Drosophila E protein homologue, Daughterless,in vitro. Using tethered dimers to assess directly the function of these two particular dimers in vivo, we show that Twist homodimers specify mesoderm and the subsequent allocation of mesodermal cells to the somatic muscle fate. Misexpression of Twist-tethered homodimers in the ectoderm or mesoderm leads to ectopic somatic muscle formation overriding other developmental cell fates. In addition, expression of tethered Twist homodimers in embryos null fortwist can rescue mesoderm induction as well as somatic muscle development. Loss of function analyses, misexpression and dosage experiments, and biochemical studies indicate that heterodimers of Twist and Daughterless repress genes required for somatic myogenesis. We propose that these two opposing roles explain how modulated Twist levels promote the allocation of cells to the somatic muscle fate during the subdivision of the mesoderm. Moreover, this work provides a paradigm for understanding how the same protein controls a sequence of events within a single lineage.

scholarly journals The LINC complex transmits integrin-dependent tension to the nuclear lamina and represses epidermal differentiation

2020 ◽  
Author(s):  
Emma Carley ◽  
Rachel K. Stewart ◽  
Abigail Zieman ◽  
Iman Jalilian ◽  
Diane. E. King ◽  
...  
Keyword(s):  
Cell Fate ◽  
Control Cell ◽  
Nuclear Lamina ◽  
Epidermal Differentiation ◽  
Keratinocyte Differentiation ◽  
Linc Complex ◽  
Force Transmission ◽  
Cell Fate Decisions

AbstractWhile the mechanisms by which chemical signals control cell fate have been well studied, how mechanical inputs impact cell fate decisions are not well understood. Here, using the well-defined system of keratinocyte differentiation in the skin, we examine whether and how direct force transmission to the nucleus regulates epidermal cell fate. Using a molecular biosensor, we find that tension on the nucleus through Linker of Nucleoskeleton and Cytoskeleton (LINC) complexes requires integrin engagement in undifferentiated epidermal stem cells, and is released during differentiation concomitant with decreased tension on A-type lamins. LINC complex ablation in mice reveals that LINC complexes are required to repress epidermal differentiation in vivo and in vitro and influence accessibility of epidermal differentiation genes, suggesting that force transduction from engaged integrins to the nucleus plays a role in maintaining keratinocyte progenitors. This work reveals a direct mechanotransduction pathway capable of relaying adhesion-specific signals to regulate cell fate.

The SCL Transcription Factor Supports Erythroid Cell Survival and Differentiation Downstream of the Erythropoietin Receptor.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 818-818
Author(s):  
Rachid Lahlil ◽  
Richard Martin ◽  
Peter D. Aplan ◽  
C. Glenn Begley ◽  
Jacqueline E. Damen ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Cell Survival ◽  
Cell Fate ◽  
Genetic Interaction ◽  
Fetal Liver ◽  
Erythropoietin Receptor ◽  
Erythroid Cell ◽  
Loss Of Function

Abstract Erythroid cell development critically depends on the SCL/Tal1 transcription factor and on erythropoietin signalling. In the present study, we have taken several approaches to show that the two genes operate within the same pathway to consolidate the erythroid lineage. Signaling through the erythropoietin receptor (EpoR) upregulates SCL protein levels in a clonal cell line (TF-1) in vitro, and in murine fetal liver cells in vivo, when Epor−/− cells were compared to those of wild type littermates at E12.5. In addition, we provide functional evidence for a linear pathway from EpoR to SCL that regulates erythropoiesis. Interfering with SCL induction or SCL function prevents the anti-apoptotic effect of Epo in TF-1 cells and conversely, ectopic SCL expression is sufficient to substitute for Epo to transiently maintain cell survival. In vivo, SCL gain of function complements the cellular defects in Epor−/− embryos to support cell survival and maturation during primitive and definitive erythropoiesis, as assessed by cellular and histological analyses of Epor−/− SCLtg embryos. Moreover, several erythroid specific genes that are decreased in Epor−/− embryos are rescued by the SCL transgene including glycophorinA, bH1 and bmaj globin, providing molecular confirmation of the functional and genetic interaction between Epor and SCL. Conversely, erythropoiesis becomes deficient in compound Epor+/−SCL+/− heterozygote mice, indicating that the genetic interaction between EpoR and SCL is synthetic. Finally, using EpoR mutants that harbour well defined signalling deficiencies, combined with gain and loss of function approaches for specific kinases, we identify MAPK as the major signal transduction pathway downstream of EpoR that upregulates SCL function, necessary for erythroid cell survival and differentiation. Taken together, our observations are consistent with the view that cytokines can influence cell fate by altering the dosage of lineage transcriptional regulators.

Runx1 Is Required for Notch-Induced Specification of Megakaryocyte Development from Early Hematopoietic Stem and Progenitor Cells

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1370-1370
Author(s):  
Melanie G Cornejo ◽  
Thomas Mercher ◽  
Joseph D. Growney ◽  
Jonathan Jesneck ◽  
Ivan Maillard ◽  
...  
Keyword(s):  
Notch Signaling ◽  
Cell Fate ◽  
Stromal Cells ◽  
Gfp Expression ◽  
Hematopoietic Stem ◽  
Cell Fate Decisions ◽  
Insight Into ◽  
Megakaryocyte Differentiation

Abstract The Notch signaling pathway is involved in a broad spectrum of cell fate decisions during development, and in the hematopoietic system, it is known to favor T cell- vs B cell lineage commitment. However, its role in myeloid lineage development is less well understood. We have shown, using heterotypic co-cultures of murine primary hematopoietic stem cells (Lin-Sca-1+ckit+ HSCs) and OP9 stromal cells expressing the Notch ligand Delta1 (OP9-DL1), that Notch signaling derived from cell non-autonomous cues acts as a positive regulator of megakaryocyte fate from LSK cells. Bone marrow transplantation experiments with a constitutively active Notch mutant resulted in enhanced megakaryopoiesis in vivo, with increased MEP numbers and megakaryocyte colony formation. In contrast, expression of dnMAML using a conditional ROSA26 knock-in mouse model significantly impaired megakaryopoiesis in vivo, with a marked decrease in megakaryocyte progenitors. In order to understand the cellular differentiation pathways controlled by Notch, we first examined the ability of various purified progenitor populations to differentiate toward megakaryocytes upon Notch stimulation in vitro. We observed that CMP and MEP, but not GMP, can engage megakaryopoiesis upon Notch stimulation. Our results were consistent with expression analysis of Notch signaling genes in these purified progenitors and were supported by the observation that transgenic Notch reporter mice display higher levels of reporter (i.e. GFP) expression in HSC and MEP, vs. CMP and GMP in vivo. Furthermore, purified progenitors with high GFP expression gave rise to increased numbers of megakarocyte-containing colonies when plated in vitro compared to GFP-negative progenitors. In addition, further purification of the HSC population into long-term (LT), short-term (ST), and lymphoid-primed myeloid progenitors (LMPP) before plating on OP9-DL1 stroma showed that LMPP have a reduced ability to give rise to megakaryocytes compared to the other two populations. These data support the hypothesis that there is an early commitment to erythro/megakaryocytic fate from HSC prior to lymphoid commitment. To gain insight into the molecular mechanism underlying Notch-induced megakaryopoiesis, we performed global gene expression analysis that demonstrated the engagement of a megakaryopoietic transcriptional program when HSC were co-cultured with OP9-DL1 vs. OP9 stroma or OP9-DL1 treated with gamma-secretase inhibitor. Of interest, Runx1 was among the most upregulated genes in HSC co-cultured on OP9-DL1 stroma. To assess whether Notch signaling engages megakaryocytic fate through induction of Runx1, we plated HSC from Runx1 −/− mice on OP9-DL1 stroma. Compared to WT cells, Runx1 −/− HSC had a severely reduced ability to develop into CD41+ cells. In contrast, overexpression of Runx1 in WT HSC was sufficient to induce megakaryocyte fate on OP9 stroma without Notch stimulation. Together, our results indicate that Notch pathway activation induced by stromal cells is an important regulator of cell fate decisions in early progenitors. We show that Notch signaling is upstream of Runx1 during Notch-induced megakaryocyte differentiation and that Runx1 is an essential target of Notch signaling. We believe that these results provide important insight into the pathways controlling megakaryocyte differentiation, and may have important therapeutic potential for megakaryocyte lineage-related disorders.

scholarly journals Activated Notch4 Inhibits Angiogenesis: Role of β1-Integrin Activation

2002 ◽  
Vol 22 (8) ◽  
pp. 2830-2841 ◽  
Author(s):  
Kevin G. Leong ◽  
Xiaolong Hu ◽  
Linheng Li ◽  
Michela Noseda ◽  
Bruno Larrivée ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Fate ◽  
Chorioallantoic Membrane ◽  
Surface Expression ◽  
Cell Phenotype ◽  
Β1 Integrin ◽  
Cell Fate Decisions ◽  
Β1 Integrins

ABSTRACT Notch4 is a member of the Notch family of transmembrane receptors that is expressed primarily on endothelial cells. Activation of Notch in various cell systems has been shown to regulate cell fate decisions. The sprouting of endothelial cells from microvessels, or angiogenesis, involves the modulation of the endothelial cell phenotype. Based on the function of other Notch family members and the expression pattern of Notch4, we postulated that Notch4 activation would modulate angiogenesis. Using an in vitro endothelial-sprouting assay, we show that expression of constitutively active Notch4 in human dermal microvascular endothelial cells (HMEC-1) inhibits endothelial sprouting. We also show that activated Notch4 inhibits vascular endothelial growth factor (VEGF)-induced angiogenesis in the chick chorioallantoic membrane in vivo. Activated Notch4 does not inhibit HMEC-1 proliferation or migration through fibrinogen. However, migration through collagen is inhibited. Our data show that Notch4 cells exhibit increased β1-integrin-mediated adhesion to collagen. HMEC-1 expressing activated Notch4 do not have increased surface expression of β1-integrins. Rather, we demonstrate that Notch4-expressing cells display β1-integrin in an active, high-affinity conformation. Furthermore, using function-activating β1-integrin antibodies, we demonstrate that activation of β1-integrins is sufficient to inhibit VEGF-induced endothelial sprouting in vitro and angiogenesis in vivo. Our findings suggest that constitutive Notch4 activation in endothelial cells inhibits angiogenesis in part by promoting β1-integrin-mediated adhesion to the underlying matrix.

Postmitotic cells fated to become rod photoreceptors can be respecified by CNTF treatment of the retina

Development ◽  
1997 ◽  
Vol 124 (5) ◽  
pp. 1055-1067 ◽  
Author(s):  
Z.D. Ezzeddine ◽  
X. Yang ◽  
T. DeChiara ◽  
G. Yancopoulos ◽  
C.L. Cepko
Keyword(s):  
Cell Fate ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Extrinsic Factors ◽  
Rod Photoreceptors ◽  
Cell Fate Decisions ◽  
Retinal Explants ◽  
A Cell

Lineage analyses of vertebrate retinae have led to the suggestions that cell fate decisions are made during or after the terminal cell division and that extrinsic factors can influence fate choices. The evidence for a role of extrinsic factors is strongest for development of rodent rod photoreceptors ('rods'). In an effort to identify molecules that may regulate rod development, a number of known factors were assayed in vitro. Ciliary neurotrophic factor (CNTF) was found to have a range of effects on retinal cells. Addition of CNTF to postnatal rat retinal explants resulted in a dramatic reduction in the number of differentiating rods. Conversly, the number of cells expressing markers of bipolar cell differentiation was increased to a level not normally seen in vivo or in vitro. In addition, a small increase in the percentage of cells expressing either a marker of amacrine cells or a marker of Muller glia was noted. It was determined that many of the cells that would normally differentiate into rods were the cells that differentiated as bipolar cells in the presence of CNTF. Prospective rod photoreceptors could make this change even when they were postmitotic, indicating that at least a subset of cells fated to be rods were not committed to this fate at the time they were born. These findings highlight the distinction between cell fate and commitment. Resistance to the effect of CNTF on rod differentiation occurred at about the time that a cell began to express opsin. The time of commitment to terminal rod differentiation may thus coincide with the initiation of opsin expression. In agreement with the hypothesis that CNTF plays a role in rod differentiation in vivo, a greater percentage of cells were observed differentiating as rod photoreceptors in mouse retinal explants lacking a functional CNTF receptor, relative to wild-type littermates.

Abstract 442: Epigenetic Regulation of Ezh2 in Direct Human Cardiac Reprogramming

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Yang Zhou ◽  
Yawen Tang ◽  
Lianzhong Zhao ◽  
Rui Lu ◽  
Jianyi Zhang
Keyword(s):  
Cardiovascular Disease ◽  
Cell Fate ◽  
Epigenetic Regulation ◽  
Ectopic Expression ◽  
The United States ◽  
Inhibitory Effect ◽  
Loss Of Function ◽  
Lower Efficiency

Cardiovascular disease is still the leading cause of death in the United States. Due to the limited regenerative capacity of adult hearts, the damage caused by heart injury could not be reversed and often progressed into heart failure. In need of cardiovascular disease treatment, many therapies aimed at either cell transplantation or cell regeneration have been proposed. Direct reprogramming of somatic cells into induced cardiomyocytes (iCMs) is considered to be a promising strategy for regenerative medicine. The induction of cardiomyocytes from non-myocytes has been achieved efficiently via ectopic expression of reprogramming factors both in vitro and in vivo with mice models. However, as human cells are more resistant to the reprogramming process, the generation of human iCMs (hiCMs) has been restricted by the factor that using more complex cocktails generated only functionally immature cells with lower efficiency and longer conversion time. The inefficiency of hiCMs production called for the identification and elucidation of underlying species-specific regulatory mechanisms in human, and removal of the additional epigenetic barriers which might be damping the hiCMs reprogramming. Here, we identified a human-specific epigenetic barrier, Enhancer of zesta homolog 2 (EZH2), via an unbiased loss-of-function screening. With the knockdown of EZH2, the hiCM reprogramming efficiency was significantly increased, accompanied with profound repression of collagen and extracellular matrix genes, which are related to the formation of fibrosis. Consistently, Inhibition of EZH2 catalytic activity via small molecules promotes hiCM reprogramming, suggesting that EZH2’s inhibitory effect was mediated by epigenetic regulation of histone modifications. Therefore, our study revealed a previously unrecognized regulatory mechanism of human cardiac reprogramming, which allows us to overcome the fibroblast fate barriers and ease the cardiac cell fate conversion.

scholarly journals Notch Inhibits Osteoblast Differentiation and Causes Osteopenia

Endocrinology ◽  
2008 ◽  
Vol 149 (8) ◽  
pp. 3890-3899 ◽  
Author(s):  
Stefano Zanotti ◽  
Anna Smerdel-Ramoya ◽  
Lisa Stadmeyer ◽  
Deena Durant ◽  
Freddy Radtke ◽  
...  
Keyword(s):  
Cell Fate ◽  
Type I Collagen ◽  
Cre Recombinase ◽  
Low Fertility ◽  
Type I ◽  
Cmv Promoter ◽  
Cell Fate Decisions ◽  
Skeletal Phenotype

Notch receptors are determinants of cell fate decisions. To define the role of Notch in the adult skeleton, we created transgenic mice overexpressing the Notch intracellular domain (NICD) under the control of the type I collagen promoter. First-generation transgenics were small and osteopenic. Bone histomorphometry revealed that NICD caused a decrease in bone volume, secondary to a reduction in trabecular number; osteoblast and osteoclast number were decreased. Low fertility of founder mice and lethality of young pups did not allow the complete establishment of transgenic lines. To characterize the effect of Notch overexpression in vitro, NICD was induced in osteoblasts and stromal cells from Rosanotch mice, in which a STOP cassette flanked by loxP sites is upstream of NICD, by transduction with an adenoviral vector expressing Cre recombinase (Cre) under the control of the cytomegalovirus (CMV) promoter (Ad-CMV-Cre). NICD impaired osteoblastogenesis and inhibited Wnt/β-catenin signaling. To determine the effects of notch1 deletion in vivo, mice in which notch1 was flanked by loxP sequences (notch1loxP/loxP) were mated with mice expressing Cre recombinase under the control of the osteocalcin promoter. Conditional null notch1 mice had no obvious skeletal phenotype, possibly because of rescue by notch2; however, 1-month-old females exhibited a modest increase in osteoclast surface and eroded surface. Osteoblasts from notch1loxP/loxP mice, transduced with Ad-CMV-Cre and transfected with Notch2 small interfering RNA, displayed increased alkaline phosphatase activity. In conclusion, Notch signaling in osteoblasts causes osteopenia and impairs osteo-blastogenesis by inhibiting the Wnt/β-catenin pathway.

scholarly journals PDTM-28. AN OTX2-PAX3 SIGNALLING AXIS REGULATES GROUP 3 MEDULLOBLASTOMA CELL FATE

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi193-vi193
Author(s):  
Jamie Zagozewski ◽  
Ghazaleh Shahriary ◽  
Ludivine Morrison ◽  
Margaret Stromecki ◽  
Agnes Fresnoza ◽  
...  
Keyword(s):  
Cell Fate ◽  
Tumor Size ◽  
Prolonged Survival ◽  
Pax6 Expression ◽  
Self Renewal ◽  
Cell Fate Decisions ◽  
Group 3

Abstract The majority of Group 3 medulloblastomas (MB) exhibit amplification or increased expression of OTX2. OTX2 is primarily known as an oncogenic driver of tumor growth and cell cycle progression in Group 3 MB; however, its role as a repressor of differentiation is poorly characterized. Therefore, we utilized extensive patient data and mapped Group 3 MB chromatin dynamics in stem cell-enriched cultures to evaluate the divergent role of OTX2 in cell fate decisions in Group 3 MB pathogenesis. Several PAX genes were identified as novel OTX2 targets in Group 3 MB. Examination of patient data revealed that PAX3 and PAX6 expression is significantly reduced in Group 3 MB patients and is associated with significantly reduced survival. Functional evaluation of PAX3 and PAX6 expression showed that PAX3 expression significantly reduced self-renewal capacity of Group 3 MB tumorspheres in vitro and significantly prolonged survival and reduced tumor size in orthotopic xenograft models in vivo. RNA-sequencing of PAX3 and PAX6 gain of function (GOF) tumorspheres revealed mTORC1 signalling was specifically downregulated in PAX3 GOF, indicating this pathway may be critical for the survival and self-renewal differences observed between PAX3/PAX6 GOF models. Treatment of Group 3 MB with mTOR inhibitors reduced self-renewal in vitro and significantly prolonged survival and reduced tumor size in vivo. To further evaluate the role for this signalling axis in the Group 3 MB neural lineage hierarchy, we carried out scRNA-sequencing in tumorspheres from 4 Group 3 MB cell lines. Interestingly, a broad range of OTX2 expression was observed across single cell clusters, suggesting distinct OTX2 regulatory hierarchies are present in Group 3 MB. Collectively, our work demonstrates the multifaceted role of OTX2 as a regulator of cell fate decisions in Group 3 MB and identifies a novel role for mTORC1 signalling in Group 3 MB self-renewal and differentiation.

scholarly journals Developmental and Transcriptional Consequences of Mutations in Drosophila TAFII60

2001 ◽  
Vol 21 (20) ◽  
pp. 6808-6819 ◽  
Author(s):  
Norikazu Aoyagi ◽  
David A. Wassarman
Keyword(s):  
Rna Polymerase Ii ◽  
Cell Fate ◽  
Transcription Initiation ◽  
Developmental Regulation ◽  
Regulation Of Gene Expression ◽  
Loss Of Function ◽  
Activator Proteins ◽  
Regulate Cell Growth

ABSTRACT In vitro, the TAFII60 component of the TFIID complex contributes to RNA polymerase II transcription initiation by serving as a coactivator that interacts with specific activator proteins and possibly as a promoter selectivity factor that interacts with the downstream promoter element. In vivo roles for TAFII60 in metazoan transcription are not as clear. Here we have investigated the developmental and transcriptional requirements for TAFII60 by analyzing four independent Drosophila melanogaster TAF II 60 mutants. Loss-of-function mutations in Drosophila TAF II 60 result in lethality, indicating that TAFII60 provides a nonredundant function in vivo. Molecular analysis of TAF II 60alleles revealed that essential TAFII60 functions are provided by two evolutionarily conserved regions located in the N-terminal half of the protein. TAFII60 is required at all stages of Drosophila development, in both germ cells and somatic cells. Expression of TAFII60 from a transgene rescued the lethality of TAF II 60mutants and exposed requirements for TAFII60 during imaginal development, spermatogenesis, and oogenesis. Phenotypes of rescued TAF II 60 mutant flies implicate TAFII60 in transcriptional mechanisms that regulate cell growth and cell fate specification and suggest that TAFII60 is a limiting component of the machinery that regulates the transcription of dosage-sensitive genes. Finally, TAFII60 plays roles in developmental regulation of gene expression that are distinct from those of other TAFIIproteins.

Ectopic expression of individual E(spl) genes has differential effects on different cell fate decisions and underscores the biphasic requirement for notch activity in wing margin establishment in Drosophila

Development ◽  
1999 ◽  
Vol 126 (10) ◽  
pp. 2205-2214 ◽  
Author(s):  
P. Ligoxygakis ◽  
S.J. Bray ◽  
Y. Apidianakis ◽  
C. Delidakis
Keyword(s):  
Cell Fate ◽  
Transcriptional Activation ◽  
Expression Patterns ◽  
Ectopic Expression ◽  
Loss Of Function ◽  
Wing Vein ◽  
Cell Fate Decisions ◽  
Notch Activity ◽  
Sequence Of Events ◽  
Spl Genes

A common consequence of Notch signalling in Drosophila is the transcriptional activation of seven Enhancer of split [E(spl)] genes, which encode a family of closely related basic-helix-loop-helix transcriptional repressors. Different E(spl) proteins can functionally substitute for each other, hampering loss-of-function genetic analysis and raising the question of whether any specialization exists within the family. We expressed each individual E(spl) gene using the GAL4-UAS system in order to analyse their effect in a number of cell fate decisions taking place in the wing imaginal disk. We focussed on sensory organ precursor determination, wing vein determination and wing pattern formation. All of the E(spl) proteins affect the first two processes in the same way, namely they antagonize neural precursor and vein fates. Yet, the efficacy of this antagonism is quite distinct: E(spl)mbeta has the strongest vein suppression effect, whereas E(spl)m8 and E(spl)m7 are the most active bristle suppressors. During wing patterning, Notch activity orchestrates a complex sequence of events that define the dorsoventral boundary of the wing. We have discerned two phases within this process based on the sensitivity of N loss-of-function phenotypes to concomitant expression of E(spl) genes. E(spl) proteins are initially involved in repression of the vg quadrant enhancer, whereas later they appear to relay the Notch signal that triggers activation of cut expression. Of the seven proteins, E(spl)mgamma is most active in both of these processes. In conclusion, E(spl) proteins have partially redundant functions, yet they have evolved distinct preferences in implementing different cell fate decisions, which closely match their individual normal expression patterns.

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