scholarly journals Chromatin organization changes during the establishment and maintenance of the postmitotic state

2017 ◽  
Author(s):  
Yiqin Ma ◽  
Laura Buttitta
Keyword(s):  
Cell Cycle ◽  
Gene Silencing ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Chromatin Organization ◽  
Cell Cycle Exit ◽  
Heterochromatin Protein 1 ◽  
Developmental Potential ◽  
Close Relationship ◽  
The Face

SummaryBackgroundGenome organization changes during development as cells differentiate. Chromatin motion becomes increasingly constrained and heterochromatin clusters as cells become restricted in their developmental potential. These changes coincide with slowing of the cell cycle, which can also influence chromatin organization and dynamics. Terminal differentiation is often coupled with permanent exit from the cell cycle and existing data suggests a close relationship between a repressive chromatin structure and silencing of the cell cycle in postmitotic cells. Here we examine the relationship between chromatin organization, terminal differentiation and cell cycle exit.ResultsWe focused our studies on the Drosophila wing, where epithelial cells transition from active proliferation to a postmitotic state in a temporally controlled manner. We find there are two stages of G0 in this tissue, a flexible G0 period where cells can be induced to re-enter the cell cycle under specific genetic manipulations and a state we call “robust”, where cells become strongly refractory to cell cycle re-entry. Compromising the flexible G0 by driving ectopic expression of cell cycle activators causes a global disruption of the clustering of heterochromatin-associated histone modifications such as H3K27 trimethylation and H3K9 trimethylation, as well as their associated repressors, Polycomb and heterochromatin protein 1(HP1). However, this disruption is reversible. When cells enter a robust G0 state, even in the presence of ectopic cell cycle activity, clustering of heterochromatin associated modifications are restored. If cell cycle exit is bypassed, cells in the wing continue to terminally differentiate, but heterochromatin clustering is severely disrupted. Heterochromatin-dependent gene silencing does not appear to be required for cell cycle exit, as compromising the H3K27 methyltransferase Enhancer of zeste, and/or HP1 cannot prevent the robust cell cycle exit, even in the face of normally oncogenic cell cycle activities.ConclusionsHeterochromatin clustering during terminal differentiation is a consequence of cell cycle exit, rather than differentiation. Compromising heterochromatin-dependent gene silencing does not disrupt cell cycle exit.

Cell heterogeneity upon myogenic differentiation: down-regulation of MyoD and Myf-5 generates ‘reserve cells’

1998 ◽  
Vol 111 (6) ◽  
pp. 769-779 ◽  
Author(s):  
N. Yoshida ◽  
S. Yoshida ◽  
K. Koishi ◽  
K. Masuda ◽  
Y. Nabeshima
Keyword(s):  
Cell Cycle ◽  
Myogenic Differentiation ◽  
Significant Proportion ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Growth Conditions ◽  
Down Regulation ◽  
Undifferentiated Cells ◽  
Myoblast Cells ◽  
Myod Expression

When a proliferating myoblast culture is induced to differentiate by deprivation of serum in the medium, a significant proportion of cells escape from terminal differentiation, while the rest of the cells differentiate. Using C2C12 mouse myoblast cells, this heterogeneity observed upon differentiation was investigated with an emphasis on the myogenic regulatory factors. The differentiating part of the cell population followed a series of well-described events, including expression of myogenin, p21(WAF1), and contractile proteins, permanent withdrawal from the cell cycle and cell fusion, whereas the rest of the cells did not initiate any of these events. Interestingly, the latter cells showed an undetectable or greatly reduced level of MyoD and Myf-5 expression, which had been originally expressed in the undifferentiated proliferating myoblasts. When these undifferentiated cells were isolated and returned to the growth conditions, they progressed through the cell cycle and regained MyoD expression. These cells demonstrated identical features with the original culture on the deprivation of serum. They produced both MyoD-positive differentiating and MyoD-negative undifferentiated populations once again. Thus the undifferentiated cells in the serum-deprived culture were designated ‘reserve cells’. Upon serum deprivation, MyoD expression rapidly decreased as a result of down-regulation in approximately 50% of the cells. After this heterogenization, MyoD positive cells expressed myogenin, which is the earliest known event of terminal differentiation and marks irreversible commitment to this, while MyoD-negative cells did not differentiate and became the reserve cells. We also demonstrated that ectopic expression of MyoD converted the reserve cells to differentiating cells, indicating that down-regulation of MyoD is a causal event in the formation of reserve cells.

scholarly journals The Drosophila Sp8 transcription factor Buttonhead prevents premature differentiation of intermediate neural progenitors

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Yonggang Xie ◽  
Xiaosu Li ◽  
Xian Zhang ◽  
Shaolin Mei ◽  
Hongyu Li ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Neural Progenitor Cells ◽  
Neural Progenitors ◽  
Homeodomain Protein ◽  
Cell Cycle Exit ◽  
Developmental Potential ◽  
Drosophila Homolog ◽  
Ets Transcription Factor ◽  
Mother Cells

Intermediate neural progenitor cells (INPs) need to avoid differentiation and cell cycle exit while maintaining restricted developmental potential, but mechanisms preventing differentiation and cell cycle exit of INPs are not well understood. In this study, we report that the Drosophila homolog of mammalian Sp8 transcription factor Buttonhead (Btd) prevents premature differentiation and cell cycle exit of INPs in Drosophila larval type II neuroblast (NB) lineages. We show that the loss of Btd leads to elimination of mature INPs due to premature differentiation of INPs into terminally dividing ganglion mother cells. We provide evidence to demonstrate that Btd prevents the premature differentiation by suppressing the expression of the homeodomain protein Prospero in immature INPs. We further show that Btd functions cooperatively with the Ets transcription factor Pointed P1 to promote the generation of INPs. Thus, our work reveals a critical mechanism that prevents premature differentiation and cell cycle exit of Drosophila INPs.

scholarly journals A Double-Assurance Mechanism Controls Cell Cycle Exit upon Terminal Differentiation in Drosophila

2007 ◽  
Vol 12 (4) ◽  
pp. 631-643 ◽  
Author(s):  
Laura A. Buttitta ◽  
Alexia J. Katzaroff ◽  
Carissa L. Perez ◽  
Aida de la Cruz ◽  
Bruce A. Edgar
Keyword(s):  
Cell Cycle ◽  
Terminal Differentiation ◽  
Cell Cycle Exit

scholarly journals Terminal osteoblast differentiation, mediated by runx2 and p27KIP1, is disrupted in osteosarcoma

2004 ◽  
Vol 167 (5) ◽  
pp. 925-934 ◽  
Author(s):  
David M. Thomas ◽  
Sandra A. Johnson ◽  
Natalie A. Sims ◽  
Melanie K. Trivett ◽  
John L. Slavin ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Osteoblast Differentiation ◽  
Ectopic Expression ◽  
Osteosarcoma Cell ◽  
Cell Cycle Exit ◽  
Retinoblastoma Tumor Suppressor ◽  
Cycle Arrest ◽  
Permanent Cell ◽  
Retinoblastoma Tumor

The molecular basis for the inverse relationship between differentiation and tumorigenesis is unknown. The function of runx2, a master regulator of osteoblast differentiation belonging to the runt family of tumor suppressor genes, is consistently disrupted in osteosarcoma cell lines. Ectopic expression of runx2 induces p27KIP1, thereby inhibiting the activity of S-phase cyclin complexes and leading to the dephosphorylation of the retinoblastoma tumor suppressor protein (pRb) and a G1 cell cycle arrest. Runx2 physically interacts with the hypophosphorylated form of pRb, a known coactivator of runx2, thereby completing a feed-forward loop in which progressive cell cycle exit promotes increased expression of the osteoblast phenotype. Loss of p27KIP1 perturbs transient and terminal cell cycle exit in osteoblasts. Consistent with the incompatibility of malignant transformation and permanent cell cycle exit, loss of p27KIP1 expression correlates with dedifferentiation in high-grade human osteosarcomas. Physiologic coupling of osteoblast differentiation to cell cycle withdrawal is mediated through runx2 and p27KIP1, and these processes are disrupted in osteosarcoma.

scholarly journals Quantitative Changes in Integrin and Focal Adhesion Signaling Regulate Myoblast Cell Cycle Withdrawal

1999 ◽  
Vol 144 (6) ◽  
pp. 1295-1309 ◽  
Author(s):  
Sarita K. Sastry ◽  
Margot Lakonishok ◽  
Stanley Wu ◽  
Tho Q. Truong ◽  
Anna Huttenlocher ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Map Kinase ◽  
Focal Adhesion ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Cytoplasmic Domain ◽  
Cytoplasmic Domains ◽  
Α Subunit ◽  
Kinase Activation ◽  
Quantitative Changes

We previously demonstrated contrasting roles for integrin α subunits and their cytoplasmic domains in controlling cell cycle withdrawal and the onset of terminal differentiation (Sastry, S., M. Lakonishok, D. Thomas, J. Muschler, and A.F. Horwitz. 1996. J. Cell Biol. 133:169–184). Ectopic expression of the integrin α5 or α6A subunit in primary quail myoblasts either decreases or enhances the probability of cell cycle withdrawal, respectively. In this study, we addressed the mechanisms by which changes in integrin α subunit ratios regulate this decision. Ectopic expression of truncated α5 or α6A indicate that the α5 cytoplasmic domain is permissive for the proliferative pathway whereas the COOH-terminal 11 amino acids of α6A cytoplasmic domain inhibit proliferation and promote differentiation. The α5 and α6A cytoplasmic domains do not appear to initiate these signals directly, but instead regulate β1 signaling. Ectopically expressed IL2R-α5 or IL2R-α6A have no detectable effect on the myoblast phenotype. However, ectopic expression of the β1A integrin subunit or IL2R-β1A, autonomously inhibits differentiation and maintains a proliferative state. Perturbing α5 or α6A ratios also significantly affects activation of β1 integrin signaling pathways. Ectopic α5 expression enhances expression and activation of paxillin as well as mitogen-activated protein (MAP) kinase with little effect on focal adhesion kinase (FAK). In contrast, ectopic α6A expression suppresses FAK and MAP kinase activation with a lesser effect on paxillin. Ectopic expression of wild-type and mutant forms of FAK, paxillin, and MAP/erk kinase (MEK) confirm these correlations. These data demonstrate that (a) proliferative signaling (i.e., inhibition of cell cycle withdrawal and the onset of terminal differentiation) occurs through the β1A subunit and is modulated by the α subunit cytoplasmic domains; (b) perturbing α subunit ratios alters paxillin expression and phosphorylation and FAK and MAP kinase activation; (c) quantitative changes in the level of adhesive signaling through integrins and focal adhesion components regulate the decision of myoblasts to withdraw from the cell cycle, in part via MAP kinase.

scholarly journals Tropomodulin3-null mice are embryonic lethal with anemia due to impaired erythroid terminal differentiation in the fetal liver

Blood ◽  
2014 ◽  
Vol 123 (5) ◽  
pp. 758-767 ◽  
Author(s):  
Zhenhua Sui ◽  
Roberta B. Nowak ◽  
Andrea Bacconi ◽  
Nancy E. Kim ◽  
Hui Liu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Fetal Liver ◽  
Terminal Differentiation ◽  
Cell Types ◽  
Cell Cycle Exit ◽  
Erythroid Progenitors ◽  
Island Formation ◽  
Erythroid Terminal Differentiation ◽  
Embryonic Lethal ◽  
Key Points

Key Points Tmod3 deletion leads to reduced erythroid progenitors and impaired erythroblast survival, cell-cycle exit, and enucleation. Erythroblast-macrophage islands are reduced in the absence of Tmod3, which is required in both cell types for island formation.

scholarly journals The coordination of terminal differentiation and cell cycle exit is mediated through the regulation of chromatin accessibility

2018 ◽  
Author(s):  
Yiqin Ma ◽  
Daniel J McKay ◽  
Laura Buttitta
Keyword(s):  
Cell Cycle ◽  
Terminal Differentiation ◽  
Chromatin Accessibility ◽  
Cell Cycle Gene ◽  
Cell Cycle Regulators ◽  
Cell Cycle Exit ◽  
Cell Cycle Genes ◽  
Repressor Complex ◽  
Pupal Wing ◽  
A Cell

During terminal differentiation most cells will exit the cell cycle and enter into a prolonged or permanent G0. Cell cycle exit is usually initiated through the repression of cell cycle gene expression by formation of a transcriptional repressor complex called DREAM. However when DREAM repressive function is compromised during terminal differentiation, additional unknown mechanisms act to stably repress cycling and ensure robust cell cycle exit. Here we provide evidence that developmentally programmed, temporal changes in chromatin accessibility at a subset of critical cell cycle genes acts to enforce cell cycle exit during terminal differentiation in the Drosophila melanogaster wing. We show that during terminal differentiation, chromatin closes at a set of pupal wing enhancers for the key rate-limiting cell cycle regulators cycE, e2f1 and stg. This closing coincides with wing cells entering a robust postmitotic state that is strongly refractory to cell cycle re-activation. When cell cycle exit is genetically disrupted, chromatin accessibility at cell cycle genes remains largely unaffected and the closing of enhancers at cycE, e2f1 and stg proceeds independent of the cell cycling status. Instead, disruption of cell cycle exit leads to changes in accessibility and expression of a subset of hormone-induced transcription factors involved in the progression of terminal differentiation. Our results uncover a mechanism that acts as a cell cycle-independent timer to limit aberrant cycling in terminally differentiating tissues. In addition, we provide a new molecular description of the cross-talk between cell cycle exit and terminal differentiation during metamorphosis.

Sign in / Sign up

Export Citation Format

Share Document