scholarly journals Transient primary cilia mediate robust Hedgehog pathway-dependent cell cycle control

2019 ◽  
Author(s):  
Emily K. Ho ◽  
Anaïs E. Tsai ◽  
Tim Stearns
Keyword(s):  
Cell Cycle ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Cell Cycle Control ◽  
Proliferating Cells ◽  
Pathway Activity ◽  
Cell Cycles ◽  
Medulloblastoma Cell Line ◽  
Multiple Cell ◽  
Hh Signaling

SummaryThe regulation of proliferation is one of the primary functions of Hedgehog (Hh) signaling in development. Transduction of Hh signaling requires the primary cilium, a microtubule-based organelle that is necessary for several steps in the pathway (Corbit et al., 2005; Huangfu and Anderson, 2005; Huangfu et al., 2003; Liu et al., 2005; Rohatgi et al., 2007). Many cells only build a primary cilium upon cell cycle arrest in G0. In those proliferating cells that do make a cilium, it is a transient organelle, being assembled in G1 and disassembled sometime after, although exactly when is not well-characterized (Ford et al., 2018; Pugacheva et al., 2007; Wang and Dynlacht, 2018). Thus the requirement for primary cilia presents a conundrum: how are proliferative signals conveyed through an organelle that is present for only part of the cell cycle? Here we investigate this question in a mouse medulloblastoma cell line, SMB55, that requires cilium-mediated Hh pathway activity for proliferation (Zhao et al., 2015). We show that SMB55 cells are often ciliated beyond G1 into S phase, and the presence of the cilium determines the periods of Hh pathway activity. Using live imaging over multiple cell cycles, we define two windows of opportunity for Hh pathway activity, either of which is sufficient to effect cell cycle entry. The first is in the ciliated phase of the previous cell cycle, and the second is in G1 of the cell cycle in which the decision is made. We propose that the ability of cells to integrate Hh pathway activity from more than one cell cycle imparts robustness on Hh pathway control of proliferation and may have implications for other Hh-mediated events in development.

scholarly journals KIF14 controls ciliogenesis via regulation of Aurora A and is important for Hedgehog signaling

2020 ◽  
Vol 219 (6) ◽  
Author(s):  
Petra Pejskova ◽  
Madeline Louise Reilly ◽  
Lucia Bino ◽  
Ondrej Bernatik ◽  
Linda Dolanska ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Primary Cilium ◽  
Hedgehog Signaling ◽  
Cell Cycle Progression ◽  
Primary Cilia ◽  
Aurora A ◽  
Pathway Activation ◽  
Cilia Formation ◽  
Tightly Coupled ◽  
Hh Signaling

Primary cilia play critical roles in development and disease. Their assembly and disassembly are tightly coupled to cell cycle progression. Here, we present data identifying KIF14 as a regulator of cilia formation and Hedgehog (HH) signaling. We show that RNAi depletion of KIF14 specifically leads to defects in ciliogenesis and basal body (BB) biogenesis, as its absence hampers the efficiency of primary cilium formation and the dynamics of primary cilium elongation, and disrupts the localization of the distal appendage proteins SCLT1 and FBF1 and components of the IFT-B complex. We identify deregulated Aurora A activity as a mechanism contributing to the primary cilium and BB formation defects seen after KIF14 depletion. In addition, we show that primary cilia in KIF14-depleted cells are defective in response to HH pathway activation, independently of the effects of Aurora A. In sum, our data point to KIF14 as a critical node connecting cell cycle machinery, effective ciliogenesis, and HH signaling.

scholarly journals The master cell cycle regulator APC-Cdc20 regulates ciliary length and disassembly of the primary cilium

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Weiping Wang ◽  
Tao Wu ◽  
Marc W Kirschner
Keyword(s):  
Cell Cycle ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Cell Cycle Control ◽  
Critical Role ◽  
Anaphase Promoting Complex ◽  
Serum Stimulation ◽  
Basic Biology ◽  
The Stability

The primary cilium has an important role in signaling; defects in structure are associated with a variety of human diseases. Much of the most basic biology of this organelle is poorly understood, even basic mechanisms, such as control of growth and resorption. We show that the activity of the anaphase-promoting complex (APC), an E3 that regulates the onset of anaphase, destabilizes axonemal microtubules in the primary cilium. Furthermore, the metaphase APC co-activator, Cdc20, is specifically recruited to the basal body of primary cilia. Inhibition of APC-Cdc20 activity increases the ciliary length, while overexpression of Cdc20 suppresses cilium formation. APC-Cdc20 activity is required for the timely resorption of the cilium after serum stimulation. In addition, APC regulates the stability of axonemal microtubules through targeting Nek1, the ciliary kinase, for proteolysis. These data demonstrate a novel function of APC beyond cell cycle control and implicate critical role of ubiquitin-mediated proteolysis in ciliary disassembly.

Expression of the cell cycle control gene, cdc25, is constitutive in the segmental founder cells but is cell-cycle-regulated in the micromeres of leech embryos

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3035-3043 ◽  
Author(s):  
S.T. Bissen
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Cycle Control ◽  
Control Gene ◽  
Cdc25 Phosphatase ◽  
Cell Cycles ◽  
Cell Divisions ◽  
Zygotic Transcription ◽  
Founder Cells ◽  
Drosophila Embryos

The identifiable cells of leech embryos exhibit characteristic differences in the timing of cell division. To elucidate the mechanisms underlying these cell-specific differences in cell cycle timing, the leech cdc25 gene was isolated because Cdc25 phosphatase regulates the asynchronous cell divisions of postblastoderm Drosophila embryos. Examination of the distribution of cdc25 RNA and the zygotic expression of cdc25 in identified cells of leech embryos revealed lineage-dependent mechanisms of regulation. The early blastomeres, macromeres and teloblasts have steady levels of maternal cdc25 RNA throughout their cell cycles. The levels of cdc25 RNA remain constant throughout the cell cycles of the segmental founder cells, but the majority of these transcripts are zygotically produced. Cdc25 RNA levels fluctuate during the cell cycles of the micromeres. The levels peak during early G2, due to a burst of zygotic transcription, and then decline as the cell cycles progress. These data suggest that cells of different lineages employ different strategies of cell cycle control.

scholarly journals The trans cell cycle effects of PARP inhibitors underlie their selectivity toward BRCA1/2-deficient cells

2021 ◽  
Author(s):  
Antoine Simoneau ◽  
Rosalinda Xiong ◽  
Lee Zou
Keyword(s):  
Cell Cycle ◽  
Parp Inhibitor ◽  
Parp Inhibitors ◽  
S Phase ◽  
Replication Forks ◽  
Dna Double Strand Breaks ◽  
Origin Firing ◽  
Cell Cycles ◽  
Strand Breaks ◽  
Multiple Cell

PARP inhibitor (PARPi) is widely used to treat BRCA1/2-deficient tumors, but why PARPi is more effective than other DNA-damaging drugs is unclear. Here, we show that PARPi generates DNA double-strand breaks (DSBs) predominantly in a trans cell cycle manner. During the first S phase after PARPi exposure, PARPi induces single-stranded DNA (ssDNA) gaps behind DNA replication forks. By trapping PARP on DNA, PARPi prevents the completion of gap repair until the next S phase, leading to collisions of replication forks with ssDNA gaps and a surge of DSBs. In the second S phase, BRCA1/2-deficient cells are unable to suppress origin firing through ATR, resulting in continuous DNA synthesis and more DSBs. Furthermore, BRCA1/2-deficient cells cannot recruit RAD51 to repair collapsed forks. Thus, PARPi induces DSBs progressively through trans cell cycle ssDNA gaps, and BRCA1/2-deficient cells fail to slow down and repair DSBs over multiple cell cycles, explaining the unique efficacy of PARPi in BRCA1/2-deficient cells.

scholarly journals The primary cilium dampens proliferative signaling and represses a G2/M transcriptional network in quiescent myoblasts

2020 ◽  
Author(s):  
Nisha Venugopal ◽  
Ananga Ghosh ◽  
Hardik Gala ◽  
Ajoy Aloysius ◽  
Neha Vyas ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Primary Cilium ◽  
Developmental Disorders ◽  
Adult Stem Cells ◽  
Primary Cilia ◽  
Translational Repressor ◽  
Elevated Protein ◽  
Proliferative Signaling

Abstract Background Reversible cell cycle arrest (quiescence/G0) is characteristic of adult stem cells and is actively controlled at multiple levels. Quiescent cells also extend a primary cilium, which functions as a signaling hub. Primary cilia have been shown to be important in multiple developmental processes, and are implicated in numerous developmental disorders. Although the association of the cilium with G0 is established, the role of the cilium in the control of the quiescence program is still poorly understood. Results Primary cilia are dynamically regulated across different states of cell cycle exit in skeletal muscle myoblasts: quiescent myoblasts elaborate a primary cilium in vivo and in vitro , but terminally differentiated myofibers do not. Myoblasts where ciliogenesis is ablated using RNAi against a key ciliary assembly protein (IFT88) can exit the cell cycle but display an altered quiescence program and impaired self-renewal. Specifically, the G0 transcriptome in IFT88 knockdown cells is aberrantly enriched for G2/M regulators, suggesting a focused repression of this network by the cilium. Cilium-ablated cells also exhibit features of activation including enhanced activity of Wnt and mitogen signaling and elevated protein synthesis via inactivation of the translational repressor 4E-BP1. Conclusions Taken together, our results show that the primary cilium integrates and dampens proliferative signaling, represses translation and G2/M genes, and is integral to the establishment of the quiescence program.

Systems-level feedback in cell-cycle control

2010 ◽  
Vol 38 (5) ◽  
pp. 1242-1246 ◽  
Author(s):  
Béla Novák ◽  
P.K. Vinod ◽  
Paula Freire ◽  
Orsolya Kapuy
Keyword(s):  
Cell Cycle ◽  
Feedback Loop ◽  
Cell Cycle Control ◽  
Double Negative ◽  
Cyclin Dependent Kinase ◽  
Successful Completion ◽  
Cell Cycles ◽  
Underlying Network ◽  
Oscillatory Mechanism ◽  
Negative Feedbacks

Alternation of chromosome replication and segregation is essential for successful completion of the cell cycle and it requires an oscillation of Cdk1 (cyclin-dependent kinase 1)–CycB (cyclin B) activity. In the present review, we illustrate the essential features of checkpoint controlled and uncontrolled cell-cycle oscillations by using mechanical metaphors. Despite variations in the molecular details of the oscillatory mechanism, the underlying network motifs responsible for the oscillations are always well-conserved. The checkpoint-controlled cell cycles are always driven by a negative-feedback loop amplified by double-negative feedbacks (antagonism).

scholarly journals Rab7 regulates primary cilia disassembly through cilia excision

2019 ◽  
Vol 218 (12) ◽  
pp. 4030-4041 ◽  
Author(s):  
Guang Wang ◽  
Huai-Bin Hu ◽  
Yan Chang ◽  
Yan Huang ◽  
Zeng-Qing Song ◽  
...  
Keyword(s):  
Cell Surface ◽  
Cell Signaling ◽  
Primary Cilium ◽  
Actin Polymerization ◽  
Essential Role ◽  
Primary Cilia ◽  
Small Gtpase ◽  
Proliferating Cells ◽  
Dynamic Transitions

The primary cilium is a sensory organelle that protrudes from the cell surface. Primary cilia undergo dynamic transitions between assembly and disassembly to exert their function in cell signaling. In this study, we identify the small GTPase Rab7 as a novel regulator of cilia disassembly. Depletion of Rab7 potently induced spontaneous ciliogenesis in proliferating cells and promoted cilia elongation during quiescence. Moreover, Rab7 performs an essential role in cilia disassembly; knockdown of Rab7 blocked serum-induced ciliary resorption, and active Rab7 was required for this process. Further, we demonstrate that Rab7 depletion significantly suppresses cilia tip excision, referred to as cilia ectocytosis, which has been identified as required for cilia disassembly. Mechanically, the failure of F-actin polymerization at the site of excision of cilia tips caused suppression of cilia ectocytosis on Rab7 depletion. Overall, our results suggest a novel function for Rab7 in regulating cilia ectocytosis and cilia disassembly via control of intraciliary F-actin polymerization.

scholarly journals The cell cycle of glial cells grown in vitro: an immunocytochemical method of analysis.

1992 ◽  
Vol 40 (9) ◽  
pp. 1405-1411 ◽  
Author(s):  
P E Knapp
Keyword(s):  
Cell Cycle ◽  
Glial Cells ◽  
Average Length ◽  
Proliferating Cells ◽  
Cell Cycles ◽  
Mouse Cerebral Cortex ◽  
Immunocytochemical Method ◽  
Autoradiographic Technique

Studies of cell cycles have traditionally employed [3H]- and [14C]-thymidine to label the DNA of proliferating cells and autoradiography to reveal the thymidine label. The development of antibodies to the thymidine analogue 5-bromodeoxyuridine (BrdU) has allowed the development of an immunocytochemical method analogous to the thymidine autoradiographic technique. In direct comparisons, we found that the immunocytochemical method consistently detected a larger number of proliferating cells. This suggests that it may be a more sensitive index of proliferation than thymidine autoradiography in some systems. We used the BrdU method to analyze the cycle of astroglia cultured from neonatal mouse cerebral cortex. Cells were exposed to BrdU for 1 hr to label a discrete subpopulation of proliferating cells. At 2-36 hr after the pulse, a combination of anti-BrdU immunocytochemistry and counterstaining with propidium iodide was used to identify proliferating cells. The length of the cell cycle was determined by charting the percent of BrdU-labeled mitotic cells vs time after the pulse. We found the average length of the cell cycle of astrocytes grown in vitro to be 20.5 hr. The combined G2 + M phases were 2-3 hr. These values are virtually identical with those found for glial cells in vivo, suggesting that the culture environment does not interfere with the normal control of cell cycle length.

scholarly journals The primary cilium dampens proliferative signaling and represses a G2/M transcriptional network in quiescent myoblasts

2019 ◽  
Author(s):  
Nisha Venugopal ◽  
Ananga Ghosh ◽  
Hardik Gala ◽  
Ajoy Aloysius ◽  
Neha Vyas ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Primary Cilium ◽  
Developmental Disorders ◽  
Adult Stem Cells ◽  
Primary Cilia ◽  
Translational Repressor ◽  
Elevated Protein ◽  
Proliferative Signaling

Abstract Background: Reversible cell cycle arrest (quiescence/G0) is characteristic of adult stem cells and is actively controlled at multiple levels. Quiescent cells also extend a primary cilium, which functions as a signaling hub. Primary cilia have been shown to be important in multiple developmental processes, and are implicated in numerous developmental disorders. Although the association of the cilium with G0 is established, the role of the cilium in the control of the quiescence program is still poorly understood.Results: Primary cilia are dynamically regulated across different states of cell cycle exit in skeletal muscle myoblasts: quiescent myoblasts elaborate a primary cilium in vivo and in vitro , but terminally differentiated myofibers do not. Myoblasts where ciliogenesis is ablated using RNAi against a key ciliary assembly protein (IFT88) can exit the cell cycle but display an altered quiescence program and impaired self-renewal. Specifically, the G0 transcriptome in IFT88 knockdown cells is aberrantly enriched for G2/M regulators, suggesting a focused repression of this network by the cilium. Cilium-ablated cells also exhibit features of activation including enhanced activity of Wnt and mitogen signaling and elevated protein synthesis via inactivation of the translational repressor 4E-BP1.Conclusions: Taken together, our results show that the primary cilium integrates and dampens proliferative signaling, represses translation and G2/M genes, and is integral to the establishment of the quiescence program.

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