scholarly journals Defective Dendrite Elongation but Normal Fertility in Mice Lacking the Rho-Like GTPase Activator Dbl

2002 ◽  
Vol 22 (9) ◽  
pp. 3140-3148 ◽  
Author(s):  
Emilio Hirsch ◽  
Michela Pozzato ◽  
Alessandro Vercelli ◽  
Laura Barberis ◽  
Ornella Azzolino ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Embryonic Stem ◽  
Large Family ◽  
Small Gtpases ◽  
Normal Morphology ◽  
Targeted Deletion ◽  
Cortical Pyramidal Neurons ◽  
Rho Family

ABSTRACT Dbl is the prototype of a large family of GDP-GTP exchange factors for small GTPases of the Rho family. In vitro, Dbl is known to activate Rho and Cdc42 and to induce a transformed phenotype. Dbl is specifically expressed in brain and gonads, but its in vivo functions are largely unknown. To assess its role in neurogenesis and gametogenesis, targeted deletion of the murine Dbl gene was accomplished in embryonic stem cells. Dbl-null mice are viable and did not show either decreased reproductive performances or obvious neurological defects. Histological analysis of mutant testis showed normal morphology and unaltered proliferation and survival of spermatogonia. Dbl-null brains indicated a correct disposition of the major neural structures. Analysis of cortical stratification indicated that Dbl is not crucial for neuronal migration. However, in distinct populations of Dbl-null cortical pyramidal neurons, the length of dendrites was significantly reduced, suggesting a role for Dbl in dendrite elongation.

Activation of Serotonin Receptors Modulates Synaptic Transmission in Rat Cerebral Cortex

1999 ◽  
Vol 82 (6) ◽  
pp. 2989-2999 ◽  
Author(s):  
Fu-Ming Zhou ◽  
John J. Hablitz
Keyword(s):  
Cerebral Cortex ◽  
Pyramidal Neurons ◽  
Short Pulse ◽  
Inhibitory Neurons ◽  
Cellular Mechanisms ◽  
Postsynaptic Currents ◽  
Cortical Pyramidal Neurons ◽  
Immunohistochemical Studies

The cerebral cortex receives an extensive serotonergic (5-hydroxytryptamine, 5-HT) input. Immunohistochemical studies suggest that inhibitory neurons are the main target of 5-HT innervation. In vivo extracellular recordings have shown that 5-HT generally inhibited cortical pyramidal neurons, whereas in vitro studies have shown an excitatory action. To determine the cellular mechanisms underlying the diverse actions of 5-HT in the cortex, we examined its effects on cortical inhibitory interneurons and pyramidal neurons. We found that 5-HT, through activation of 5-HT2A receptors, induced a massive enhancement of spontaneous inhibitory postsynaptic currents (sIPSCs) in pyramidal neurons, lasting for ∼6 min. In interneurons, this 5-HT-induced enhancement of sIPSCs was much weaker. Activation of 5-HT2Areceptors also increased spontaneous excitatory postsynaptic currents (sEPSCs) in pyramidal neurons. This response desensitized less and at a slower rate. In contrast, 5-HT slightly decreased evoked IPSCs (eIPSCs) and eEPSCs. In addition, 5-HT via 5-HT3 receptors evoked a large and rapidly desensitizing inward current in a subset of interneurons and induced a transient enhancement of sIPSCs. Our results suggest that 5-HT has widespread effects on both interneurons and pyramidal neurons and that a short pulse of 5-HT is likely to induce inhibition whereas the prolonged presence of 5-HT may result in excitation.

Control of neutrophil pseudopods by fluid shear: role of Rho family GTPases

2005 ◽  
Vol 288 (4) ◽  
pp. C863-C871 ◽  
Author(s):  
Ayako Makino ◽  
Michael Glogauer ◽  
Gary M. Bokoch ◽  
Shu Chien ◽  
Geert W. Schmid-Schönbein
Keyword(s):  
Signal Transduction ◽  
Shear Stress ◽  
Fluid Shear Stress ◽  
Small Gtpases ◽  
Dependent Manner ◽  
Fluid Shear ◽  
Rho Family

Blood vessels and blood cells are under continuous fluid shear. Studies on vascular endothelium and smooth muscle cells have shown the importance of this mechanical stress in cell signal transduction, gene expression, vascular remodeling, and cell survival. However, in circulating leukocytes, shear-induced signal transduction has not been investigated. Here we examine in vivo and in vitro the control of pseudopods in leukocytes under the influence of fluid shear stress and the role of the Rho family small GTPases. We used a combination of HL-60 cells differentiated into neutrophils (1.4% dimethyl sulfoxide for 5 days) and fresh leukocytes from Rac knockout mice. The cells responded to shear stress (5 dyn/cm2) with retraction of pseudopods and reduction of their projected cell area. The Rac1 and Rac2 activities were decreased by fluid shear in a time- and magnitude-dependent manner, whereas the Cdc42 activity remained unchanged (up to 5 dyn/cm2). The Rho activity was transiently increased and recovered to static levels after 10 min of shear exposure (5 dyn/cm2). Inhibition of either Rac1 or Rac2 slightly but significantly diminished the fluid shear response. Transfection with Rac1-positive mutant enhanced the pseudopod formation during shear. Leukocytes from Rac1-null and Rac2-null mice had an ability to form pseudopods in response to platelet-activating factor but did not respond to fluid shear in vitro. Leukocytes in wild-type mice retracted pseudopods after physiological shear exposure, whereas cells in Rac1-null mice showed no retraction during equal shear. On leukocytes from Rac2-null mice, however, fluid shear exerted a biphasic effect. Leukocytes with extended pseudopods slightly decreased in length, whereas initially round cells increased in length after shear application. The disruption of Rac activity made leukocytes nonresponsive to fluid shear, induced cell adhesion and microvascular stasis, and decreased microvascular density. These results suggest that deactivation of Rac activity by fluid shear plays an important role in stable circulation of leukocytes.

scholarly journals MFF-dependent mitochondrial fission regulates presynaptic release and axon branching by limiting axonal mitochondria size

2018 ◽  
Author(s):  
Tommy L. Lewis ◽  
Seok-Kyu Kwon ◽  
Annie Lee ◽  
Reuben Shaw ◽  
Franck Polleux
Keyword(s):  
Pyramidal Neurons ◽  
Mitochondrial Fission ◽  
Axon Branching ◽  
Atp Production ◽  
Terminal Axon ◽  
Cortical Pyramidal Neurons ◽  
Presynaptic Release ◽  
Organelle Morphology

ABSTRACTNeurons display extreme degrees of polarization, including compartment-specific organelle morphology. In cortical pyramidal neurons, dendritic mitochondria are long and tubular whereas axonal mitochondria display uniformly short length. Here, we explored the functional significance of maintaining small mitochondria for axonal development in vitro and in vivo. We report that the Drp1 ‘receptor’ Mitochondrial fission factor (MFF) is required for determining the size of mitochondria entering the axon and then for maintenance of their size along the distal portions of the axon without affecting their trafficking properties, presynaptic capture, membrane potential or capacity for ATP production. Strikingly, this increase in presynaptic mitochondrial size upon MFF downregulation augments their capacity for Ca2+ ([Ca2+]m) uptake during neurotransmission, leading to reduced presynaptic [Ca2+]c accumulation, decreased presynaptic release and terminal axon branching. Our results uncover a novel mechanism controlling neurotransmitter release and axon branching through fission-dependent regulation of presynaptic mitochondrial size.

scholarly journals Implantable microcoils for intracortical magnetic stimulation

2016 ◽  
Vol 2 (12) ◽  
pp. e1600889 ◽  
Author(s):  
Seung Woo Lee ◽  
Florian Fallegger ◽  
Bernard D. F. Casse ◽  
Shelley I. Fried
Keyword(s):  
Cortical Neurons ◽  
Magnetic Stimulation ◽  
Pyramidal Neurons ◽  
Brain Slices ◽  
Behavioral Responses ◽  
Wide Range ◽  
Cortical Pyramidal Neurons ◽  
Over Time

Neural prostheses that stimulate the neocortex have the potential to treat a wide range of neurological disorders. However, the efficacy of electrode-based implants remains limited, with persistent challenges that include an inability to create precise patterns of neural activity as well as difficulties in maintaining response consistency over time. These problems arise from fundamental limitations of electrodes as well as their susceptibility to implantation and have proven difficult to overcome. Magnetic stimulation can address many of these limitations, but coils small enough to be implanted into the cortex were not thought strong enough to activate neurons. We describe a new microcoil design and demonstrate its effectiveness for both activating cortical neurons and driving behavioral responses. The stimulation of cortical pyramidal neurons in brain slices in vitro was reliable and could be confined to spatially narrow regions (<60 μm). The spatially asymmetric fields arising from the coil helped to avoid the simultaneous activation of passing axons. In vivo implantation was safe and resulted in consistent and predictable behavioral responses. The high permeability of magnetic fields to biological substances may yield another important advantage because it suggests that encapsulation and other adverse effects of implantation will not diminish coil performance over time, as happens to electrodes. These findings suggest that a coil-based implant might be a useful alternative to existing electrode-based devices. The enhanced selectivity of microcoil-based magnetic stimulation will be especially useful for visual prostheses as well as for many brain-computer interface applications that require precise activation of the cortex.

scholarly journals Macropinocytosis requires Gal-3 in a subset of patient-derived glioblastoma stem cells

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Laetitia Seguin ◽  
Soline Odouard ◽  
Francesca Corlazzoli ◽  
Sarah Al Haddad ◽  
Laurine Moindrot ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Survival ◽  
Small Gtpases ◽  
Molecular Signature ◽  
Carbohydrate Binding ◽  
Pancreatic Cancers ◽  
Galectin 3 ◽  
Pharmacologic Inhibition

AbstractRecently, we involved the carbohydrate-binding protein Galectin-3 (Gal-3) as a druggable target for KRAS-mutant-addicted lung and pancreatic cancers. Here, using glioblastoma patient-derived stem cells (GSCs), we identify and characterize a subset of Gal-3high glioblastoma (GBM) tumors mainly within the mesenchymal subtype that are addicted to Gal-3-mediated macropinocytosis. Using both genetic and pharmacologic inhibition of Gal-3, we showed a significant decrease of GSC macropinocytosis activity, cell survival and invasion, in vitro and in vivo. Mechanistically, we demonstrate that Gal-3 binds to RAB10, a member of the RAS superfamily of small GTPases, and β1 integrin, which are both required for macropinocytosis activity and cell survival. Finally, by defining a Gal-3/macropinocytosis molecular signature, we could predict sensitivity to this dependency pathway and provide proof-of-principle for innovative therapeutic strategies to exploit this Achilles’ heel for a significant and unique subset of GBM patients.

scholarly journals Grafts Derived from an α-Synuclein Triplication Patient Mediate Functional Recovery but Develop Disease-Associated Pathology in the 6-OHDA Model of Parkinson’s Disease

2020 ◽  
pp. 1-14
Author(s):  
Shelby Shrigley ◽  
Fredrik Nilsson ◽  
Bengt Mattsson ◽  
Alessandro Fiorenzano ◽  
Janitha Mudannayake ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Cell Lines ◽  
Functional Recovery ◽  
Embryonic Stem ◽  
Hesc Line ◽  
Alternative Source ◽  
And Function

Background: Human induced pluripotent stem cells (hiPSCs) have been proposed as an alternative source for cell replacement therapy for Parkinson’s disease (PD) and they provide the option of using the patient’s own cells. A few studies have investigated transplantation of patient-derived dopaminergic (DA) neurons in preclinical models; however, little is known about the long-term integrity and function of grafts derived from patients with PD. Objective: To assess the viability and function of DA neuron grafts derived from a patient hiPSC line with an α-synuclein gene triplication (AST18), using a clinical grade human embryonic stem cell (hESC) line (RC17) as a reference control. Methods: Cells were differentiated into ventral mesencephalic (VM)-patterned DA progenitors using an established GMP protocol. The progenitors were then either terminally differentiated to mature DA neurons in vitro or transplanted into 6-hydroxydopamine (6-OHDA) lesioned rats and their survival, maturation, function, and propensity to develop α-synuclein related pathology, were assessed in vivo. Results: Both cell lines generated functional neurons with DA properties in vitro. AST18-derived VM progenitor cells survived transplantation and matured into neuron-rich grafts similar to the RC17 cells. After 24 weeks, both cell lines produced DA-rich grafts that mediated full functional recovery; however, pathological changes were only observed in grafts derived from the α-synuclein triplication patient line. Conclusion: This data shows proof-of-principle for survival and functional recovery with familial PD patient-derived cells in the 6-OHDA model of PD. However, signs of slowly developing pathology warrants further investigation before use of autologous grafts in patients.

scholarly journals Genome-Wide Binding Analyses of HOXB1 Revealed a Novel DNA Binding Motif Associated with Gene Repression

2021 ◽  
Vol 9 (1) ◽  
pp. 6
Author(s):  
Narendra Pratap Singh ◽  
Bony De Kumar ◽  
Ariel Paulson ◽  
Mark E. Parrish ◽  
Carrie Scott ◽  
...  
Keyword(s):  
Dna Binding ◽  
Target Genes ◽  
Embryonic Stem ◽  
Binding Motif ◽  
Binding Assays ◽  
Histone Marks ◽  
Genome Wide ◽  
Hox Cofactors

Knowledge of the diverse DNA binding specificities of transcription factors is important for understanding their specific regulatory functions in animal development and evolution. We have examined the genome-wide binding properties of the mouse HOXB1 protein in embryonic stem cells differentiated into neural fates. Unexpectedly, only a small number of HOXB1 bound regions (7%) correlate with binding of the known HOX cofactors PBX and MEIS. In contrast, 22% of the HOXB1 binding peaks display co-occupancy with the transcriptional repressor REST. Analyses revealed that co-binding of HOXB1 with PBX correlates with active histone marks and high levels of expression, while co-occupancy with REST correlates with repressive histone marks and repression of the target genes. Analysis of HOXB1 bound regions uncovered enrichment of a novel 15 base pair HOXB1 binding motif HB1RE (HOXB1 response element). In vitro template binding assays showed that HOXB1, PBX1, and MEIS can bind to this motif. In vivo, this motif is sufficient for direct expression of a reporter gene and over-expression of HOXB1 selectively represses this activity. Our analyses suggest that HOXB1 has evolved an association with REST in gene regulation and the novel HB1RE motif contributes to HOXB1 function in part through a repressive role in gene expression.

scholarly journals EXTH-64. SMALL GTPASES IN MENINGIOMAS: PROLIFERATION, MIGRATION, SURVIVAL, POTENTIAL TREATMENT AND INTERACTIONS

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii101-ii101
Author(s):  
Christoph Kesseler ◽  
Julian Kahr ◽  
Natalie Waldt ◽  
Nele Stroscher ◽  
Josephine Liebig ◽  
...  
Keyword(s):  
Overall Survival ◽  
Cell Lines ◽  
Small Gtpases ◽  
Potential Treatment ◽  
Rock Inhibitor ◽  
Meningioma Cell ◽  
And Migration ◽  
Proliferation And Migration

Abstract PURPOSE To evaluate the role of the small GTPases RhoA, Rac1 and Cdc42 in meningiomas as therapeutic targets and their interactions in meningiomas. EXPERIMENTAL DESIGN We analyzed expression of GTPases in human meningioma samples and meningioma cell lines of various WHO grades. Malignant IOMM-Lee meningioma cells were used to generate shRNA mediated knockdowns of GTPases RhoA, Rac1 or Cdc42 and to study knockdown effects on proliferation and migration, as well as analysis of cell morphology by confocal microscopy. The same tests were used to investigate effects of the two inhibitors Fasudil and EHT-1864 of malignant IOMM-Lee, KT21 and benign Ben-Men cells and the effects of these drugs on IOMM-Lee knockdown cells. The effects of GTPase knockdowns and Fasudil treatment were studied in terms of overall survival by intracranial xenografts of mice. Potential interactions of GTPases regarding NF2, mTOR and FAK-Paxillin were examined. RESULTS Small GTPases were upregulated in meningiomas of higher tumor grades. Reduced proliferation and migration could be achieved by GTPase knockdown in IOMM-Lee cells. Additionally, the ROCK-inhibitor Fasudil and Rac1-inhibitor EHT-1864 reduced proliferation in different meningioma cell lines and reduced proliferation and migration independent of GTPase knockdowns/status. Moreover, overall survival in vivo could also be increased by knockdowns of RhoA and Rac1 as well as Fasudil treatment. GTPase expression was affected dependent on the NF2 status but effects were not very distinct, indicating that NF2 is not strongly involved in GTPase regulation in meningiomas. In terms of mTOR and FAK-Paxillin signaling, each GTPase changes those pathways in a different manner. CONCLUSION Small GTPases are important effectors in meningioma proliferation and migration in vitro as well as survival in vivo and their inhibition should be considered as potential treatment option.

Novel pathway for thyroid hormone receptor action through interaction with jun and fos oncogene activities

1991 ◽  
Vol 11 (12) ◽  
pp. 6016-6025
Author(s):  
X K Zhang ◽  
K N Wills ◽  
M Husmann ◽  
T Hermann ◽  
M Pfahl
Keyword(s):  
Signal Transduction ◽  
Dna Binding ◽  
Thyroid Hormone Receptor ◽  
Gene Activation ◽  
Signal Transduction Pathway ◽  
Large Family ◽  
Transduction Pathway ◽  
Regulatory Pathway

Many essential biological pathways, including cell growth, development, and metabolism, are regulated by thyroid hormones (THs). TH action is mediated by intracellular receptors that belong to a large family of ligand-dependent transcription factors, including the steroid hormone and retinoic acid receptors. So far it has been assumed that TH receptors (TRs) regulate gene transcription only through the classical protein-DNA interaction mechanism. Here we provide evidence for a regulatory pathway that allows cross-talk between TRs and the signal transduction pathway used by many growth factors, oncogenes, and tumor promoters. In transient transfection studies, we observed that the oncogenes c-jun and c-fos inhibit TR activities, while TRs inhibit induction of the c-fos promoter and repress AP-1 site-dependent gene activation. A truncated TR that lacks only 17 amino acids from the carboxy terminus can no longer antagonize AP-1 activity. The cross-regulation between TRs and the signal transduction pathway appears to be based on the ability of TRs to inhibit DNA binding of the transcription factor AP-1 in the presence of THs. The constituents of AP-1, c-Jun, and c-Fos, vice versa, can inhibit TR-induced gene activation in vivo, and c-Jun inhibits TR DNA binding in vitro. This novel regulatory pathway is likely to play a major role in growth control and differentiation by THs.

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