scholarly journals Role of sodium channel subtype in action potential generation by neocortical pyramidal neurons

2018 ◽  
Vol 115 (30) ◽  
pp. E7184-E7192 ◽  
Author(s):  
Efrat Katz ◽  
Ohad Stoler ◽  
Anja Scheller ◽  
Yana Khrapunsky ◽  
Sandra Goebbels ◽  
...  
Keyword(s):  
Action Potentials ◽  
Pyramidal Neurons ◽  
Sodium Current ◽  
Na Channel ◽  
Loss Of Function ◽  
Wild Type ◽  
Strong Reduction ◽  
Hyperpolarizing Shift ◽  
Neocortical Pyramidal Neurons

Neocortical pyramidal neurons express several distinct subtypes of voltage-gated Na+ channels. In mature cells, Nav1.6 is the dominant channel subtype in the axon initial segment (AIS) as well as in the nodes of Ranvier. Action potentials (APs) are initiated in the AIS, and it has been proposed that the high excitability of this region is related to the unique characteristics of the Nav1.6 channel. Knockout or loss-of-function mutation of the Scn8a gene is generally lethal early in life because of the importance of this subtype in noncortical regions of the nervous system. Using the Cre/loxP system, we selectively deleted Nav1.6 in excitatory neurons of the forebrain and characterized the excitability of Nav1.6-deficient layer 5 pyramidal neurons by patch-clamp and Na+ and Ca2+ imaging recordings. We now report that, in the absence of Nav1.6 expression, the AIS is occupied by Nav1.2 channels. However, APs are generated in the AIS, and differences in AP propagation to soma and dendrites are minimal. Moreover, the channels that are expressed in the AIS still show a clear hyperpolarizing shift in voltage dependence of activation, compared with somatic channels. The only major difference between Nav1.6-null and wild-type neurons was a strong reduction in persistent sodium current. We propose that the molecular environment of the AIS confers properties on whatever Na channel subtype is present and that some other benefit must be conferred by the selective axonal presence of the Nav1.6 channel.

scholarly journals The Constitutive Centromere Component CENP-50 Is Required for Recovery from Spindle Damage

2005 ◽  
Vol 25 (23) ◽  
pp. 10315-10328 ◽  
Author(s):  
Yukinori Minoshima ◽  
Tetsuya Hori ◽  
Masahiro Okada ◽  
Hiroshi Kimura ◽  
Tokuko Haraguchi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Mitotic Checkpoint ◽  
Loss Of Function ◽  
Wild Type ◽  
Centromere Function ◽  
Dt40 Cells ◽  
Precise Role ◽  
Chicken Dt40 Cell

ABSTRACT We identified CENP-50 as a novel kinetochore component. We found that CENP-50 is a constitutive component of the centromere that colocalizes with CENP-A and CENP-H throughout the cell cycle in vertebrate cells. To determine the precise role of CENP-50, we examined its role in centromere function by generating a loss-of-function mutant in the chicken DT40 cell line. The CENP-50 knockout was not lethal; however, the growth rate of cells with this mutation was slower than that of wild-type cells. We observed that the time for CENP-50-deficient cells to complete mitosis was longer than that for wild-type cells. Centromeric localization of CENP-50 was abolished in both CENP-H- and CENP-I-deficient cells. Coimmunoprecipitation experiments revealed that CENP-50 interacted with the CENP-H/CENP-I complex in chicken DT40 cells. We also observed severe mitotic defects in CENP-50-deficient cells with apparent premature sister chromatid separation when the mitotic checkpoint was activated, indicating that CENP-50 is required for recovery from spindle damage.

scholarly journals pigkMutation underliesmachobehavior and affects Rohon-Beard cell excitability

2015 ◽  
Vol 114 (2) ◽  
pp. 1146-1157 ◽  
Author(s):  
V. Carmean ◽  
M. A. Yonkers ◽  
M. B. Tellez ◽  
J. R. Willer ◽  
G. B. Willer ◽  
...  
Keyword(s):  
Action Potential ◽  
Sensory Neurons ◽  
Sodium Current ◽  
Genetic Defect ◽  
Sensory Cells ◽  
Loss Of Function ◽  
Wild Type ◽  
Action Potential Firing ◽  
Potential Firing ◽  
Touch Response

The study of touch-evoked behavior allows investigation of both the cells and circuits that generate a response to tactile stimulation. We investigate a touch-insensitive zebrafish mutant, macho (maco), previously shown to have reduced sodium current amplitude and lack of action potential firing in sensory neurons. In the genomes of mutant but not wild-type embryos, we identify a mutation in the pigk gene. The encoded protein, PigK, functions in attachment of glycophosphatidylinositol anchors to precursor proteins. In wild-type embryos, pigk mRNA is present at times when mutant embryos display behavioral phenotypes. Consistent with the predicted loss of function induced by the mutation, knock-down of PigK phenocopies maco touch insensitivity and leads to reduced sodium current (INa) amplitudes in sensory neurons. We further test whether the genetic defect in pigk underlies the maco phenotype by overexpressing wild-type pigk in mutant embryos. We find that ubiquitous expression of wild-type pigk rescues the touch response in maco mutants. In addition, for maco mutants, expression of wild-type pigk restricted to sensory neurons rescues sodium current amplitudes and action potential firing in sensory neurons. However, expression of wild-type pigk limited to sensory cells of mutant embryos does not allow rescue of the behavioral touch response. Our results demonstrate an essential role for pigk in generation of the touch response beyond that required for maintenance of proper INa density and action potential firing in sensory neurons.

scholarly journals Similarities and differences between IL11 and IL11RA1 knockout mice for lung fibro-inflammation, fertility and craniosynostosis

2020 ◽  
Author(s):  
Benjamin Ng ◽  
Anissa A. Widjaja ◽  
Sivakumar Viswanathan ◽  
Jinrui Dong ◽  
Sonia P. Chothani ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Lung Fibroblasts ◽  
Loss Of Function ◽  
Wild Type ◽  
Reduced Body ◽  
Body Weights ◽  
Show Evidence ◽  
Similarities And Differences ◽  
The Impact

AbstractGenetic loss of function (LOF) in IL11RA infers IL11 signaling as important for fertility, fibrosis, inflammation and craniosynostosis. The impact of genetic LOF in IL11 has not been characterized. We generated IL11-knockout (Il11-/-) mice, which are born in normal Mendelian ratios, have normal hematological profiles and are protected from bleomycin-induced lung fibro-inflammation. Noticeably, baseline IL6 levels in the lungs of Il11-/- mice are lower than those of wild-type mice and are not induced by bleomycin damage, placing IL11 upstream of IL6. Lung fibroblasts from Il11-/- mice are resistant to pro-fibrotic stimulation and show evidence of reduced autocrine IL11 activity. Il11-/- female mice are infertile. Unlike Il11ra1-/- mice, Il11-/- mice do not have a craniosynostosis-like phenotype and exhibit mildly reduced body weights. These data highlight similarities and differences between LOF in IL11 or IL11RA while establishing further the role of IL11 signaling in fibrosis and stromal inflammation.

Abstract 361: Creg1 Interacts With Sec8 to Promote Cell-cell Adhesion During Cardiomyogenesis

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Jie Liu ◽  
Yanmei Qi ◽  
Shu-Chan Hsu ◽  
Siavash Saadat ◽  
Saum Rahimi ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Es Cells ◽  
Embryonic Stem ◽  
Intercellular Junctions ◽  
Amino Acid Residues ◽  
Loss Of Function ◽  
Wild Type ◽  
Adhesion Sites ◽  
Cell Cell

Cellular repressor of E1A-stimulated genes 1 (CREG1) is a 24 kD glycoprotein essential for early embryonic development. Our immunofluorescence studies revealed that CREG1 is highly expressed at myocyte junctions in both embryonic and adult hearts. To explore it role in cardiomyogenesis, we employed gain- and loss-of-function analyses demonstrating that CREG1 is required for the differentiation of mouse embryonic stem (ES) cell into cohesive myocardium-like structures. Chimeric cultures of wild-type and CREG1 knockout ES cells expressing cardiac-specific reporters showed that the cardiomyogenic effect of CREG1 is cell autonomous. Furthermore, we identified a novel interaction between CREG1 and Sec8 of the exocyst complex, which tethers vesicles to the plasma membrane. Mutations of the amino acid residues D141 and P142 to alanine in CREG1 abolished its binding to Sec8. To address the role of the CREG1-Sec8 interaction in cardiomyogenesis, we rescued CREG1 knockout ES cells with wild-type and Sec8-binding mutant CREG1 and showed that CREG1 binding to Sec8 promotes cardiomyocyte differentiation and cohesion. Mechanistically, CREG1, Sec8 and N-cadherin all localize at cell-cell adhesion sites. CREG1 overexpression enhances the assembly of adherens and gap junctions. By contrast, its knockout inhibits the Sec8-N-cadherin interaction and induces their degradation. Finally, shRNA-mediated knockdown of Sec8 leads to cardiomyogenic defects similar to CREG1 knockout. These results suggest that the CREG1 binding to Sec8 enhances the assembly of intercellular junctions and promotes cardiomyogenesis.

scholarly journals MtBZR1 Plays an Important Role in Nodule Development in Medicago truncatula

2019 ◽  
Vol 20 (12) ◽  
pp. 2941
Author(s):  
Can Cui ◽  
Hongfeng Wang ◽  
Limei Hong ◽  
Yiteng Xu ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Normal Growth ◽  
Dry Mass ◽  
Growth Conditions ◽  
Nodule Development ◽  
Functional Study ◽  
Loss Of Function ◽  
Wild Type

Brassinosteroid (BR) is an essential hormone in plant growth and development. The BR signaling pathway was extensively studied, in which BRASSINAZOLE RESISTANT 1 (BZR1) functions as a key regulator. Here, we carried out a functional study of the homolog of BZR1 in Medicago truncatula R108, whose expression was induced in nodules upon Sinorhizobium meliloti 1021 inoculation. We identified a loss-of-function mutant mtbzr1-1 and generated 35S:MtBZR1 transgenic lines for further analysis at the genetic level. Both the mutant and the overexpression lines of MtBZR1 showed no obvious phenotypic changes under normal growth conditions. After S. meliloti 1021 inoculation, however, the shoot and root dry mass was reduced in mtbzr1-1 compared with the wild type, caused by partially impaired nodule development. The transcriptomic analysis identified 1319 differentially expressed genes in mtbzr1-1 compared with wild type, many of which are involved in nodule development and secondary metabolite biosynthesis. Our results demonstrate the role of MtBZR1 in nodule development in M. truncatula, shedding light on the potential role of BR in legume–rhizobium symbiosis.

scholarly journals Revisiting an IgG Fc Loss-of-Function Experiment: the Role of Complement in HIV Broadly Neutralizing Antibody b12 Activity

mBio ◽  
2021 ◽  
Author(s):  
Benjamin S. Goldberg ◽  
Chengzi I. Kaku ◽  
Jérémy Dufloo ◽  
Timothée Bruel ◽  
Olivier Schwartz ◽  
...  
Keyword(s):  
Neutralizing Antibody ◽  
Loss Of Function ◽  
Wild Type ◽  
Suboptimal Outcome ◽  
Antiviral Activities ◽  
Broadly Neutralizing Antibody ◽  
Hiv 1 ◽  
Prevention Of Hiv

Given the suboptimal outcome of VRC01 antibody-mediated prevention of HIV-1 infection in its first field trial, means to improve diverse antiviral activities in vivo have renewed importance. This work revisits a loss-of-function experiment that investigated the mechanism of action of b12, a similar antibody, and finds that the reason why complement-mediated antiviral activities were not observed to contribute to protection may be the inherent lack of activity of wild-type b12, raising the prospect that this mechanism may contribute in the context of other HIV-specific antibodies.

scholarly journals Usp14 is required for spermatogenesis and ubiquitin stress responses in Drosophila melanogaster

2019 ◽  
Author(s):  
Levente Kovács ◽  
Ágota Nagy ◽  
Margit Pál ◽  
Peter Deák
Keyword(s):  
Male Sterility ◽  
Stress Responses ◽  
Expression Patterns ◽  
Loss Of Function ◽  
Wild Type ◽  
Cellular Processes ◽  
Protein Conjugates ◽  
Covalently Linked ◽  
Mutant Phenotypes

ABSTRACTDeubiquitinating (DUB) enzymes free covalently linked ubiquitins from ubiquitin-ubiquitin and ubiquitin-protein conjugates, and thereby maintain the equilibrium between free and conjugated ubiquitins and regulate ubiquitin-mediated cellular processes. The present genetic analyses of mutant phenotypes demonstrate that loss of Usp14 function results in male sterility, with defects in spermatid individualization and reduced testicular free monoubiquitin levels. These phenotypes were rescued by germline specific overexpression of wild type Usp14. Synergistic genetic interactions with Ubi-p63E and cycloheximide sensitivity suggest that ubiquitin shortage is a primary cause of male sterility. In addition, Usp14 is predominantly expressed in testes in Drosophila, and differential expression patterns may be causative of testis-specific loss of function Usp14 phenotypes. Collectively, these results suggest a major role of Usp14 in maintaining normal steady state free monoubiquitin levels during the later stages of Drosophila spermatogenesis.

scholarly journals Mechanistic insights into the deleterious role of nasu-hakola disease associated TREM2 variants

2019 ◽  
Author(s):  
Raju Dash ◽  
Ho Jin Choi ◽  
Il Soo Moon
Keyword(s):  
Myeloid Cells ◽  
Structural Features ◽  
Dynamics Simulation ◽  
Loss Of Function ◽  
Wild Type ◽  
Structural Impact ◽  
Collective Motions ◽  
Loop Regions ◽  
Complementarity Determining Region

AbstractRecently, critical roles of genetic variants in Triggering Receptor Expressed on Myeloid cells 2 (TREM2) for myeloid cells to Alzhimer’s disease have been aggressively highlighted. However, little studies focused to the deleterious role of Nasu-Hakola disease (NHD) associated TREM2 variants. In order to get insights into the contributions of these variants in neurodegeneration, we investigated the influences of three well-known NHD associated TREM2 mutations (Y38C, T66M and V126G) on the loss-of-function by using conventional molecular dynamics simulation. Compared to the wild type, the mutants produced substantial differences in the collective motions in the loop regions, which not only promotes structural remodelling in complementarity-determining region 2 (CDR2) loop but also in CDR1 loop, through changing the inter and intra-loop hydrogen bonding network. In addition, the structural studies from free energy landscape showed that Y38, T66 and V126 are crucial for maintaining structural features of CDR1 and CDR2 loops, while their mutation at this position produced steric clash and thus contributes to the structural impact and loss of ligand binding. These results revealed that the presence of the mutations in TREM2 ectodomain induced flexibility and promotes structural alterations. Dynamical scenarios, which are provided by the present study, may be critical to our understanding of the role of the three TREM2 mutations in neurodegenerative diseases.

Sign in / Sign up

Export Citation Format

Share Document