The role of resistance to inhibitors of cholinesterase 8b in the control of heart rate

We have assessed the role of ric-b8 in the control of heart rate after the gene was implicated in a recent genome-wide association study of resting heart rate. We developed a novel murine model in which it was possible to conditionally delete ric-8b in the sinoatrial (SA) node after the addition of tamoxifen. Despite this, we were unable to obtain homozygotes and thus studied heterozygotes. Haploinsufficiency of ric-8b in the sinoatrial node induced by the addition of tamoxifen in adult animals leads to mice with a reduced heart rate. However, other electrocardiographic intervals (e.g., PR and QRS) were normal, and there was no apparent arrhythmia such as heart block. The positive chronotropic response to isoprenaline was abrogated, whereas the response to carbachol was unchanged. The pacemaker current If(funny current) has an important role in regulating heart rate, and its function is modulated by both isoprenaline and carbachol. Using a heterologous system expressing HCN4, we show that ric-8b can modulate the HCN4 current. Overexpression of ric-8b led to larger HCN4 currents, whereas silencing ric-8b led to smaller currents. Ric-8b modulates heart rate responses in vivo likely via its actions on the stimulatory G-protein.

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Reduction of intrinsic sinoatrial frequency and norepinephrine response of the exercised rat

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y77-109 ◽

1977 ◽

Vol 55 (4) ◽

pp. 813-820 ◽

Cited By ~ 25

Author(s):

Richard L. Hughson ◽

John R. Sutton ◽

J. Desmond Fitzgerald ◽

Norman L. Jones

Keyword(s):

Sinoatrial Node ◽

Parasympathetic Nervous System ◽

Control Group ◽

Response Curves ◽

Chronotropic Response ◽

In Vitro Measurements ◽

The Right

Physical training is associated with a reduction of intrinsic sinoatrial activity; the present study examined the role of the parasympathetic nervous system in this reduction. Six groups of rats were studied for 10 weeks: inactive control; treadmill exercised; parasympathetic receptor blockade with atropine; exercise plus atropine; parasympathetic receptor stimulation with carbachol; and exercise plus carbachol. In vivo ISF (cardiac frequency 20 min after injection of propranolol and atropine) was measured at 3-week intervals. At the end of 10 weeks the right atrium was excised, in vitro measurements were made of ISF, and chronotropic dose–response curves to acetylcholine and norepinephrine were established. In vivo, ISF was reduced with time, the greatest reduction being found in the exercise plus atropine group; the treadmill-exercised and the atropine-treated groups also had a greater reduction than the control group. In vitro, no differences were observed in acetylcholine responses. The maximum norepinephrine chronotropic response was reduced in the treadmill-exercised and the exercise plus atropine groups. The maximum norepinephrine-induced frequency correlated with the in vitro ISF (r = 0.75). Thus, ISF was reduced with training, but this effect was independent of parasympathetic activity. The properties of the sinoatrial node which set ISF also influenced the maximum norepinephrine response.

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The in vivo regulation of heart rate in the murine sinoatrial node by stimulatory and inhibitory heterotrimeric G proteins

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00037.2013 ◽

2013 ◽

Vol 305 (4) ◽

pp. R435-R442 ◽

Cited By ~ 8

Author(s):

Sonia Sebastian ◽

Richard Ang ◽

Joel Abramowitz ◽

Lee S. Weinstein ◽

Min Chen ◽

...

Keyword(s):

Heart Rate ◽

G Protein ◽

Sinoatrial Node ◽

Conduction System ◽

Sa Node ◽

Conditional Deletion ◽

Inhibitory G Protein ◽

Frequency Power

Reciprocal physiological modulation of heart rate is controlled by the sympathetic and parasympathetic systems acting on the sinoatrial (SA) node. However, there is little direct in vivo work examining the role of stimulatory and inhibitory G protein signaling in the SA node. Thus, we designed a study to examine the role of the stimulatory (Gαs) and inhibitory G protein (Gαi2) in in vivo heart rate regulation in the SA node in the mouse. We studied mice with conditional deletion of Gαs and Gαi2 in the conduction system using cre-loxP technology. We crossed mice in which cre recombinase expression was driven by a tamoxifen-inducible conduction system-specific construct with “Gαs floxed” and “Gαi2 floxed” mice. We studied the heart rate responses of adult mice compared with littermate controls by using radiotelemetry before and after administration of tamoxifen. The mice with conditional deletion of Gαs and Gαi2 had a loss of diurnal variation and were bradycardic or tachycardic, respectively, in the daytime. In mice with conditional deletion of Gαs, there was a selective loss of low-frequency power, while with deletion of Gαi2, there was a loss of high-frequency power in power spectral analysis of heart rate variability. There was no evidence of pathological arrhythmia. Pharmacological modulation of heart rate by isoprenaline was impaired in the Gαs mice, but a muscarinic agonist was still able to slow the heart rate in Gαi2 mice. We conclude that Gαs- and Gαi2-mediated signaling in the sinoatrial node is important in the reciprocal regulation of heart rate through the autonomic nervous system.

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HKDC1 Is a Novel Hexokinase Involved in Whole-Body Glucose Use

Endocrinology ◽

10.1210/en.2016-1288 ◽

2016 ◽

Vol 157 (9) ◽

pp. 3452-3461 ◽

Cited By ~ 25

Author(s):

Anton E. Ludvik ◽

Carolina M. Pusec ◽

Medha Priyadarshini ◽

Anthony R. Angueira ◽

Cong Guo ◽

...

Keyword(s):

Glucose Tolerance ◽

Mouse Model ◽

Glucose Homeostasis ◽

Genome Wide Association Study ◽

Whole Body ◽

Glucose Levels ◽

Genome Wide ◽

Glucose Tolerance Tests

In a recent genome-wide association study, hexokinase domain-containing protein 1, or HKDC1, was found to be associated with gestational glucose levels during 2-hour glucose tolerance tests at 28 weeks of pregnancy. Because our understanding of the mediators of gestational glucose homeostasis is incomplete, we have generated the first transgenic mouse model to begin to understand the role of HKDC1 in whole-body glucose homeostasis. Interestingly, deletion of both HKDC1 alleles results in in utero embryonic lethality. Thus, in this study, we report the in vivo role of HKDC1 in whole-body glucose homeostasis using a heterozygous-deleted HKDC1 mouse model (HKDC1+/−) as compared with matched wild-type mice. First, we observed no weight, fasting or random glucose, or fasting insulin abnormalities with aging in male and female HKDC1+/− mice. However, during glucose tolerance tests, glucose levels were impaired in both female and male HKDC1+/− mice at 15, 30, and 120 minutes at a later age (28 wk of age). These glucose tolerance differences also existed in the female HKDC1+/− mice at earlier ages but only during pregnancy. And finally, the impaired glucose tolerance in HKDC1+/− mice was likely due to diminished whole-body glucose use, as indicated by the decreased hepatic energy storage and reduced peripheral tissue uptake of glucose in HKDC1+/− mice. Collectively, these data highlight that HKDC1 is needed to maintain whole-body glucose homeostasis during pregnancy but also with aging, possibly through its role in glucose use.

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Translating GWAS-identified loci for cardiac rhythm and rate using an in vivo image- and CRISPR/Cas9-based approach

10.1101/385500 ◽

2018 ◽

Cited By ~ 1

Author(s):

Benedikt von der Heyde ◽

Anastasia Emmanouilidou ◽

Eugenia Mazzaferro ◽

Silvia Vicenzi ◽

Ida Höijer ◽

...

Keyword(s):

Heart Rate ◽

Candidate Genes ◽

Association Studies ◽

Meta Analysis ◽

Automated Analysis ◽

Zebrafish Embryos ◽

Genome Wide Association Studies ◽

Genome Wide

AbstractA meta-analysis of genome-wide association studies (GWAS) identified eight loci that are associated with heart rate variability (HRV), but candidate genes in these loci remain uncharacterized. We developed an image- and CRISPR/Cas9-based pipeline to systematically characterize candidate genes for HRV in live zebrafish embryos. Nine zebrafish orthologues of six human candidate genes were targeted simultaneously in eggs from fish that transgenically express GFP on smooth muscle cells (Tg[acta2:GFP]), to visualize the beating heart. An automated analysis of repeated 30s recordings of beating atria in 381 live, intact zebrafish embryos at 2 and 5 days post-fertilization highlighted genes that influence HRV (hcn4 and si:dkey-65j6.2 [KIAA1755]); heart rate (rgs6 and hcn4); and the risk of sinoatrial pauses and arrests (hcn4). Exposure to 10 or 25µM ivabradine – an open channel blocker of HCNs – for 24h resulted in a dose-dependent higher HRV and lower heart rate at 5 days post-fertilization. Hence, our screen confirmed the role of established genes for heart rate and rhythm (RGS6 and HCN4); showed that ivabradine reduces heart rate and increases HRV in zebrafish embryos, as it does in humans; and highlighted a novel gene that plays a role in HRV (KIAA1755).

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Major role of iron uptake systems in the intrinsic extra-intestinal virulence of the genus Escherichia revealed by a genome-wide association study

10.1101/712034 ◽

2019 ◽

Cited By ~ 4

Author(s):

Marco Galardini ◽

Olivier Clermont ◽

Alexandra Baron ◽

Bede Busby ◽

Sara Dion ◽

...

Keyword(s):

Association Study ◽

Iron Uptake ◽

Genome Wide Association Study ◽

Opportunistic Pathogen ◽

Genome Wide Association ◽

E Coli ◽

Genome Wide ◽

A Genome

AbstractThe genus Escherichia is composed of several species and cryptic clades, including E. coli, which behave as a vertebrate gut commensal, but also as an opportunistic pathogen involved in both diarrheic and extra-intestinal diseases. To characterize the genetic determinants of extra-intestinal virulence within the genus, we carried out an unbiased genome-wide association study (GWAS) on 370 commensal, pathogenic and environmental strains representative of the Escherichia genus phylogenetic diversity and including E. albertii (n=7), E. fergusonii (n=5), Escherichia clades (n=32) and E. coli (n=326), tested in a mouse model of sepsis. We found that the high-pathogenicity island (HPI), a ∼35 kbp gene island encoding the yersiniabactin siderophore, is highly associated with death in mice, surpassing other associated genetic factors also related to iron uptake, such as the aerobactin and the sitABCD operons. We validated the association in vivo by deleting key components of the HPI in E. coli strains in two phylogenetic backgrounds, and found that virulence is correlated in E. coli with growth in the presence of various stressors including several antimicrobials, which hints at collateral sensitivities associated with intrinsic virulence. This study points to the major role of iron capture systems in the extra-intestinal virulence of the genus Escherichia and the collateral effects on cell growth of such systems.

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Inflammation and JNK's Role in Niacin-GPR109A Diminished Flushed Effect in Microglial and Neuronal Cells With Relevance to Schizophrenia

Frontiers in Psychiatry ◽

10.3389/fpsyt.2021.771144 ◽

2021 ◽

Vol 12 ◽

Author(s):

Sabrina H. Ansarey

Keyword(s):

Inflammatory Mediators ◽

Neuronal Death ◽

Microglial Activation ◽

Negative Symptoms ◽

Genome Wide Association Study ◽

Genetic Mutation ◽

Genome Wide ◽

Ultra High Risk ◽

Altered Proteins

Schizophrenia is a neuropsychiatric illness with no single definitive aetiology, making its treatment difficult. Antipsychotics are not fully effective because they treat psychosis rather than the cognitive or negative symptoms. Antipsychotics fail to alleviate symptoms when patients enter the chronic stage of illness. Topical application of niacin showed diminished skin flush in the majority of patients with schizophrenia compared to the general population who showed flushing. The niacin skin flush test is useful for identifying patients with schizophrenia at their ultra-high-risk stage, and understanding this pathology may introduce an effective treatment. This review aims to understand the pathology behind the diminished skin flush response, while linking it back to neurons and microglia. First, it suggests that there are altered proteins in the GPR109A-COX-prostaglandin pathway, inflammatory imbalance, and kinase signalling pathway, c-Jun N-terminal kinase (JNK), which are associated with diminished flush. Second, genes from the GPR109A-COX-prostaglandin pathway were matched against the 128-loci genome wide association study (GWAS) for schizophrenia using GeneCards, suggesting that G-coupled receptor-109A (GPR109A) may have a genetic mutation, resulting in diminished flush. This review also suggests that there may be increased pro-inflammatory mediators in the GPR109A-COX-prostaglandin pathway, which contributes to the diminished flush pathology. Increased levels of pro-inflammatory markers may induce microglial-activated neuronal death. Lastly, this review explores the role of JNK on pro-inflammatory mediators, proteins in the GPR109A-COX-prostaglandin pathway, microglial activation, and neuronal death. Inhibiting JNK may reverse the changes observed in the diminished flush response, which might make it a good therapeutic target.

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A Genome-Wide RNA Interference Screen Identifies a Differential Role of the Mediator CDK8 Module Subunits for GATA/ RUNX-Activated Transcription in Drosophila

Molecular and Cellular Biology ◽

10.1128/mcb.01625-09 ◽

2010 ◽

Vol 30 (11) ◽

pp. 2837-2848 ◽

Cited By ~ 25

Author(s):

Vanessa Gobert ◽

Dani Osman ◽

Stéphanie Bras ◽

Benoit Augé ◽

Muriel Boube ◽

...

Keyword(s):

Cell Differentiation ◽

Rna Interference ◽

Cell Fate ◽

Gata Factor ◽

Hematopoietic System ◽

Crystal Cell ◽

Genome Wide ◽

A Genome

ABSTRACT Transcription factors of the RUNX and GATA families play key roles in the control of cell fate choice and differentiation, notably in the hematopoietic system. During Drosophila hematopoiesis, the RUNX factor Lozenge and the GATA factor Serpent cooperate to induce crystal cell differentiation. We used Serpent/Lozenge-activated transcription as a paradigm to identify modulators of GATA/RUNX activity by a genome-wide RNA interference screen in cultured Drosophila blood cells. Among the 129 factors identified, several belong to the Mediator complex. Mediator is organized in three modules plus a regulatory “CDK8 module,” composed of Med12, Med13, CycC, and Cdk8, which has long been thought to behave as a single functional entity. Interestingly, our data demonstrate that Med12 and Med13 but not CycC or Cdk8 are essential for Serpent/Lozenge-induced transactivation in cell culture. Furthermore, our in vivo analysis of crystal cell development show that, while the four CDK8 module subunits control the emergence and the proliferation of this lineage, only Med12 and Med13 regulate its differentiation. We thus propose that Med12/Med13 acts as a coactivator for Serpent/Lozenge during crystal cell differentiation independently of CycC/Cdk8. More generally, we suggest that the set of conserved factors identified herein may regulate GATA/RUNX activity in mammals.

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The FAM171A2 gene is a key regulator of progranulin expression and modifies the risk of multiple neurodegenerative diseases

Science Advances ◽

10.1126/sciadv.abb3063 ◽

2020 ◽

Vol 6 (43) ◽

pp. eabb3063

Author(s):

Wei Xu ◽

Si-Da Han ◽

Can Zhang ◽

Jie-Qiong Li ◽

Yan-Jiang Wang ◽

...

Keyword(s):

Neurodegenerative Diseases ◽

Genome Wide Association Study ◽

In Vitro Study ◽

Genome Wide ◽

A Genome ◽

Increased Risk ◽

Pathophysiological Role ◽

Independent Cohort

Progranulin (PGRN) is a secreted pleiotropic glycoprotein associated with the development of common neurodegenerative diseases. Understanding the pathophysiological role of PGRN may help uncover biological underpinnings. We performed a genome-wide association study to determine the genetic regulators of cerebrospinal fluid (CSF) PGRN levels. Common variants in region of FAM171A2 were associated with lower CSF PGRN levels (rs708384, P = 3.95 × 10−12). This was replicated in another independent cohort. The rs708384 was associated with increased risk of Alzheimer’s disease, Parkinson’s disease, and frontotemporal dementia and could modify the expression of the FAM171A2 gene. FAM171A2 was considerably expressed in the vascular endothelium and microglia, which are rich in PGRN. The in vitro study further confirmed that the rs708384 mutation up-regulated the expression of FAM171A2, which caused a decrease in the PGRN level. Collectively, genetic, molecular, and bioinformatic findings suggested that FAM171A2 is a key player in regulating PGRN production.

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Identification of Genes That Contribute to the Pathogenesis of Invasive Pneumococcal Disease byIn VivoTranscriptomic Analysis

Infection and Immunity ◽

10.1128/iai.00295-12 ◽

2012 ◽

Vol 80 (9) ◽

pp. 3268-3278 ◽

Cited By ~ 44

Author(s):

Abiodun D. Ogunniyi ◽

Layla K. Mahdi ◽

Claudia Trappetti ◽

Nadine Verhoeven ◽

Daphne Mermans ◽

...

Keyword(s):

Invasive Pneumococcal Disease ◽

Pneumococcal Disease ◽

Targeted Mutagenesis ◽

Content Type ◽

Genome Wide ◽

Blood Relative ◽

High Level ◽

Upregulated Genes

ABSTRACTStreptococcus pneumoniae(the pneumococcus) continues to be responsible for a high level of global morbidity and mortality resulting from pneumonia, bacteremia, meningitis, and otitis media. Here we have used a novel technique involving niche-specific, genome-widein vivotranscriptomic analyses to identify genes upregulated in distinct niches during pathogenesis after intranasal infection of mice with serotype 4 or 6A pneumococci. The analyses yielded 28 common, significantly upregulated genes in the lungs relative to those in the nasopharynx and 25 significantly upregulated genes in the blood relative to those in the lungs in both strains, some of which were previously unrecognized. The role of five upregulated genes from either the lungs or the blood in pneumococcal pathogenesis and virulence was then evaluated by targeted mutagenesis. One of the mutants (ΔmalX) was significantly attenuated for virulence in the lungs, two (ΔaliAand ΔilvH) were significantly attenuated for virulence in the blood relative to the wild type, and two others (ΔcbiOand ΔpiuA) were completely avirulent in a mouse intranasal challenge model. We also show that the products ofaliA,malX, andpiuAare promising candidates for incorporation into multicomponent protein-based pneumococcal vaccines currently under development. Importantly, we suggest that this new approach is a viable complement to existing strategies for the discovery of genes critical to the distinct stages of invasive pneumococcal disease and potentially has broad application for novel protein antigen discovery in other pathogens such asS. pyogenes,Haemophilus influenzaetype b, andNeisseria meningitidis.

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