scholarly journals Dravet variant SCN1AA1783V impairs interneuron firing predominantly by altered channel activation

2021 ◽  
Author(s):  
N. Layer ◽  
L. Sonnenberg ◽  
E. Pardo González ◽  
J. Benda ◽  
H. Lerche ◽  
...  
Keyword(s):  
Voltage Dependence ◽  
Dravet Syndrome ◽  
Slice Culture ◽  
List Type ◽  
Slow Inactivation ◽  
Loss Of Function ◽  
Peak Current Density ◽  
Action Potential Firing ◽  
Channel Activation

AbstractDravet syndrome (DS) is a developmental epileptic encephalopathy mainly caused by functional NaV1.1 haploinsufficiency in interneurons (IN). Recently, a new conditional mouse model expressing the recurrent human p.A1783V missense variant has become available. Here we provide an electrophysiological characterization of this variant in tsA201 cells, revealing both altered voltage-dependence of activation and slow inactivation without reduced sodium peak current density. Simulating IN excitability in a Hodgkin-Huxley one-compartment model suggested surprisingly similar firing deficits for Scn1aA1783V and full haploinsufficiency as caused by heterozygous truncation variants. Impaired NaVA1783V channel activation was predicted to have a significantly larger impact on channel function than altered slow inactivation and is therefore proposed as the main mechanism underlying IN dysfunction. The computational model was validated in cortical organotypic slice cultures derived from conditional Scn1aA1783V mice. Pan-neuronal activation of the p.A1783V variant in vitro confirmed the predicted IN firing deficit while demonstrating normal excitability of pyramidal neurons. Taken together these data demonstrate that despite maintained physiological peak currents density LOF gating properties may match effects of full haploinsufficiency on neuronal level, thereby causing DS.HighlightsNaV1.1A1783V alters voltage-dependence of activation and slow inactivation while not affecting fast inactivation.Depolarizing and hyperpolarizing shifts of activation and slow inactivation curves result in combined channel loss of function (LOF).Simulations of NaV1.1A1783V interneuronal properties indicate reduced action potential firing rates comparable to full SCN1A haploinsufficiency, which is often found in Dravet syndrome.In silico modelling identifies impaired channel activation as the predominant mechanism of channel LOF.Panneuronal induction of Scn1a+/A1783V in a cortical slice culture model confirms restriction of loss of function and its restriction to interneurons.

scholarly journals Dravet Variant SCN1AA1783V Impairs Interneuron Firing Predominantly by Altered Channel Activation

2021 ◽  
Vol 15 ◽  
Author(s):  
Nikolas Layer ◽  
Lukas Sonnenberg ◽  
Emilio Pardo González ◽  
Jan Benda ◽  
Ulrike B. S. Hedrich ◽  
...  
Keyword(s):  
Current Density ◽  
Input Resistance ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Slow Inactivation ◽  
Loss Of Function ◽  
Peak Current Density ◽  
Channel Activation ◽  
Peak Current

Dravet syndrome (DS) is a developmental epileptic encephalopathy mainly caused by functional NaV1.1 haploinsufficiency in inhibitory interneurons. Recently, a new conditional mouse model expressing the recurrent human p.(Ala1783Val) missense variant has become available. In this study, we provided an electrophysiological characterization of this variant in tsA201 cells, revealing both altered voltage-dependence of activation and slow inactivation without reduced sodium peak current density. Based on these data, simulated interneuron (IN) firing properties in a conductance-based single-compartment model suggested surprisingly similar firing deficits for NaV1.1A1783V and full haploinsufficiency as caused by heterozygous truncation variants. Impaired NaV1.1A1783V channel activation was predicted to have a significantly larger impact on channel function than altered slow inactivation and is therefore proposed as the main mechanism underlying IN dysfunction. The computational model was validated in cortical organotypic slice cultures derived from conditional Scn1aA1783V mice. Pan-neuronal activation of the p.Ala1783V in vitro confirmed a predicted IN firing deficit and revealed an accompanying reduction of interneuronal input resistance while demonstrating normal excitability of pyramidal neurons. Altered input resistance was fed back into the model for further refinement. Taken together these data demonstrate that primary loss of function (LOF) gating properties accompanied by altered membrane characteristics may match effects of full haploinsufficiency on the neuronal level despite maintaining physiological peak current density, thereby causing DS.

scholarly journals Febrile temperatures unmask biophysical defects in Nav1.1 epilepsy mutations supportive of seizure initiation

2013 ◽  
Vol 142 (6) ◽  
pp. 641-653 ◽  
Author(s):  
Linda Volkers ◽  
Kristopher M. Kahlig ◽  
Joost H.G. Das ◽  
Marjan J.A. van Kempen ◽  
Dick Lindhout ◽  
...  
Keyword(s):  
Voltage Dependence ◽  
Febrile Seizures ◽  
Dravet Syndrome ◽  
Slow Inactivation ◽  
Loss Of Function ◽  
Peak Current Density ◽  
Delayed Recovery ◽  
Generalized Epilepsy ◽  
Use Dependency ◽  
Febrile Seizures Plus

Generalized epilepsy with febrile seizures plus (GEFS+) is an early onset febrile epileptic syndrome with therapeutic responsive (a)febrile seizures continuing later in life. Dravet syndrome (DS) or severe myoclonic epilepsy of infancy has a complex phenotype including febrile generalized or hemiclonic convulsions before the age of 1, followed by intractable myoclonic, complex partial, or absence seizures. Both diseases can result from mutations in the Nav1.1 sodium channel, and initially, seizures are typically triggered by fever. We previously characterized two Nav1.1 mutants—R859H (GEFS+) and R865G (DS)—at room temperature and reported a mixture of biophysical gating defects that could not easily predict the phenotype presentation as either GEFS+ or DS. In this study, we extend the characterization of Nav1.1 wild-type, R859H, and R865G channels to physiological (37°C) and febrile (40°C) temperatures. At physiological temperature, a variety of biophysical defects were detected in both mutants, including a hyperpolarized shift in the voltage dependence of activation and a delayed recovery from fast and slow inactivation. Interestingly, at 40°C we also detected additional gating defects for both R859H and R865G mutants. The GEFS+ mutant R859H showed a loss of function in the voltage dependence of inactivation and an increased channel use-dependency at 40°C with no reduction in peak current density. The DS mutant R865G exhibited reduced peak sodium currents, enhanced entry into slow inactivation, and increased use-dependency at 40°C. Our results suggest that fever-induced temperatures exacerbate the gating defects of R859H or R865G mutants and may predispose mutation carriers to febrile seizures.

scholarly journals Testosterone-induced increase in libido in a patient with a loss-of-function mutation in the AR gene

2021 ◽  
Vol 2021 ◽  
Author(s):  
Laura Marino ◽  
Andrea Messina ◽  
James S Acierno ◽  
Franziska Phan-Hug ◽  
Nicolas J Niederländer ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Androgen Insensitivity Syndrome ◽  
Surgical Removal ◽  
List Type ◽  
Loss Of Function ◽  
Testosterone Treatment ◽  
Androgen Insensitivity ◽  
Increased Risk ◽  
Loss Of Libido

Summary Complete androgen-insensitivity syndrome (CAIS), a disorder of sex development (46,XY DSD), is caused primarily by mutations in the androgen receptor (AR). Gonadectomy is recommended due to the increased risk of gonadoblastoma, however, surgical intervention is often followed by loss of libido. We present a 26-year-old patient with CAIS who underwent gonadectomy followed by a significant decrease in libido, which was improved with testosterone treatment but not with estradiol. Genetic testing was performed and followed by molecular characterization. We found that this patient carried a previously unidentified start loss mutation in the androgen receptor. This variant resulted in an N-terminal truncated protein with an intact DNA binding domain and was confirmed to be loss-of-function in vitro. This unique CAIS case and detailed functional studies raise intriguing questions regarding the relative roles of testosterone and estrogen in libido, and in particular, the potential non-genomic actions of androgens. Learning points N-terminal truncation of androgen receptor can cause androgen-insensitivity syndrome. Surgical removal of testosterone-producing gonads can result in loss of libido. Libido may be improved with testosterone treatment but not with estradiol in some forms of CAIS. A previously unreported AR mutation – p.Glu2_Met190del (c.2T>C) – is found in a CAIS patient and results in blunted AR transcriptional activity under testosterone treatment.

DER EINFLUSS VON RESERPIN AUF DIE ANTITHYREOIDALE WIRKUNG VON KALIUMPERCHLORAT

1962 ◽  
Vol 39 (3) ◽  
pp. 423-430
Author(s):  
H. L. Krüskemper ◽  
F. J. Kessler ◽  
E. Steinkrüger
Keyword(s):  
Thyroid Gland ◽  
Male Rats ◽  
Normal Male ◽  
Tissue Respiration ◽  
List Type ◽  
Morphological Alterations ◽  
Hormone Synthesis ◽  
Stimulation Of

ABSTRACT 1. Reserpine does not inhibit the tissue respiration of liver in normal male rats (in vitro). 2. The decrease of tissue respiration of the liver with simultaneous morphological stimulation of the thyroid gland after long administration of reserpine is due to a minute inhibition of the hormone synthesis in the thyroid gland. 3. The morphological alterations of the thyroid in experimental hypothyroidism due to perchlorate can not be prevented with reserpine.

LACK OF EFFECT OF CORTICOSTEROIDS ON THE IN VIVO DISAPPEARANCE OF SULFHYDRYL-INHIBITED AND ANTIBODY-COATED ERYTHROCYTES

1964 ◽  
Vol 47 (3_Suppl) ◽  
pp. S28-S36
Author(s):  
Kailash N. Agarwal
Keyword(s):  
Red Cells ◽  
List Type ◽  
Red Cell

ABSTRACT Red cells were incubated in vitro with sulfhydryl inhibitors and Rhantibody with and without prior incubation with prednisolone-hemisuccinate. These erythrocytes were labelled with Cr51 and P32 and their disappearance in vivo after autotransfusion was measured. Prior incubation with prednisolone-hemisuccinate had no effect on the rate of red cell disappearance. The disappearance of the cells was shown to take place without appreciable intravascular destruction.

ÉTUDE IN VITRO DU MÉTABOLISME DES HYDRATES DE CARBONE DANS LE LEUCOCYTE CIRCULANT DU COBAYE TRAITÉ À LA CORTISONE

1966 ◽  
Vol 51 (2) ◽  
pp. 193-202
Author(s):  
J. A. Antonioli ◽  
A. Vannotti
Keyword(s):  
Glucose Concentration ◽  
Intramuscular Injection ◽  
Acute Inflammation ◽  
Glycogen Content ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Glucose Consumption ◽  
List Type ◽  
Hydrates De Carbone

ABSTRACT 1. The metabolism of suspensions of circulating leucocytes has been studied after intramuscular injection of a dose of 50 mg/kg of a corticosteroid (cortisone acetate). The suspensions were incubated under aerobic conditions in the presence of a glucose concentration of 5.6 mm. Glucose consumption, lactate production, and variations in intracellular glycogen concentration were measured. After the administration of the corticosteroid, the anabolic processes of granulocyte metabolism were reversibly stimulated. Glucose consumption and lactate production increased 12 hours after the injection, but tended to normalize after 24 hours. The glycogen content of the granulocytes was enhanced, and glycogen synthesis during the course of the incubation was greatly stimulated. The action of the administered corticosteroid is more prolonged in females than in males. The injection of the corticosteroid caused metabolic modifications which resemble in their modulations and in their chronological development those found in circulating granulocytes of guinea-pigs suffering from sterile peritonitis. These results suggest, therefore, that, in the case of acute inflammation, the glucocorticosteroids may play an important role in the regulation of the metabolism of the blood leucocytes.

scholarly journals Mutations in fbiD (Rv2983) as a Novel Determinant of Resistance to Pretomanid and Delamanid in Mycobacterium tuberculosis

2020 ◽  
Vol 65 (1) ◽  
pp. e01948-20
Author(s):  
Dalin Rifat ◽  
Si-Yang Li ◽  
Thomas Ioerger ◽  
Keshav Shah ◽  
Jean-Philippe Lanoix ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Evidence ◽  
Clinical Samples ◽  
Loss Of Function ◽  
Wild Type ◽  
Content Type ◽  
Solid Media ◽  
High Level ◽  
Level Resistance

ABSTRACTThe nitroimidazole prodrugs delamanid and pretomanid comprise one of only two new antimicrobial classes approved to treat tuberculosis (TB) in 50 years. Prior in vitro studies suggest a relatively low barrier to nitroimidazole resistance in Mycobacterium tuberculosis, but clinical evidence is limited to date. We selected pretomanid-resistant M. tuberculosis mutants in two mouse models of TB using a range of pretomanid doses. The frequency of spontaneous resistance was approximately 10−5 CFU. Whole-genome sequencing of 161 resistant isolates from 47 mice revealed 99 unique mutations, of which 91% occurred in 1 of 5 genes previously associated with nitroimidazole activation and resistance, namely, fbiC (56%), fbiA (15%), ddn (12%), fgd (4%), and fbiB (4%). Nearly all mutations were unique to a single mouse and not previously identified. The remaining 9% of resistant mutants harbored mutations in Rv2983 (fbiD), a gene not previously associated with nitroimidazole resistance but recently shown to be a guanylyltransferase necessary for cofactor F420 synthesis. Most mutants exhibited high-level resistance to pretomanid and delamanid, although Rv2983 and fbiB mutants exhibited high-level pretomanid resistance but relatively small changes in delamanid susceptibility. Complementing an Rv2983 mutant with wild-type Rv2983 restored susceptibility to pretomanid and delamanid. By quantifying intracellular F420 and its precursor Fo in overexpressing and loss-of-function mutants, we provide further evidence that Rv2983 is necessary for F420 biosynthesis. Finally, Rv2983 mutants and other F420H2-deficient mutants displayed hypersusceptibility to some antibiotics and to concentrations of malachite green found in solid media used to isolate and propagate mycobacteria from clinical samples.

scholarly journals Cockayne syndrome B protein acts as an ATP-dependent processivity factor that helps RNA polymerase II overcome nucleosome barriers

2020 ◽  
Vol 117 (41) ◽  
pp. 25486-25493 ◽  
Author(s):  
Jun Xu ◽  
Wei Wang ◽  
Liang Xu ◽  
Jia-Yu Chen ◽  
Jenny Chong ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Neurological Diseases ◽  
Transcription Elongation ◽  
Cockayne Syndrome ◽  
Stable Complex ◽  
Loss Of Function ◽  
Pol Ii ◽  
Chromatin Remodelers ◽  
Processivity Factor

While loss-of-function mutations in Cockayne syndrome group B protein (CSB) cause neurological diseases, this unique member of the SWI2/SNF2 family of chromatin remodelers has been broadly implicated in transcription elongation and transcription-coupled DNA damage repair, yet its mechanism remains largely elusive. Here, we use a reconstituted in vitro transcription system with purified polymerase II (Pol II) and Rad26, a yeast ortholog of CSB, to study the role of CSB in transcription elongation through nucleosome barriers. We show that CSB forms a stable complex with Pol II and acts as an ATP-dependent processivity factor that helps Pol II across a nucleosome barrier. This noncanonical mechanism is distinct from the canonical modes of chromatin remodelers that directly engage and remodel nucleosomes or transcription elongation factors that facilitate Pol II nucleosome bypass without hydrolyzing ATP. We propose a model where CSB facilitates gene expression by helping Pol II bypass chromatin obstacles while maintaining their structures.

scholarly journals TRIM27 interacts with Iκbα to promote the growth of human renal cancer cells through regulating the NF-κB pathway

BMC Cancer ◽  
2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Chengwu Xiao ◽  
Wei Zhang ◽  
Meimian Hua ◽  
Huan Chen ◽  
Bin Yang ◽  
...  
Keyword(s):  
Cell Lines ◽  
Prognostic Indicator ◽  
The Cancer Genome Atlas ◽  
Mrna Levels ◽  
Loss Of Function ◽  
Protein Levels ◽  
Kaplan Meier ◽  
Cancer Genome Atlas

Abstract Background The tripartite motif (TRIM) family proteins exhibit oncogenic roles in various cancers. The roles of TRIM27, a member of the TRIM super family, in renal cell carcinoma (RCC) remained unexplored. In the current study, we aimed to investigate the clinical impact and roles of TRIM27 in the development of RCC. Methods The mRNA levels of TRIM27 and Kaplan–Meier survival of RCC were analyzed from The Cancer Genome Atlas database. Real-time PCR and Western blotting were used to measure the mRNA and protein levels of TRIM27 both in vivo and in vitro. siRNA and TRIM27 were exogenously overexpressed in RCC cell lines to manipulate TRIM27 expression. Results We discovered that TRIM27 was elevated in RCC patients, and the expression of TRIM27 was closely correlated with poor prognosis. The loss of function and gain of function results illustrated that TRIM27 promotes cell proliferation and inhibits apoptosis in RCC cell lines. Furthermore, TRIM27 expression was positively associated with NF-κB expression in patients with RCC. Blocking the activity of NF-κB attenuated the TRIM27-mediated enhancement of proliferation and inhibition of apoptosis. TRIM27 directly interacted with Iκbα, an inhibitor of NF-κB, to promote its ubiquitination, and the inhibitory effects of TRIM27 on Iκbα led to NF-κB activation. Conclusions Our results suggest that TRIM27 exhibits an oncogenic role in RCC by regulating NF-κB signaling. TRIM27 serves as a specific prognostic indicator for RCC, and strategies targeting the suppression of TRIM27 function may shed light on future therapeutic approaches.

scholarly journals Multiple Pathways of LRRK2-G2019S/Rab10 Interaction in Dopaminergic Neurons

2021 ◽  
pp. 1-16
Author(s):  
Alison Fellgett ◽  
C. Adam Middleton ◽  
Jack Munns ◽  
Chris Ugbode ◽  
David Jaciuch ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Dopaminergic Neurons ◽  
Genetic Interaction ◽  
In Vitro Assays ◽  
Rab Proteins ◽  
Circadian Activity ◽  
Loss Of Function ◽  
Lrrk2 G2019s

Background: Inherited mutations in the LRRK2 protein are the common causes of Parkinson’s disease, but the mechanisms by which increased kinase activity of mutant LRRK2 leads to pathological events remain to be determined. In vitro assays (heterologous cell culture, phospho-protein mass spectrometry) suggest that several Rab proteins might be directly phosphorylated by LRRK2-G2019S. An in vivo screen of Rab expression in dopaminergic neurons in young adult Drosophila demonstrated a strong genetic interaction between LRRK2-G2019S and Rab10. Objective: To determine if Rab10 is necessary for LRRK2-induced pathophysiological responses in the neurons that control movement, vision, circadian activity, and memory. These four systems were chosen because they are modulated by dopaminergic neurons in both humans and flies. Methods: LRRK2-G2019S was expressed in Drosophila dopaminergic neurons and the effects of Rab10 depletion on Proboscis Extension, retinal neurophysiology, circadian activity pattern (‘sleep’), and courtship memory determined in aged flies. Results: Rab10 loss-of-function rescued LRRK2-G2019S induced bradykinesia and retinal signaling deficits. Rab10 knock-down, however, did not rescue the marked sleep phenotype which results from dopaminergic LRRK2-G2019S. Courtship memory is not affected by LRRK2, but is markedly improved by Rab10 depletion. Anatomically, both LRRK2-G2019S and Rab10 are seen in the cytoplasm and at the synaptic endings of dopaminergic neurons. Conclusion: We conclude that, in Drosophila dopaminergic neurons, Rab10 is involved in some, but not all, LRRK2-induced behavioral deficits. Therefore, variations in Rab expression may contribute to susceptibility of different dopaminergic nuclei to neurodegeneration seen in people with Parkinson’s disease.

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