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https://www.readbyqxmd.com/read/28747464/lethal-digenic-mutations-in-the-k-channels-kir4-1-kcnj10-and-slack-kcnt1-associated-with-severe-disabling-seizures-and-neurodevelopmental-delay
#1
Sonia Majed Hasan, Ameera Balobaid, Alessandro Grottesi, Omar Dabbagh, Marta Cenciarini, Rifaat Rawashdeh, Afaf Al-Sagheir, Cecilia Bove, Lara Macchioni, Mauro Pessia, Mohammed Al-Owain, Maria Cristina D'Adamo
A 2-year-old boy presented profound developmental delay, failure to thrive, ataxia, hypotonia and tonic-clonic seizures that caused the death of the patient. Targeted and whole-exome sequencing revealed two heterozygous missense variants: a novel mutation in KCNJ10 gene that encodes for the inwardly-rectifying K(+) channel Kir4.1 and another previously characterized mutation in KCNT1 that encodes for the Na(+)-activated K(+) channel known as Slo2.2 or SLACK. The objectives of this study were to perform the clinical and genetic characterization of the proband and his family and to examine the functional consequence of the Kir4...
July 26, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28679838/fluorocitrate-mediated-depolarization-of-astrocytes-in-the-retrotrapezoid-nucleus-stimulates-breathing
#2
Cleyton R Sobrinho, Christopher M Gonçalves, Ana C Takakura, Daniel K Mulkey, Thiago S Moreira
Evidence indicates that CO2/H(+)-evoked ATP released from retrotrapezoid nucleus (RTN) astrocytes modulates the activity of CO2-sensitive neurons. RTN astrocytes also sense H(+) by inhibition of Kir4.1 channels; however, the relevance of this pH-sensitive current remains unclear since ATP release appears to involve CO2-dependent gating of connexin 26 hemichannels. Considering that depolarization mediated by H(+) inhibition of Kir4.1 channels is expected to increase sodium bicarbonate cotransporter (NBC) conductance and favor Ca(2+) influx via the sodium calcium exchanger (NCX), we hypothesize that depolarization in the presence of CO2 is sufficient to facilitate ATP release and enhance respiratory output...
September 1, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28615682/improved-retinal-function-in-rcs-rats-after-suppressing-the-over-activation-of-mglur5
#3
Jiaman Dai, Yan Fu, Yuxiao Zeng, Shiying Li, Zheng Qin Yin
Müller cells maintain retinal synaptic homeostasis by taking up glutamate from the synaptic cleft and transporting glutamine back to the neurons. To study the interaction between Müller cells and photoreceptors, we injected either DL-α-aminoadipate or L-methionine sulfoximine-both inhibitors of glutamine synthetase-subretinally in rats. Following injection, the a-wave of the electroretinogram (ERG) was attenuated, and metabotropic glutamate receptor 5 (mGluR5) was activated. Selective antagonism of mGluR5 by 2-methyl-6-(phenylethynyl)-pyridine increased the ERG a-wave amplitude and also increased rhodopsin expression...
June 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28597918/inflammation-in-the-developing-rat-modulates-astroglial-reactivity-to-seizures-in-the-mature-brain
#4
Zuzanna Setkowicz, Emilia Kosonowska, Krzysztof Janeczko
Astrocytes participate in neuronal development and excitability, and produce factors enhancing or suppressing inflammatory processes occurring due to neurodegenerative diseases, such as epilepsy. Seizures, in turn, trigger the release of inflammatory mediators, causing structural and functional changes in the brain. Therefore, it appears reasonable to determine whether generalized inflammation at developmental periods can affect astrocyte reactivity to epileptic seizures occurring in the adult brain. Lipopolysaccharide (LPS) was injected in 6- or 30-day-old rats (P6 or P30, respectively)...
June 9, 2017: Journal of Anatomy
https://www.readbyqxmd.com/read/28577853/loss-of-transcriptional-activation-of-the-potassium-channel-kir5-1-by-hnf1%C3%AE-drives-autosomal-dominant-tubulointerstitial-kidney-disease
#5
Andreas Kompatscher, Jeroen H F de Baaij, Karam Aboudehen, Anke P W M Hoefnagels, Peter Igarashi, René J M Bindels, Gertjan J C Veenstra, Joost G J Hoenderop
Hepatocyte nuclear factor 1 homeobox B (HNF1β) is an essential transcription factor for the development and functioning of the kidney. Mutations in HNF1β cause autosomal dominant tubulointerstitial kidney disease characterized by renal cysts and maturity-onset diabetes of the young (MODY). Moreover, these patients suffer from a severe electrolyte phenotype consisting of hypomagnesemia and hypokalemia. Until now, genes that are regulated by HNF1β are only partially known and do not fully explain the phenotype of the patients...
May 31, 2017: Kidney International
https://www.readbyqxmd.com/read/28562601/multifunctional-glial-support-by-semper-cells-in-the-drosophila-retina
#6
Mark A Charlton-Perkins, Edward D Sendler, Elke K Buschbeck, Tiffany A Cook
Glial cells play structural and functional roles central to the formation, activity and integrity of neurons throughout the nervous system. In the retina of vertebrates, the high energetic demand of photoreceptors is sustained in part by Müller glia, an intrinsic, atypical radial glia with features common to many glial subtypes. Accessory and support glial cells also exist in invertebrates, but which cells play this function in the insect retina is largely undefined. Using cell-restricted transcriptome analysis, here we show that the ommatidial cone cells (aka Semper cells) in the Drosophila compound eye are enriched for glial regulators and effectors, including signature characteristics of the vertebrate visual system...
May 2017: PLoS Genetics
https://www.readbyqxmd.com/read/28548026/low-reliability-of-anti-kir4-183-120-peptide-auto-antibodies-in-multiple-sclerosis-patients
#7
Mariapaola Marino, Giovanni Frisullo, Gabriele Di Sante, Daniela Maria Samengo, Carlo Provenzano, Massimiliano Mirabella, Giovambattista Pani, Francesco Ria, Emanuela Bartoccioni
BACKGROUND: Multiple sclerosis (MS) is an autoimmune disease for which auto-antibodies fully validated as diagnostic and prognostic biomarkers are widely desired. Recently, an immunoreactivity against the inward rectifying potassium channel 4.1 (KIR4.1) has been reported in a large proportion of a group of MS patients, with amino acids 83-120 being the major epitope. Moreover, a strong correlation between anti-KIR4.183-120 and anti-full-length-protein auto-antibodies titer was reported...
May 1, 2017: Multiple Sclerosis: Clinical and Laboratory Research
https://www.readbyqxmd.com/read/28520217/the-gene-encoding-the-inwardly-rectifying-potassium-channel-kir4-1-may-be-involved-in-sudden-infant-death-syndrome
#8
Siri H Opdal, Åshild Vege, Arne Stray-Pedersen, Torleiv O Rognum
AIM: Disturbances in brain function and development may play a role in sudden infant death syndrome (SIDS). This Norwegian study aimed to test the hypothesis that specific variants of genes involved in water transport and potassium homeostasis would be predisposing factors for SIDS. METHODS: Genetic variation in the genes encoding aquaporin-4 (AQP4), Kir4.1 (KCNJ10) and α-syntrophin was analysed in 171 SIDS cases (62.6% male) with a median age of 15.5 (2-52) weeks and 398 adult controls (70...
May 18, 2017: Acta Paediatrica
https://www.readbyqxmd.com/read/28414733/absence-of-antibodies-against-kir4-1-in-multiple-sclerosis-a-three-technique-approach-and-systematic-review
#9
Miquel Navas-Madroñal, Ana Valero-Mut, María José Martínez-Zapata, Manuel Javier Simón-Talero, Sebastián Figueroa, Nuria Vidal-Fernández, Mariana López-Góngora, Antonio Escartín, Luis Querol
INTRODUCTION: Antibodies targeting the inward-rectifying potassium channel KIR4.1 have been associated with multiple sclerosis (MS) but studies using diverse techniques have failed to replicate this association. The detection of these antibodies is challenging; KIR4.1 glycosylation patterns and the use of diverse technical approaches may account for the disparity of results. We aimed to replicate the association using three different approaches to overcome the technical limitations of a single technique...
2017: PloS One
https://www.readbyqxmd.com/read/28391264/anti-kir4-1-antibodies-in-chinese-patients-with-central-nervous-system-inflammatory-demyelinating-disorders
#10
Rong Zhong, Junyan Liang, Ailin Tao, Linzhan Wu, Xinguang Yang, Huiming Xu, Qingmei Huang, Shunzhi Zhuang, Youming Long, Cong Gao
OBJECTIVES: The aim of this study was to explore the frequency of KIR4.1 antibodies in patients with multiple sclerosis (MS) and in control groups using a cell-based assay. MATERIALS AND METHODS: A transfected HEK-293A cell line expressing KIR4.1 was established to test for the presence of KIR4.1 antibodies in blood serum. We tested 904 subjects, including 188 patients with MS, 264 patients with neuromyelitis optica spectrum disorders (NMOSD), 209 patients with other inflammatory neurologic disease (OIND), 203 patients with other noninflammatory neurological disease (OND), and 40 healthy controls...
2016: Neuroimmunomodulation
https://www.readbyqxmd.com/read/28345117/inwardly-rectifying-k-currents-in-cultured-oligodendrocytes-from-rat-optic-nerve-are-insensitive-to-ph
#11
Alberto Pérez-Samartín, Edith Garay, Juan Pablo H Moctezuma, Abraham Cisneros-Mejorado, María Victoria Sánchez-Gómez, Guadalupe Martel-Gallegos, Leticia Robles-Martínez, Manuel Canedo-Antelo, Carlos Matute, Rogelio O Arellano
Inwardly rectifying K(+) (Kir) channel expression signals at an advanced stage of maturation during oligodendroglial differentiation. Knocking down their expression halts the generation of myelin and produces severe abnormalities in the central nervous system. Kir4.1 is the main subunit involved in the tetrameric structure of Kir channels in glial cells; however, the precise composition of Kir channels expressed in oligodendrocytes (OLs) remains partially unknown, as participation of other subunits has been proposed...
March 27, 2017: Neurochemical Research
https://www.readbyqxmd.com/read/28216048/chloroquine-blocks-the-kir4-1-channels-by-an-open-pore-blocking-mechanism
#12
Leticia G Marmolejo-Murillo, Iván A Aréchiga-Figueroa, Eloy G Moreno-Galindo, Ricardo A Navarro-Polanco, Aldo A Rodríguez-Menchaca, Meng Cui, José A Sánchez-Chapula, Tania Ferrer
Kir4.1 channels have been implicated in various physiological processes, mainly in the K(+) homeostasis of the central nervous system and in the control of glial function and neuronal excitability. Even though, pharmacological research of these channels is very limited. Chloroquine (CQ) is an amino quinolone derivative known to inhibit Kir2.1 and Kir6.2 channels with different action mechanism and binding site. Here, we employed patch-clamp methods, mutagenesis analysis, and molecular modeling to characterize the molecular pharmacology of Kir4...
April 5, 2017: European Journal of Pharmacology
https://www.readbyqxmd.com/read/28214987/severe-convulsions-and-dysmyelination-in-both-jimpy-and-cx32-47-mice-may-associate-astrocytic-l-channel-function-with-myelination-and-oligodendrocytic-connexins-with-internodal-kv-channels
#13
Y H Gerald Chaban, Ye Chen, Elna Hertz, Leif Hertz
The Jimpy mouse illustrates the importance of interactions between astrocytes and oligodendrocytes. It has a mutation in Plp coding for proteolipid protein and DM20. Its behavior is normal at birth but from the age of ~2 weeks it shows severe convulsions associated with oligodendrocyte/myelination deficits and early death. A normally occurring increase in oxygen consumption by highly elevated K(+) concentrations is absent in Jimpy brain slices and cultured astrocytes, reflecting that Plp at early embryonic stages affects common precursors as also shown by the ability of conditioned medium from normal astrocytes to counteract histological abnormalities...
February 18, 2017: Neurochemical Research
https://www.readbyqxmd.com/read/27965079/diversity-of-astrocyte-potassium-channels-an-update
#14
REVIEW
Gerald Seifert, Christian Henneberger, Christian Steinhäuser
Astrocyte K(+) channels and the K(+) currents they mediate dwarf all other transmembrane conductances in these cells. This defining feature of astrocytes and its functional implications have been investigated intensely over the past decades. Nonetheless, many aspects of astrocyte K(+) handling and signaling remain incompletely understood. In this review, we provide an update on the diversity of K(+) channels expressed by astrocytes and new functional implications. We focus on inwardly-rectifying K(+) channels (particularly Kir4...
December 11, 2016: Brain Research Bulletin
https://www.readbyqxmd.com/read/27693230/importance-of-astrocytes-for-potassium-ion-k-homeostasis-in-brain-and-glial-effects-of-k-and-its-transporters-on-learning
#15
REVIEW
Leif Hertz, Ye Chen
Initial clearance of extracellular K(+) ([K(+)]o) following neuronal excitation occurs by astrocytic uptake, because elevated [K(+)]o activates astrocytic but not neuronal Na(+),K(+)-ATPases. Subsequently, astrocytic K(+) is re-released via Kir4.1 channels after distribution in the astrocytic functional syncytium via gap junctions. The dispersal ensures widespread release, preventing renewed [K(+)]o increase and allowing neuronal Na(+),K(+)-ATPase-mediated re-uptake. Na(+),K(+)-ATPase operation creates extracellular hypertonicity and cell shrinkage which is reversed by the astrocytic cotransporter NKCC1...
December 2016: Neuroscience and Biobehavioral Reviews
https://www.readbyqxmd.com/read/27671501/hmg-coa-synthase-isoenzymes-1-and-2-localize-to-satellite-glial-cells-in-dorsal-root-ganglia-and-are-differentially-regulated-by-peripheral-nerve-injury
#16
Fei Wang, Hongfei Xiang, Gregory Fischer, Zhen Liu, Matthew J Dupont, Quinn H Hogan, Hongwei Yu
In dorsal root ganglia (DRG), satellite glial cells (SGCs) tightly ensheathe the somata of primary sensory neurons to form functional sensory units. SGCs are identified by their flattened and irregular morphology and expression of a variety of specific marker proteins. In this report, we present evidence that the 3-hydroxy-3-methylglutaryl coenzyme A synthase isoenzymes 1 and 2 (HMGCS1 and HMGCS2) are abundantly expressed in SGCs. Immunolabeling with the validated antibodies revealed that both HMGCS1 and HMGCS2 are highly colabeled with a selection of SGC markers, including GS, GFAP, Kir4...
December 1, 2016: Brain Research
https://www.readbyqxmd.com/read/27489866/lack-of-kir4-1-autoantibodies-in-japanese-patients-with-ms-and-nmo
#17
Osamu Higuchi, Shunya Nakane, Waka Sakai, Yasuhiro Maeda, Masaaki Niino, Toshiyuki Takahashi, Toshiyuki Fukazawa, Seiji Kikuchi, Kazuo Fujihara, Hidenori Matsuo
OBJECTIVES: To examine anti-KIR4.1 antibodies by 2 different assays in Japanese patients with multiple sclerosis (MS) or neuromyelitis optica (NMO). METHODS: One hundred sixty serum samples from 57 patients with MS, 40 patients with NMO/NMO spectrum disorder (NMOSD), and 50 healthy controls (all were Japanese) were tested with ELISA using a synthetic peptide of the first extracellular portion of human KIR4.1. In addition, we attempted to detect anti-KIR4.1 immunoglobulin G in the serum by the luciferase immunoprecipitation systems (LIPS) with the full length of human KIR4...
October 2016: Neurology® Neuroimmunology & Neuroinflammation
https://www.readbyqxmd.com/read/27191611/changes-in-aquaporin-4-and-kir4-1-expression-in-rats-with-inherited-retinal-dystrophy
#18
S Lassiale, F Valamanesh, C Klein, D Hicks, M Abitbol, C Versaux-Botteri
Muller glial cells (MGC) are essential for normal functioning of retina. They are especially involved in potassium (K+) and water homeostasis, via inwardly rectifying K+ (Kir 4.1) and aquaporin-4 (AQP4) channels respectively. Because MGC appear morphologically and functionally altered in most retinal pathologies, we studied the expression of AQP 4 and Kir 4.1 during the time course of progressive retinal degeneration in Royal College of Surgeons (RCS) rats, an animal model for the hereditary human retinal degenerative disease Retinitis pigmentosa...
July 2016: Experimental Eye Research
https://www.readbyqxmd.com/read/27184474/ml418-the-first-selective-sub-micromolar-pore-blocker-of-kir7-1-potassium-channels
#19
Daniel R Swale, Haruto Kurata, Sujay V Kharade, Jonathan Sheehan, Rene Raphemot, Karl R Voigtritter, Eric E Figueroa, Jens Meiler, Anna L Blobaum, Craig W Lindsley, Corey R Hopkins, Jerod S Denton
The inward rectifier potassium (Kir) channel Kir7.1 (KCNJ13) has recently emerged as a key regulator of melanocortin signaling in the brain, electrolyte homeostasis in the eye, and uterine muscle contractility during pregnancy. The pharmacological tools available for exploring the physiology and therapeutic potential of Kir7.1 have been limited to relatively weak and nonselective small-molecule inhibitors. Here, we report the discovery in a fluorescence-based high-throughput screen of a novel Kir7.1 channel inhibitor, VU714...
July 20, 2016: ACS Chemical Neuroscience
https://www.readbyqxmd.com/read/27161034/myelinating-satellite-oligodendrocytes-are-integrated-in-a-glial-syncytium-constraining-neuronal-high-frequency-activity
#20
Arne Battefeld, Jan Klooster, Maarten H P Kole
Satellite oligodendrocytes (s-OLs) are closely apposed to the soma of neocortical layer 5 pyramidal neurons but their properties and functional roles remain unresolved. Here we show that s-OLs form compact myelin and action potentials of the host neuron evoke precisely timed Ba(2+)-sensitive K(+) inward rectifying (Kir) currents in the s-OL. Unexpectedly, the glial K(+) inward current does not require oligodendrocytic Kir4.1. Action potential-evoked Kir currents are in part mediated by gap-junction coupling with neighbouring OLs and astrocytes that form a syncytium around the pyramidal cell body...
2016: Nature Communications
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