An Epilepsy-Associated KCNT1 Mutation Enhances Excitability of Human iPSC-Derived Neurons by Increasing Slack K Na Currents.

Autor: Quraishi IH; Department of Neurology, Yale Comprehensive Epilepsy Center, Yale School of Medicine, New Haven, Connecticut 06520., Stern S; Laboratory of Genetics-G, The Salk Institute for Biological Studies, La Jolla, California 92037., Mangan KP; FUJIFILM Cellular Dynamics, Inc., Madison, Wisconsin 53711., Zhang Y; Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, and., Ali SR; Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, and., Mercier MR; Department of Neurology, Yale Comprehensive Epilepsy Center, Yale School of Medicine, New Haven, Connecticut 06520., Marchetto MC; Laboratory of Genetics-G, The Salk Institute for Biological Studies, La Jolla, California 92037., McLachlan MJ; FUJIFILM Cellular Dynamics, Inc., Madison, Wisconsin 53711., Jones EM; FUJIFILM Cellular Dynamics, Inc., Madison, Wisconsin 53711., Gage FH; Laboratory of Genetics-G, The Salk Institute for Biological Studies, La Jolla, California 92037., Kaczmarek LK; Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, and leonard.kaczmarek@yale.edu.; Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut 06520.
Jazyk: angličtina
Zdroj: The Journal of neuroscience : the official journal of the Society for Neuroscience [J Neurosci] 2019 Sep 11; Vol. 39 (37), pp. 7438-7449. Date of Electronic Publication: 2019 Jul 26.
DOI: 10.1523/JNEUROSCI.1628-18.2019
Abstrakt: Mutations in the KCNT1 (Slack, K Na 1.1) sodium-activated potassium channel produce severe epileptic encephalopathies. Expression in heterologous systems has shown that the disease-causing mutations give rise to channels that have increased current amplitude. It is not known, however, whether such gain of function occurs in human neurons, nor whether such increased K Na current is expected to suppress or increase the excitability of cortical neurons. Using genetically engineered human induced pluripotent stem cell (iPSC)-derived neurons, we have now found that sodium-dependent potassium currents are increased several-fold in neurons bearing a homozygous P924L mutation. In current-clamp recordings, the increased K Na current in neurons with the P924L mutation acts to shorten the duration of action potentials and to increase the amplitude of the afterhyperpolarization that follows each action potential. Strikingly, the number of action potentials that were evoked by depolarizing currents as well as maximal firing rates were increased in neurons expressing the mutant channel. In networks of spontaneously active neurons, the mean firing rate, the occurrence of rapid bursts of action potentials, and the intensity of firing during the burst were all increased in neurons with the P924L Slack mutation. The feasibility of an increased K Na current to increase firing rates independent of any compensatory changes was validated by numerical simulations. Our findings indicate that gain-of-function in Slack K Na channels causes hyperexcitability in both isolated neurons and in neural networks and occurs by a cell-autonomous mechanism that does not require network interactions. SIGNIFICANCE STATEMENT KCNT1 mutations lead to severe epileptic encephalopathies for which there are no effective treatments. This study is the first demonstration that a KCNT1 mutation increases the Slack current in neurons. It also provides the first explanation for how this increased potassium current induces hyperexcitability, which could be the underlining factor causing seizures.
(Copyright © 2019 the authors.)
Databáze: MEDLINE
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