Fluoxetine as a Precision-medicine Approach for Epileptic Encephalopathies Caused by KCNT1 Variants
Abstract number :
3.022
Submission category :
1. Basic Mechanisms / 1B. Epileptogenesis of genetic epilepsies
Year :
2024
Submission ID :
589
Source :
www.aesnet.org
Presentation date :
12/9/2024 12:00:00 AM
Published date :
Authors :
Presenting Author: deborah Puzo, MSc – University Of Molise
Ilaria Mosca, PhD – University Of Molise
Elena Freri, MD – 2Dept. of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico “C. Besta”, Milan, IT
Paolo Ambrosino, PhD – University of Sannio, Benevento (IT)
Giorgio Belperio, MSc – University of Sannio, Benevento (IT)
Tiziana Granata, MD – Fondazione IRCCS Istituto Neurologico “C. Besta”
Laura Canafoglia, MD, PhD – Fondazione IRCCS Istituto Neurologico Carlo Besta
Francesca Ragona, MD – IRCCS Foundation Carlo Besta Neurological Institute
Roberta Solazzi, MD – Fondazione IRCCS Istituto Neurologico “C. Besta”, Milan, IT
Ilaria Filareto, MD – Fondazione IRCCS Istituto Neurologico “C. Besta”, Milan, IT
Barbara Castellotti, MSc – Fondazione IRCCS Istituto Neurologico “C. Besta”, Milan, IT
Giuliana Messina, MSc – Fondazione IRCCS Istituto Neurologico “C. Besta”, Milan, IT
Cinzia Gellera, MSc – Fondazione IRCCS Istituto Neurologico “C. Besta”, Milan, IT
Marina Trivisano, MD – Bambino Gesù Children’s Hospital, IRCCS, Rome (IT)
Angela De Dominicis, MD – Bambino Gesù Children’s Hospital, IRCCS, Rome (IT)
Nicola Specchio, MD, PhD – Bambino Gesu’ Children’s Hospital, IRCCS, Full Member of European Reference Network on Rare and Complex Epilepsies EpiCARE
Jacopo DiFrancesco, MD – Fondazione IRCCS San Gerardo Dei Tintori
Mark Shapiro, PhD – University of Texas Health San Antonio
Maria Virginia Soldovieri, PhD – University of Molise
Maurizio Taglialatela, MD/PhD – University of Naples “Federico II” Naples, IT
Rationale: The KCNT1 gene encodes for K+ channels (“Slack,” Slo2.2, KCa4.1) composed of six transmembrane segments (S1-S6) and intracellular N- and C-terminal domains. The C terminus contains two domains, called RCK1 and RCK2, able to regulate opening of these K+ channels through Na+ and NAD-dependent mechanisms. The proteins are of intense interest to the Epilepsy community, as mutations in KCNT1 are associated with a number of severe and pharmacoresistant epilepsies that begin in early childhood, such as migrating partial seizures of infancy (MMPSI). It has also been reported that acquired epilepsies from traumatic brain injuries are associated with up-regulation of KCNT1/2 expression near the loci of traumatic insult, making their role in the pathophysiology of acquired epileptogenesis potentially very widespread.
The aims of the study are to: 1) evaluate the presence of mutations in patients affected by KCNT1-related drug-resistant and severe forms of epilepsy; 2) characterize functional and pharmacological properties of KCNT1 channels incorporating each variant, and 3) test the ability of selected clinically-approved or investigational drugs to counteract variant-induced functional effects.
Methods: Genetic analysis of patient DNA were performed by next-generation sequencing approaches and the functional coding region of identified variants inserted in plasmids for mammalian expression by “Quick-Change” PCR. Wild-type or mutant channels were expressed by transient transfection in Chinese Hamster Ovary mammalian tissue-culture cells maintained under standard conditions. KCNT1 K+ currents were measured using the patch-clamp technique in the whole-cell configuration.
Results: Four de novo variants in KCNT1 were identified in five unrelated patients. Among them, one localized to the RCK2 domain (S937G), representing a novel mutation locus, whereas the others localized to between the S6 segment and the RCK1 domain (R356W, R398Q, and R428Q) loci have been previously reported. Electrophysiological experiments reveal that all variants cause gain-of-function (GoF) effects, compared to wild-type channels and that the antidepressant drug fluoxetine is able to counteract these variant-induced functional effects. Notably, in patients, “add-on” therapy with fluoxetine results in the disappearance of seizures and cognitive/behavioural improvements. The studies were conducted in accordance with the local legislation and institutional.
Conclusions: Fluoxetine is a precision-medicine approach effective in patients with severe epilepsies caused by Gain-of-Function variants of KCNT1 channels.
Funding: The present work was supported by the Italian Ministry for University and Research (A multiscale integrated approach to the study of the nervous system in health and disease – MNESYS; Next Generation EU, National Recovery and Resilience Plan, Mission 4 Component 2 Investment 1.3 - Project code PE0000006), and by the following Ricerca Finalizzata Projects from the Italian Ministry of Health: GR-2016-02363337, RF-2019-12370491, and PNRR-MR1-2022-12376528.
Basic Mechanisms