Abnormal Parvalbumin-Positive Interneuron Excitability in a Novel Mouse Model of Epileptic Encephalopathy Due to a Recurrent Kcnc1-p.A421V Variant
Abstract number :
3.012
Submission category :
1. Basic Mechanisms / 1B. Epileptogenesis of genetic epilepsies
Year :
2023
Submission ID :
641
Source :
www.aesnet.org
Presentation date :
12/4/2023 12:00:00 AM
Published date :
Authors :
Presenting Author: Eric Wengert, PhD – Children's Hospital of Philadelphia
Melody Cheng, NA – Undergraduate Researcher, School of Arts and Sciences, University of Pennsylvania; Ethan Goldberg, MD, PhD – Associate Professor, Pediatrics, Children's Hospital of Philadelphia
Rationale: Pathogenic variants in the KCNC1 gene, which encodes the voltage-gated potassium channel subunit KV3.1, have been identified as a cause of developmental and epileptic encephalopathy (DEE), a severe childhood epilepsy syndrome. Patients exhibit multiple seizure types typically including myoclonic seizures, developmental delay/intellectual disability, and motor dysfunction. How KCNC1 variants lead to disease is poorly understood. Here, we utilized a novel mouse model of KCNC1 DEE expressing the recurrent patient-derived variant p.Ala421Val and collected electrophysiology recordings from individual neocortical parvalbumin-positive (PV) fast-spiking GABAergic inhibitory interneurons, which specifically express high levels of KV3.1. Prior work has shown that KV3.1-Ala421Val exhibits loss of function with a dominant-negative action on tetrameric KV3 channels. We hypothesized that the A421V variant would lead to physiological impairment at the level of PV interneuron excitability and PV interneuron-mediated synaptic neurotransmission.
Methods: We generated a mouse line that expresses the Kcnc1 missense variant p.Ala421Val in a Cre-dependent manner. We bred those mice to double transgenic mice expressing the global ACTB-Cre and Pvalb-TdT to yield triple transgenic Pvalb.tdT-Kcnc1-A421V/+ and Pvalb.tdT-WT littermate controls. Mouse body/brain weights were measured and neocortical PV interneuron numbers were counted. Mice were monitored for seizures and death. The outside-out macropatch technique was used to measure somatic voltage-gated ion channel currents. Multiple whole-cell patch-clamp electrophysiology recordings were collected from PV-INs and pyramidal cells in acute brain slices prepared from mice between the ages of postnatal day 16-21 to determine intrinsic excitability and properties of unitary PV-IN:pyramidal cell synaptic transmission.
Results: The novel Kcnc1-A421V/+ mouse model recapitulates key phenotypes of KCNC1 DEE including spontaneous seizures and premature lethality. Immunohistochemical analysis revealed a normal number of PV-INs. Outside-out macropatch recordings from PV interneurons showed a loss of voltage-gated potassium channel current magnitude. PV interneuron intrinsic excitability was strongly impaired in the Kcnc1-A421V/+ mice, with clear alterations in the action potential waveform and generation of fast-spiking behavior in response to depolarizing current injections. Recordings of unitary synaptic currents from PV interneurons onto nearby pyramidal cells was unaffected.
Conclusions: In this study, we generated a novel mouse model of KCNC1 DEE to explore the neurophysiological mechanisms underlying disease pathogenesis. Our results indicate a likely role for PV interneurons as a mechanistic contributor to brain dysfunction. Loss of PV interneuron excitability may result in network disinhibition in cortical microcircuits leading to network hyperexcitability and seizures.
Funding: This work was funded by the NIH NINDS F32 NS126234 to E.R.W., the College Alumni Society Undergraduate Research Grant, Frances Velay Women's Research Fellowship, and Pincus-Magaziner Family Award to M.A.C., and NIH NINDS R01 NS122887 to E.M.G.
Basic Mechanisms