Epilepsy and neurobehavioral abnormalities in mice with a dominant-negative KCNB1 pathogenic variant

Abstract

Developmental and epileptic encephalopathies (DEE) are a group of severe epilepsies that usually present with intractable seizures, developmental delay, and often have elevated risk for premature mortality. Numerous genes have been identified as a monogenic cause of DEE, including KCNB1 . The voltage-gated potassium channel K v 2.1, encoded by KCNB1 , is primarily responsible for delayed rectifier potassium currents that are important regulators of excitability in electrically excitable cells, including neurons. In addition to its canonical role as a voltage-gated potassium conductance, K v 2.1 also serves a highly conserved structural function organizing endoplasmic reticulum-plasma membrane junctions clustered in the soma and proximal dendrites of neurons. The de novo pathogenic variant KCNB1 -p.G379R was identified in an infant with epileptic spasms, and atonic, focal and tonic-clonic seizures that were refractory to treatment with standard antiepileptic drugs. Previous work demonstrated deficits in potassium conductance, but did not assess non-conducting functions. To determine if the G379R variant affected K v 2.1 clustering at endoplasmic reticulum-plasma membrane junctions, K v 2.1-G379R was expressed in HEK293T cells. K v 2.1-G379R expression did not induce formation of endoplasmic reticulum-plasma membrane junctions, and co-expression of K v 2.1-G379R with K v 2.1-wild-type lowered induction of these structures relative to K v 2.1-WT alone, consistent with a dominant negative effect. To model this variant in vivo, we introduced Kcnb1 G379R into mice using CRISPR/Cas9 genome editing. We characterized neuronal expression, neurological and neurobehavioral phenotypes of Kcnb1 G379R/+ ( Kcnb1 R/+ ) and Kcnb1 G379R/G379R ( Kcnb1 R/R ) mice. Immunohistochemistry studies on brains from Kcnb1 +/+ , Kcnb1 R/+ and Kcnb1 R/R mice revealed genotype-dependent differences in the expression levels of K v 2.1 protein, as well as associated K v 2.2 and AMIGO-1 proteins. Kcnb1 R/+ and Kcnb1 R/R mice displayed profound hyperactivity, repetitive behaviors, impulsivity and reduced anxiety. Spontaneous seizures were observed in Kcnb1 R/R mice, as well as seizures induced by exposure to novel environments and/ or handling. Both Kcnb1 R/+ and Kcnb1 R/R ...

Recent Developments in Autism Genetic Research: A Scientometric Review from 2018 to 2022

“…The naming of this cluster is based on a series of two papers written by Hakami [ 208 , 209 ] on antiseizure drugs, and may be related to ASD due to the higher prevalence of seizure and epilepsy diagnoses among these individuals [ 210 ]. Similarly, other contributing papers focused on understanding the genetic bases of epilepsy [ 211 , 212 , 213 ] and epilepsy treatment [ 214 , 215 ]. In this cluster, contributing papers frequently cited references from the International League Against Epilepsy (ILAE) in their clinical descriptions and classifications of different seizures and epilepsies (e.g., Scheffer et al [ 216 ], Fisher et al [ 217 , 218 ] with citation frequencies of 43, 12, and 8, respectively).…”

Correlation Analyses of Clinical Manifestations and Variant Effects in KCNB1-Related Neurodevelopmental Disorder

“…DN effect is a classical molecular mechanism in genetic diseases, which is defined as the variant that will adversely affect the co-expressed wild-type activity. Many KCNB1 variants have disease effects in this way, such as the well-validated variant p.G379R, which interferes with wild-type functions in both potassium conductance and non-conductance aspects ( 7 , 15 ). We found that not all variants could be considered to have DN effects according to their functional results.…”

“…We found that not all variants could be considered to have DN effects according to their functional results. On the one hand, previous work has been mainly focused on unveiling their deficits in potassium conductance rather than their non-conductance roles ( 15 ). Here, we added an experiment on the KCNB1 protein expression in the heteromeric models, which aided us in identifying p.V408S as a DN effect variant.…”

“…Now, it has been proven that causative KCNB1 variants result in loss of Kv2.1 channel function, which is classified into “partial loss of function (LoF)” and “complete LoF” according to the amplitude of Kv2.1 currents in homotetrameric expression models ( 7 , 11 – 13 ). Like other genetic variants of ionic channels ( 14 ), the dominant-negative (DN) phenomenon that variants could interfere with the co-expressed wild type, has also been confirmed as the pathogenesis of the disorder ( 15 ). Conversely, those variants that do not have sufficient evidence to support the DN phenomenon could be subgrouped as the non-dominant-negative (non-DN) effect.…”

Channelopathy of Dravet Syndrome and Potential Neuroprotective Effects of Cannabidiol

“…113 KCNB1 G379R mice recapitulate many features observed in individuals with developmental and epileptic encephalopathies (DEE) due to pathogenic variants in KCNB1 which encodes KV2.1. 114 Mutations of KCNB1 -(G379R, S347R, T374I) KV2.1 channel result in the early onset epileptic encephalopathy. 115 Voltage-gated potassium channel (KV2.1) functional defects caused by KCNB1 variants are associated with DEE.…”