The M-current works in tandem with the persistent sodium current to set the speed of locomotion

Selective KCNQ2/3 Potassium Channel Opener ICA-069673 Inhibits Excitability in Mouse Vagal Sensory Neurons

Heightened excitability of vagal sensory neurons in inflammatory visceral diseases contributes to unproductive and difficult-to-treat neuronally based symptoms such as visceral pain and dysfunction. Identification of targets and modulators capable of regulating the excitability of vagal sensory neurons may lead to novel therapeutic options. KCNQ1-KCNQ5 genes encode KV7.1-7.5 potassium channel α-subunits. Homotetrameric or heterotetrameric KV7.2-7.5 channels can generate the so-called M-current (IM) known to decrease the excitability of neurons including visceral sensory neurons. This study aimed to address the hypothesis that KV7.2/7.3 channels are key regulators of vagal sensory neuron excitability by evaluating the effects of KCNQ2/3-selective activator, ICA-069673, on IM in mouse nodose neurons and determining its effects on excitability and action potential firings using patch clamp technique. The results showed that ICA-069673 enhanced IM density, accelerated the activation, and delayed the deactivation of M-channels in a concentration-dependent manner. ICA-069673 negatively shifted the voltage-dependent activation of IM and increased the maximal conductance. Consistent with its effects on IM, ICA-069673 induced a marked hyperpolarization of resting potential and reduced the input resistance. The hyperpolarizing effect was more pronounced in partially depolarized neurons. Moreover, ICA-069673 caused a 3-fold increase in the minimal amount of depolarizing current needed to evoke an action potential, and significantly limited the action potential firings in response to sustained suprathreshold stimulations. ICA-069673 had no effect on membrane currents when Kcnq2 and Kcnq3 were deleted. These results indicate that opening KCNQ2/3-mediated M-channels is sufficient to suppress the excitability and enhance spike accommodation in vagal visceral sensory neurons. SIGNIFICANCE STATEMENT: This study supports the hypothesis that selectively activating KCNQ2/3-mediated M-channels is sufficient to suppress the excitability and action potential firings in vagal sensory neurons. These results provide evidence in support of further investigations into the treatment of various visceral disorders that involve nociceptor hyperexcitability with selective KCNQ2/3 M-channel openers.

Exercise-induced adaptation of neurons in the vertebrate locomotor system

Vertebrate neurons are highly dynamic cells that undergo several alterations in their functioning and physiologies in adaptation to various external stimuli. In particular, how these neurons respond to physical exercise has long been an area of active research. Studies of the vertebrate locomotor system's adaptability suggest multiple mechanisms are involved in the regulation of neuronal activity and properties during exercise. In this brief review, we highlight recent results and insights from the field with a focus on the following mechanisms: (a) alterations in neuronal excitability during acute exercise; (b) alterations in neuronal excitability after chronic exercise; (c) exercise-induced changes in neuronal membrane properties via modulation of ion channel activity; (d) exercise-enhanced dendritic plasticity; and (e) exercise-induced alterations in neuronal gene expression and protein synthesis. Our hope is to update the community with a cellular and molecular understanding of the recent mechanisms underlying the adaptability of the vertebrate locomotor system in response to both acute and chronic physical exercise.

Modeling Effects of Variable preBötzinger Complex Network Topology and Cellular Properties on Opioid-Induced Respiratory Depression and Recovery

The preBötzinger complex (preBötC), located in the medulla, is the essential rhythm-generating neural network for breathing. The actions of opioids on this network impair its ability to generate robust, rhythmic output, contributing to life-threatening opioid-induced respiratory depression (OIRD). The occurrence of OIRD varies across individuals and internal and external states, increasing the risk of opioid use, yet the mechanisms of this variability are largely unknown. In this study, we utilize a computational model of the preBötC to perform several in silico experiments exploring how differences in network topology and the intrinsic properties of preBötC neurons influence the sensitivity of the network rhythm to opioids. We find that rhythms produced by preBötC networks in silico exhibit variable responses to simulated opioids, similar to the preBötC network in vitro. This variability is primarily due to random differences in network topology and can be manipulated by imposed changes in network connectivity and intrinsic neuronal properties. Our results identify features of the preBötC network that may regulate its susceptibility to opioids.

A Developmental Switch in Cholinergic Mechanisms of Modulation in the Medial Nucleus of the Trapezoid Body

The medial nucleus of the trapezoid body (MNTB) has been intensively investigated as a primary source of inhibition in brainstem auditory circuitry. MNTB-derived inhibition plays a critical role in the computation of sound location, as temporal features of sounds are precisely conveyed through the calyx of Held/MNTB synapse. In adult gerbils, cholinergic signaling influences sound-evoked responses of MNTB neurons via nicotinic acetylcholine receptors (nAChRs; Zhang et al., 2021) establishing a modulatory role for cholinergic input to this nucleus. However, the cellular mechanisms through which acetylcholine (ACh) mediates this modulation in the MNTB remain obscure. To investigate these mechanisms, we used whole-cell current and voltage-clamp recordings to examine cholinergic physiology in MNTB neurons from Mongolian gerbils (Meriones unguiculatus) of both sexes. Membrane excitability was assessed in brain slices, in pre-hearing (postnatal days 9-13) and post-hearing onset (P18-20) MNTB neurons during bath application of agonists and antagonists of nicotinic (nAChRs) and muscarinic receptors (mAChRs). Muscarinic activation induced a potent increase in excitability most prominently prior to hearing onset with nAChR modulation emerging at later time points. Pharmacological manipulations further demonstrated that the voltage-gated K+ channel KCNQ (Kv7) is the downstream effector of mAChR activation that impacts excitability early in development. Cholinergic modulation of Kv7 reduces outward K+ conductance and depolarizes resting membrane potential. Immunolabeling revealed expression of Kv7 channels as well as mAChRs containing M1 and M3 subunits. Together, our results suggest that mAChR modulation is prominent but transient in the developing MNTB and that cholinergic modulation functions to shape auditory circuit development.

Timing and precision of rattlesnake spinal motoneurons are determined by the KV72/3 potassium channel

The evolution of novel motor behaviors requires modifications in the central pattern generators (CPGs) controlling muscle activity. How such changes gradually lead to novel behaviors remains enigmatic due to the long time course of evolution. Rattlesnakes provide a unique opportunity to investigate how a locomotor CPG was evolutionarily modified to generate a novel behavior-in this case, acoustic signaling. We show that motoneurons (MNs) in the body and tail spinal cord of rattlesnakes possess fundamentally different physiological characteristics, which allow MNs in the tail to integrate and transmit CPG output for controlling superfast muscles with high temporal precision. Using patch-clamp electrophysiology, we demonstrate that these differences in locomotor and rattle MNs are mainly determined by KV72/3 potassium channels. However, although KV72/3 exerted a significantly different influence on locomotor and rattle MN physiology, single-cell RNA-seq unexpectedly did not reveal any differences in KV72/3 channels' expression. VIDEO ABSTRACT.

M-type potassium currents differentially affect activation of motoneuron subtypes and tune recruitment gain

The size principle is a key mechanism governing the orderly recruitment of motor units and is believed to be dependent on passive properties of the constituent motoneurons. However, motoneurons are endowed with voltage-sensitive ion channels that create non-linearities in their input-output functions. Here we describe a role for the M-type potassium current, conducted by KCNQ channels, in the control of motoneuron recruitment in mice. Motoneurons were studied with whole-cell patch clamp electrophysiology in transverse spinal slices and identified based on delayed (fast) and immediate (slow) onsets of repetitive firing. M-currents were larger in delayed compared to immediate firing motoneurons, which was not reflected by variations in the presence of Kv7.2 or Kv7.3 subunits. Instead, a more depolarized spike threshold in delayed-firing motoneurons afforded a greater proportion of the total M-current to become activated within the subthreshold voltage range, which translated to a greater influence on their recruitment with little influence on their firing rates. Pharmacological activation of M-currents also influenced motoneuron recruitment at the population level, producing a rightward shift in the recruitment curve of monosynaptic reflexes within isolated mouse spinal cords. These results demonstrate a prominent role for M-type potassium currents in regulating the function of motor units, which occurs primarily through the differential control of motoneuron subtype recruitment. More generally, these findings highlight the importance of active properties mediated by voltage-sensitive ion channels in the differential control of motoneuron recruitment, which is a key mechanism for the gradation of muscle force. KEY POINTS: M-currents exert an inhibitory influence on spinal motor output. This inhibitory influence is exerted by controlling the recruitment, but not the firing rate, of high-threshold fast-like motoneurons, with limited influence on low-threshold slow-like motoneurons. Preferential control of fast motoneurons may be linked to a larger M-current that is activated within the subthreshold voltage range compared to slow motoneurons. Larger M-currents in fast compared to slow motoneurons are not accounted for by differences in Kv7.2 or Kv7.3 channel composition. The orderly recruitment of motoneuron subtypes is shaped by differences in the contribution of voltage-gated ion channels, including KCNQ channels. KCNQ channels may provide a target to dynamically modulate the recruitment gain across the motor pool and readily adjust movement vigour.

Interdependence of cellular and network properties in respiratory rhythmogenesis

How breathing is generated by the preBötzinger Complex (preBötC) remains divided between two ideological frameworks, and the persistent sodium current (INaP) lies at the heart of this debate. Although INaP is widely expressed, the pacemaker hypothesis considers it essential because it endows a small subset of neurons with intrinsic bursting or "pacemaker" activity. In contrast, burstlet theory considers INaP dispensable because rhythm emerges from "pre-inspiratory" spiking activity driven by feed-forward network interactions. Using computational modeling, we discover that changes in spike shape can dissociate INaP from intrinsic bursting. Consistent with many experimental benchmarks, conditional effects on spike shape during simulated changes in oxygenation, development, extracellular potassium, and temperature alter the prevalence of intrinsic bursting and pre-inspiratory spiking without altering the role of INaP. Our results support a unifying hypothesis where INaP and excitatory network interactions, but not intrinsic bursting or pre-inspiratory spiking, are critical interdependent features of preBötC rhythmogenesis.

Persistent Nav1.1 and Nav1.6 currents drive spinal locomotor functions through nonlinear dynamics

Persistent sodium current (INaP) in the spinal locomotor network promotes two distinct nonlinear firing patterns: a self-sustained spiking triggered by a brief excitation in bistable motoneurons and bursting oscillations in interneurons of the central pattern generator (CPG). Here, we identify the NaV channels responsible for INaP and their role in motor behaviors. We report the axonal Nav1.6 as the main molecular player for INaP in lumbar motoneurons. The inhibition of Nav1.6, but not of Nav1.1, in motoneurons impairs INaP, bistability, postural tone, and locomotor performance. In interneurons of the rhythmogenic CPG region, both Nav1.6 and Nav1.1 equally mediate INaP. Inhibition of both channels is required to abolish oscillatory bursting activities and the locomotor rhythm. Overall, Nav1.6 plays a significant role both in posture and locomotion by governing INaP-dependent bistability in motoneurons and working in tandem with Nav1.1 to provide INaP-dependent rhythmogenic properties of the CPG.

KCNQ2 channels regulate the population activity of neonatal GABAergic neurons ex vivo

Over the last decade KCNQ2 channels have arisen as fundamental and indispensable regulators of neonatal brain excitability, with KCNQ2 loss-of-function pathogenic variants being increasingly identified in patients with developmental and epileptic encephalopathy. However, the mechanisms by which KCNQ2 loss-of-function variants lead to network dysfunction are not fully known. An important remaining knowledge gap is whether loss of KCNQ2 function alters GABAergic interneuron activity early in development. To address this question, we applied mesoscale calcium imaging ex vivo in postnatal day 4-7 mice lacking KCNQ2 channels in interneurons (Vgat-ires-cre;Kcnq2f/f;GCamp5). In the presence of elevated extracellular potassium concentrations, ablation of KCNQ2 channels from GABAergic cells increased the interneuron population activity in the hippocampal formation and regions of the neocortex. We found that this increased population activity depends on fast synaptic transmission, with excitatory transmission promoting the activity and GABAergic transmission curtailing it. Together, our data show that loss of function of KCNQ2 channels from interneurons increases the network excitability of the immature GABAergic circuits, revealing a new function of KCNQ2 channels in interneuron physiology in the developing brain.

Vascular mechanotransduction

This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.

Mouse models of Kcnq2 dysfunction

Variants in the Kv7.2 channel subunit encoded by the KCNQ2 gene cause epileptic disorders ranging from a benign form with self-limited epileptic seizures and normal development to severe forms with intractable epileptic seizures and encephalopathy. The biological mechanisms involved in these neurological diseases are still unclear. The disease remains intractable in patients affected by the severe form. Over the past 20 years, KCNQ2 models have been developed to elucidate pathological mechanisms and to identify new therapeutic targets. The diversity of Kcnq2 mouse models has proven invaluable to access neuronal networks and evaluate the associated cognitive deficits. This review summarizes the available models and their contribution to our current understanding of KCNQ2 epileptic disorders.

Time-limited alterations in cortical activity of a knock-in mice model of KCNQ2-related developmental and epileptic encephalopathy

KEY POINTS

The electrophysiological impact of the pathogenic c.821C>T mutation of the KCNQ2 gene (p.T274M variant in Kv7.2 subunit) related to Developmental and Epileptic Encephalopathy has been analyzed both in vivo and ex-vivo in layers II/III and V of motor cortical slice from a knock-in mice model during development at neonatal, post-weaning and juvenile stages. M current density and conductance are decreased and excitability of layers II/III pyramidal cells is increased in slices from neonatal and post-weaning KI mice but not from juvenile KI mice. M current and excitability of layer V pyramidal cells are impacted in KI mice only at post-weaning stage. Spontaneous GABAergic network-driven events are recorded until post-weaning stage and their frequency are increased in layers II/III of the KI mice. KI mice displayed spontaneous seizures preferentially at post-weaning rather than at juvenile stages.

ABSTRACT

De novo missense variants in the KCNQ2 gene encoding the Kv7.2 subunit of the voltage-gated potassium Kv7/M channels are the main cause of Developmental and Epileptic Encephalopathy (DEE) with neonatal onset. While seizures usually resolve during development, cognitive/motor deficits persist. To better understand the cellular mechanisms underlying network dysfunction and their progression over time, we investigated in vivo, using local field potential recordings of freely moving animals, and ex-vivo in layers II/III and V of motor cortical slices, using patch-clamp recordings, the electrophysiological properties of pyramidal cells from a heterozygous knock-in (KI) mouse model carrying the Kv7.2 p.T274M pathogenic variant during neonatal, post-weaning and juvenile developmental stages. We found that KI mice displayed spontaneous seizures preferentially at post-weaning rather than at juvenile stages. At the cellular level, the variant led to a reduction in M ​​current density/conductance and to neuronal hyperexcitability. These alterations were observed during the neonatal period in pyramidal cells of layers II /III and during post-weaning stage in pyramidal cells of layer V. Moreover, there was an increase in the frequency of spontaneous network driven events mediated by GABA receptors suggesting that the excitability of interneurons was also increased. However, all these alterations were no more observed in layers II/III and V of juvenile mice. Thus, our data indicate that the action of the variant is developmentally regulated. This raises the possibility that the age related seizure remission observed in KCNQ2-related DEE patient results from a time limited alteration of Kv7 channels activity and neuronal excitability. Abstract figure legend Knock-in mice harboring the heterozygous pathogenic p.T274M variant in the Kv7.2 subunit (c.821C>T mutation of the KCNQ2 gene) related to Developmental and Epileptic Encephalopathy displayed epileptic seizures preferentially at post-weaning rather than at juvenile developmental stages. At cellular level, in motor cortical slices the variant led to a reduction in M current density, to a hyperexcitability of pyramidal cells and to an increase in the frequency of spontaneous network driven events mediated by GABA receptors. All these alterations are time limited and are observed in pyramidal cells of neonatal mice until post-weaning but not of juvenile mice in which the pyramidal cells have electrophysiological properties similar to those of wild-type mice. This article is protected by copyright. All rights reserved.

Poly-dipeptides produced from C9orf72 hexanucleotide repeats cause selective motor neuron hyperexcitability in ALS

SignificanceThe GGGGCC hexanucleotide repeat expansion in the chromosome 9 open reading frame 72 (C9orf72) gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS). Despite myriad studies on the toxic effects of poly-dipeptides produced from the C9orf72 repeats, the mechanisms underlying the selective hyperexcitability of motor cortex that characterizes the early stages of C9orf72 ALS patients remain elusive. Here, we show that the proline-arginine poly-dipeptides cause hyperexcitability in cortical motor neurons by increasing persistent sodium currents conducted by the Nav1.2/β4 sodium channel complex, which is highly expressed in the motor cortex. These findings provide the basis for understanding how the C9orf72 mutation causes motor neuron hyperactivation that can lead to the motor neuron death in C9orf72 ALS.

Contributions of h- and Na+/K+ Pump Currents to the Generation of Episodic and Continuous Rhythmic Activities

Developing spinal motor networks produce a diverse array of outputs, including episodic and continuous patterns of rhythmic activity. Variation in excitability state and neuromodulatory tone can facilitate transitions between episodic and continuous rhythms; however, the intrinsic mechanisms that govern these rhythms and their transitions are poorly understood. Here, we tested the capacity of a single central pattern generator (CPG) circuit with tunable properties to generate multiple outputs. To address this, we deployed a computational model composed of an inhibitory half-center oscillator (HCO). Following predictions of our computational model, we tested the contributions of key properties to the generation of an episodic rhythm produced by isolated spinal cords of the newborn mouse. The model recapitulates the diverse state-dependent rhythms evoked by dopamine. In the model, episodic bursting depended predominantly on the endogenous oscillatory properties of neurons, with Na⁺/K⁺ ATPase pump (I_Pump) and hyperpolarization-activated currents (I_h) playing key roles. Modulation of either I_Pump or I_h produced transitions between episodic and continuous rhythms and silence. As maximal activity of I_Pump decreased, the interepisode interval and period increased along with a reduction in episode duration. Decreasing maximal conductance of I_h decreased episode duration and increased interepisode interval. Pharmacological manipulations of I_h with ivabradine, and I_Pump with ouabain or monensin in isolated spinal cords produced findings consistent with the model. Our modeling and experimental results highlight key roles of I_h and I_Pump in producing episodic rhythms and provide insight into mechanisms that permit a single CPG to produce multiple patterns of rhythmicity.

Maturation of persistent and hyperpolarization-activated inward currents shapes the differential activation of motoneuron subtypes during postnatal development

The size principle underlies the orderly recruitment of motor units; however, motoneuron size is a poor predictor of recruitment amongst functionally defined motoneuron subtypes. Whilst intrinsic properties are key regulators of motoneuron recruitment, the underlying currents involved are not well defined. Whole-cell patch-clamp electrophysiology was deployed to study intrinsic properties, and the underlying currents, that contribute to the differential activation of delayed and immediate firing motoneuron subtypes. Motoneurons were studied during the first three postnatal weeks in mice to identify key properties that contribute to rheobase and may be important to establish orderly recruitment. We find that delayed and immediate firing motoneurons are functionally homogeneous during the first postnatal week and are activated based on size, irrespective of subtype. The rheobase of motoneuron subtypes becomes staggered during the second postnatal week, which coincides with the differential maturation of passive and active properties, particularly persistent inward currents. Rheobase of delayed firing motoneurons increases further in the third postnatal week due to the development of a prominent resting hyperpolarization-activated inward current. Our results suggest that motoneuron recruitment is multifactorial, with recruitment order established during postnatal development through the differential maturation of passive properties and sequential integration of persistent and hyperpolarization-activated inward currents.

Post-stroke epileptogenesis is associated with altered intrinsic properties of hippocampal pyramidal neurons leading to increased theta resonance

Brain insults like stroke, trauma or infections often lead to blood-brain barrier-dysfunction (BBBd) frequently resulting into epileptogenesis. Affected patients suffer from seizures and cognitive comorbidities that are potentially linked to altered network oscillations. It has been shown that a hippocampal BBBd in rats leads to in vivo seizures and increased power at theta (3-8 Hz), an important type of network oscillations. However, the underlying cellular mechanisms remain poorly understood. At membrane potentials close to the threshold for action potentials (APs) a subpopulation of CA1 pyramidal cells (PCs) displays intrinsic resonant properties due to an interplay of the muscarine-sensitive K⁺-current (I_M) and the persistent Na⁺-current (I_NaP). Such resonant neurons are more excitable and generate more APs when stimulated at theta frequencies, being strong candidates for contributing to hippocampal theta oscillations during epileptogenesis. We tested this hypothesis by characterizing changes in intrinsic properties of hippocampal PCs one week after post-stroke epileptogenesis, a model associated with BBBd, using slice electrophysiology and computer modeling. We find a higher proportion of resonant neurons in BBBd compared to sham animals (47 vs. 29%), accompanied by an increase in their excitability. In contrast, BBBd non-resonant neurons showed a reduced excitability, presented with lower impedance and more positive AP threshold. We identify an increase in I_M combined with either a reduction in I_NaP or an increase in I_Leak as possible mechanisms underlying the observed changes. Our results support the hypothesis that a higher proportion of more excitable resonant neurons in the hippocampus contributes to increased theta oscillations and an increased likelihood of seizures in a model of post-stroke epileptogenesis.

Loss of KCNQ2 or KCNQ3 Leads to Multifocal Time-Varying Activity in the Neonatal Forebrain Ex Vivo

Epileptic encephalopathies represent a group of disorders often characterized by refractory seizures, regression in cognitive development, and typically poor prognosis. Dysfunction of KCNQ2 and KCNQ3 channels has emerged as a major cause of neonatal epilepsy. However, our understanding of the cellular mechanisms that may both explain the origins of epilepsy and inform treatment strategies for KCNQ2 and KCNQ3 dysfunction is still lacking. Here, using mesoscale calcium imaging and pharmacology, we demonstrate that in mouse neonatal brain slices, conditional loss of Kcnq2 from forebrain excitatory neurons (Pyr:Kcnq2 mice) or constitutive deletion of Kcnq3 leads to sprawling hyperactivity across the neocortex. Surprisingly, the generation of time-varying hypersynchrony in slices from Pyr:Kcnq2 mice does not require fast synaptic transmission. This is in contrast to control littermates and constitutive Kcnq3 knock-out mice where activity is primarily driven by fast synaptic transmission in the neocortex. Unlike in the neocortex, hypersynchronous activity in the hippocampal formation from Kcnq2 conditional and Kcnq3 constitutive knock-out mice persists in the presence of synaptic transmission blockers. Thus, we propose that loss of KCNQ2 or KCNQ3 function differentially leads to network hyperactivity across the forebrain in a region-specific and macro-circuit-specific manner.

Flexible Stoichiometry: Implications for KCNQ2- and KCNQ3-Associated Neurodevelopmental Disorders

KCNQ2 and KCNQ3 pathogenic channel variants have been associated with a spectrum of developmentally regulated diseases that vary in age of onset, severity, and whether it is transient (i.e., benign familial neonatal seizures) or long-lasting (i.e., developmental and epileptic encephalopathy). KCNQ2 and KCNQ3 channels have also emerged as a target for novel antiepileptic drugs as their activation could reduce epileptic activity. Consequently, a great effort has taken place over the last 2 decades to understand the mechanisms that control the assembly, gating, and modulation of KCNQ2 and KCNQ3 channels. The current view that KCNQ2 and KCNQ3 channels assemble as heteromeric channels (KCNQ2/3) forms the basis of our understanding of KCNQ2 and KCNQ3 channelopathies and drug design. Here, we review the evidence that supports the formation of KCNQ2/3 heteromers in neurons. We also highlight functional and transcriptomic studies that suggest channel composition might not be necessarily fixed in the nervous system, but rather is dynamic and flexible, allowing some neurons to express KCNQ2 and KCNQ3 homomers. We propose that to fully understand KCNQ2 and KCNQ3 channelopathies, we need to adopt a more flexible view of KCNQ2 and KCNQ3 channel stoichiometry, which might differ across development, brain regions, cell types, and disease states.