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Pathogenic variants in KCNT1 represent an important cause of treatment-resistant epilepsy, for which an effective therapy has been elusive. Reports about the effectiveness of quinidine, a candidate precision therapy, have been mixed. We sought to evaluate the treatment responsiveness of patients with KCNT1-related epilepsy. We performed an observational study of 43 patients using a collaborative KCNT1 patient registry. We assessed treatment efficacy based upon clinical seizure reduction, side effects of quinidine therapy, and variant-specific responsiveness to treatment. Quinidine treatment resulted in a > 50% seizure reduction in 20% of patients, with rare patients achieving transient seizure freedom. Multiple other therapies demonstrated some success in reducing seizure frequency, including the ketogenic diet and vigabatrin, the latter particularly in patients with epileptic spasms. Patients with the best quinidine response had variants that clustered distal to the NADP domain within the RCK2 domain of the protein. Half of patients did not receive a quinidine trial. In those who did, nearly half did not achieve therapeutic blood levels. More favorable response to quinidine in patients with KCNT1 variants distal to the NADP domain within the RCK2 domain may suggest a variant-specific response.

Our purpose was to determine the role of CHRNA4 and CHRNB2 in insular epilepsy. We identified two patients with drug-resistant predominantly sleep-related hypermotor seizures, one harboring a heterozygous missense variant (c.77C>T; p. Thr26Met) in the CHRNB2 gene and the other a heterozygous missense variant (c.1079G>A; p. Arg360Gln) in the CHRNA4 gene. The patients underwent electrophysiological and neuroimaging studies, and we performed functional characterization of the p. Thr26Met (c.77C>T) in the CHRNB2 gene. We localized the epileptic foci to the left insula in the first case (now seizure-free following epilepsy surgery) and to both insulae in the second case. Based on tools predicting the possible impact of amino acid substitutions on the structure and function of proteins (sorting intolerant from tolerant and PolyPhen-2), variants identified in this report could be deleterious. Functional expression in human cell lines of α4β2 (wild-type), α4β2-Thr26Met (homozygote), and α4β2/β2-Thr26Met (heterozygote) nicotinic acetylcholine receptors revealed that the mutant subunit led to significantly higher whole-cell nicotinic currents. This feature was observed in both homo- and heterozygous conditions and was not accompanied by major alterations of the current reversal potential or the shape of the concentration-response relation. This study suggests that variants in CHRNB2 and CHRNA4, initially linked to autosomal dominant nocturnal frontal lobe epilepsy, are also found in patients with predominantly sleep-related insular epilepsy. Although the reported variants should be considered of unknown clinical significance for the moment, identification of additional similar cases and further functional studies could eventually strengthen this association.

Mutations in genes coding for subunits of the neuronal nicotinic acetylcholine receptor (nAChR) have been involved in familial sleep-related hypermotor epilepsy (also named autosomal dominant nocturnal frontal lobe epilepsy, ADNFLE). Most of these mutations reside in and genes, coding for the α4 and β2 nAChR subunits, respectively. Two mutations with contrasting functional effects were also identified in the gene coding for the α2 subunit. Here, we report the third mutation in the , found in a patient showing ADNFLE. The patient was examined by scalp EEG, contrast-enhanced brain magnetic resonance imaging (MRI), and nocturnal video-polysomnographic recording. All exons and the exon-intron boundaries of , , , , were amplified and Sanger sequenced. In the proband, we found a c.754T>C (p.Tyr252His) missense mutation located in the N-terminal ligand-binding domain and inherited from the mother. Functional studies were performed by transient co-expression of α2 and α2 , with either β2 or β4, in human embryonic kidney (HEK293) cells. Equimolar amounts of subunits expression were obtained by using F2A-based multi-cistronic constructs encoding for the genes relative to the nAChR subunits of interest and for the enhanced green fluorescent protein. The mutation reduced the maximal currents by approximately 80% in response to saturating concentrations of nicotine in homo- and heterozygous form, in both the α2β4 and α2β2 nAChR subtypes. The effect was accompanied by a strong right-shift of the concentration-response to nicotine. Similar effects were observed using ACh. Negligible effects were produced by α2 on the current reversal potential. Moreover, binding of (±)-[ H]Epibatidine revealed an approximately 10-fold decrease of both K and B (bound ligand in saturating conditions), in cells expressing α2 . The reduced B and whole-cell currents were not caused by a decrease in mutant receptor expression, as minor effects were produced by α2 on the level of transcripts and the membrane expression of α2β4 nAChR. Overall, these results suggest that α2 strongly reduced the number of channels bound to the agonist, without significantly altering the overall channel expression. We conclude that mutations in are more commonly linked to ADNFLE than previously thought, and may cause a loss-of-function phenotype.

Sleep-related hypermotor epilepsy (SHE) is characterized by hyperkinetic focal seizures, mainly arising in the neocortex during non-rapid eye movements (NREM) sleep. The familial form is autosomal dominant SHE (ADSHE), which can be caused by mutations in genes encoding subunits of the neuronal nicotinic acetylcholine receptor (nAChR), Na+-gated K+ channels, as well as non-channel signaling proteins, such as components of the gap activity toward rags 1 (GATOR1) macromolecular complex. The causative genes may have different roles in developing and mature brains. Under this respect, nicotinic receptors are paradigmatic, as different pathophysiological roles are exerted by distinct nAChR subunits in adult and developing brains. The widest evidence concerns α4 and β2 subunits. These participate in heteromeric nAChRs that are major modulators of excitability in mature neocortical circuits as well as regulate postnatal synaptogenesis. However, growing evidence implicates mutant α2 subunits in ADSHE, which poses interpretive difficulties as very little is known about the function of α2-containing (α2*) nAChRs in the human brain. Planning rational therapy must consider that pharmacological treatment could have different effects on synaptic maturation and adult excitability. We discuss recent attempts towards precision medicine in the mature brain and possible approaches to target developmental stages. These issues have general relevance in epilepsy treatment, as the pathogenesis of genetic epilepsies is increasingly recognized to involve developmental alterations.

Accumulating evidence suggests that neuronal nicotinic acetylcholine receptors (nAChRs) may play a key role in the pathophysiology of some neurological diseases such as epilepsy. Based on genetic studies in patients with epileptic disorders worldwide and animal models of seizure, it has been demonstrated that nAChR activity is altered in some specific types of epilepsy, including autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) and juvenile myoclonic epilepsy (JME). Neuronal nAChR antagonists also have antiepileptic effects in pre-clinical studies. There is some evidence that conventional antiepileptic drugs may affect neuronal nAChR function. In this review, we re-examine the evidence for the involvement of nAChRs in the pathophysiology of some epileptic disorders, especially ADNFLE and JME, and provide an overview of nAChR antagonists that have been evaluated in animal models of seizure.

We describe a Chinese family with severe autosomal-dominant nocturnal frontal lobe epilepsy (ADNFLE) and psychiatric problems in whom whole-exome family trio sequencing identified a heterozygous mutation in the potassium channel subfamily T, member 1 ( ), a sodium-gated potassium channel gene, which was a novel missense mutation c.2153A>T (p. Asp718Val). The typical characteristics of the three patients in the family were refractory epilepsy, acquired cognitive impairment, and psychiatric problems, which include hallucinations and suicidal thoughts and behaviors. The age at onset was found to be earlier in son and daughter of the proband than that of the proband, as proven by the proband’s history of an epileptic seizure at the age of 16 years and her son’s and daughter’s history of seizures at the age of 8 years. Magnetic resonance imaging findings were negative for any abnormalities. Because of psychiatric symptoms, these three patients were administered risperidone at different times during their illness. The protestor’s son had tried fenofibrate treatment, but clinical remission was unclear. In summary, our findings broadened the mutation database in relation to and implicated the sodium-gated potassium channel complex in ADNFLE, more broadly, in the pathogenesis of focal epilepsies.

High-affinity nicotinic receptors containing β2 subunits (β2 * ) are widely expressed in the brain, modulating many neuronal processes and contributing to neuropathologies such as Alzheimer's disease, Parkinson's disease and epilepsy. Mutations in both the α4 and β2 subunits are associated with a rare partial epilepsy, autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). In this study, we introduced one such human missense mutation into the mouse genome to generate a knock-in strain carrying a valine-to-leucine mutation β2V287L. β2 V287L mice were viable and born at an expected Mendelian ratio. Surprisingly, mice did not show an overt seizure phenotype; however, homozygous mice did show significant alterations in their activity–rest patterns. This was manifest as an increase in activity during the light cycle suggestive of disturbances in the normal sleep patterns of mice; a parallel phenotype to that found in human ADNFLE patients. Consistent with the role of nicotinic receptors in reward pathways, we found that β2 V287L mice did not develop a normal proclivity to voluntary wheel running, a model for natural reward. Anxiety-related behaviors were also affected by the V287L mutation. Mutant mice spent more time in the open arms on the elevated plus maze suggesting that they had reduced levels of anxiety. Together, these findings emphasize several important roles of β2 * nicotinic receptors in complex biological processes including the activity–rest cycle, natural reward and anxiety.

Frontal lobe seizures have a tendency to occur from sleep, and in some cases occur exclusively (or almost exclusively) from sleep; these individuals are said to have nocturnal frontal lobe epilepsy (NFLE). NFLE can be difficult to distinguish clinically from various other sleep disorders, particularly parasomnias, which also present with paroxysmal motor activity in sleep. Here, the manifestations of frontal lobe epilepsy are reviewed in detail, with particular reference to the influence of sleep and the characteristics of NFLE. Key aspects of differential diagnosis are also considered, and the underlying mechanisms involved in NFLE discussed.

Autosomal dominant frontal lobe epilepsy (ADNFLE) can be caused by mutations in either the α4 or β2 subunit of the neuronal nicotinic Ach receptor. In vitro expression studies in Xenopus oocytes or human embryonic kidney cells have been proven to be valuable tools for the characterization of these mutations, but they do not fully resemble the situation in vivo. Compared with them, animal models have the advantage that the functional consequences of a given mutation can be studied in the complex context of an intact living organism. Recent transgenic and knock-in animal models and their valuable contributions to our current understanding of ADNFLE epileptogenesis are discussed in this article. Several of the mouse and rat models support the hypothesis that ADNFLE mutations cause seizures mainly by increasing GABAergic inhibition, and a conditional knock-in mouse model adds early embryonal structural changes as another possible pathogenetic mechanism.

Genes coding for the α5, α3, and β4 subunits ( CHRNA5 , CHRNA3 , and CHRNB4 ) of the neuronal nicotinic acetylcholine receptors (nAChRs) are clustered on chromosome 15q24. Linkage of this chromosomal region to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), an idiopathic partial epilepsy, was reported in one family. Moreover, mutations in other neuronal nAChR subunit genes coding for the α4 ( CHRNA4 ) and the β2 ( CHRNB2 ) subunits were associated with ADNFLE. Apart from the exon-intron structure of CHRNA3 , the geno-mic organization of this gene cluster was unknown, making comprehensive mutational analyses impossible. The genomic structure of CHRNA5 and CHRNB4 is here reported. Moreover, two hitherto unknown introns were identified within the 3′ untranslated region of CHRNA3 , causing a partial tail-to-tail overlap with CHRNA5 . Four novel intragenic polymorphisms were identified and characterized in the cluster.