The CHRNB2 mutation I312M is associated with epilepsy and distinct memory deficits.
ABSTRACT Mutations in nAChRs are found in a rare form of nocturnal frontal lobe epilepsy (ADNFLE). Previously, some nAChR mutations have been described that are associated with additional neurological features such as psychiatric disorders or cognitive defects. Here, we report a new CHRNB2 mutation located in transmembrane region 3 (M3), outside the known ADNFLE mutation cluster. The CHRNB2 mutation I312M, which occurred de novo in twins, markedly increases the receptor's sensitivity to acetylcholine. Phenotypically, the mutation is associated not only with typical ADNFLE, but also with distinct deficits in memory. The cognitive problems are most obvious in tasks requiring the organization and storage of verbal information.
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Article: Nocturnal frontal lobe epilepsy.[Show abstract] [Hide abstract]
ABSTRACT: Nocturnal frontal lobe epilepsy (NFLE) is a syndrome of heterogeneous etiology, characterized by the occurrence of sleep-related seizures with different complexity and duration. Genetic, lesional, and cryptogenetic NFLE forms have been described. NFLE is generally considered a benign clinical entity, although severe, drug-resistant forms do exist. A significant proportion of sleep-related complex motor seizures, hardly distinguishable from NFLE, originate outside the frontal lobe. Moreover, the distinction of NFLE from the non-rapid eye movement arousal parasomnias may be challenging. A correct diagnosis of NFLE should be based on a diagnostic approach that includes the anamnestic, video-polysomnographic, morphological, and genetic aspects. Studies on the relationships between genes, arousal regulatory mechanisms, and epileptogenesis, using both clinical and experimental models of NFLE might provide key insights in the interrelationship between sleep and epilepsy.Current Neurology and Neuroscience Reports 02/2014; 14(2):424. DOI:10.1007/s11910-013-0424-6 · 3.67 Impact Factor
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ABSTRACT: Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is a focal epilepsy with attacks typically arising in the frontal lobe during non-rapid eye movement (NREM) sleep. It is characterized by clusters of complex and stereotyped hypermotor seizures, frequently accompanied by sudden arousals. Cognitive and psychiatric symptoms may be also observed. Approximately 12% of the ADNFLE families carry mutations on genes coding for subunits of the heteromeric neuronal nicotinic receptors (nAChRs). This is consistent with the widespread expression of these receptors, particularly the α4β2(*) subtype, in the neocortex and thalamus. However, understanding how mutant nAChRs lead to partial frontal epilepsy is far from being straightforward because of the complexity of the cholinergic regulation in both developing and mature brains. The relation with the sleep-waking cycle must be also explained. We discuss some possible pathogenetic mechanisms in the light of recent advances about the nAChR role in prefrontal regions as well as the studies carried out in murine models of ADNFLE. Functional evidence points to alterations in prefrontal GABA release, and the synaptic unbalance probably arises during the cortical circuit maturation. Although most of the available functional evidence concerns mutations on nAChR subunit genes, other genes have been recently implicated in the disease, such as KCNT1 (coding for a Na(+)-dependent K(+) channel), DEPD5 (Disheveled, Egl-10 and Pleckstrin Domain-containing protein 5), and CRH (Corticotropin-Releasing Hormone). Overall, the uncertainties about both the etiology and the pathogenesis of ADNFLE point to the current gaps in our knowledge the regulation of neuronal networks in the cerebral cortex.Frontiers in Physiology 02/2015; 6:22. DOI:10.3389/fphys.2015.00022
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ABSTRACT: Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) was the first epilepsy in humans that could be linked to specific mutations. It had been initially described as a channelopathy due to the fact that for nearly two decades mutations were exclusively found in subunits of the nicotinic acetylcholine receptor. However, newer findings demonstrate that the molecular pathology of ADNFLE is much more complex insofar as this rare epilepsy can also be caused by genes coding for non-ion channel proteins. It is becoming obvious that the different subtypes of focal epilepsies are not strictly genetically separate entities but that mutations within the same gene might cause a clinical spectrum of different types of focal epilepsies.Progress in brain research 01/2014; 213C:1-15. DOI:10.1016/B978-0-444-63326-2.00001-6 · 5.10 Impact Factor