Therefore, the mutation in the α4 subunit could lead to reduced GABA release, causing hyperexcitability. Pathophysiology
CHRNA4
The first mutation associated with ADNFLE is a serine to phenylalanine transition at position 248 (S248F), located in the second transmembrane spanning region of the gene encoding a nicotinic acetylcholine receptor α4 subunit. Using the numbering based on the human CHRNA4 protein, this mutation is called S280F. Receptors containing this mutant subunit are functional, but desensitize at a much faster pace compared to wild-type only receptors. These mutant containing receptors also recover from desensitization at a much slower rate than wild-type only receptors. These mutant receptors also have a decreased single channel conductance than wild-type and have a lower affinity for acetylcholine. Also importantly, this mutation along with the others in CHRNA4 produce receptors less sensitive to calcium.The second discovered ADNFLE mutation was also in CHRNA4. This mutation, L259_I260insL, is caused by the insertion of three nucleotides (GCT) between a stretch of leucine amino acids and an isoleucine. As with the S248F mutation, the L259_I260insL mutation is located in the second transmembrane spanning region. Electrophysiological experiments have shown that this mutant is tenfold more sensitive to acetylcholine than wild-type. Calcium permeability, however is notably decreased in mutant compared to wild-type containing receptors. Furthermore, this mutant shows slowed desensitization compared to both wild-type and S248F mutant receptors.Also located in the second transmembrane spanning region, the S252L mutation has also been associated with ADNFLE.
This mutant shows a higher sensitivity to acetylcholine and unchanged desensitization compared to wild-type. Diagnosis
Diagnosis is typically made upon patient history, although EEG recordings can be confirmatory if they occur during attacks. Management
Anti-epileptic drugs are normally used to combat ADNFLE. These drugs are discussed in the main epilepsy article. Footnotes
Further reading
GeneReviews/NCBI/NIH/UW entry on Autosomal Dominant Nocturnal Frontal Lobe Epilepsy


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