title: Divergent effects of the T1174S SCN1A mutation associated with seizures and hemiplegic migraine.
abstract: OBJECTIVE
  To report the identification of the T1174S SCN1A (NaV 1.1) mutation in a three-generation family with both epileptic and familial hemiplegic migraine (FHM) phenotypes and clarify the pathomechanism.
  
  
  METHODS
  The five affected individuals underwent detailed clinical analyses. Mutation analyses was performed by direct sequencing of SCN1A; functional studies by expression in tsA-201 cells. A computational model was used to compare the effects of T1174S with those of a typical FHM mutation (Q1489K).
  
  
  RESULTS
  The proband had benign occipital epilepsy (BOE); two relatives had simple febrile seizures (FS) and later developed BOE. Two additional relatives had FHM without epilepsy or FS. All affected members and one obliged carrier carried the T1174S mutation. Functional effects were divergent: positive shift of the activation curve and deceleration of recovery from fast inactivation, consistent with loss of function, and increase of persistent current (I(NaP)), consistent with gain of function. The I(NaP) increase was inhibited by dialysis of the cytoplasm, consistent with a modulation. Therefore, as shown by the computational model, T1174S could in some conditions induce overall loss of function, and in others gain of function; Q1489K induced gain of function in all the conditions.
  
  
  CONCLUSIONS
  Modulation of the properties of T1174S can lead to a switch between overall gain and loss of function, consistent with a switch between promigraine end epileptogenic effect and, thus, with coexistence of epileptic and FHM phenotypes in the same family. These findings may help to shed light on the complex genotype-phenotype relationship of SCN1A mutations.
authors: Institute of Molecular and Cellular Pharmacology, LabEx ICST, CNRS UMR7275, University of Nice-Sophia Antipolis, Valbonne, France.
authors: Sandrine
authors: S
authors: Cestèle
authors: Angelo
authors: A
authors: Labate
authors: Raffaella
authors: R
authors: Rusconi
authors: Patrizia
authors: P
authors: Tarantino
authors: Laura
authors: L
authors: Mumoli
authors: Silvana
authors: S
authors: Franceschetti
authors: Grazia
authors: G
authors: Annesi
authors: Massimo
authors: M
authors: Mantegazza
authors: Antonio
authors: A
authors: Gambardella
mesh_terms: D000293:Adolescent; D000328:Adult; D002461:Cell Line, Transformed; D003198:Computer Simulation; D004252:DNA Mutational Analysis; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D008875:Middle Aged; D020325:Migraine with Aura / Q000150:complications* / Q000235:genetics*; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics*; D062550:NAV1.1 Voltage-Gated Sodium Channel / Q000235:genetics*; D018408:Patch-Clamp Techniques; D010641:Phenotype; D012640:Seizures / Q000150:complications* / Q000235:genetics*; D012694:Serine / Q000235:genetics; D013912:Threonine / Q000235:genetics; D055815:Young Adult
chemical_list: D062550:NAV1.1 Voltage-Gated Sodium Channel; C568242:SCN1A protein, human; D013912:Threonine; D012694:Serine