A childhood epilepsy mutation reveals a role for developmentally regulated splicing of a sodium channel

• Published in: Molecular and cellular neuroscience 2007-06, Vol.35 (2), p.292-301
• Main Authors: Xu, Ruwei, Thomas, Evan A., Jenkins, Misty, Gazina, Elena V., Chiu, Cindy, Heron, Sarah E., Mulley, John C., Scheffer, Ingrid E., Berkovic, Samuel F., Petrou, Steven
• Format: Article
• Language: English
• Subjects: Adult; BFNIS; Cell Line, Transformed; Computer Simulation; Developmentally regulated splicing; DNA Mutational Analysis; Dose-Response Relationship, Radiation; Electric Stimulation; Epilepsy; Epilepsy - genetics; Humans; Infant; Membrane Potentials - genetics; Models, Biological; Mutation; NAV1.2 Voltage-Gated Sodium Channel; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; RNA Splicing - physiology; Sodium channels; Sodium Channels - genetics; Sodium Channels - metabolism
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1016/j.mcn.2007.03.003

Seizure susceptibility is high in human infants compared to adults, presumably because of developmentally regulated changes in neural excitability. Benign familial neonatal–infantile seizures (BFNIS), characterized by both early onset and remission, are caused by mutations in the gene encoding a human sodium channel (Na V1.2). We analyzed neonatal and adult splice forms of Na V1.2 with a BFNIS mutation (L1563V) in human embryonic kidney cells. Computer modeling revealed that neonatal channels are less excitable than adult channels. Introduction of the mutation increased excitability in the neonatal channels to a level similar to adult channels. By contrast, the mutation did not affect the adult channel variant. This “adult-like” increased excitability is likely to be the mechanism underlying BFNIS in infants with this mutation. More generally, developmentally regulated Na V1.2 splicing may be one mechanism that counters the normally high excitability of neonatal neurons and helps to reduce seizure susceptibility in normal human infants.