title: A Cav3.2 T-type calcium channel point mutation has splice-variant-specific effects on function and segregates with seizure expression in a polygenic rat model of absence epilepsy.
abstract: Low-voltage-activated, or T-type, calcium (Ca(2+)) channels are believed to play an essential role in the generation of absence seizures in the idiopathic generalized epilepsies (IGEs). We describe a homozygous, missense, single nucleotide (G to C) mutation in the Ca(v)3.2 T-type Ca(2+) channel gene (Cacna1h) in the genetic absence epilepsy rats from Strasbourg (GAERS) model of IGE. The GAERS Ca(v)3.2 mutation (gcm) produces an arginine to proline (R1584P) substitution in exon 24 of Cacna1h, encoding a portion of the III-IV linker region in Ca(v)3.2. gcm segregates codominantly with the number of seizures and time in seizure activity in progeny of an F1 intercross. We have further identified two major thalamic Cacna1h splice variants, either with or without exon 25. gcm introduced into the splice variants acts "epistatically," requiring the presence of exon 25 to produce significantly faster recovery from channel inactivation and greater charge transference during high-frequency bursts. This gain-of-function mutation, the first reported in the GAERS polygenic animal model, has a novel mechanism of action, being dependent on exonic splicing for its functional consequences to be expressed.
authors.affiliation: Department of Medicine, The Royal Melbourne Hospital, University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Kim L
authors.initials: KL
authors.lastname: Powell
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Cain
authors.forename: Caroline
authors.initials: C
authors.lastname: Ng
authors.forename: Shreerang
authors.initials: S
authors.lastname: Sirdesai
authors.forename: Laurence S
authors.initials: LS
authors.lastname: David
authors.forename: Mervyn
authors.initials: M
authors.lastname: Kyi
authors.forename: Esperanza
authors.initials: E
authors.lastname: Garcia
authors.forename: John R
authors.initials: JR
authors.lastname: Tyson
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Reid
authors.forename: Melanie
authors.initials: M
authors.lastname: Bahlo
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Foote
authors.forename: Terrance P
authors.initials: TP
authors.lastname: Snutch
authors.forename: Terence J
authors.initials: TJ
authors.lastname: O'Brien
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001120:Arginine / Q000235:genetics; D001703:Biophysics; D020747:Calcium Channels, T-Type / Q000235:genetics*; D002461:Cell Line, Transformed; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004569:Electroencephalography; D004832:Epilepsy, Absence / Q000235:genetics* / Q000503:physiopathology; D005091:Exons / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed / Q000379:methods; D018408:Patch-Clamp Techniques; D017354:Point Mutation / Q000235:genetics*; D011392:Proline / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics*; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D055647:Rats, Transgenic; D012640:Seizures / Q000235:genetics* / Q000503:physiopathology; D014162:Transfection
chemical_list: C509958:Cacna1h protein, rat; D020747:Calcium Channels, T-Type; D020033:Protein Isoforms; D001120:Arginine; D011392:Proline