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.
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.
Powell
Kim L
KL
Department of Medicine, The Royal Melbourne Hospital, University of Melbourne, Melbourne, Victoria, Australia.
Cain
Stuart M
SM
Ng
Caroline
C
Sirdesai
Shreerang
S
David
Laurence S
LS
Kyi
Mervyn
M
Garcia
Esperanza
E
Tyson
John R
JR
Reid
Christopher A
CA
Bahlo
Melanie
M
Foote
Simon J
SJ
Snutch
Terrance P
TP
O'Brien
Terence J
TJ
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
C509958:Cacna1h protein, rat; D020747:Calcium Channels, T-Type; D020033:Protein Isoforms; D001120:Arginine; D011392:Proline