Effects of a patient-derived de novo coding alteration of CACNA1I in mice connect a schizophrenia risk gene with sleep spindle deficits

Abstract

CACNA1I, a schizophrenia risk gene, encodes a subtype of voltage-gated T-type calcium channel Ca V 3.3. We previously reported that a patient-derived missense de novo mutation (R1346H) of CACNA1I impaired Ca V 3.3 channel function. Here, we generated Ca V 3.3-RH knock-in animals, along with mice lacking Ca V 3.3, to investigate the biological impact of R1346H (RH) variation. We found that RH mutation altered cellular excitability in the thalamic reticular nucleus (TRN), where Ca V 3.3 is abundantly expressed. Moreover, RH mutation produced marked deficits in sleep spindle occurrence and morphology throughout non-rapid eye movement (NREM) sleep, while Ca V 3.3 haploinsufficiency gave rise to largely normal spindles. Therefore, mice harboring the RH mutation provide a patient derived genetic model not only to dissect the spindle biology but also to evaluate the effects of pharmacological reagents in normalizing sleep spindle deficits. Importantly, our analyses highlighted the significance of characterizing individual spindles and strengthen the inferences we can make across species over sleep spindles. In conclusion, this study established a translational link between a genetic allele and spindle deficits during NREM observed in schizophrenia patients, representing a key step toward testing the hypothesis that normalizing spindles may be beneficial for schizophrenia patients.

Global genetic deletion of CaV3.3 channels facilitates anaesthetic induction and enhances isoflurane-sparing effects of T-type calcium channel blockers

“…Furthermore, it has been well established that Ca V 3.3T-channels in nRT are crucial contributors to burst firing mode because during hyperpolarization more T-channels recover from inactivation and may be readily activated during return to resting membrane potentials. Indeed, previous studies with Ca V 3.3 KO mice reported largely decreased rebound bursting in nRT neurons 14,24,25 . At more depolarized membrane potentials, when most of the T-channels are inactivated, the tonic firing mode is the predominant form of spike discharge.…”

“…Indeed, we demonstrate here that a combination of TTA-P2 and subhypnotic concentrations of isoflurane induced more prominent slow wave oscillations in δ range in the mutant mice. Previous studies with Ca V 3.3 KO mice have established that burst firing on nRT neurons is required for generation of spindle oscillations (7-14 Hz) during slow-wave sleep 14,30 . Although T-channels in nRT neurons alone are sufficient for the rhythmicity of spindles, they are not sufficient for synchrony across the thalamus and cortex 30 .…”

“…We also found that Ca V 3.3 KO mice have decreased baseline θ oscillations during wakefulness. Additionally, molecular studies demonstrated rich expression of Ca V 3.3 channels in the cerebral cortex 5,14 . Our results indicate that Ca V 3.3 channels contribute to wake θ oscillations in the mouse barrel cortex (present study) but not in frontal and parietal cortex 14 .…”

Neuronal Cav3 channelopathies: recent progress and perspectives

“…(SCZ) Fig. 4 Schematic localization of the main Cav3 mutations described in the text, including (i) the Cav3.1 mutations: p.Arg1715His in SCA42 [44,65], p.Arg961Thr and p.Met1531Val in ChCA [6,34]; (ii) the Cav3.2 mutations: p.Arg1549Val and p.Arg1549Ile in PA/FH4 [47,130], and p.Cys456Ser in CAE [53,155]; and (iii) the Cav3.3 mutation: p.Arg1346His in SCZ [2,62] considered a risk factor for developing epilepsy, most likely implicating other genetic and/or environmental factors [67].…”

“…4), resulted in a lower expression level of the Cav3.3 protein, a reduced N-glycosylation, and a reduced expression at the plasma membrane, reducing the Cav3.3 current but with no change in the electrophysiological properties [2]. A KI mouse model was generated using the CRISPR/Cas9 editing approach to introduce the p.Arg1305His orthologous mutation [62]. The homozygous animals show altered excitability in the nRT and deficits in sleep spindle occurrence and at NREM/REM transitions.…”