Purkinje Cell-Specific Ablation of CaV2.1 Channels is Sufficient to Cause Cerebellar Ataxia in Mice

Abstract

The Cacna1a gene encodes the α1A subunit of voltage-gated CaV2.1 Ca2+ channels that are involved in neurotransmission at central synapses. CaV2.1-α1-knockout (α1KO) mice, which lack CaV2.1 channels in all neurons, have a very severe phenotype of cerebellar ataxia and dystonia, and usually die around postnatal day 20. This early lethality, combined with the wide expression of CaV2.1 channels throughout the cerebellar cortex and nuclei, prohibited determination of the contribution of particular cerebellar cell types to the development of the severe neurobiological phenotype in Cacna1a mutant mice. Here, we crossed conditional Cacna1a mice with transgenic mice expressing Cre recombinase, driven by the Purkinje cell-specific Pcp2 promoter, to specifically ablate the CaV2.1-α1A subunit and thereby CaV2.1 channels in Purkinje cells. Purkinje cell CaV2.1-α1A-knockout (PCα1KO) mice aged without difficulties, rescuing the lethal phenotype seen in α1KO mice. PCα1KO mice exhibited cerebellar ataxia starting around P12, much earlier than the first signs of progressive Purkinje cell loss, which appears in these mice between P30 and P45. Secondary cell loss was observed in the granular and molecular layers of the cerebellum and the volume of all individual cerebellar nuclei was reduced. In this mouse model with a cell type-specific ablation of CaV2.1 channels, we show that ablation of CaV2.1 channels restricted to Purkinje cells is sufficient to cause cerebellar ataxia. We demonstrate that spatial ablation of CaV2.1 channels may help in unraveling mechanisms of human disease.Electronic supplementary materialThe online version of this article (doi:10.1007/s12311-011-0302-1) contains supplementary material, which is available to authorized users.

Cav2.1 in Cerebellar Purkinje Cells Regulates Competitive Excitatory Synaptic Wiring, Cell Survival, and Cerebellar Biochemical Compartmentalization

“…4 A, D). The reduced cerebellar size and normal dendritic branching are consistent with another line of PC-specific Ca v 2.1 KO mice, Cacna1a purk(Ϫ/Ϫ) (Mark et al, 2011;Todorov et al, 2011) and global Ca v 2.1 KO mice (Miyazaki et al, 2004). The surface of the somata and proximal dendrites was smooth in control mice ( Fig.…”

The first knockin mouse model of episodic ataxia type 2

“…We therefore exploited this genotype/phenotype relationship to determine if abnormal PCs were the major determinants of the ataxia associated with the EA2 allele. We have demonstrated that selective elimination of Ca V 2.1 channels within PCs causes ataxia (Todorov et al, 2012) by breeding the L7-Cre transgene, which expresses Cre recombinase in postnatal PCs, onto the floxed Cacna1a mouse strain (flox/flox). Therefore, we used a conditional approach to isolate the ataxia-causing genotype to PCs by breeding the L7-Cre transgene onto EA2/flox mice, creating mice that expressed only the EA2 allele in PCs, but in all other cells, the mice were heterozygous with one normoactive allele and one EA2 allele (EA2/flox; L7-Cre/-).…”

“…Furthermore, PCs are the sole output neurons of the cerebellar cortex and PC-specific lesions induce ataxia in humans and animal models (Holmes, 1917, Diener and Dichgans, 1992, Feddersen et al, 1992). Indeed, selective elimination of Ca V 2.1 channels from PCs causes a severe and chronic motor syndrome in mice that includes ataxia (Mark et al, 2011, Todorov et al, 2012). In other spontaneous mouse mutants with point mutations within Cacna1a that lead to moderately hypoconductive Ca V 2.1 channels, the motor dysfunction is somewhat less severe with both chronic and episodic components (Wakamori et al, 1998, Kodama et al, 2006, Shirley et al, 2008).…”

Silver nanoparticle exposure induces rat motor dysfunction through decrease in expression of calcium channel protein in cerebellum

“…According to previously reported protocol (Todorov et al, 2012), the samples were processed by fixation with 4% paraformaldehyde (PFA), dehydration with series of ethanol solution, infiltration and embedding in paraffin. The 5-mm-thick sections of the cerebellum were cut and subsequently processed with H&E staining.…”