Floxed allele for conditional inactivation of the voltage-gated sodium channel Scn8a (Na_v1.6)

The sodium channel gene Scn8a encodes the channel Na_v1.6, which is widely distributed in the central and peripheral nervous system. Na _v1.6 is the major channel at the nodes of Ranvier in myelinated axons. Mutant alleles of mouse Scn8a result in neurological disorders including ataxia, tremor, paralysis, and dystonia. We generated a floxed allele of Scn8a by inserting loxP sites around the first coding exon. The initial targeted allele containing the neo-cassette was a severe hypomorph. In vivo deletion of the neo-cassette by Flp recombinase produced a floxed allele that generates normal expression of Na_v1.6 protein. Ubiquitous deletion of the floxed exon by Cre recombinase in ZP3-Cre transgenic mice produced the Scn8a^del allele. The null phenotype of Scn8a^del hornozygotes confirms the in vivo inactivation of Scn8a. Conditional inactivation of the floxed allele will make it possible to circumvent the lethality that results from complete loss of Scn8a in order to investigate the physiologic role of Na_v1.6 in subpopulations of neurons.