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DEVELOPING

CaVβ4, encoded by Cacnb4 as the ortholog of human CACNB4, is the cerebellum-enriched β subunit that partners CaV2.1 at parallel and climbing fiber terminals, engaging the α-interaction domain through its guanylate kinase domain to control surface expression and inactivation kinetics; a short nuclear isoform additionally binds chromatin regulators and the phosphatase regulatory subunit B56δ, giving the gene a transcriptional arm independent of conductance. The spontaneous lethargic allele, a splice mutation that abolishes α1 binding, causes ataxia, absence-like spike-wave discharges and lymphocyte defects, and human variants segregate with juvenile myoclonic epilepsy and episodic ataxia. Because homozygous loss produces severe ataxia and seizures with poor postweaning survival, a conditional null crossed to Pcp2-Cre or a granule cell driver is the practical route to adult cerebellar physiology, while a patient missense knockin separates trafficking from nuclear signaling. Cacnb1, Cacnb2 and Cacnb3 partially substitute, so quantify β subunit stoichiometry directly.

A floxed Cacnb4 allele paired with Cre gives spatial control that whole body knockouts cannot offer. People use it to separate developmental roles from adult homeostasis, to model somatic mutations, and to match disease that begins in one organ.