Ablation of P/Q-type Ca²⁺ channel currents, altered synaptic transmission, and progressive ataxia in mice lacking the α(1A)-subunit

The Ca²⁺ channel α(1A)-subunit is a voltage-gated, pore-forming membrane protein positioned at the intersection of two important lines of research: one exploring the diversity of Ca²⁺ channels and their physiological roles, and the other pursuing mechanisms of ataxia, dystonia, epilepsy, and migraine. α(1A)-Subunits are thought to support both P- and Q- type Ca²⁺ channel currents, but the most direct test, a null mutant, has not been described, nor is it known which changes in neurotransmission might arise from elimination of the predominant Ca²⁺ delivery system at excitatory nerve terminals. We generated α(1A)-deficient mice (α(1A)(-/-)) and found that they developed a rapidly progressive neurological deficit with specific characteristics of ataxia and dystonia before dying ≃3-4 weeks after birth. P-type currents in Purkinje neurons and P- and Q-type currents in cerebellar granule cells were eliminated completely whereas other Ca²⁺ channel types, including those involved in triggering transmitter release, also underwent concomitant changes in density. Synaptic transmission in α(1A)(-/-) hippocampal slices persisted despite the lack of P/Q-type channels but showed enhanced reliance on N-type and R-type Ca²⁺ entry. The α(1A)(-/-) mice provide a starting point for unraveling neuropathological mechanisms of human diseases generated by mutations in α(1A).