Knock‐in mouse model of alternating hemiplegia of childhood: Behavioral and electrophysiologic characterization

Abstract

SUMMARYObjectives: Mutations in the ATP1a3 subunit of the neuronal Na + /K + -ATPase are thought to be responsible for seizures, hemiplegias, and other symptoms of alternating hemiplegia of childhood (AHC). However, the mechanisms through which ATP1A3 mutations mediate their pathophysiologic consequences are not yet understood. The following hypotheses were investigated: (1) Our novel knock-in mouse carrying the most common heterozygous mutation causing AHC (D801N) will exhibit the manifestations of the human condition and display predisposition to seizures; and (2) the underlying pathophysiology in this mouse model involves increased excitability in response to electrical stimulation of Schaffer collaterals and abnormal predisposition to spreading depression (SD). Methods: We generated the D801N mutant mouse (Mashlool, Mashl +/À ) and compared mutant and wild-type (WT) littermates. Behavioral tests, amygdala kindling, flurothyl-induced seizure threshold, spontaneous recurrent seizures (SRS), and other paroxysmal activities were compared between groups. In vitro electrophysiologic slice experiments on hippocampus were performed to assess predisposition to hyperexcitability and SD. Results: Mutant mice manifested a distinctive phenotype similar to that of humans with AHC. They had abnormal impulsivity, memory, gait, motor coordination, tremor, motor control, endogenous nociceptive response, paroxysmal hemiplegias, diplegias, dystonias, and SRS, as well as predisposition to kindling, to flurothyl-induced seizures, and to sudden unexpected death. Hippocampal slices of mutants, in contrast to WT animals, showed hyperexcitable responses to 1 Hz pulse-trains of electrical stimuli delivered to the Schaffer collaterals and had significantly longer duration of K + -induced SD responses. Significance: Our model reproduces the major characteristics of human AHC, and indicates that ATP1a3 dysfunction results in abnormal short-term plasticity with increased excitability (potential mechanism for seizures) and a predisposition to more

Cognitive deficits caused by a disease-mutation in the α3 Na+/K+-ATPase isoform

“…Memory deficits were noted in the heterozygous knock-in mouse models Myshkin 50 and Mashl +/− 29 as well as the heterozygous knock-out model α 3 +/KOI4 mice23, strongly supporting the role of the α 3 in hippocampus-dependent cognition. The α 3 +/KOI4 mice showed reduced expression of the N-methyl-D-aspartic acid receptor (NMDR)51.…”

“…Corresponding to the high rate of seizures reported for AHC patients, reduced Na + /K + -ATPase activity was shown to influence seizure activity in the Myshkin mouse model26 and contribute to SUDEP in the Mashl +/− mouse model29. The α 3 +/D801Y mice did not develop spontaneous seizures.…”

“…The Myshkin and Mashl +/− mice were originally maintained in the 129S1/SvImJ and 129 SV background, respectively, and developed spontaneous tonic-clonic seizures and epileptic discharges as well as a SUDEP-like phenotype2629.…”

“…The D801N mutation is found in more than one third of AHC patients3. A recent study reported that heterozygous D801N knock-in mice ( Mashl +/− , Mashlool, α 3 +/I801N )29 manifested several AHC-like symptoms including neuromuscular deficits, spontaneous recurrent seizures, and predispositions to kindling, to flurothyl-induced seizures and to Sudden Unexpected Death in Epilepsy (SUDEP)29.…”

Hypothermia-induced dystonia and abnormal cerebellar activity in a mouse model with a single disease-mutation in the sodium-potassium pump

“…The same appears true for mice, as the α 3 +/D801Y mice in some aspects phenotypically differ from Mashlool (α 3 +/D801N ) mice [39] and Myshkin (α 3 +/I810N ) mice [40] that are heterozygous for the AHC mutations, D801N and I810N, respectively (Table 1). Both Mashlool and Myshkin mice exhibited spontaneous recurrent tonic clonic seizures [39, 40]. In contrast, although α 3 +/D801Y mice have a lowered threshold for PTZ-induced seizure, they did not develop spontaneous seizures [22].…”