Mice homozygous for the tottering spontaneous mutation (Cacna1atg) are characterized by a wobbly gait beginning at around 3 to 4 weeks of age and affecting, particularly, the hindquarters and by intermittent, spontaneous seizures. The seizures are of two kinds: i) Sudden arrests of movement (behavioral absence seizures) begin at about 3 weeks and are accompanied by abnormal bursts of bilaterally synchronous spike waves in ECG; they last about 0.3 to 10 seconds, occur hundreds of times per day, and continue throughout life; ii) Stereotyped partial motor seizures begin at about 4 weeks and are accompanied by abnormal ECG activity; they last 20 to 30 minutes, occur once or twice a day, and persist throughout life. Homozygous mutant mice of both sexes are fertile, but breeding performance is poor.
Leaner/tottering heterozygotes (Cacna1atg-la/Cacna1atg) show ataxia, stiffness, and retarded motor activity at 15 to 17 days of age. Within a few days, they develop a wobbly gait and intermittent focal seizures which continue throughout life.
|Allele Type||Spontaneous (Not Specified)|
|Allele Synonym(s)||alpha1Atg; tg|
|Gene Symbol and Name||Cacna1a, calcium channel, voltage-dependent, P/Q type, alpha 1A subunit|
|Strain of Origin||DBA/2J|
|General Note|| |
Sudden arrests of movement (behavioral absence seizures) begin at about 3 weeks of age and are accompanied by abnormal bursts of bilaterally synchronous spike waves in electrocorticograms (EEG); they last about 0.3 to 10.0 seconds, occur hundreds of times per day, and continue throughout life (J:6154). Resemblance to human epileptic absence seizures suggests the use of these mutants in epilepsy research (J:1254). Prolonged paroxysmal depolarizing shifts in hippocampal pyramidal neurons of tottering mice occur in response to elevated extracellular potassium and are age-correlated with the appearance of seizures (J:1180). Genetically altered sensitivity to increased K+, however, is not the cause of the hyperexcitability of hippocampal neurons in mutant mice (J:15775).Stereotyped partial motor seizures begin at about 4 weeks of age and are accompanied by abnormal EEG activity; they last 20 to 30 minutes, occur once or twice a day, and persist throughout life (J:6154). The central nervous system appears normal by light microscopy (J:7519). There is no discernible cerebellar hypoplasia (J:15016).In fluorescent histochemistry studies Cacna1atg homozygous mice show a marked increase in number of noradrenergic fibers in the terminal fields innervated by locus ceruleus axons, the hippocampus, cerebellum, and dorsal lateral geniculate (J:6615). Treatment of neonatal mutant mice with 6-hydroxydopamine, which selectively causes degeneration of distal noradrenergic axons from the locus ceruleus, almost completely abolishes the ataxic and seizure symptoms and the abnormal EEG patterns (J:7519). These results suggest that the primary effect of Cacna1atg may be in the neurons of the locus ceruleus. However, there was no quantitative difference in tyrosine hydroxylase (TH) mRNA or protein in the locus ceruleus of Cacna1atg/Cacna1atg or Cacna1atg/Cacna1atg-la mice, whereas these mutants expressed high levels of TH mRNA and protein in cerebellar Purkinje cells (J:2495). Normal cerebellar Purkinje cells express TH transiently during development, but expression persists into adulthood in mutant mice (J:10927). Levels of oxidized glutathione are lowered in hippocampus and occipital cortex of Cacna1atg homozygotes, whereas reduced glutathione was lowered in the cerebellum (J:28460). The level of methionine-enkephalin, but not those of [?]-endorphin or dynorphin, was increased in several brain areas (J:633).
|Molecular Note||A C to T point mutation results in a replacement of proline with leucine at position 649 (p.P649L) in a conserved domain of the encoded protein.|
When using the tottering mouse strain in a publication, please cite the originating article(s) and include JAX stock #000544 in your Materials and Methods section.