Laforin and Malin Deletions in Mice Produce Similar Neurologic Impairments

Lafora disease is a progressive myoclonus epilepsy caused by mutations in the EPM2A gene encoding laforin or in the EPM2B gene encoding malin. It is characterized by the presence of polyglucosan intracellular inclusion bodies (Lafora bodies) in brain and other tissues. Targeted disruption of Epm2a or Epm2b genes in mice produced widespread neuronal degeneration and accumulation of Lafora bodies in neuronal and nonneuronal tissues. Here we analyzed the neurologic alterations produced by disruption of the laforin gene in Epm2a(-/-) mice and compared them to those in malin-deficient mice. Both Epm2a(-/-) and Epm2b(-/-) mice showed altered motor activity, impaired motor coordination, abnormal hind limb clasping, and episodic memory deficits. Epm2a(-/-) mice also had tonic-clonic seizures, whereas both Epm2a(-/-) and Epm2b(-/-) mice had spontaneous single spikes, spike-wave, polyspikes, and polyspike-wave complexes with correlated myoclonic jerks. Neurologic alterations observed in the mutants were comparable and correlated with the accumulation of abundant Lafora bodies in the cerebral cortex, the hippocampus, the basal ganglia, the cerebellum, and the brainstem, suggesting that these inclusions could cause cognitive and behavioral deterioration. Thus, both Epm2a(-/-) and Epm2b(-/-) mice exhibit many pathologic aspects seen in patients with Lafora disease and may be valuable for the study of this disorder.