Laforin is a cell membrane and endoplasmic reticulum-associated protein tyrosine phosphatase

Lafora disease (LD) is the only progressive myoclonus epilepsy with polyglu cosan bodies. Among conditions with polyglucosan bodies, LD is unique for t he subcellular location of its polyglucosans in neuronal perikarya and dend rites and not in axons. Here we report that the protein encoded by the EPM2 A gene, which is mutated in LD, localizes at the plasma membrane and the en doplasmic reticulum and that it is a functional protein tyrosine phosphatas e. The significance of these findings in the epilepsy of LD and in the orig in and characteristic subcellular location of Lafora bodies is discussed.