ORIGINAL ARTICLE

Genetic mapping of a new Lafora progressive myoclonus epilepsy locus (EPM2B) on 6p22

E M Chan¹, D E Bulman², A D Paterson³, J Turnbull⁴, E Andermann⁵, F Andermann⁶, G A Rouleau⁷, A V Delgado-Escueta⁸, S W Scherer⁹, B A Minassian¹⁰

¹ Program in Genetics and Genomic Biology, The Hospital for Sick Children and Department of Molecular and Medical Genetics, The University of Toronto, 555 University Ave, Toronto, Ontario M5G 1X8, Canada
² Division of Neurology, Ottawa Health Research Institute, Ottawa Hospital - General Campus, 501 Smyth Rd, Ottawa, Ontario K1H 8L6, Canada
³ Program in Genetics and Genomic Biology, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario M5G 1X8, Canada
⁴ Program in Genetics and Genomic Biology, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario M5G 1X8, Canada
⁵ Neurogenetics Unit, Montreal Neurological Hospital and Institute, Departments of Neurology and Neurosurgery, and Human Genetics, McGill University, 3801 University St, Montreal, Quebec H3A 2B4, Canada
⁶ Epilepsy Service, Montreal Neurological Hospital and Institute and Departments of Neurology and Neurosurgery, and Paediatrics, McGill University, 3801 University St, Montreal, Quebec H3A 2B4, Canada
⁷ Centre for Research in Neuroscience, McGill University Health Centre Research Institute, Montreal General Hospital, 1650 Cedar Ave, Montreal, Quebec H3G 1A4, Canada
⁸ Comprehensive Epilepsy Program, Department of Neurology and Brain Research Institute, University of California, Los Angeles School of Medicine, West Los Angeles DVA Medical Center, 11301 Wilshire Blvd, Los Angeles, California 90073, USA
⁹ Program in Genetics and Genomic Biology, The Hospital for Sick Children and The University of Toronto, 555 University Ave, Toronto, Ontario M5G 1X8, Canada
¹⁰ Division of Neurology, Department of Pediatrics, Program in Genetics and Genomic Biology, The Hospital for Sick Children and Department of Molecular and Medical Genetic, The University of Toronto, 555 University Ave, Toronto, Ontario M5G 1X8, Canada

Correspondence to:
Correspondence to:
Dr B Minassian Division of Neurology, Department of Pediatrics, Program in Genetics and Genomic Biology, The Hospital for Sick Children and The University of Toronto, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada;
bminass{at}sickkids.ca

Background: Lafora disease is a progressive myoclonus epilepsy with polyglucosan accumulations and a peculiar neurodegeneration with generalised organellar disintegration. It causes severe seizures, leading to dementia and eventually death in early adulthood.

Methods: One Lafora disease gene, EPM2A, has been identified on chromosome 6q24. Locus heterogeneity led us to search for a second gene using a genome wide linkage scan in French-Canadian families.

Results: We mapped a second Lafora disease locus, EPM2B, to a 2.2 Mb region at 6p22, a region known to code for several proteins, including kinesins. Kinesins are microtubule dependent motor proteins that are involved in transporting cellular components. In neurones, they play a major role in axonal and dendritic transport.

Conclusion: Analysis of the present locus in other non-EPM2A families will reveal whether there is further locus heterogeneity. Identification of the disease gene will be of major importance towards our understanding of the pathogenesis of Lafora disease.

Abbreviations: LB, Lafora bodies; LD, Lafora disease; RER, rough endoplasmic reticulum

Keywords: epilepsy; gene; linkage; homozygosity mapping

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