MUTATIONS IN THE GENE ENCODING CYSTATIN-B IN PROGRESSIVE MYOCLONUS EPILEPSY (EPM1)

Progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1) is an autosomal recessive inherited form of epilepsy, previously linke d to human chromosome 21q22.3. The gene encoding cystatin B was shown to be localized to this region, and levels of messenger RNA encoded by this gene were found to be decreased in cells from affected individua ls. Two mutations, a 3' splice site mutation and a stop codon mutation , were identified in the gene encoding cystatin B in EPM1 patients but were not present in unaffected individuals. These results provide evi dence that mutations in the gene encoding cystatin B are responsible f or the primary defect in patients with EPM1.