NOVEL CYSTATIN-B MUTATION AND DIAGNOSTIC PCR ASSAY IN AN UNVERRICHT-LUNDBORG PROGRESSIVE MYOCLONUS EPILEPSY PATIENT

Two mutations in the cystatin B gene, a 3' splice mutation and a stop codon mutation, were previously found in patients with progressive myo clonus epilepsy of Unverricht-Lundborg type [Pennacchio et al, (1996): Science 271:1731-1734], We present here a new mutation 2404 Delta TC: a 2-bp deletion within the third exon of the cystatin B gene in an Un verricht-Lundborg patient, This mutation results in a frameshift and c onsequently premature termination of protein synthesis, Complete seque ncing of the coding region and splice junctions of the cystatin B gene showed that neither of the two previously known mutations was present in this patient, The level of cystatin B mRNA in an immortalized cell line was found to be decreased, as had been reported for other Unverr icht-Lundborg patients, The new mutation further supports the argument that defects in the cystatin B gene cause the Unverricht-Lundborg for m of progressive myoclonus epilepsy, We describe a simple PCR method w hich can detect the 2404 Delta TC deletion, This assay, together with previously described PCR assays for the other two known mutations, sho uld prove useful in confirming clinically difficult diagnoses of Unver richt-Lundborg disease. (C) 1997 Wiley-Liss, Inc.