title: Dodecamer repeat expansion in cystatin B gene in progressive myoclonus epilepsy.
abstract: Progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1; MIM 254800) is an autosomal recessive disorder with onset between 6 and 13 years followed by variable progression to mental deterioration and cerebellar ataxia. It is a rare disorder but more common in Finland (1 in 20,000) and the western Mediterranean. Two point mutations in the cysteine proteinase inhibitor gene cystatin B (CSTB), proved that this gene is responsible for EPM1 (ref. 3). An extensive search in the CSTB gene revealed mutations accounting only for 14% of the 58 unrelated EPM1 alleles studied. Here we report that the majority of EPM1 alleles contain expansions of a dodecamer (12-mer) repeat located about 70 nucleotides upstream of the transcription start site nearest to the 5' end of the CSTB gene. Normal alleles contain 2 or 3 copies of this repeat whereas mutant alleles contain more than 60 such repeats and have reduced levels of CSTB messenger RNA in blood but not in cell lines. 'Premutation' CSTB alleles with 12-17 repeats show marked instability when transmitted to offspring.
authors.affiliation: Laboratory of Human Molecular Genetics, Department of Genetics and Microbiology, University of Geneva Medical School, Switzerland.
authors.forename: M D
authors.initials: MD
authors.lastname: Lalioti
authors.forename: H S
authors.initials: HS
authors.lastname: Scott
authors.forename: C
authors.initials: C
authors.lastname: Buresi
authors.forename: C
authors.initials: C
authors.lastname: Rossier
authors.forename: A
authors.initials: A
authors.lastname: Bottani
authors.forename: M A
authors.initials: MA
authors.lastname: Morris
authors.forename: A
authors.initials: A
authors.lastname: Malafosse
authors.forename: S E
authors.initials: SE
authors.lastname: Antonarakis
mesh_terms: D000483:Alleles; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D055313:Cystatin B; D015891:Cystatins / Q000235:genetics*; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics*; D004247:DNA; D004831:Epilepsies, Myoclonic / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010375:Pedigree; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: C524994:CSTB protein, human; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D055313:Cystatin B; D004247:DNA