Abstracts

RATIONALE: Juvenile Myoclonic Epilepsy (JME), a common subtype of idiopathic epilepsy, accounts for approximately 7-20% of all epilepsies. Three major susceptibility loci have been reported for JME, namely, chromosome 6p12-11, 6p21.3 and 15q14. Our objective was to perform linkage analyses in JME families from Mexico using chromosome 6p21.3-pter microsatellites. METHODS: Fifteen multiplex multigenerational families (average >3 affecteds) of Spanish-Amerind racial/ethnic origin were ascertained through JME probands. 109 individuals (41 affecteds) were genotyped with chromosome 6p polymorphic microsatellites using standard Polymerase Chain Reaction protocols (Weber and May, 1989). Two-point linkage analysis was performed by LINKAGE version 5.21. Haplotype analyses searched for recombinations. RESULTS: Family members who had myoclonic seizures only (11 persons), myoclonic seizures and grand mal (5 persons), myoclonic seizures and absences (4 persons), absence only (2 persons), grand mal only (7 persons), grand mal and absence (2 persons), and EEG 3-6Hz multispike waves only (10 persons) were considered affected during linkage analyses. We obtained significant Zmax values of 3.48 for D6S294 and 3.04 for D6S465 at recombination frequency of ?m=f=0.00 assuming autosomal dominant mode of inheritance with 50% penetrance. We also obtained Zmax values of 2.58 for D6S1960, 2.19 for D6S1573, and 1.88 for D6S466. Chromosome 6p21-11 haplotypes segregated with all affected members of 15 families. Recombinations in five affected members from four linked families place the JME region below D6S272. CONCLUSIONS: JME families from Mexico, like JME families from California (USA) and Belize, are linked to chromosome 6p21-11. The susceptibility locus is below D6S272.