Rearrangements of chromosome 15 in epilepsy.

A number of observations point to chromosome 15 as a good candidate to harbor genes involved in epilepsy. This hypothesis is supported by at least two lines of evidence: one is the finding that haploinsufficiency of the 15q11-q13 region, of maternal origin, is responsible for Angelman syndrome, one of the cardinal manifestations of which is epilepsy; the second is the observation that extra copies of this same genomic region, in the form of inv-dup(15) or intrachromosomal duplications, again of maternal origin, are usually associated with a severe neurological phenotype characterized by developmental delay and untreatable seizures. Therefore, both reduced and increased dosage of genes from the 15q11-q13 region, possibly subjected to maternal imprinting, appear to be causally involved in severe forms of epilepsy. We tested the hypothesis that submicroscopic rearrangements of this genomic region might be responsible for nonsyndromic epilepsy in both familial and sporadic forms. To this purpose, we genotyped 118 epileptic patients and their parents with closely spaced microsatellite markers mapped within the 15q11-q13 region. We report on the results of these studies and review the relevant literature.