Linkage analysis of the 15q25-15q22 region in an extended multigenerational family segregating for idiopathic epilepsy

Linkage analyses provide strong evidence of how genetic factors influence epilepsy, due to the fact that they involve the determination of the cosegregation of specific marker alleles with epilepsy within families. Our aim was to determine whether there was some kind of propensity to develop generalised idiopathic epilepsy (GIE) in the 15q22.1-q25.1 region in an extended multigenerational family from the Paisa de Antioquia community, which is a genetic isolate located in Colombia that segregates for GIE and has a strong capacity to detect linkage. We selected a family containing a number of individuals suffering from epilepsy who visited the Antioquia Neurological Institute. Each affected individual had to have been diagnosed by a neurologist as suffering from non-myoclonic idiopathic epilepsy or from partial idiopathic epilepsy. All patients suspected of suffering from idiopathic epilepsy were submitted to video monitoring in order to characterise seizures electroencephalographically. Of the 106 individuals in this family who were included in the family tree, 76 were genotyped; 15 of them suffered from generalised clonic tonic seizures and six were considered as being possibly affected. Lod score results were significantly negative for all the markers in relation to each of the models under consideration. The possibility of the genes that code for the a-3, a-5 and b-4 subunits of the neuronal nicotinic acetylcholine receptor (CHRNA3, CHRNA5 and CHRNB4) situated in the 15q region being responsible for the familial aggregation of GIE in this family, as has been suggested in previous studies in other families, was ruled out.