Exclusion of linkage of nine neuronal nicotinic acetylcholine receptor subunit genes expressed in brain in autosomal dominant nocturnal frontal lobe epilepsy in four unrelated families

Members of the ligand-gated neuronal nicotinic acetylcholine receptor (nAChR) gene family (CHRNA4 and CHRNB2, coding for the α4 and β2 subunits, respectively) are involved in autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). However, ADNFLE is genetically heterogeneous and mutations in CHRNA4 and CHRNB2 account for only a minority of ADNFLE cases. Additional nAChR subunits expressed in the brain are candidates for this epilepsy. The involvement of all genes coding for brain-expressed nAChR subunits, with known chromosome localization (CHRNB2, 1q21; CHRNA2, 8p21; CHRNA6, CHRNB3, 8p11.2; CHRNA7, 15q14; CHRNA5/A3/B4, 15q24 and CHRNA4, 20q13.2) was investigated in four unrelated ADNFLE Italian families for at least three generations. Families were selected on the basis of anamnestic and videopolysomnographic analyses. Individuals were typed for polymorphic markers located in the above mentioned chromosome regions. Linkage and mutation analyses were performed. In none of the families was linkage between ADNFLE and the analysed chromosome regions detected. These findings support the hypothesis that genes different from those coding for α2-7 and β2-4 neuronal nAChR subunits could be responsible for ADNFLE.