Characterization of the genomic structure of the human neuronal nicotinic acetylcholine receptor CHRNA5/A3/B4 gene cluster and identification of novel intragenic polymorphisms

Genes coding for the alpha5, alpha3, and beta4 subunits (CHRNA5, CHRNA3, an d CHRNB4) of the neuronal nicotinic acetylcholine receptors (nAChRs) are cl ustered on chromosome 15q24. Linkage of this chromosomal region to autosoma l dominant nocturnal frontal lobe epilepsy (ADNFLE), an idiopathic partial epilepsy, was reported in one family. Moreover, mutations in other neuronal nAChR subunit genes coding for the alpha4 (CHRNA4) and the beta2 (CHRNB2) subunits were associated with ADNFLE. Apart from the exon-intron structure of CHRNA3, the genomic organization of this gene cluster was unknown, makin g comprehensive mutational analyses impossible. The genomic structure of CH RNA5 and CHRNB4 is here reported. Moreover, two hitherto unknown introns we re identified within the 3' untranslated region of CHRNA3, causing a partia l tail-to-tail overlap with CHRNA5. Four novel intragenic polymorphisms wer e identified and characterized in the cluster.