We have used human beta 2 and beta 4 cDNA probes to map the genes encoding two 
isoforms of the regulatory beta subunit of voltage-activated Ca2+ channels, viz. 
CACNB2 (beta 2) and CACNB4 (beta 4), to human chromosomes 10p12 and 2q22-q23, 
respectively, by fluorescence in situ hybridization. The gene encoding the beta 
2 protein, first described as a Lambert-Eaton myasthenic syndrome (LEMS) antigen 
in humans, is found close to a region that undergoes chromosome rearrangements 
in small cell lung cancer, which occurs in association with LEMS. CACNB2 (beta 
2) and CACNB4 (beta 4) genes are members of the ion-channel gene superfamily and 
it should now be possible to examine their loci by linkage analysis of 
ion-channel-related disorders. To date, no such disease-related gene has been 
assigned to 10p12 and 2q22-q23.