ISOLATION AND CHARACTERIZATION OF THE BETA-SUBUNIT AND EPSILON-SUBUNIT GENES OF MOUSE MUSCLE ACETYLCHOLINE-RECEPTOR

Abstract

The genes coding for the .beta. and .epsilon. subunits of the mouse muscle nicotinic acetylcholine receptor (nAChR) were mapped by Southern blot analysis, and the entire loci for both genes cloned. The results indicate that they are single-copy genes. Both were sequenced to determine their size and structural organization. The .beta. subunit gene spans approximately 8 kilobases and is organized into 11 exons. A region containing cysteines, which are thought to form a disulfide bond and which are highly conserved, is encoded by one exon in all muscle acetylcholine receptor genes with the exception of the .beta. subunit gene, where it is spilt into two exons. The .epsilon. subunit gene spans 4.3 kilobases and contains 12 exons; it has the same structure as the .gamma. and .delta. nAChR genes. The intron-exon boundaries and exonic organization of the five known nAChR genes were compared. The analysis showed that the first 4 exons and the last exon of all muscle and brain nAChR subunit genes have the same boundaries, with the exception of a nAChR-related gene in Drosophila.