The murine mutant delta subunit of the acetylcholine receptor which has a threonine for serine substitution at position 262 (S262T) of the second transmembrane domain is under the control of the mouse creatine kinase muscle promoter. A neomycin resistance gene was also inserted downstream of the Chrnd cDNA. Four lines were established: 18, 22, 31, and 40. Line 40 has a transgene copy number of about 25 and is the medium expressing line.