CLONING OF A CDNA CODING FOR THE ACETYLCHOLINE-RECEPTOR ALPHA-SUBUNITFROM A THYMOMA ASSOCIATED WITH MYASTHENIA-GRAVIS

To investigate the role of the acetylcholine receptor (AchR) in the pa thogenesis of paraneoplastic Myasthenia gravis (MG), we screened a cDN A library of a MG-associated thymoma with a DNA oligonucleotide coding for aa 371-378, i.e. for part of the very immunogenic cytoplasmatic e pitope (VICE-alpha, aa 373-380) of the human AChR alpha-subunit. We is olated two cDNA clones. Analysis of these clones has identified an ope n reading frame of 1371 bp, coding for the AChR alpha-subunit. No poin t mutation, insertion or deletion could be detected. Since the thymoma did not contain thymic myoid cells, which normally express AChR, the origin of the AChR transcripts must be the tumor cells itself. These f indings confirm former results, where AChR alpha-subunit sequences fro m MG-thymomas were amplified by PCR.