Sequential expression of acetylcholine receptor isoforms in mesodermalized Xenopus animal caps

Exposure of Xenopus animal pole explants to transforming growth factor beta 2 (TGF-beta 2) induced the sequential expression of muscle nicotinic acetylcholine receptor (AChRs) isoforms and their corresponding mRNAs in cells which normally give rise to ectoderm. Single channel recordings revealed two functional classes of receptors with properties similar to those expressed during normal development of skeletal muscle in vivo. The predominant class of receptors in all patches corresponded to those of embryonic myotomal muscle. Additional receptors resembling those of mature myotomal muscle were observed in older explants. Levels of transcripts encoding the embryonic and adult AChR subunit isoforms varied accordingly. TGF-beta 2 appears to initiate a developmental program of AChR gene expression which is similar to that found in normally developing muscle.