Nicotinic acetylcholine receptor gene expression in developing chick autonomic ganglia

The developmental expression patterns of ten genes encoding nicotinic acety lcholine receptor subunits were analyzed using Northern blots and in situ h ybridization in chick peripheral ganglia of neural crest, placodal and dual embryonic origin. The superior cervical and ciliary ganglia were investiga ted in detail because they accumulated relatively abundant transcripts of t he alpha 3, beta 4, alpha 5 and alpha 7 genes. In the superior cervical gan glion, these four mRNA species had similar developmental time-courses. They appeared at embryonic day 8 (E8), increased steadily until E16 and maintai ned a rather high plateau level until E18. In the ciliary ganglion, alpha 7 transcripts were already abundant at E6, increased until E10, and consider ably decreased thereafter. High-resolution in situ hybridization showed tha t alpha 7 transcripts were present in all cell types of the E6 ciliary gang lion, whereas they were restricted to large neuronal somas at E16. Transfec tions with a reporter gene under the control of the alpha 7 promoter demons trated that a sharp developmental divide occurred at E11-12, after which st age the promoter was activatable in neurons exclusively. (C) 2000 Elsevier Science B.V. All rights reserved.