Nicotinic acetylcholine receptor gene expression in developing chick autonomic ganglia

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