Acetylcholine synthesis by mesencephalic neural crest cells in the process of migration in vivo

Abstract

Specific to the vertebrate embryo, the neural crest is a transitory structure whose constituent cells migrate extensively through the developing animal and ultimately give rise to many distinct cell types, including the components of the peripheral nervous system^1,2. The earliest clear indices of their differentiation have so far been detected only when cells from the crest have reached their destination. This is exemplified by the acquisition of the ability to synthesise and store catecholamines; absent from crest cells before and during their dorso–ventral migration, this ability appears concomitantly with their aggregation into the primary sympathetic ganglia^3–6. The chronology of cholinergic maturation, however, is less well defined. Appropriate biochemical markers are demonstrable as soon as parasympathetic or enteric ganglia are formed^3–6, but the lack of a suitable cytochemical method is a major obstacle to the identification of any cholinergic cells before then. Although acetylcholinesterase (AChE) is present in migrating neural crest¹⁰, choline acetyltransferase (CAT), the enzyme catalysing acetvlcholine (ACh) synthesis, is a much more relevant correlate^7,11,12, and definitive evidence for cholinergic differentiation should include the demonstration of ACh-synthesising activity in intact cells^13,14 or their extracts. We show here that neural crest, as soon as it begins migration, can synthesise ACh.