Patterns of cholinesterase staining during neural crest cell morphogenesis in mouse and chick embryos.

Cholinesterase (ChE) activity has been reported previously in nonneuronal tissues of a variety of avian and mammalian embryos. We report here a comparison study of ChE staining in chick and mouse embryos. Transmission electron microscopy was used to study the distribution of this activity in neuroepithelial, neural crest, somite, and ectodermal cells. Our cytochemical studies show that the distribution of nonspecific ChE staining in these tissues during neurulation is similar in the two species but that acetylcholinesterase (AChE) staining, previously shown to be intense in the chick, is absent in the mouse; the only cells showing the presence of this enzyme at these stages of development in mouse are blood cells. However, AChE staining does appear later in the brain, in neural tissues derived from the neural crest and, perhaps, in some migratory neural crest cells. The differences between AChE distribution in these two species (and that reported previously in the rabbit) indicate that the timing of first appearance of AChE is unrelated to neuroepithelial morphogenesis or to neural crest cell motility. The correlation between nonspecific cholinesterases and morphogenetic movements, however, is supported by these studies.