The control of avian cephalic neural crest cytodifferentiation: I. Skeletal and connective tissues

Abstract

The neural crest is the embryonic source of many skeletal and connective tissues associated with the visceral arches of vertebrate embryos. By transplanting quail premigratory neural crest cells, which contain a distinctive nuclear marker [Le Douarin, N. M. (1971). Ann. Embryol. Morphol. 4, 125–135], orthotopically into various preotic regions of the chick, it has been shown that all cartilages and bones and most connective tissues of the facial and oral regions are of crest cell origin. These derivatives include the frontal, prefrontal, nasal, maxilla, premaxilla, parasphenoid, palatine, pterygoid, and squamosal bones, in addition to lower jaw skeletal elements. Most connective tissues found in the facial and periprosencephalic regions are of crest origin, including the corneal endothelium, stromal cells, and leptomeningeal tissues. To examine whether crest cells were restricted to specific developmental pathways, quail crest cells from one part of the head were grafted in the place of a different population of chick crest cells. In all cases these host embryos were identical to controls, indicating that cytodifferentiation, growth, and histogenesis of crest-derived tissues are directed by environmental influences encountered by migrating crest cells after they leave their origin.