Pathways of trunk neural crest cell migration in the mouse embryo as revealed by vital dye labelling

Abstract

Analysis of neural crest cell migration in the mouse has been difficult due to the lack of reliable cell markers. Recently, we found that injection of Dil into the chick neural tube marks premigratory neural crest cells whose endfeet are in contact with the lumen of the neural tube (Serbedzija et al. Development 106, 809-819 (1989)). In the present study, this technique was applied to study neural crest cell migratory pathways in the trunk of the mouse embryo. Embryos were removed from the mother between the 8th and the 10th days of development and Dil was injected into the lumen of the neural tube. The embryos were then cultured for 12 to 24 h, and analyzed at the level of the forelimb. We observed two predominant pathways of neural crest cell migration: (1) a ventral pathway through the rostral portion of the somite and (2) a dorsolateral pathway between the dermamyotome and the epidermis. Neural crest cells were observed along the dorsolateral pathway throughout the period of migration. The distribution of labelled cells along the ventral pathway suggested that there were two overlapping phases of migration. An early ventrolateral phase began before E9 and ended by E9.5; this pathway consisted of a stream of cells within the rostral sclerotome, adjacent to the dermamyotome, that extended ventrally to the region of the sympathetic ganglia and the dorsal aorta. A later ventromedial phase was apparent after E9.5 and continued through E10.5; this pathway consisted of a thin strand of Dil-labelled cells along the lateral surface of the neural tube which later protruded into the rostral sclerotome to form the dorsal root ganglia and Schwann cells. Those embryos injected at later stages contained labelled cells only in dorsal derivatives, suggesting that neural crest derivatives are populated in a ventral-to-dorsal order. While the overall pattern and order of neural crest migration was similar to that previously observed in avians and rats, some details of the timing and trajectories apparently differed, most notably the timing of neural crest migration along the dorsolateral pathway.