Migration of Hindbrain Neural Crest Cells in the Mouse

Background: Neural crest cells are a special group of embryonic cells which are able to emigrate from the dorsal neural tube (the developing central nervous system) to the mesenchyme and form different derivatives in embryos. In contrast to the situation in the avian embryo, where the use of quail-chick chimeras has provided much information on neural crest migration, the early migratory pathways of hindbrain neural crest cells are not well understood in mammals. Aims: In the present study, an exogenous dye, wheat germ agglutinin-gold conjugate (WGA-Au), was used to label the early migrating hindbrain neural crest cells to track their migration at three axial levels, namely (1) pre-otic, (2) post-otic and pre-somitic, and (3) somitic (somites 1–4) levels, in mouse embryos cultured in vitro. Results: It was found that neural crest cells had already started their emigration from the dorsal part of the neural tube at the 9-somite stage and migrated into the mesenchyme subjacent to the neural tube. When the labelled embryos were cultured to more advanced stages, neural crest cells migrated to more ventral regions. At the 13-somite stage, most neural crest cells at the pre-somitic hindbrain migrated to the mesenchyme lateral to the dorsal aorta, while by the 17-somite stage, labelled cells reached the mesenchyme adjacent to the pharynx, which is located more ventrally than the dorsal aorta. At the 21-somite stage, more labelled cells were found in the mesenchyme lateral and ventral to the pharynx. At the somitic level, neural crest cells migrated along three distinct routes, namely the dorsolateral (between the surface epithelium and the somite), medial (between the somite and the neural tube) and intersomitic (between two consecutive somites) pathways. Conclusions: Our results indicate that whole embryo culture is able to support the normal development of mouse embryos at early organogenesis in vitro for 26 h, and that WGA-Au is an ideal short-term cell marker for tracking neural crest migration in the mouse. We also show that the migratory patterns of hindbrain neural crest cells in the mouse largely resemble those observed in the chick.