The α_4 Subunit of Integrin Is Important for Neural Crest Cell Migration

We identify the α_4 subunit of integrin as a predominant integrin expressed by neural crest cells in both avian and murine embryos. Using degenerate primers, we obtained a PCR fragment of the chick integrin α_4 subunit that was subsequently used to clone the full-length subunit with a predicted amino acid sequence 60% identical to human and mouse α_4 subunits.In situhybridization demonstrates that chick integrin α_4 mRNA is expressed at high levels by migrating neural crest cells and neural crest-derived ganglia at both cranial and trunk levels. An antibody against the murine α_4 subunit revealed similar distribution patterns in mouse to chick. In addition to neural crest cells, the integrin α_4 subunit was later observed on the muscle masses of the limb, the apical ectodermal ridge, and the developing liver. To examine the functional role of the integrin α_4 subunit in neural crest cell migration, we used an explant preparation that allows visualization of neural crest cells in their normal environment with or without perturbing reagents. In the presence of a blocking antibody against the mouse integrin α_4 subunit, there was a profound abrogation of neural crest cell migration at trunk and hindbrain levels. Both the numbers of migrating neural crest cells and the total distance traversed were markedly reduced. Similarly, avian embryos injected with synthetic peptides that contain the integrin α_4 binding site in fibronectin displayed abnormal neural crest cell migration. Our results suggest that the integrin α_4 subunit is important for normal neural crest cell migration and may be one of the primary α subunits used for neural crest cell migrationin vivo.Furthermore, the integrin α_4 subunit represents a useful neural crest marker in the mouse

Neural crest cells and motor axons in avians: Common and distinct migratory molecules

It has long been thought that the same molecules guide both trunk neural crest cells and motor axons as these cell types grow and extend to their target regions in developing embryos. There are common territories that are navigated by these cell types: both cells grow through the rostral portion of the somitic sclerotomes and avoid the caudal half of the sclerotomes. However, these cell types seem to use different molecules to guide them to their target regions. In this Review, I will discuss the common and distinct methods of migration taken by trunk neural crest cells and motor axons as they grow and populate their target regions through chick embryos at the level of the trunk