Emigration of neuroepithelial cells from the hindbrain neural tube in the chick embryo

Abstract

It is generally believed that after the emigration of neural crest, the neuroepithelial cells of the neural tube are committed to differentiate only as neurons and supporting cells of the central nervous system. Neural crest cells arise from the dorsal portion of the developing neural tube and contribute to the formation of the peripheral nervous system and a variety of non-neural structures. In contrast to this view we have recently shown, by focal application of the vital dye Dil in duck embryos, that an additional population of cells emigrates from the neural tube. By using an entirely different technique we confirm and extend these observations in the chick embryo. Replication-deficient retroviral vector LZ12 containing the gene LacZ was utilized to label the neural tube cells. The viral concentrate was microinjected into the lumen of the rostral hind-brain neural tube, considerably after the completion of emigration of neural crest cells. The labeled cells were monitored in whole mounts and histological sections. Initially, the labeled cells were restricted to the neuroepithelium of the hindbrain neural tube. Subsequently, they were seen in the neural tube and in the ganglion of the fifth cranial nerve (trigeminal ganglion). Later, they migrated beyond the trigeminal ganglion, i.e., into the mesenchyme of the first pharyngeal arch. Immunostaining with the neural crest cell marker, HNK-1, indicated that the emigrated neuroepithelial cells were HNK-1 negative. It is concluded that in the chick embryo some neuroepithelial cells emigrate at the site of attachment of the trigeminal nerve, migrate into the ganglion and then into the mesenchyme of the first arch. This cell population differs antigenically from the neural crest cells.

Spatial relations between avian craniofacial neural crest and paraxial mesoderm cells

“…However, these embryos showed no labeling of cardiomyocytes, striated muscle, or endothelial cells. This finding confirms the results of Yaneza et al (2002) and Boot et al (2003), who were unable to confirm the presence of a late-emerging population of multipotential ventral hindbrain (VENT) cells (Sohal et al, 1998).…”

Ventrally emigrating neural tube cells contribute to the formation of Meckel's and quadrate cartilage

“…By using three different labeling techniques, i.e., focal application of the vital dye DiI, homeobox gene Islet-1 expression pattern, and recombinant retroviral labeling, it was found that some neural tube cells also emigrate from the cranial neural tube in the chick and duck embryos (Sohal et al, 1996(Sohal et al, , 1998a. They originate in the ventral portion of the hindbrain and emigrate at the site of attachment of the cranial nerves, considerably after the emigration of neural crest is finished.…”

“…Third, they do not express the neural crest antigen HNK-1. Fourth, they differentiate into all four basic tissues: the nerve, muscle, connective, and epithelium (Bockman and Sohal, 1998;Sohal, 1998;Sohal et al, 1996Sohal et al, , 1998aSohal et al, ,b, 1999a. This cell population has been named as the Ventrally Emigrating Neural Tube cells, or VENT cells, on the basis of its origin and emigration.…”

“…A recent study described the initial emigration of the VENT cells from the rostral hindbrain of the chick embryo (Sohal et al, 1998a). Replication-deficient retroviral vectors containing the LacZ gene were used to label the neural tube cells, after the emigration of neural crest is finished, but before the onset of emigration of the VENT cells.…”

“…The neural tube cells were labeled by microinjecting retroviral vectors into the lumen of the neural tube. It was found that the VENT cells populated the mesenchyme of the first pharyngeal (branchial) arch (Sohal et al, 1998a). A variety of craniofacial structures develop from this mesenchyme.…”