A critical role for Cadherin6B in regulating avian neural crest emigration.

Neural crest cells originate in the dorsal neural tube but subsequently undergo an epithelial-to-mesenchymal transition (EMT), delaminate, and migrate to diverse locations in the embryo where they contribute to a variety of derivatives. Cadherins are a family of cell-cell adhesion molecules expressed in a broad range of embryonic tissues, including the neural tube. In particular, cadherin6B (Cad6B) is expressed in the dorsal neural tube prior to neural crest emigration but is then repressed by the transcription factor Snail2, expressed by premigratory and early migrating cranial neural crest cells. To examine the role of Cad6B during neural crest EMT, we have perturbed Cad6B protein levels in the cranial neural crest-forming region and have examined subsequent effects on emigration and migration. The results show that knock-down of Cad6B leads to premature neural crest cell emigration, whereas Cad6B overexpression disrupts migration. Our data reveal a novel role for Cad6B in controlling the proper timing of neural crest emigration and delamination from the neural tube of the avian embryo.

Screening from a subtracted embryonic chick hindbrain cDNA library: identification of genes expressed during hindbrain, midbrain and cranial neural crest development.

The vertebrate hindbrain is segmented into a series of transient structures called rhombomeres. Despite knowing several factors that are responsible for the segmentation and maintenance of the rhombomeres, there are still large gaps in understanding the genetic pathways that govern their development. To find previously unknown genes that are expressed within the embryonic hindbrain, a subtracted chick hindbrain cDNA library has been made and 445 randomly picked clones from this library have been analysed using whole mount in situ hybridisation. Thirty-six of these clones (8%) display restricted expression patterns within the hindbrain, midbrain or cranial neural crest and of these, twenty-two are novel and eleven encode peptides that correspond to or are highly related to proteins with previously uncharacterised roles during early neural development. The large proportion of genes with restricted expression patterns and previously unknown functions in the embryonic brain identified during this screen provides insights into the different types of molecules that have spatially regulated expression patterns in cranial neural tissue.

Molecular control of neural crest formation, migration and differentiation.

Induction, migration and differentiation of the neural crest are crucial for the development of the vertebrate embryo, and elucidation of the underlying mechanisms remains an important challenge. In the past year, a novel signal regulating the formation of neural crest cells has been identified, and advances have been made in uncovering roles for bone morphogenetic protein signals and for a transcription factor in the onset of neural crest migration. There have been new insights into the migration and plasticity of branchial neural crest cells. Important progress has been made in dissecting the roles of bone morphogenetic protein, Wnt and Notch signalling systems and their associated downstream transcription factors in the control of neural crest cell differentiation.