Graduate Training in Neuroscience
University of Washington
David W. Raible
Professor, Department of Biological Structure; Adjunct, Department of Genome Sciences; Adjunct, Department of Biology
My lab is interested in how, during embryonic development, cells of the nervous system acquire their specific fates, so that they display the distinct characteristics necessary for their proper function. We have been examining how neural crest cells make cell fate choices in the zebrafish embryo, an emerging vertebrate developmental system with distinct advantages for cellular, molecular and genetic study. The neural crest generates the neurons and glia of the peripheral nervous system, as well as pigment cells and craniofacial cartilages. By labeling cells with fluorescent vital dyes and following their migration in living embryos, by transplanting individual cells between embryos and by specifically ablating subsets of neural crest cells, we have determined that interactions among neural crest cells themselves play an important role in sorting out the derivative types they will produce.
In collaboration with Randy Moon's lab, we have examined how the Wnt signals influence neural crest cell fate choice. Wnts expressed in the dorsal neural tube are adjacent to medial neural crest cells that generate pigment cells and distant from lateral cells that form neurons. We have dissected this process by injecting individual neural crest cells with mRNAs encoding activators and inhibitors of the Wnt signalling pathway along with mRNA for Green Fluorescent Protein to act as a lineage tracer. Activating the Wnt pathway in lateral crest cells generates pigment cells at the expense of neurons, and blocking the Wnt pathway in medial crest cells next to endogenous Wnt signal generates neurons at the expense of pigment cells. The mRNA injection technique should be a general way to manipulate neural crest cell fate.
We have also performed a genetic screen for mutations disrupting the development of subsets of neural crest derivatives. These mutations may identify genes that are targets of signals such as Wnt that specify neural crest cell fate. Several mutations affect pigment cell fates, including pasty, terminally dull, and nacre. We have identified nacre as a null mutation in a bHLH transcription factor, and are currently looking for genes upstream and downstream. Other mutations such as spike, which is missing specific crest-derived neurons, and flat top,which is missing craniofacial cartilages, may help us uncover key regulators in in the process of neural crest cell fate specification.