In the developing vertebrate central nervous system, radial glial cells play critical roles in supporting brain architecture and, more recently discovered, possess self-renewing capabilities as well as gliogenic and neurogenic potential. Radial glial cells have been known since the time of Cajal, but over the last few decades the increase of available markers particularly glial fibrillary acidic protein has made their identification as astroglial cells increasingly easier. Much of our understanding of radial glial cells originates from their function as a scaffold for the migration of newly born neurons in the developing mammalian cerebral cortex. However, current knowledge of the stem cell-like potential of radial glial cells is very limited, and in particular what the surrounding radial glial niche of the embryonic ventricular zone looks like. What glial or neuronal cell types are derived from radial glia in the embryonic spinal cord? Do radial glia have a unique intrinsic regulator of cell division to carry out the mechanics of continued self-renewal? The investigator proposes to fully exploit the embryological, molecular, and genetic techniques that are in some cases uniquely amenable to zebrafish to address these questions. He proposes to (1) establish a three-dimensional map of astroglia and radial glia within the embryonic spinal cord, and (2) determine whether the eg5 kinesin motor protein is required cell autonomously for radial glial cell division. By combining both a gfap transgenic line driving the expression of GFP with elegant gastrula staged transplantations, The investigator will target clusters of scattered gfap:GFP+ cells into a non-transgenic spinal cord. Imaging of these astroglial cells with high resolution confocal microscopy will provide a full cellular morphological analysis, shedding light on the types of astroglia present in the embryonic spinal cord and how they interact with other cell types. Furthermore, the investigator identified an eg5 zebrafish mutant that exhibits cell proliferative defects in radial glial cells. By utilizing this mutant as well as testing several anti-cancer drugs targeting Eg5, he will determine how this gene regulates radial glial cell division and whether other cell types derived from radial glia are also affected by the loss of Eg5. In this revitalized field of glial biology and a model system lacking foundational data on astroglial development, these results will provide fundamental information of radial glial development that can be the springboard for many new avenues of research. Understanding the role of Eg5 in the developing embryo will also provide critical information regarding the use of anti-cancer drugs targeting Eg5 in humans especially for glial derived tumors, such as congenital gliomas.
The proposed research provides both basic knowledge and direct therapeutic evaluation in the area of glial derived congenital CNS tumors. We propose to characterize the stem cell-like radial glial cell within the embryonic spinal cord, and determine whether they contribute to other glial or neuronal lineages in zebrafish. We will also test, genetically and by using anti-cancer drugs for the first time in a whole vertebrate organism, the role of the eg5 kinesin motor protein in regulating radial glial cell division during embryogenesis.
