IOS- ABR: RUI: Investigating astroglial development in the zebrafish forebrain.

Smith College, Northampton MA

Investigators

Abstract

Historically, the field of neuroscience has been neuron-centric, which has left a large gap in our understanding of the development and function of the other cells in the nervous system, called glia. Glial cells were traditionally thought to passively support neurons. The present research tries to answer foundational questions about how glial cells are involved in brain development, such as what the differences are among the types of glial cells that exist in developing brains, how glial cells support the actively-dividing cell populations that build the brain (neural stem cells), the role that glial cells play in the development of the blood-brain-barrier, and how glial cells affect the intricate pattern of connections that form in the developing brain. Zebrafish are used for this research because of the ease with which these questions can be studied in a vertebrate animal that is optically clear. This work combines the advantages of zebrafish genetics and embryology together with high resolution 5D microscopy (3 spatial dimensions followed over time for several different cell-marking colors) to precisely measure glial cell development, and to assess the role that an important molecule involved in cell-cell communication called Roundabout4 plays in these processes. In addition to greatly furthering scientific understanding of glial cell biology and development, this award will support the recruitment of a diverse set of student scientists through the establishment of a peer mentor training program, and the continuation of a primary and secondary education outreach program using zebrafish called Student Scientists. This project explores the hypotheses that heterogeneous astroglia exist in the zebrafish embryonic forebrain to guide cell types at the midline that build neurons, commissures, blood vessels, and cartilage, and that Slit-Robo4 signaling underlies this astroglial mechanism of cell guidance. These hypotheses will be tested in three specific ways. First, the developmental ontogeny of forebrain astroglia will be characterized in detail. New transgenic reporters will be used to track every astroglial cell in the diencephalon with time lapse Lightsheet microcopy, and live cell behaviors will be used to chart the developmental derivation of forebrain astroglia during neurogenesis, commissure and blood vessel formation. Next, experiments will be carried out to see if Robo4 is required cell-autonomously for astroglial guidance during neural stem cell niche, postoptic commissure, and blood-brain barrier formation. A newly-created robo4 knockout will be used to determine exactly which cell populations require Robo4 function for progenitor cell generation in the stem cell niche, for the midline crossing of axons, and for astroglial-endothelial cell interactions during blood-brain-barrier development. Finally, Robo4 functions downstream of Slit signaling will be examined during commissure formation. Because Roundabout receptors mediate Slit signaling, functional interactions between Robo4 and Slit1a/2 will be investigated to see if they are responsible for Robo4-dependent astroglial behaviors.