Role of Polyploid Glial Cells in Drosophila Neural Development. Laura E. Frawley, Yingdee Unhavaithaya, Terry L. Orr-Weaver. Whitehead Institute for Biomedical Research, Cambridge, MA.

   Development of an organ relies on the coordinated growth among different cell types within given tissues. Our recent work (1) has established that subperineurial glia (SPG) in the Drosophila brain lobe, ventral nerve cord, and peripheral nervous system (PNS) are polyploid. Importantly, we observed that SPG ploidy must be coordinated with neuronal mass, as ablation of SPG polyploidy breached the septate junctions that form the blood-brain barrier. The increased cell size of SPG due to increased ploidy is therefore required for the integrity of the blood-brain barrier. When we increased the neuronal mass by using aurA mutants, the SPG responded by increasing ploidy and cell size, allowing the blood-brain barrier to remain intact. We have found that Notch signaling is important in controlling SPG ploidy. In addition to the SPG, we found that a subpopulation of wrapping glia (WG) in the PNS is polyploid. We are currently investigating the function of WG polyploidy and the mechanism by which WG become polyploid.

(1) Unhavaithaya Y. and Orr-Weaver T.L. 2012. Polyploidization of glia in neural development links tissue growth to blood-brain barrier integrity. Genes Dev 26: 31-6.