Glial Precursors Clear Sensory Neuron Corpses during Development via Jedi-1, an Engulfment Receptor

During the development of peripheral ganglia 50 % of the neurons generated undergo apoptosis. How the massive numbers of corpses are removed is unknown. We report that satellite glial cell precursors are the primary phagocytic cells for apoptotic corpse removal in developing mouse dorsal root ganglia (DRG). Confocal and electron microscopic analysis revealed that glial precursors, not macrophages, are responsible for clearing most of the dead DRG neurons. Moreover, we identified Jedi-1, a novel engulfment receptor, and MEGF10, a purported engulfment receptor, as homologs of the invertebrate engulfment receptors Draper and CED-1 expressed in the glial precursor cells. Expression of Jedi-1 or MEGF10 in fibroblasts facilitated binding to dead neurons and knocking down either protein in glial cells, or over expressing truncated forms lacking the intracellular domain, inhibited engulfment of apoptotic neurons. Together, these results reveal the cellular and molecular mechanism by which neuronal corpses are culled during DRG development.