Self-eating embryos

Abstract

Embryonic cells that cannot eat themselves also can't signal for other cells to eat them, report Xueping Qu, Beth Levine, and colleagues (University of Texas, Dallas, TX). Figure 1 Embryoid bodies can't cavitate (top) if their cells don't eat themselves (bottom). During embryonic development, the carving out of the body's shape requires a vast number of cells to be eliminated. Coincident with this large-scale programmed cell death, cells also perform autophagy, but whether this self-eating is required for normal embryogenesis was unclear. To address this question, Qu et al. grew autophagy-deficient embryo-like structures in culture. These embryoid bodies normally develop internal cavities, but, in the absence of autophagy, the bodies remained solid. The lack of cavitation was not due to a lack of programmed cell death but instead to a failure in clearance of the dead cells. Apoptotic cells normally express signals that tell waste disposal cells to clean-up their dying remains. In the autophagy-lacking embryoid bodies, however, these signals were missing. The signals could be restored by providing the embryoid bodies with an energy boost. By breaking down and recycling cell components, autophagy provides the cell with energy. The autophagy-deficient embryoid bodies thus had reduced energy production, which seems to prevent their dying cells from calling the clean-up crew. Reference: Qu, X., et al. 2007. Cell. 128:931–946. [PubMed]