Cell death

Engulfment Without Apoptosis?

Science's STKE  28 Oct 2003:
Vol. 2003, Issue 206, pp. tw422
DOI: 10.1126/stke.2003.206.tw422

Mergliano and Minden report the development of a fluorogenic assay for detecting cell engulfment in Drosophila. Cell engulfment occurs in response to poorly defined signals that arise as part of the cell death process. Their assay involved injecting a fluorogenic β-galactosidase substrate (VGAL) into cells and then monitoring the development of fluorescence as the injected cells are engulfed either by neighboring cells or by macrophages. This process allows the β-galactosidase substrate to be cleaved and to produce a fluorescent signal in the engulfing cells' lysosomal compartment. Studies in wild-type Drosophila embryos showed that the VGAL signal closely matched the acridine orange (AO) signal used to detect cells undergoing apoptosis. There was both a temporal and spatial correlation: generally VGAL signal appeared after the AO signal and was within one cell body's distance of the AO signal. Surprisingly, in embryos in which apoptosis was inhibited either by genetic disruption of genes required for apoptosis or through overexpression of a caspase inhibitor, VGAL engulfment signals were still detectable. For example, in epidermis, where neighboring cells engulf dying cells, VGAL signals were essentially the same in the cell death-inhibited embryos as the wild-type embryos. Engulfment by macrophages was impaired in cell death-inhibited embryos. Thus, it appears that cell death and cell engulfment may be separable processes and that there may be at least two types of engulfment signals, a close-range signal for neighboring cells and a long-range one that attracts macrophages.

J. Mergliano, J. S. Minden, Caspase-independent cell engulfment mirrors cell death pattern in Drosophila embryos. Development 130, 5779-5789 (2003). [Abstract] [Full Text]