Nuclear degradation dynamics in a nonapoptotic programmed cell death

摘要

Lamin is degraded as morphological changes in chromatin are observed during caspase-dependent apoptosis. a Schematic of a D. melanogaster ovariole composed of progressively developing egg chambers. Environmental stress, such as nutrient starvation, can induce a caspase-dependent cell death program of nurse cells (NCs) in mid-stage egg chambers. In contrast, NCs are eliminated through a caspase-independent and nonapoptotic developmental death during the late stages of oogenesis. b–g” Representative mid-stage egg chambers of starved wild-type (w1118) flies stained with DAPI to mark DNA (cyan), anticleaved-Dcp-1 (cDcp-1, yellow) to mark egg chambers undergoing apoptosis, and ADL84.12 to mark B-type Lamin (green). Mid-stage phasing previously described by Etchegaray et al. [37]. b–b” Phase 0 (not dying) mid-stage egg chamber: NC chromatin is dispersed (b arrowhead), a layer of follicle cells (FCs) line the perimeter of the egg chamber (b arrow indicating FC nuclei), and cDcp-1 is absent (b’). Both NC (b” inset) and FC nuclei (b” arrow) have continuous peripheral Lamin. c–c” Phase 1 dying egg chamber: NC chromatin is disorganized and cDcp-1 is present in the germline. Lamin begins to appear cytoplasmic and continues to at least partially associate with NC nuclei (c” inset). d–d” Phase 2 egg chamber: chromatin is condensed. Lamin generally no longer associates with condensed NC nuclei and continues to appear cytoplasmic (d” inset). Asterisks indicate a healthy egg chamber anterior to the dying egg chamber. e, f” Phase 3–4 egg chambers: NC chromatin progressively condenses and fragments. Lamin is not associated with degrading chromatin. Asterisks indicate a healthy egg chamber anterior to the dying egg chamber (e–e”). g–g” Phase 5 egg chamber: few remnants of NC chromatin remain (g arrowhead), and FC nuclei are disorganized surrounding the germline material (g arrow). Most of the germline material has been engulfed (g’). Lamin is observed surrounding only FC nuclei (g” arrow compared with arrowhead pointing to NC chromatin). Scale bar = 50 µm