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Effector caspase Dcp-1 and IAP protein Bruce regulate starvation-induced autophagy during Drosophila melanogaster oogenesis.

Hou YC, Chittaranjan S, Barbosa SG, McCall K, Gorski SM - J. Cell Biol. (2008)

Bottom Line: During D. melanogaster oogenesis, we found that autophagy is induced at two nutrient status checkpoints: germarium and mid-oogenesis.Mutations in Atg1 and Atg7 resulted in reduced DNA fragmentation in degenerating midstage egg chambers but did not appear to affect nuclear condensation, which indicates that autophagy contributes in part to cell death in the ovary.Our study provides new insights into the molecular mechanisms that coordinately regulate autophagic and apoptotic events in vivo.

View Article: PubMed Central - PubMed

Affiliation: The Genome Sciences Centre, British Columbia Cancer Research Centre, Vancouver, British Columbia V5Z 1L3, Canada.

ABSTRACT
A complex relationship exists between autophagy and apoptosis, but the regulatory mechanisms underlying their interactions are largely unknown. We conducted a systematic study of Drosophila melanogaster cell death-related genes to determine their requirement in the regulation of starvation-induced autophagy. We discovered that six cell death genes--death caspase-1 (Dcp-1), hid, Bruce, Buffy, debcl, and p53-as well as Ras-Raf-mitogen activated protein kinase signaling pathway components had a role in autophagy regulation in D. melanogaster cultured cells. During D. melanogaster oogenesis, we found that autophagy is induced at two nutrient status checkpoints: germarium and mid-oogenesis. At these two stages, the effector caspase Dcp-1 and the inhibitor of apoptosis protein Bruce function to regulate both autophagy and starvation-induced cell death. Mutations in Atg1 and Atg7 resulted in reduced DNA fragmentation in degenerating midstage egg chambers but did not appear to affect nuclear condensation, which indicates that autophagy contributes in part to cell death in the ovary. Our study provides new insights into the molecular mechanisms that coordinately regulate autophagic and apoptotic events in vivo.

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Dcp-1 is required for nutrient starvation–induced germarium cell death, and the IAP protein Bruce inhibits germarium and mid-oogenesis cell death. (A) Ovaries were stained with TUNEL (green) to detect DNA fragmentation. Clusters of cysts with TUNEL staining were observed in region 2 in nutrient-deprived w1118 files. In Dcp-1Prev flies, fewer TUNEL-positive cysts in region 2 were observed. Under well-fed conditions, numerous TUNEL-positive cysts were observed in BruceE81 flies. DAPI staining of nuclei is shown in white. (B) Numerous degenerating stage 8 egg chambers (arrows) with TUNEL-positive staining (green) were observed in well-fed BruceE81 flies. DAPI staining of nuclei (white) is shown on the right. Bars: (A) 20 μm; (B) 50 μm.
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fig6: Dcp-1 is required for nutrient starvation–induced germarium cell death, and the IAP protein Bruce inhibits germarium and mid-oogenesis cell death. (A) Ovaries were stained with TUNEL (green) to detect DNA fragmentation. Clusters of cysts with TUNEL staining were observed in region 2 in nutrient-deprived w1118 files. In Dcp-1Prev flies, fewer TUNEL-positive cysts in region 2 were observed. Under well-fed conditions, numerous TUNEL-positive cysts were observed in BruceE81 flies. DAPI staining of nuclei is shown in white. (B) Numerous degenerating stage 8 egg chambers (arrows) with TUNEL-positive staining (green) were observed in well-fed BruceE81 flies. DAPI staining of nuclei (white) is shown on the right. Bars: (A) 20 μm; (B) 50 μm.

Mentions: Our previous work showed that nutrient-deprived Dcp-1 mutants (Dcp-1Prev) have defects in mid-oogenesis germ line cell death (Laundrie et al., 2003). To determine whether Dcp-1 is also required for germ line cell death in region 2 within the germarium, we used the TUNEL assay to detect levels of DNA fragmentation as an indication of cell death. We found that nutrient-deprived Dcp-1 mutants had decreased levels of TUNEL-positive cells in region 2 within the germarium compared with nutrient-deprived wild-type flies (Fig. 6 A and Table III), which indicates that Dcp-1 is also required for germarium stage cell death.


Effector caspase Dcp-1 and IAP protein Bruce regulate starvation-induced autophagy during Drosophila melanogaster oogenesis.

Hou YC, Chittaranjan S, Barbosa SG, McCall K, Gorski SM - J. Cell Biol. (2008)

Dcp-1 is required for nutrient starvation–induced germarium cell death, and the IAP protein Bruce inhibits germarium and mid-oogenesis cell death. (A) Ovaries were stained with TUNEL (green) to detect DNA fragmentation. Clusters of cysts with TUNEL staining were observed in region 2 in nutrient-deprived w1118 files. In Dcp-1Prev flies, fewer TUNEL-positive cysts in region 2 were observed. Under well-fed conditions, numerous TUNEL-positive cysts were observed in BruceE81 flies. DAPI staining of nuclei is shown in white. (B) Numerous degenerating stage 8 egg chambers (arrows) with TUNEL-positive staining (green) were observed in well-fed BruceE81 flies. DAPI staining of nuclei (white) is shown on the right. Bars: (A) 20 μm; (B) 50 μm.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2542474&req=5

fig6: Dcp-1 is required for nutrient starvation–induced germarium cell death, and the IAP protein Bruce inhibits germarium and mid-oogenesis cell death. (A) Ovaries were stained with TUNEL (green) to detect DNA fragmentation. Clusters of cysts with TUNEL staining were observed in region 2 in nutrient-deprived w1118 files. In Dcp-1Prev flies, fewer TUNEL-positive cysts in region 2 were observed. Under well-fed conditions, numerous TUNEL-positive cysts were observed in BruceE81 flies. DAPI staining of nuclei is shown in white. (B) Numerous degenerating stage 8 egg chambers (arrows) with TUNEL-positive staining (green) were observed in well-fed BruceE81 flies. DAPI staining of nuclei (white) is shown on the right. Bars: (A) 20 μm; (B) 50 μm.
Mentions: Our previous work showed that nutrient-deprived Dcp-1 mutants (Dcp-1Prev) have defects in mid-oogenesis germ line cell death (Laundrie et al., 2003). To determine whether Dcp-1 is also required for germ line cell death in region 2 within the germarium, we used the TUNEL assay to detect levels of DNA fragmentation as an indication of cell death. We found that nutrient-deprived Dcp-1 mutants had decreased levels of TUNEL-positive cells in region 2 within the germarium compared with nutrient-deprived wild-type flies (Fig. 6 A and Table III), which indicates that Dcp-1 is also required for germarium stage cell death.

Bottom Line: During D. melanogaster oogenesis, we found that autophagy is induced at two nutrient status checkpoints: germarium and mid-oogenesis.Mutations in Atg1 and Atg7 resulted in reduced DNA fragmentation in degenerating midstage egg chambers but did not appear to affect nuclear condensation, which indicates that autophagy contributes in part to cell death in the ovary.Our study provides new insights into the molecular mechanisms that coordinately regulate autophagic and apoptotic events in vivo.

View Article: PubMed Central - PubMed

Affiliation: The Genome Sciences Centre, British Columbia Cancer Research Centre, Vancouver, British Columbia V5Z 1L3, Canada.

ABSTRACT
A complex relationship exists between autophagy and apoptosis, but the regulatory mechanisms underlying their interactions are largely unknown. We conducted a systematic study of Drosophila melanogaster cell death-related genes to determine their requirement in the regulation of starvation-induced autophagy. We discovered that six cell death genes--death caspase-1 (Dcp-1), hid, Bruce, Buffy, debcl, and p53-as well as Ras-Raf-mitogen activated protein kinase signaling pathway components had a role in autophagy regulation in D. melanogaster cultured cells. During D. melanogaster oogenesis, we found that autophagy is induced at two nutrient status checkpoints: germarium and mid-oogenesis. At these two stages, the effector caspase Dcp-1 and the inhibitor of apoptosis protein Bruce function to regulate both autophagy and starvation-induced cell death. Mutations in Atg1 and Atg7 resulted in reduced DNA fragmentation in degenerating midstage egg chambers but did not appear to affect nuclear condensation, which indicates that autophagy contributes in part to cell death in the ovary. Our study provides new insights into the molecular mechanisms that coordinately regulate autophagic and apoptotic events in vivo.

Show MeSH
Related in: MedlinePlus