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Transcriptional upregulation of both egl-1 BH3-only and ced-3 caspase is required for the death of the male-specific CEM neurons.

Nehme R, Grote P, Tomasi T, Löser S, Holzkamp H, Schnabel R, Conradt B - Cell Death Differ. (2010)

Bottom Line: We found that in the CEMs, the transcriptional activation of both the egl-1 and ced-3 gene is necessary for apoptosis induction.Furthermore, we identified three genes, unc-86, lrs-1, and unc-132, which encode a POU homeodomain transcription factor, a leucyl-tRNA synthetase, and a novel protein with limited sequence similarity to the mammalian proto-oncoprotein and kinase PIM-1, respectively, that promote the expression of the ceh-30 gene in the CEMs. On the basis of these results, we propose that egl-1 and ced-3 transcription are coregulated in the CEMs to compensate for limiting proCED-3 levels, which most probably are a result of proCED-3 turn over.Finally, we present evidence that the timing of the death of the CEMs is controlled by TRA-1 Gli, the terminal global regulator of somatic sexual fate in C. elegans.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Dartmouth Medical School, Norris Cotton Cancer Center, Hanover, NH 3755, USA.

ABSTRACT
Most of the 131 cells that die during the development of a Caenorhabditis elegans hermaphrodite do so approximately 30 min after being generated. Furthermore, in these cells, the pro-caspase proCED-3 is inherited from progenitors and the transcriptional upregulation of the BH3-only gene egl-1 is thought to be sufficient for apoptosis induction. In contrast, the four CEM neurons, which die in hermaphrodites, but not males, die approximately 150 min after being generated. We found that in the CEMs, the transcriptional activation of both the egl-1 and ced-3 gene is necessary for apoptosis induction. In addition, we show that the Bar homeodomain transcription factor CEH-30 represses egl-1 and ced-3 transcription in the CEMs, thereby permitting their survival. Furthermore, we identified three genes, unc-86, lrs-1, and unc-132, which encode a POU homeodomain transcription factor, a leucyl-tRNA synthetase, and a novel protein with limited sequence similarity to the mammalian proto-oncoprotein and kinase PIM-1, respectively, that promote the expression of the ceh-30 gene in the CEMs. On the basis of these results, we propose that egl-1 and ced-3 transcription are coregulated in the CEMs to compensate for limiting proCED-3 levels, which most probably are a result of proCED-3 turn over. Similar coregulatory mechanisms for BH3-only proteins and pro-caspases may function in higher organisms to allow efficient apoptosis induction. Finally, we present evidence that the timing of the death of the CEMs is controlled by TRA-1 Gli, the terminal global regulator of somatic sexual fate in C. elegans.

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Analysis of ced-3 transcription in the CEMs(A) DIC and fluorescence images (Pced-3gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type (+/+), sel-10(n1077), sel-10(n1077); ceh-30(bc272) or lrs-1(bc155);sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pced-3gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and blue bars indicate the percentage of CEMs that acquired a corpse-like morphology. All strains analyzed were homozygous for the integrated Ppkd-2gfp array bcIs9 and carried extrachromosomal arrays of Pced-3gfp (+/+ [bcEx834, bcEX836], sel-10(n1077) [bcEx839, bcEx840], ceh-30(bc272); sel-10(n1077) [bcEx876], unc-86(bc151);sel-10(n1077) [bcEx870, bcEx871], lrs-1(bc155);sel-10(n1077) [bcEx872, bcEx873], unc-132(bc159); sel-10(n1077) [bcEx874, bcEx875]).
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Figure 4: Analysis of ced-3 transcription in the CEMs(A) DIC and fluorescence images (Pced-3gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type (+/+), sel-10(n1077), sel-10(n1077); ceh-30(bc272) or lrs-1(bc155);sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pced-3gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and blue bars indicate the percentage of CEMs that acquired a corpse-like morphology. All strains analyzed were homozygous for the integrated Ppkd-2gfp array bcIs9 and carried extrachromosomal arrays of Pced-3gfp (+/+ [bcEx834, bcEX836], sel-10(n1077) [bcEx839, bcEx840], ceh-30(bc272); sel-10(n1077) [bcEx876], unc-86(bc151);sel-10(n1077) [bcEx870, bcEx871], lrs-1(bc155);sel-10(n1077) [bcEx872, bcEx873], unc-132(bc159); sel-10(n1077) [bcEx874, bcEx875]).

Mentions: Using a transcriptional reporter (Pced-3gfp), we found that ced-3 is transcribed in most CEMs in wild-type hermaphrodites, in which the CEMs die (Figure 4 A, B, +/+). Therefore, the ced-3 gene is transcriptionally active in the CEMs. Furthermore, we found that in masculinized hermaphrodites, in which the CEMs survive, ced-3 is not transcribed (Figure 4 A, B, sel-10(n1077)). These observations are consistent with the notion that, like egl-1 transcription, the transcription of ced-3 in the CEMs correlates with CEM death. Next we determined the role of ceh-30 in ced-3 transcription in the CEMs. We found that in masculinized hermaphrodites lacking ceh-30 function, in which the CEMs inappropriately die, ced-3 was expressed in the CEMs (Figure 4 A, B). Therefore, we conclude that ceh-30 functions to repress ced-3 transcription in the CEMs in masculinized hermaphrodites (Figure 5).


Transcriptional upregulation of both egl-1 BH3-only and ced-3 caspase is required for the death of the male-specific CEM neurons.

Nehme R, Grote P, Tomasi T, Löser S, Holzkamp H, Schnabel R, Conradt B - Cell Death Differ. (2010)

Analysis of ced-3 transcription in the CEMs(A) DIC and fluorescence images (Pced-3gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type (+/+), sel-10(n1077), sel-10(n1077); ceh-30(bc272) or lrs-1(bc155);sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pced-3gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and blue bars indicate the percentage of CEMs that acquired a corpse-like morphology. All strains analyzed were homozygous for the integrated Ppkd-2gfp array bcIs9 and carried extrachromosomal arrays of Pced-3gfp (+/+ [bcEx834, bcEX836], sel-10(n1077) [bcEx839, bcEx840], ceh-30(bc272); sel-10(n1077) [bcEx876], unc-86(bc151);sel-10(n1077) [bcEx870, bcEx871], lrs-1(bc155);sel-10(n1077) [bcEx872, bcEx873], unc-132(bc159); sel-10(n1077) [bcEx874, bcEx875]).
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Figure 4: Analysis of ced-3 transcription in the CEMs(A) DIC and fluorescence images (Pced-3gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type (+/+), sel-10(n1077), sel-10(n1077); ceh-30(bc272) or lrs-1(bc155);sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pced-3gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and blue bars indicate the percentage of CEMs that acquired a corpse-like morphology. All strains analyzed were homozygous for the integrated Ppkd-2gfp array bcIs9 and carried extrachromosomal arrays of Pced-3gfp (+/+ [bcEx834, bcEX836], sel-10(n1077) [bcEx839, bcEx840], ceh-30(bc272); sel-10(n1077) [bcEx876], unc-86(bc151);sel-10(n1077) [bcEx870, bcEx871], lrs-1(bc155);sel-10(n1077) [bcEx872, bcEx873], unc-132(bc159); sel-10(n1077) [bcEx874, bcEx875]).
Mentions: Using a transcriptional reporter (Pced-3gfp), we found that ced-3 is transcribed in most CEMs in wild-type hermaphrodites, in which the CEMs die (Figure 4 A, B, +/+). Therefore, the ced-3 gene is transcriptionally active in the CEMs. Furthermore, we found that in masculinized hermaphrodites, in which the CEMs survive, ced-3 is not transcribed (Figure 4 A, B, sel-10(n1077)). These observations are consistent with the notion that, like egl-1 transcription, the transcription of ced-3 in the CEMs correlates with CEM death. Next we determined the role of ceh-30 in ced-3 transcription in the CEMs. We found that in masculinized hermaphrodites lacking ceh-30 function, in which the CEMs inappropriately die, ced-3 was expressed in the CEMs (Figure 4 A, B). Therefore, we conclude that ceh-30 functions to repress ced-3 transcription in the CEMs in masculinized hermaphrodites (Figure 5).

Bottom Line: We found that in the CEMs, the transcriptional activation of both the egl-1 and ced-3 gene is necessary for apoptosis induction.Furthermore, we identified three genes, unc-86, lrs-1, and unc-132, which encode a POU homeodomain transcription factor, a leucyl-tRNA synthetase, and a novel protein with limited sequence similarity to the mammalian proto-oncoprotein and kinase PIM-1, respectively, that promote the expression of the ceh-30 gene in the CEMs. On the basis of these results, we propose that egl-1 and ced-3 transcription are coregulated in the CEMs to compensate for limiting proCED-3 levels, which most probably are a result of proCED-3 turn over.Finally, we present evidence that the timing of the death of the CEMs is controlled by TRA-1 Gli, the terminal global regulator of somatic sexual fate in C. elegans.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Dartmouth Medical School, Norris Cotton Cancer Center, Hanover, NH 3755, USA.

ABSTRACT
Most of the 131 cells that die during the development of a Caenorhabditis elegans hermaphrodite do so approximately 30 min after being generated. Furthermore, in these cells, the pro-caspase proCED-3 is inherited from progenitors and the transcriptional upregulation of the BH3-only gene egl-1 is thought to be sufficient for apoptosis induction. In contrast, the four CEM neurons, which die in hermaphrodites, but not males, die approximately 150 min after being generated. We found that in the CEMs, the transcriptional activation of both the egl-1 and ced-3 gene is necessary for apoptosis induction. In addition, we show that the Bar homeodomain transcription factor CEH-30 represses egl-1 and ced-3 transcription in the CEMs, thereby permitting their survival. Furthermore, we identified three genes, unc-86, lrs-1, and unc-132, which encode a POU homeodomain transcription factor, a leucyl-tRNA synthetase, and a novel protein with limited sequence similarity to the mammalian proto-oncoprotein and kinase PIM-1, respectively, that promote the expression of the ceh-30 gene in the CEMs. On the basis of these results, we propose that egl-1 and ced-3 transcription are coregulated in the CEMs to compensate for limiting proCED-3 levels, which most probably are a result of proCED-3 turn over. Similar coregulatory mechanisms for BH3-only proteins and pro-caspases may function in higher organisms to allow efficient apoptosis induction. Finally, we present evidence that the timing of the death of the CEMs is controlled by TRA-1 Gli, the terminal global regulator of somatic sexual fate in C. elegans.

Show MeSH