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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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unc-86, lrs-1 and unc-132 are required for ceh-30 expression in the CEMs in masculinized hermaphrodites(A) DIC and fluorescence images (Pceh-30ceh-30∷gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type hermaphrodites (+/+), males (XO +/+), sel-10(n1077) hermaphrodites or lrs-1(bc155); sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pceh-30ceh-30∷gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and green numbers above indicate the fraction of CEMs analyzed that were GFP-positive. Blue bars indicate the percentage of CEMs that acquired a corpse-like morphology and blue numbers above indicate the fraction of CEMs analyzed that had a corpse-like morphology. All strains analyzed were homozygous for unc-76(e911) and carried the extrachromosomal array nEx1171 (Pceh-30ceh-30∷gfp). The wild-type hermaphrodites and males analyzed were homozygous for him-5(e1467ts). The strains unc-86(bc151); sel-10(n1077) and lrs-1(bc155); sel-10(n1077) were also homozygous for dpy-17(e164).
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Figure 2: unc-86, lrs-1 and unc-132 are required for ceh-30 expression in the CEMs in masculinized hermaphrodites(A) DIC and fluorescence images (Pceh-30ceh-30∷gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type hermaphrodites (+/+), males (XO +/+), sel-10(n1077) hermaphrodites or lrs-1(bc155); sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pceh-30ceh-30∷gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and green numbers above indicate the fraction of CEMs analyzed that were GFP-positive. Blue bars indicate the percentage of CEMs that acquired a corpse-like morphology and blue numbers above indicate the fraction of CEMs analyzed that had a corpse-like morphology. All strains analyzed were homozygous for unc-76(e911) and carried the extrachromosomal array nEx1171 (Pceh-30ceh-30∷gfp). The wild-type hermaphrodites and males analyzed were homozygous for him-5(e1467ts). The strains unc-86(bc151); sel-10(n1077) and lrs-1(bc155); sel-10(n1077) were also homozygous for dpy-17(e164).

Mentions: The Bar homeodomain transcription factor CEH-30, whose expression is under the direct control of the terminal, global regulator of somatic sexual fate, TRA-1, acts to block the death of the CEMs (21, 22). Specifically, the loss of ceh-30 function causes the CEMs to inappropriately die in males as well as in masculinized hermaphrodites, indicating that ceh-30 is required for CEM survival (21, 22) (Grote, P. and Conradt, B., unpublished data). Using a translational ceh-30 reporter (Pceh-30ceh-30∷gfp) (22), we determined the expression pattern of the ceh-30 gene in the CEMs in embryos ~450 min after the first cell division, which is just prior to the time at which the CEMs normally die in hermaphrodites (~470 min) (12, 16). The CEMs were identified based on their position using DIC and observed for ~30 min. We found that in wild-type hermaphrodites, the CEMs do not express ceh-30 and adopt a corpse-like morphology (Figure 2A, B, +/+). In contrast, in males (XO +/+) or masculinized hermaphrodites (sel-10(n1077)), the CEMs do express ceh-30 and do not adopt a corpse-like morphology (Figure 2A, B). These observations confirm that ceh-30 expression correlates with CEM survival. These observations also confirm that inappropriately surviving CEMs in masculinized hermaphrodites faithfully recapitulate molecular events that occur in the CEMs in males.


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)

unc-86, lrs-1 and unc-132 are required for ceh-30 expression in the CEMs in masculinized hermaphrodites(A) DIC and fluorescence images (Pceh-30ceh-30∷gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type hermaphrodites (+/+), males (XO +/+), sel-10(n1077) hermaphrodites or lrs-1(bc155); sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pceh-30ceh-30∷gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and green numbers above indicate the fraction of CEMs analyzed that were GFP-positive. Blue bars indicate the percentage of CEMs that acquired a corpse-like morphology and blue numbers above indicate the fraction of CEMs analyzed that had a corpse-like morphology. All strains analyzed were homozygous for unc-76(e911) and carried the extrachromosomal array nEx1171 (Pceh-30ceh-30∷gfp). The wild-type hermaphrodites and males analyzed were homozygous for him-5(e1467ts). The strains unc-86(bc151); sel-10(n1077) and lrs-1(bc155); sel-10(n1077) were also homozygous for dpy-17(e164).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2902690&req=5

Figure 2: unc-86, lrs-1 and unc-132 are required for ceh-30 expression in the CEMs in masculinized hermaphrodites(A) DIC and fluorescence images (Pceh-30ceh-30∷gfp) of CEM corpses (white arrow heads) or CEMs (white arrows) in wild-type hermaphrodites (+/+), males (XO +/+), sel-10(n1077) hermaphrodites or lrs-1(bc155); sel-10(n1077) hermaphrodites. (B) Summary of data obtained on Pceh-30ceh-30∷gfp expression. Green bars indicate the percentage of CEMs that were GFP-positive and green numbers above indicate the fraction of CEMs analyzed that were GFP-positive. Blue bars indicate the percentage of CEMs that acquired a corpse-like morphology and blue numbers above indicate the fraction of CEMs analyzed that had a corpse-like morphology. All strains analyzed were homozygous for unc-76(e911) and carried the extrachromosomal array nEx1171 (Pceh-30ceh-30∷gfp). The wild-type hermaphrodites and males analyzed were homozygous for him-5(e1467ts). The strains unc-86(bc151); sel-10(n1077) and lrs-1(bc155); sel-10(n1077) were also homozygous for dpy-17(e164).
Mentions: The Bar homeodomain transcription factor CEH-30, whose expression is under the direct control of the terminal, global regulator of somatic sexual fate, TRA-1, acts to block the death of the CEMs (21, 22). Specifically, the loss of ceh-30 function causes the CEMs to inappropriately die in males as well as in masculinized hermaphrodites, indicating that ceh-30 is required for CEM survival (21, 22) (Grote, P. and Conradt, B., unpublished data). Using a translational ceh-30 reporter (Pceh-30ceh-30∷gfp) (22), we determined the expression pattern of the ceh-30 gene in the CEMs in embryos ~450 min after the first cell division, which is just prior to the time at which the CEMs normally die in hermaphrodites (~470 min) (12, 16). The CEMs were identified based on their position using DIC and observed for ~30 min. We found that in wild-type hermaphrodites, the CEMs do not express ceh-30 and adopt a corpse-like morphology (Figure 2A, B, +/+). In contrast, in males (XO +/+) or masculinized hermaphrodites (sel-10(n1077)), the CEMs do express ceh-30 and do not adopt a corpse-like morphology (Figure 2A, B). These observations confirm that ceh-30 expression correlates with CEM survival. These observations also confirm that inappropriately surviving CEMs in masculinized hermaphrodites faithfully recapitulate molecular events that occur in the CEMs in males.

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