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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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ceh-30, egl-1 and ced-3 expression in embryonic CEMs in wild-type hermaphroditesSchematic representation of time course analyses of the expression of the reporters Pceh-30ceh-30∷gfp, Pegl-1his-24∷gfp, and Pced-3gfp in the ventral left embryonic CEM (CEMVL) in wild-type hermaphrodites. Time (min) is indicated on the left. Three embryos were analyzed. White dots represent the CEM mother cells, green dots indicate CEMs expressing a particular gfp reporter. Green dots surrounded by purple circles indicate CEMs at the time when expression of the gfp reporter was first detected. (See Figure S1 for corresponding DIC and fluorescent images.) Gray dots indicate CEMs lacking reporter expression. Embryos were prepared for 4-D microscopy and lineaged starting at the 2- or 4-cell stage as described in Materials and Methods. Fluorescent stacks were taken every ~20 min after the CEM mother cell was born. No expression was detected for any of the reporters in the CEM mother cell.
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Figure 6: ceh-30, egl-1 and ced-3 expression in embryonic CEMs in wild-type hermaphroditesSchematic representation of time course analyses of the expression of the reporters Pceh-30ceh-30∷gfp, Pegl-1his-24∷gfp, and Pced-3gfp in the ventral left embryonic CEM (CEMVL) in wild-type hermaphrodites. Time (min) is indicated on the left. Three embryos were analyzed. White dots represent the CEM mother cells, green dots indicate CEMs expressing a particular gfp reporter. Green dots surrounded by purple circles indicate CEMs at the time when expression of the gfp reporter was first detected. (See Figure S1 for corresponding DIC and fluorescent images.) Gray dots indicate CEMs lacking reporter expression. Embryos were prepared for 4-D microscopy and lineaged starting at the 2- or 4-cell stage as described in Materials and Methods. Fluorescent stacks were taken every ~20 min after the CEM mother cell was born. No expression was detected for any of the reporters in the CEM mother cell.

Mentions: Our results indicate that the death of the CEMs in wild-type hermaphrodites is the result of TRA-1-dependent repression of ceh-30 transcription, which results in the de-repression of egl-1 and ced-3 transcription in the CEMs. To test this hypothesis, we monitored ceh-30 expression as well as egl-1 and ced-3 transcription throughout the life span of the CEMs in hermaphrodites using 4D lineaging analysis and appropriate reporters (Pceh-30ceh-30∷gfp, Pegl-1his-24∷gfp, Pced-3gfp). We found that ceh-30 expression in the CEMs in wild-type hermaphrodites can only be detected right after the cells are generated (~340 min) (Figure 6, Figure S1). ceh-30 expression cannot be detected in the mother cell or in the CEMs at ~360 min or later time points. In contrast, egl-1 and ced-3 transcription can only be detected starting at ~390 and ~460 min, respectively (Figure 6, Figure S1). These observations demonstrate that ceh-30 expression in the CEMs inversely correlates with egl-1 and ced-3 transcription, which supports the model that TRA-1-dependent repression of ceh-30 transcription causes the de-repression of egl-1 and ced-3 transcription in the CEMs in wild-type hermaphrodites and, hence, CEM death.


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)

ceh-30, egl-1 and ced-3 expression in embryonic CEMs in wild-type hermaphroditesSchematic representation of time course analyses of the expression of the reporters Pceh-30ceh-30∷gfp, Pegl-1his-24∷gfp, and Pced-3gfp in the ventral left embryonic CEM (CEMVL) in wild-type hermaphrodites. Time (min) is indicated on the left. Three embryos were analyzed. White dots represent the CEM mother cells, green dots indicate CEMs expressing a particular gfp reporter. Green dots surrounded by purple circles indicate CEMs at the time when expression of the gfp reporter was first detected. (See Figure S1 for corresponding DIC and fluorescent images.) Gray dots indicate CEMs lacking reporter expression. Embryos were prepared for 4-D microscopy and lineaged starting at the 2- or 4-cell stage as described in Materials and Methods. Fluorescent stacks were taken every ~20 min after the CEM mother cell was born. No expression was detected for any of the reporters in the CEM mother cell.
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Figure 6: ceh-30, egl-1 and ced-3 expression in embryonic CEMs in wild-type hermaphroditesSchematic representation of time course analyses of the expression of the reporters Pceh-30ceh-30∷gfp, Pegl-1his-24∷gfp, and Pced-3gfp in the ventral left embryonic CEM (CEMVL) in wild-type hermaphrodites. Time (min) is indicated on the left. Three embryos were analyzed. White dots represent the CEM mother cells, green dots indicate CEMs expressing a particular gfp reporter. Green dots surrounded by purple circles indicate CEMs at the time when expression of the gfp reporter was first detected. (See Figure S1 for corresponding DIC and fluorescent images.) Gray dots indicate CEMs lacking reporter expression. Embryos were prepared for 4-D microscopy and lineaged starting at the 2- or 4-cell stage as described in Materials and Methods. Fluorescent stacks were taken every ~20 min after the CEM mother cell was born. No expression was detected for any of the reporters in the CEM mother cell.
Mentions: Our results indicate that the death of the CEMs in wild-type hermaphrodites is the result of TRA-1-dependent repression of ceh-30 transcription, which results in the de-repression of egl-1 and ced-3 transcription in the CEMs. To test this hypothesis, we monitored ceh-30 expression as well as egl-1 and ced-3 transcription throughout the life span of the CEMs in hermaphrodites using 4D lineaging analysis and appropriate reporters (Pceh-30ceh-30∷gfp, Pegl-1his-24∷gfp, Pced-3gfp). We found that ceh-30 expression in the CEMs in wild-type hermaphrodites can only be detected right after the cells are generated (~340 min) (Figure 6, Figure S1). ceh-30 expression cannot be detected in the mother cell or in the CEMs at ~360 min or later time points. In contrast, egl-1 and ced-3 transcription can only be detected starting at ~390 and ~460 min, respectively (Figure 6, Figure S1). These observations demonstrate that ceh-30 expression in the CEMs inversely correlates with egl-1 and ced-3 transcription, which supports the model that TRA-1-dependent repression of ceh-30 transcription causes the de-repression of egl-1 and ced-3 transcription in the CEMs in wild-type hermaphrodites and, hence, CEM death.

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