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Derivation of Thymic Lymphoma T-cell Lines from Atm-/- and p53-/- Mice
Published on: April 3, 2011
Defective control of apoptosis, radiosensitivity, and spindle checkpoint in ataxia telangiectasia
1Department of Virology, The National Children's Medical Research Center, Tokyo, Japan.
Abstract:
We examined the regulation of apoptosis, radiosensitivity, and spindle checkpoint in response to DNA-damaging agents in ataxia telangiectasia (AT)-derived lymphoblastoid cell lines (AT-LCLs), which lack AT mutated (ATM) protein expression. In addition to the previous findings that AT-LCLs are defective in regulation of cell cycle at the G1, S, and G2-M checkpoints in response to X-ray irradiation (X-IR) and are highly sensitive to X-IR (J. Biol. Chem., 271: 20486-20493, 1996), we showed for the first time that AT-LCLs were defective in X-IR-associated spindle checkpoint control. The cells were also resistant to early apoptosis as much as LCLs derived from patients with Li-Fraumeni syndrome (LFS-LCLs). Terminal deoxynucleotidyl transferase-mediated nick end labeling assay of LCLs, however, demonstrated a significant increase in apoptotic cells among AT-LCLs cultured over a longer period after X-IR. These findings were in contrast to those of LFS-LCL, which showed very little increase in terminal deoxynucleotidyl transferase-mediated nick end labeling-positive population, even in cells with hyperploidy. Thus, although early apoptosis and cell cycle controls in response to DNA damage are disrupted in both ATM and p53 mutations, cells from AT patients are much more susceptible to late-onset apoptosis than those of LFS. These differences may depend on the level of accumulation of DNA damage and/or threshold that triggers late-onset cell death in ATM or p53 mutations. Our findings allow a better understanding of the role of ATM in p53-dependent and independent signal transduction pathways in response to DNA damaging agents.
Insights
Ataxia telangiectasia (AT) cells lacking ATM protein show defective spindle checkpoint control and late-onset apoptosis after DNA damage, unlike Li-Fraumeni syndrome cells.
Area of Science:
- Cell Biology
- Genetics
- Cancer Research
Background:
- Ataxia telangiectasia (AT) is a genetic disorder characterized by a lack of functional AT mutated (ATM) protein.
- ATM plays a crucial role in DNA damage response, cell cycle control, and apoptosis.
- Previous studies indicated AT-derived lymphoblastoid cell lines (AT-LCLs) have defects in cell cycle checkpoints and are radiosensitive.
Purpose of the Study:
- To investigate the regulation of apoptosis, radiosensitivity, and spindle checkpoint in AT-LCLs following DNA damage.
- To compare the DNA damage response of AT-LCLs with Li-Fraumeni syndrome lymphoblastoid cell lines (LFS-LCLs), which have p53 mutations.
Main Methods:
- Utilized AT-LCLs and LFS-LCLs.
- Exposed cells to X-ray irradiation (X-IR) as a DNA-damaging agent.
- Assessed apoptosis using terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay.
- Evaluated cell cycle checkpoint control and spindle checkpoint function.
Main Results:
- AT-LCLs exhibit defects in X-IR-associated spindle checkpoint control.
- Both AT-LCLs and LFS-LCLs show resistance to early apoptosis post X-IR.
- A significant increase in late-onset apoptosis was observed in AT-LCLs, but not in LFS-LCLs, even with hyperploidy.
- Differences in late-onset apoptosis suggest varying DNA damage accumulation or cell death thresholds between ATM and p53 mutations.
Conclusions:
- ATM plays a critical role in regulating apoptosis and spindle checkpoint control following DNA damage.
- While both ATM and p53 mutations disrupt early apoptosis and cell cycle control, ATM-deficient cells are more prone to late-onset apoptosis.
- These findings enhance understanding of ATM's role in both p53-dependent and independent signaling pathways in response to DNA damage.
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