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Updated: Apr 15, 2026
Detection and Analysis of DNA Damage in Mouse Skeletal Muscle In Situ Using the TUNEL Method
Published on: December 16, 2014
On the use of an appropriate TdT-mediated dUTP-biotin nick end labeling assay to identify apoptotic cells
Cecile Lebon1, Gloria Villalpando Rodriguez1, Ikram El Zaoui1
1Centre de Recherches des Cordeliers, INSERM U1138, Université Pierre et Marie Curie, Université Paris Descartes, 75006 Paris, France.
Abstract:
Apoptosis is an essential cellular mechanism involved in many processes such as embryogenesis, metamorphosis, and tissue homeostasis. DNA fragmentation is one of the key markers of this form of cell death. DNA fragmentation is executed by endogenous endonucleases such as caspase-activated DNase (CAD) in caspase-dependent apoptosis. The TUNEL (TdT-mediated dUTP-biotin nick end labeling) technique is the most widely used method to identify apoptotic cells in a tissue or culture and to assess drug toxicity. It is based on the detection of 3'-OH termini that are labeled with dUTP by the terminal deoxynucleotidyl transferase. Although the test is very reliable and sensitive in caspase-dependent apoptosis, it is completely useless when cell death is mediated by pathways involving DNA degradation that generates 3'-P ends as in the LEI/L-DNase II pathway. Here, we propose a modification in the TUNEL protocol consisting of a dephosphorylation step prior to the TUNEL labeling. This allows the detection of both types of DNA breaks induced during apoptosis caspase-dependent and independent pathways, avoiding underestimating the cell death induced by the treatment of interest.
Insights
This study modifies the TUNEL assay to detect DNA fragmentation in both caspase-dependent and independent apoptosis. The enhanced method includes a dephosphorylation step, improving cell death detection accuracy.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Apoptosis is vital for development and tissue maintenance, characterized by DNA fragmentation.
- Caspase-activated DNase (CAD) mediates DNA fragmentation in caspase-dependent apoptosis.
- The TUNEL assay detects 3'-OH DNA ends, common in caspase-dependent apoptosis.
Purpose of the Study:
- To address limitations of the TUNEL assay in detecting DNA fragmentation from all apoptotic pathways.
- To propose a modified TUNEL protocol for comprehensive apoptosis detection.
- To improve the accuracy of cell death assessment in various biological contexts.
Main Methods:
- Modification of the TUNEL (TdT-mediated dUTP-biotin nick end labeling) protocol.
- Inclusion of a dephosphorylation step before TUNEL labeling.
- Detection of both 3'-OH and 3'-P DNA termini generated during apoptosis.
Main Results:
- The modified TUNEL assay successfully detects DNA fragmentation in both caspase-dependent and independent apoptosis.
- The protocol overcomes the limitations of the standard TUNEL assay, which fails with 3'-P ends.
- This method prevents underestimation of cell death induced by certain treatments.
Conclusions:
- The modified TUNEL assay provides a more comprehensive tool for studying apoptosis.
- This approach enhances the reliability of cell death assessment in diverse research areas.
- Accurate detection of apoptosis is crucial for understanding development, disease, and drug toxicity.
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