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Do all programmed cell deaths occur via apoptosis?
L M Schwartz1, S W Smith, M E Jones
1Department of Biology, University of Massachusetts, Amherst 01003.
Abstract:
During development, large numbers of cells die by a nonpathological process referred to as programmed cell death. In many tissues, dying cells display similar changes in morphology and chromosomal DNA organization, which has been termed apoptosis. Apoptosis is such a widely documented phenomenon that many authors have assumed all programmed cell deaths occur by this process. Two well-characterized model systems for programmed cell death are (i) the death of T cells during negative selection in the mouse thymus and (ii) the loss of intersegmental muscles of the moth Manduca sexta at the end of metamorphosis. In this report we compare the patterns of cell death displayed by T cells and the intersegmental muscles and find that they differ in terms of cell-surface morphology, nuclear ultrastructure, DNA fragmentation, and polyubiquitin gene expression. Unlike the T cells, which are known to die via apoptosis, we find that the intersegmental muscles display few of the features that characterize apoptosis. These data suggest that more than one cell death mechanism is used during development.
Insights
Programmed cell death, a natural developmental process, was investigated. Researchers found that while T cells undergo apoptosis, moth muscle cells exhibit distinct death patterns, suggesting multiple cell death mechanisms during development.
Area of Science:
- Developmental Biology
- Cell Biology
- Genetics
Background:
- Programmed cell death is crucial during development.
- Apoptosis is a well-documented form of programmed cell death.
- It is often assumed that all programmed cell deaths occur via apoptosis.
Purpose of the Study:
- To compare cell death patterns in two model systems: T cells and moth intersegmental muscles.
- To determine if both systems exhibit features of apoptosis.
- To investigate the diversity of programmed cell death mechanisms.
Main Methods:
- Comparative analysis of cell morphology and nuclear ultrastructure.
- Assessment of DNA fragmentation patterns.
- Examination of polyubiquitin gene expression.
Main Results:
- T cells displayed characteristic features of apoptosis.
- Intersegmental muscles showed significant differences from apoptotic cells.
- Distinct cell-surface morphology, nuclear ultrastructure, and DNA fragmentation were observed in moth muscles.
Conclusions:
- Programmed cell death is not exclusively mediated by apoptosis.
- The intersegmental muscles of Manduca sexta utilize a cell death mechanism distinct from apoptosis.
- Developmental processes may employ multiple, diverse cell death pathways.