atypical apoptosis
ZBIGNIEW DARZYNKIEWICZ (darzynk@nymc.edu)
Fri, 19 Jan 1996 09:12:20 -0500
Dr. KuKuruga raised an important, and difficult to respond, question
regarding identification of apoptotic cells.
Apoptosis, especially of non-hematopoietic cell types, can have many
atypical features which make its identification difficult if not
sometimes, impossible. I have a large file of the reprints on
atypical apoptosis, in which the authors describe all possible
variations: lack of the internucleosomal DNA cleavage, lack of
nuclear fragmentation, necrosis which is accompanied by
internucleosomal DNA cleavage, etc. Even morphology is not always
conclusive in identification of the mode of cell death.
Atypical apoptosis may take place when one or more pathways of the
apoptotic cascade are blocked while other pathways not (e.g.
proteolytic cascade is needed for breakdown of the nuclear envelope
and nuclear fragmentation, endonucleolytic cascade for DNA cleavage;
the latter may stop at the 50-300 kb DNA cleavage step etc.). Some
drugs (e.g. protein kinase inhibitors, protease inhibitors) affect
particular pathways resulting in atypical apoptosis.
Cell morphology, in doubtful cases electron microscopy, should be
deciding in diagnosing apoptosis. The morphology of sorted cells is
generally poor. We always prepare cytospins of the unfixed cells
(which then are fixed in formaldehyde followed by ethanol, stained
with DAPI/sulforhodamine 101 and subjected to UV microscopy) of the
samples parallel to these which are analyzed by flow cytometry.
It may be worthwile, in doubtful cases, to run two or three assays in
parallel, for example analysing integrity of cell membrane (PI
excusion, supravital Hoechst staining or annexin V), DNA cleavage
(gels, TUNEL) and/or functional tests such as mitochondrial ability
to retain Rh123, esterase activity).
Zbigniew Darzynkiewicz
CD ROM Vol 2 was produced by staff at the Purdue University Cytometry Laboratories
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If you have any comments please direct them to Dr. J. Paul Robinson, Professor & Director, PUCL,
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