A morphological and immunohistochemical study of programmed cell death in Botryllus schlosseri (Tunicata, Ascidiacea)

The blastogenic cycle of the colonial ascidian Botryllus schlosseri concludes in a phase of selective cell and zooid death called takeover. Every week, all asexually derived parental zooids synchronously regress over a 30-h period and are replaced by a new generation. Here we document the sequential...

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Bibliographic Details
Published in:Cell and tissue research 1993-04, Vol.272 (1), p.115-127
Main Authors: LAUZON, R. J, PATTON, C. W, WEISSMAN, I. L
Format: Article
Language:English
Subjects:
Animals
Apoptosis - physiology
Biological and medical sciences
Blotting, Western
Fluorescent Antibody Technique
Fundamental and applied biological sciences. Psychology
Immunohistochemistry
Intestines - cytology
Intestines - ultrastructure
Invertebrates
Less representative or incertae sedis groups: acanthocephala, chaetognatha, gnathostomulida, lophophoria, merostomata, mesozoa, myxozoa, nematorhyncha, pararthropoda, placozoa, priapuloidea, prochordata, pycnogonida, rotifera
Macrophages - cytology
Macrophages - physiology
Organelles - ultrastructure
Phagocytosis - physiology
Stomach - cytology
Stomach - ultrastructure
Ubiquitins - analysis
Urochordata - cytology
Urochordata - physiology
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Summary:The blastogenic cycle of the colonial ascidian Botryllus schlosseri concludes in a phase of selective cell and zooid death called takeover. Every week, all asexually derived parental zooids synchronously regress over a 30-h period and are replaced by a new generation. Here we document the sequential ultrastructural changes which accompany cell death during zooid degeneration. The principal mode of visceral cell death during takeover occurred by apoptosis, the majority of cells condensing and fragmenting into multiple membrane-bounded apoptotic bodies. Cytoplasmic organelles (mitochondria, basal bodies, striated rootlets) within apoptotic bodies retained ultrastructural integrity. Dying cells and fragments were then swiftly ingested by specialized blood macrophages or intraepithelial phagocytes and subsequently underwent secondary necrotic lysis. Certain organs (stomach, intestine) displayed a combination of necrotic and apoptotic changes. Lastly, the stomach, which demonstrated some of the earliest regressive changes, exhibited intense cytoplasmic immunostaining with a monoclonal antibody to ubiquitin at the onset of takeover. Affinity-purified rabbit antiserum against sodium dodecyl sulfate-denatured ubiquitin detected a characteristic 8.6-kDa mono-ubiquitin band by Western blot analysis. Collectively, these findings raise the possibility that cell death during takeover is a dynamic process which requires active participation of cells in their own destruction.
ISSN:0302-766X
1432-0878
DOI:10.1007/bf00323577