Cell and Tissue Research

, Volume 272, Issue 1, pp 115–127

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

  • Robert J. Lauzon
  • Chris W. Patton
  • Irving L. Weissman
Article

Abstract

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.

Key words

Apoptosis Necrosis Programmed cell death Macrophages Ubiquitin Botryllus schlosseri (Tunicata) 

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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Robert J. Lauzon
    • 1
    • 2
  • Chris W. Patton
    • 3
  • Irving L. Weissman
    • 4
  1. 1.Department of PediatricsAlbany Medical CollegeAlbanyUSA
  2. 2.Department of Microbiology, Immunology and Molecular GeneticsAlbany Medical CollegeAlbanyUSA
  3. 3.Hopkins Marine Station of Stanford UniversityPacific GroveUSA
  4. 4.Department of Pathology and Developmental Biology, Howard Hughes Medical Institute, Beckman Research CenterStanford University Medical CenterStanfordUSA

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