Document Detail

Programmed cell death in the ascidian embryo: modulation by FoxA5 and Manx and roles in the evolution of larval development.
MedLine Citation:
PMID:  12351175     Owner:  NLM     Status:  MEDLINE    
Programmed cell death (PCD) has been discounted in the ascidian embryo because the descendants of every embryonic cell appear to be present in the tadpole larva. Here we show that apoptotic PCD is initiated in the epidermis and central nervous system (CNS) but not in the endoderm, mesenchyme, muscle, and notochord cells during embryogenesis in molgulid ascidians. However, the affected cells do not actually die until the beginning of metamorphosis. Although specific patterns of PCD were different in distantly related ascidian species, the results suggest that removal of CNS cells by apoptosis is a urchordate feature predating the origin of the vertebrates. Certain molgulid ascidian species have evolved an anural (tailless) larva in which notochord cells fail to undergo the morphogenetic movements culminating in tail development. These anural species include Molgula occulta, the sister species of the urodele (tailed) species Molgula oculata. We show that PCD in the notochord cell lineage precedes the arrest of tail development in M. occulta and other independently evolved anural species. The notochord cells are rescued from PCD and a tail develops in hybrid embryos produced by fertilizing M. occulta eggs with M. oculata sperm, implying that apoptosis is controlled zygotically. Antisense inhibition experiments show that zygotic expression of the FoxA5 and Manx genes is required to prevent notochord PCD in urodele species and hybrids with restored tails. The results provide the first indication of PCD in the ascidian embryo and suggest that apoptosis modulated by FoxA5 and Manx is involved in notochord and tail regression during anural development. Differences in PCD that occur between ascidian species suggest that diversity in programming apoptosis may explain differences in larval form.
William R Jeffery
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Mechanisms of development     Volume:  118     ISSN:  0925-4773     ISO Abbreviation:  Mech. Dev.     Publication Date:  2002 Oct 
Date Detail:
Created Date:  2002-09-27     Completed Date:  2003-05-29     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9101218     Medline TA:  Mech Dev     Country:  Ireland    
Other Details:
Languages:  eng     Pagination:  111-24     Citation Subset:  IM    
Department of Biology, University of Maryland, College Park, MD 20742-4415, USA.
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MeSH Terms
Bacterial Outer Membrane Proteins / metabolism
Caspases / metabolism
Cell Death
Cell Division
Cell Lineage
Cell Nucleus / metabolism
DNA / metabolism
Enzyme Activation
In Situ Nick-End Labeling
Microscopy, Fluorescence
Notochord / metabolism
Oligonucleotides, Antisense / pharmacology
Spermatozoa / metabolism
Transcription Factors / genetics*,  physiology
Grant Support
Reg. No./Substance:
0/Bacterial Outer Membrane Proteins; 0/Manx protein, Molgula oculata; 0/Oligonucleotides, Antisense; 0/Transcription Factors; 9007-49-2/DNA; EC 3.4.22.-/Caspases

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