Autonomous regulation of muscle fibre fate during metamorphosis in Xenopus tropicalis.
A key event in metamorphosis of anuran amphibians is tail resorption. This composite structure includes epidermal cells, spinal cord, muscle fibres and connective tissue. It is unclear how resorption proceeds and to what extent the signals for the death process are transmitted between cells. We determined the kinetics of metamorphosis, apoptosis, and tail regression in the diploid anuran, Xenopus tropicalis, a species more suited to genetic analysis than the pseudotetraploid, Xenopus laevis. Metamorphosis was found to proceed at a regular and predictable rate in X. tropicalis but not in X. laevis. Caspase 3 activity and mRNA levels were correlated with TdT-mediated dUTP nick end-labeling (TUNEL) signalling and most markedly increased in tail muscle and spinal cord. It has been proposed that muscles die as a result of loss of connectivity with the surrounding matrix. To test this hypothesis, we used direct DNA injection in trunk and tail muscle to overexpress Xenopus Bcl-X(L) (xR11), an anti-apoptotic gene, along with a marker gene (luciferase or GFP). xR11 significantly inhibited the cell death process in both trunk and tail muscle. This protection was functional even up to stage 64 on completion of tail regression. We conclude that (1) somatic gene transfer can be applied to analyse cell fate in X. tropicalis, and (2) that muscle death can be abrogated despite extracellular matrix loss.
Laboratoire de Physiologie Générale et Comparée, Muséum National d'Histoire Naturelle, UMR CNRS 8572, Paris, France.
Isaline
I
Rowe
Laurent
L
Coen
Karine
K
Le Blay
Sébastien
S
Le Mével
Barbara A
BA
Demeneix
D000165:Acridine Orange / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D018014:Gene Transfer Techniques; D049452:Green Fluorescent Proteins; D020287:In Situ Nick-End Labeling; D008164:Luminescent Proteins / Q000378:metabolism; D008675:Metamorphosis, Biological / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D013623:Tail / Q000254:growth & development / Q000502:physiology; D014158:Transcription, Genetic; D014981:Xenopus / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism
D005456:Fluorescent Dyes; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; D049452:Green Fluorescent Proteins; D053148:Caspase 3; D020169:Caspases; D000165:Acridine Orange