Apoptosis of tail muscle during amphibian metamorphosis involves a caspase 9‐dependent mechanism

• Published in: Developmental dynamics 2005-05, Vol.233 (1), p.76-87
• Main Authors: Rowe, Isaline, Le Blay, Karine, Du Pasquier, David, Palmier, Karima, Levi, Giovanni, Demeneix, Barbara, Coen, Laurent
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Apoptosis; Apoptosis - genetics; Apoptosis - physiology; apoptosome; bcl-2-Associated X Protein; Caspase 9; Caspases; Caspases - genetics; Caspases - physiology; Development Biology; Gene Transfer Techniques; Larva; Larva - growth & development; Life Sciences; metamorphosis; mitochondrial apoptotic pathway; Molecular Sequence Data; muscle cell death; Muscle, Skeletal; Muscle, Skeletal - physiology; Mutation; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-bcl-2 - metabolism; Recombinant Fusion Proteins; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Research Support, Non-U.S. Gov't; Sequence Alignment; Tail - physiology; Xenopus
• ISSN: 1058-8388; 1097-0177
• DOI: 10.1002/dvdy.20312

The climax of amphibian metamorphosis is marked by thyroid hormone‐dependent tadpole tail resorption, implicating apoptosis of multiple cell types, including epidermal cells, fibroblasts, nerve cells, and muscles. The molecular cascades leading to and coordinating the death of different cell types are not fully elucidated. It is known that the mitochondrial pathway, and in particular the Bax and XR11 genes, regulates the balance between apoptosis and survival in muscle. However, the down‐stream factors modulated by changes in mitochondrial permeability have not been studied in a functional context. To investigate further the mitochondrial‐dependent pathway, we analyzed the regulation and the role of caspase 9 in Xenopus tadpoles. We report that caspase 9 mRNA is expressed in the tail before metamorphosis and increases before and during climax. Similarly, at the protein level, the production of active forms of caspase 9 increases in muscle tissue as metamorphosis progresses. To assess the functional role of caspase 9, we designed a dominant‐negative protein. Overexpression of this dominant‐negative abrogates both Bax‐induced cell death in vitro and muscle apoptosis in vivo during natural metamorphosis. These findings consolidate a model of metamorphic muscle death that directly implicates the mitochondrial pathway and the apoptosome. Developmental Dynamics 233:76–87, 2005. © 2005 Wiley‐Liss, Inc.