Apaf-1-independent programmed cell death in mouse development

Abstract

Many cells die during mammalian development and are engulfed by macrophages. In DNase II À/À embryos, the TUNEL-positive DNA of apoptotic cells is left undigested in macrophages, providing a system for studying programmed cell death during mouse development. Here, we showed that an Apaf-1-null mutation in the DNase II À/À embryos greatly reduced the number of macrophages carrying DNA at E11.5. However, at later stages of the embryogenesis, a significant number of macrophages carrying undigested DNA were present in Apaf-1 À/À embryos, indicating that cells died and were engulfed in an Apaf-1-independent manner. In most tissues of the Apaf-1 À/À embryos, no processed caspase-3 was detected, and the DNA of dead cells accumulated in the macrophages appeared intact. Many nonapoptotic dead cells were found in the tail of the Apaf-1 À/À embryos, suggesting that the Apaf-1-independent programmed cell death occurred, and these dead cells were engulfed by macrophages. In contrast, active caspase-3 was detected in E14.5 thymus of Apaf-1 À/À embryos. Treatment of fetal thymocytes with staurosporine, but not etoposide, induced processing of procaspases 3 and 9, indicating that the E14.5 thymocytes have the ability to undergo caspase-dependent apoptosis in an Apaf-1-independent manner. Thus, programmed cell death in mouse development, which normally proceeds in an efficient Apaf-1-depenent mechanism, appears to be backed up by Apaf-1-independent death systems.

Coordinated and sequential activation of neutral and acidic DNases during interdigital cell death in the embryonic limb

“…Furthermore, analysis of ICD in Apaf1-deficient mice suggested the activation of a necrotic cell death mechanism in the absence of activation of caspase 9 [19,20]. Consistent with these findings, lysosomal markers are intensely up-regulated in the interdigital mesenchyme committed to die [18,21] and combined chemical inhibition of caspases and cathepsin D is followed by intense inhibition of the degenerative process [18].…”

“…The morphology of the dying cells in the areas of ICD corresponds largely with apoptosis [8,10], and DNA degradation occurs predominantly by internucleosomal fragmentation [7]. Furthermore, caspase 9 is active in the regressing interdigits [52] and interdigital dying cells are positive for active caspase 3 and 7 immunolabeling [16,20]. Together these findings gave an initial idea of ICD as a typical example of cell death mediated through the canonical caspase pathway.…”

“…Other neutral endonucleases are also involved in apoptotic processes, such as the Granzyme A-activated DNase (GAAD) or the endonuclease G (see [25]). In contrast to neutral endonucleases, acidic cytoplasmic endonucleases are major effectors of necrotic processes while in physiological cell death they are thought to be responsible for the degradation of the DNA of the apoptotic cells engulfed by macrophages [20,[26][27][28]. Taking into account that both caspases and lysosomal cathepsins appear to contribute to cell death during ICD, in this work we have chosen to study the endonucleases to gain insights into the molecular mechanisms underlying this physiological degenerative process.…”

Apoptotic and Nonapoptotic Caspase Functions in Animal Development

“…These results indicate that caspase-mediated apoptosis is dispensable, or that an alternative cell-death mechanism removes cells when the apoptotic machinery is inhibited. In fact, nonapoptotic cell death is observed in the interdigital region and other areas in apaf-1 mutant mice (Chautan et al 1999;Cande et al 2002;Nagasaka et al 2010). However, the caspase functions in mammalian morphogenetic processes remain to be studied in detail.…”

Comparison of the effects of resistance modifiers on prostate cancer, mouse lymphoma and colon cancer cells

“…Apoptosis is characterized by cell membrane blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation [105,106]. There are two basic apoptotic signaling pathways: the extrinsic pathway and the intrinsic pathway [107].…”