The role of DNase II in germline apoptosis and innate immunity in C. elegans
| Autor: | Hsiang Yu, 余祥 |
|---|---|
| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 DNase II is an acidic enzyme, which mediates the apoptotic DNA degradation in engulfing cell (non-autonomous). In the mammal, the action of DNase II belongs to non-autonomous manner. However, the NUC-1 DNase II functions within the dying cells (autonomous) have been reported in Caenorhabditis elegans. Recent studies show that the DNA fragment escape from DNase II digestion would trigger the innate immune response in many model organisms. In C. elegans, UV-induced DNA fragment accumulation in the gonad activates innate immunity responses by ERK signaling pathway. However, whether the C. elegans DNase II (NUC-1, CRN-6 and CRN-7) play a role in the regulation of innate immune response is currently unknown. Furthermore, which DNase II acts in the germ cell apoptosis remains undetermined. Here, we report a method of ToLFP (topoisomerase ligation fluorescence probes) for directly visualizing DNA fragments generated by DNase II in C. elegans embryos. ToLFP analysis provided the first demonstration of a cell autonomous mode of DNase II activity in dying cells in ced-1 embryos, which are defective in engulfing apoptotic bodies. By using nuc-1-rescuing transgenic worms, ToLFP analyses revealed that anteriorly expressed NUC-1 digests apoptotic DNA in posterior blastomeres in a non-autonomous and secretion-dependent manner. Both in vitro and in vivo assays on various mutant worms demonstrated that NUC-1 and CRN-7 function in germ cell apoptosis. Moreover, results showed that loss of NUC-1 and CRN-7 led to up-regulation of antimicrobial genes (abf-2, spp-1, nlp-29, cnc-2, and lys-7). These observations suggest that an incomplete digestion of DNA fragments resulting from the absence of NUC-1 or CRN-7 in the gonad could induce the ERK signaling, consequently to activate antimicrobial gene expression. Taken together, this work demonstrates that the ToLFP method can be used to differentiate the locations of blastomeres where DNase II acts autonomously or non-autonomously in degrading apoptotic DNA. Furthermore, this is the first study to demonstrate that nuc-1 and crn-7 play a role in degrading apoptotic DNA in distinct sites of gonad, and act as negative regulators of innate immunity in C. elegans. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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