Gtdap-1 promotes autophagy and is required for planarian remodeling during regeneration and starvation

Abstract

Remodeling is an integral component of tissue homeostasis and regeneration. In planarians, these processes occur constantly in a simple tractable model organism as part of the animal's normal life history. Here, we have studied the gene Gtdap-1, the planarian ortholog of human death-associated protein-1 or DAP-1. DAP-1, together with DAP-kinase, has been identified as a positive mediator of programmed cell death induced by ␥-IFN in HeLa cells. Although the function of DAP-kinase is well characterized, the role of DAP-1 has not been studied in detail. Our findings suggest that Gtdap-1 is involved in autophagy in planarians, and that autophagy plays an essential role in the remodeling of the organism that occurs during regeneration and starvation, providing the necessary energy and building blocks to the neoblasts for cell proliferation and differentiation. The gene functions at the interface between survival and cell death during stress-inducing processes like regeneration and starvation in sexual and asexual races of planarians. Our findings provide insights into the complex interconnections among cell proliferation, homeostasis, and cell death in planarians and perspectives for the understanding of neoblast stem cell dynamics.autophagy ͉ cell death ͉ planarian ͉ homeostasis neoblast

Gtdap-1and the Role of Autophagy During Planarian Regeneration and Starvation

“…Moreover, RNAi experiments with Gtdap-1 not only showed remodeling deficiencies, but also a decrease in both the proliferation rate of neoblasts and caspase-3 activity during regeneration. Finally, we succeeded in performing the first gain-of-function experiments in planarians, 12 based on the transgenesis technique set up in our lab. 2 Gain-of-function mutants of Gtdap-1 driven in the photoreceptor cells of the planarian induced cell death in those cells.…”

Autophagy meets planarians

“…The first important advance has been the development of whole-mount in situ hybridization techniques to analyze gene expression patterns 30 and the adaptation of such protocols to embryos, 31 fine sections, 32,33 dissociated cells 34 and ultra-fine sections for electron microscopy. 35,36 This technique has recently been further improved 37 and it has been adapted for use in commercially available liquid-handling robots, permitting high-throughput analysis of gene expression patterns. 38,39 Immunocytochemical techniques have also been routinely employed, taking advantage of the range of commercial antibodies that cross-react in planarians as well as the production of some specific antibodies.…”

“…49,50 In 2003, the first transgenic planarians were generated 51 and in 2007, the first gain-of-function phenotype became available. 35 However, transgenics using specific promoter regions are still being developed. The recently developed method for delivering external material into planarian embryos using nanosecond laser pulses has opened a very attractive possibility to improve the transgenesis technique.…”

Inhibition of LTA4H expression promotes Staphylococcus aureus elimination by planarians

“…In fact, it has been suggested that inhibition of the LTA4H expression by maresin-1 (MaR1) induced a faster regeneration of the planarian head [10]. In planarians, the autophagy process is required for tissue regeneration [11] and bacterial clearance [2]. The invalidation of the LTA4H gene could result in an increase in autophagy and a disruption of the tissue homeostasis equilibrium (controlled via autophagy), thereby leading to an increase in the elimination of the bacteria.…”

“…As suggested above, it would be interesting to evaluate the contribution of autophagy in the microbicidal mechanisms mediated by LTA4H in planarians. For that, it will be important to analyze the level of the autophagy in the LTA4H knock-down planarians, the expression level of autophagy markers, such as MORN2 [2], and the planarian homologue of Hs-dap-1 [11], and the level of apoptosis by tunnel assay. It will be also interesting to determine the cell population expressing LTA4H, as well as the co-expression of LTA4H and autophagy makers in planarians.…”