Abstract
BackgroundThe planarian Schmidtea mediterranea and the cnidarian Hydra vulgaris have emerged as valuable model organisms in regeneration and stem cell research because of their prominent ability to regenerate a complete organism from any small body fragment. Under natural conditions wounding may result from predator attacks. These injuries open their innermost to a wide array of microbes present in the environment. Therefore, we established the hypothesis that regeneration processes may be linked to or at least accompanied by innate immune responses. In order to screen for septic wounding inducible genes we dissected individuals using a scalpel in the presence of a crude bacterial lipopolysaccharide preparation that is commonly used to elicit innate immune responses in animals and applied the suppression subtractive hybridization technique that selectively amplifies cDNAs of differentially expressed genes.ResultsThis analysis revealed the induced expression of 27 genes in immune challenged Schmidtea and 35 genes in immune challenged Hydra. Identified genes from both animals encode proteins that share sequence similarities with potential homologues from other organisms known to be involved in signaling (e.g. calreticulin in Schmidtea and major vault protein in Hydra), stress responses (e.g. Hsp20 in Schmidtea and a PRP19/PSO4 DNA repair protein in Hydra), or to represent potential antimicrobial effectors (e.g. perforin-like protein in Schmidtea and PR-1-like protein and neutrophil cytosolic factor 1 in Hydra). As expected, septic wounding also induces expression of genes in Schmidtea and Hydra potentially involved in tissue remodeling associated with regeneration processes (e.g. matrix metalloproteinase in Schmidtea and a potential von Willebrand factor in Hydra).ConclusionWe identified numerous immune-inducible genes in Hydra and Schmidtea that show a similar distribution corresponding to their physiological roles, although lineages of both animals split from their common ancestor for more than five hundred millions of years. The present study is the first analysis of immune-inducible genes of these two phylogenetically distant model organisms of regeneration and provide numerous candidate genes that we can use as a starting point for comparative examination of interrelationships between immunity and homeostasis.
Highlights
The planarian Schmidtea mediterranea and the cnidarian Hydra vulgaris have emerged as valuable model organisms in regeneration and stem cell research because of their prominent ability to regenerate a complete organism from any small body fragment
Subtracted cDNA libraries of immune challenged S. mediterranea and H. vulgaris A subtracted cDNA library enriched in immune-inducible genes from S. mediterranea and H. vulgaris, respectively, was constructed by using the suppression subtractive hybridization (SSH) method
We report a comparative analysis of immune-inducible genes in two phylogenetically distant model organisms of regeneration and stem cell research
Summary
The planarian Schmidtea mediterranea and the cnidarian Hydra vulgaris have emerged as valuable model organisms in regeneration and stem cell research because of their prominent ability to regenerate a complete organism from any small body fragment. The ability to replace lost or injured body parts is widely distributed among animals, whereas regeneration of a complete organism from any small body fragment is restricted to only few animal phyla and is accompanied by the ability to reproduce asexually by budding or fission [1,2] These features have been attributed to a stable population of stem cells known as neoblasts in Schmidtea mediterranea [3,4] and to both stem cellbased mechanisms and transdifferentiation in Hydra vulgaris [5,6]. These two phylogenetically distant animals with remarkable regeneration capacities attract renewed attention as powerful model organisms since both, S. mediterranea and H. vulgaris, are amenable to systemic RNAi mediated gene silencing and other genetic tools for functional gene analyses [7,8,9,10,11] In their habitats Hydra and Schmidtea may be wounded by attacks from predators. Further reasons that make Hydra and Schmidtea amenable to comparative approach analyses are that both share similar body sizes and colonize freshwater habitats allowing comparable experimental conditions
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