Its loss results selleck chemicals llc in a deregulation of planarian growth leading to lethal ectopic outgrowths as the stem cell response to injury runs out of control. We also identify the central components of mTOR signalling, arguably the nexus for signals controlling growth across animals and show that the mTORC1 complex is necessary for blastema formation and growth. We find that the novel physiological function for SMG-1 acts antagonistically with mTORC1 signalling. Our findings have broad implications for understanding regeneration, growth and cancer. Results Smed-smg-1 restricts the injury response and blastema growth by regulating neoblast proliferation In an RNAi screen attempting to identify novel signals that regulate correct growth in Schmidtea mediterranea we identified a gene with high identity to human SMG-1 (hSMG-1, suppressor with morphogenetic effect on genitalia).

Phylogenetic and conserved domains analyses supported the hypothesis that this gene is a homolog of hSMG-1 leading us to call it Smed-smg-1 (Figure 1A, Figures S1 and S2; GenBank Accession Number “type”:”entrez-nucleotide”,”attrs”:”text”:”JF894292″,”term_id”:”385139922″,”term_text”:”JF894292″JF894292). We found that Smed-smg-1 is very broadly expressed through all planarian tissues, including neoblasts (Figure 1B and 1C). SMG-1 is the most recently described member of the phosphoinositide 3-kinase-related kinase family (PIKKs) [13], [14]. An SMG-1 homolog in C. elegans has been described as having a role in the RNA surveillance nonsense-mediated mRNA decay (NMD) pathway [15]. SMG-1 loss also results in lifespan extension in C.

elegans, through an activity unrelated to its role in NMD [16]. Like other PIKKs, hSMG-1 is implicated Cilengitide in genome surveillance in human cells responding to stress. For example hSMG-1 is activated by DNA damage [17], during tumour necrosis factor-��-induced stress [18], cell cycle checkpoint signalling under oxidative stress [19] and negatively regulates HIF-1�� activity in hypoxia [20]. Despite the fact that hSMG-1-depleted human cells display an increased level of spontaneous DNA damage [17] the physiological roles of SMG-1 in the absence of genotoxic stress have not been further studied. Figure 1 Smed-smg-1 is a bona fide SMG-1 and is broadly expressed in the whole planarian body. Planarians were injected with Smed-smg-1 dsRNA and amputated in order to observe regeneration (Figure 2A). gfp dsRNA, a sequence not present in S. mediterranea genome, was used as control for all RNAi experiments. Smed-smg-1(RNAi) induced regeneration phenotypes became apparent in live animals from 7 days of regeneration (7 dR) when blastemas displayed minimal differentiation (n=121/121) compared to controls (Figure S3).