PBX/extradenticle is required to re-establish axial structures and polarity during planarian regeneration

Abstract

SUMMARYRecent advances in a number of systems suggest many genes involved in orchestrating regeneration are redeployed from similar processes in development, with others being novel to the regeneration process in particular lineages. Of particular importance will be understanding the architecture of regenerative genetic regulatory networks and whether they are conserved across broad phylogenetic distances. Here, we describe the role of the conserved TALE class protein PBX/Extradenticle in planarians, a representative member of the Lophotrocozoa. PBX/Extradenticle proteins play central roles in both embryonic and post-embryonic developmental patterning in both vertebrates and insects, and we demonstrate a broad requirement during planarian regeneration. We observe that Smed-pbx has pleiotropic functions during regeneration, with a primary role in patterning the anterior-posterior (AP) axis and AP polarity. Smed-pbx is required for expression of polarity determinants notum and wnt1 and for correct patterning of the structures polarized along the AP axis, such as the brain, pharynx and gut. Overall, our data suggest that Smed-pbx functions as a central integrator of positional information to drive patterning of regeneration along the body axis.

teashirt is required for head-versus-tail regeneration polarity in planarians

“…Anterior and posterior poles are small clusters of cells at the head and tail tip, respectively, and are required for normal planarian head and tail regeneration and PCG expression (Felix and Aboobaker, 2010;Hayashi et al, 2011;Blassberg et al, 2013;Chen et al, 2013;Scimone et al, 2014b;Vásquez-Doorman and Petersen, 2014;Vogg et al, 2014). However, in contrast to teashirt RNAi, inhibition of either anterior or posterior pole formation does not cause a reversal of the head-tail regeneration choice.…”

Genome-wide analysis of the bHLH gene family in planarians identifies factors required for adult neurogenesis and neuronal regeneration

“…We performed combinatorial RNAi experiments using ndk, which has been successfully used to investigate the role of other genes in planarian body patterning and CNS regeneration (Felix and Aboobaker, 2010;Iglesias et al, 2011;Blassberg et al, 2013), and screened 15 genes (ascl-1, ascl-2, atoh, atoh8-1, coe, da, hesl-1, -2, -3, hlh, id4, neuroD-1, neuroD-2, sim and usf) by inspecting bHLH;ndk(RNAi) animals for changes in gpas and npp-4 expression. Induction of gpas expression posterior to the cephalic ganglia was not suppressed by inhibiting any of the bHLH genes together with ndk.…”

JNK Signaling is necessary for a Wnt and stem cell dependent regeneration program

“…It has previously been demonstrated that beta-catenin1(RNAi) leads to anterior structures regenerating at all wounds and, when used in double-RNAi experiments, has proven to be a useful test of epistastic relationships and pleiotropic roles during planarian regeneration (Blassberg et al, 2013;Felix and Aboobaker, 2010;Gurley et al, 2008;Iglesias et al, 2008;Petersen and Reddien, 2008). In contrast to junl-1/gfp(RNAi) animals, which were all tailless, beta-catenin1/junl-1(RNAi) animals were able to regenerate anterior structures at posterior-facing wounds to a similar extent as beta-catenin1/gfp(RNAi) worms (supplementary material Fig.…”

“…This early wnt1 expression is required for stem cells at the posterior wound site to differentiate to form a Wnt gene-expressing pole in the regenerating blastema (Petersen and Reddien, 2009b). Active Hh signalling is required for early wound-induced Wnt gene expression and a number of other genes have now been shown to be required for the formation of the stem cell-dependent phase of later Wnt gene expression (Blassberg et al, 2013;Chen et al, 2013;Currie and Pearson, 2013;Hayashi et al, 2011;Marz et al, 2013;Rink et al, 2009;Yazawa et al, 2009). In junl-1(RNAi) worms, the early phase of wound-induced wnt1 expression was not affected and was equivalent to that observed for control animals at both anterior and posterior wounds ( Fig.…”

“…In particular, Smed-islet (Hayashi et al, 2011), Smed-pitx (Currie and Pearson, 2013;Marz et al, 2013) and Smed-pbx (Blassberg et al, 2013;Chen et al, 2013) have all been shown to be required for correct posterior regeneration. In all cases these genes are necessary for the stem celldependent phase of wnt1 expression and the subsequent activation of Smed-wnt11-2 and Smed-wnt11-5.…”