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

Abstract

Regeneration requires that the identities of new cells are properly specified to replace missing tissues. The Wnt signaling pathway serves a central role in specifying posterior cell fates during planarian regeneration. We identified a gene encoding a homolog of the Teashirt family of zinc-finger proteins in the planarian Schmidtea mediterranea to be a target of Wnt signaling in intact animals and at posterior-facing wounds. Inhibition of Smed-teashirt (teashirt) by RNA interference (RNAi) resulted in the regeneration of heads in place of tails, a phenotype previously observed with RNAi of the Wnt pathway genes β-catenin-1, wnt1, Dvl-1/2 or wntless. teashirt was required for β-catenin-1-dependent activation of posterior genes during regeneration. These findings identify teashirt as a transcriptional target of Wnt signaling required for Wnt-mediated specification of posterior blastemas.

Wnt/Notum spatial feedback inhibition controls neoblast differentiation to regulate reversible growth of the planarian brain

“…RNAi of beta-catenin-1 [at a time of regeneration prior to bodywide formation of ectopic anterior central nervous system structures (Gurley et al, 2008;Iglesias et al, 2008;Petersen and Reddien, 2008)] caused a decrease in brain size in heads regenerated from anterior-facing wounds (Fig. 4C), opposite to the wnt11-6 RNAi phenotype and consistent with previous findings (Owen et al, 2015). wnt11-6(RNAi);beta-catenin-1(RNAi) animals had large brains similar to wnt11-6 inhibition alone (Fig.…”

Localization of planarian β-CATENIN-1 reveals multiple roles during anterior-posterior regeneration and organogenesis

“…As in intact animals, β-CATENIN-1 is active both ventrally, where the brain primordium forms, and dorsally, in anterior regenerating blastemas. In accordance with this complex pattern of activity, our findings show that β-catenin-1 is required to regenerate a normal sized brain, with the correct number of neural cell populations, as well as a normal head sensory margin (Hill and Petersen, 2015;Owen et al, 2015). Importantly, the midline ventral furrow and notum expression in the anterior midline also disappears in β-catenin-1 (RNAi) animals, which suggest a problem in anterior tip patterning and the establishment of the anterior organizing region.…”

“…notum and sFRP) localize to the anterior pole, and their inhibition leads to anteriorized or posteriorized phenotypes, respectively (Adell et al, 2009;Gurley et al, 2010;Lander and Petersen, 2016;Reddien, 2009b, 2011;Scimone et al, 2016;Sureda-Gómez et al, 2015). Interestingly, recent reports have suggested that β-catenin-1 exerts additional roles in eye and brain patterning (Hill and Petersen, 2015;Owen et al, 2015), which is consistent with the ubiquitous mRNA expression of β-catenin-1 (Gurley et al, 2008;Iglesias et al, 2008;Petersen and Reddien, 2008). To date, however, no studies have described the localization of β-CATENIN-1 protein either as an AP gradient or in specific developing tissues.…”

“…2015; Iglesias et al, 2011;Owen et al, 2015). In this respect, β-CATENIN-1 localizes abundantly to the head region, both in the cephalic ganglia and in the mesenchymal cells (Figs 1, 3 and 4).…”

“…Similarly, the number of mechanosensory cells (cintillo + ) in the head margin was also significantly reduced after β-catenin-1(RNAi) (Fig. S7B) (Hill and Petersen, 2015;Owen et al, 2015). Quantification of the brain area by DAPI staining and analysis of the distance from the anterior tip of the brain to the anterior tip of the head revealed that the brain ganglia in β-catenin-1 (RNAi) animals were smaller and formed closer to the head margins than in control planarians (Fig.…”