Expression of Wnt and TGF-Beta Pathway Components during Whole-Body Regeneration from Cell Aggregates in Demosponge Halisarca dujardinii.

Ilya Borisenko,Alexander Ereskovsky,Fyodor V Bolshakov,Andrey I Lavrov

doi:10.3390/genes12060944

Abstract

The phenomenon of whole-body regeneration means rebuilding of the whole body of an animal from a small fragment or even a group of cells. In this process, the old axial relationships are often lost, and new ones are established. An amazing model for studying this process is sponges, some of which are able to regenerate into a definitive organism after dissociation into cells. We hypothesized that during the development of cell aggregates, primmorphs, new axes are established due to the activation of the Wnt and TGF-beta signaling pathways. Using in silico analysis, RNA-seq, and whole-mount in situ hybridization, we identified the participants in these signaling pathways and determined the spatiotemporal changes in their expression in demosponge Halisarca dujardinii. It was shown that Wnt and TGF-beta ligands are differentially expressed during primmorph development, and transcripts of several genes are localized at the poles of primmorphs, in the form of a gradient. We suppose that the Wnt and TGF-beta signaling cascades are involved in the initial axial patterning of the sponge body, which develops from cells after dissociation.

Highlights

Signaling pathways Wnt and TGF-beta are involved in the formation of axes in multicellular animals: they provide axial patterning in developing embryos and support it in adult animals
In the absence of a signal (OFF state), the pool of the beta-catenin is constantly degraded due to the beta-catenin destruction complex in the cytoplasm of a competent cell (Figure 1a). bCDC, consisting of the core proteins Axin and APC, glycogen synthase kinase-3 beta (GSK3b), and casein kinase 1 (CK1), phosphorylates cytoplasmic beta-catenin, which leads to its ubiquitin-dependent degradation in proteasomes
We studied the expression of the identified genes at two time points during cell reaggregation of H. dujardinii, at stages of early-stage primmorphs (ESPs)/true primmorphs (TPs), 1 day post dissociation, and developing primmorphs (DPs), 6 dpd, using RNA-seq technology

Summary

Introduction

Signaling pathways Wnt and TGF-beta are involved in the formation of axes in multicellular animals: they provide axial patterning in developing embryos and support it in adult animals. Sponges (Porifera) occupy a key position at the base of the phylogenetic tree of animals With this in mind, they are essential for understanding the origin and evolution of multicellular body patterning. Sponges have genes of the Wnt and TGF-beta pathways, and these genes are even involved in establishing axes in embryo and adult bodies. Ligands of both pathways have dynamic expression patterns during embryonic development and in the larva of Amphimedon queenslandica and Sycon ciliatum. In the adult S. ciliatum, the expression of several Wnt and TGF-beta is confined to the osculum and the entrances of the radial choanocyte chambers, i.e., axial structures [7,8,9]

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Discussion

Conclusion