A novel beta-catenin homologue from the earthworm Eisenia andrei: Identification and characterization during embryonic development, segment regeneration, and immune response

Evolutionarily, Wnt/β-catenin signaling is well-conserved and supports several key cell-biological processes (e.g. adhesion and proliferation). Its crucial component, β-catenin, has been described in several organisms, however, its identification and characterization are notably lacking in annelid earthworms. Here, we report a novel β-catenin homologue from the earthworm Eisenia andrei, termed Ea-β-catenin. The full-length 3253 nt Ea-β-catenin mRNA includes an open reading frame of 2499 nt encoding a putative protein with 833 amino acid residues that comprise 11 classical armadillo-repeat regions. Phylogenetic analysis indicates that Ea-β-catenin shows strong homology with Lophotrochozoan β-catenins. Ubiquitous, but variable expressions of Ea-β-catenin were observed in distinct earthworm tissues. During embryogenesis, Ea-β-catenin mRNA gradually increased from the E1 to E4 developmental stages. Regeneration experiments revealed an inverse correlation between Ea-β-catenin mRNA levels and the rate of EdU⁺/PY489-β-catenin⁺ proliferating cells during the second week of the posterior blastema formation. In vitro exposures to poly(I:C) and zymosan significantly increased Ea-β-catenin mRNA levels, while small molecule Wnt-pathway modulators such as LiCl or iCRT14 increased or decreased Ea-β-catenin mRNA expression, and nuclear translocation of PY489-β-catenin, respectively. These novel results pave the way for follow-up studies aimed at characterizing additional members of the Wnt/β-catenin pathway that may be involved in embryonic and/or postembryonic development, as well as innate immunity in earthworms.