No abstract

Organ regeneration is a rare phenomenon in higher vertebrates. However, members of closely related groups such as echinoderms have striking regeneration capacities. In studies of intestinal regeneration using the sea cucumber Holothuria glaberrima, recent results have shown the involvement of the Wnt signaling pathway. One important component in this intracellular cascade is β‐catenin, that, depending on its phosphorylation state, activates transcription of Wnt target genes. In one case, phosphorylation of the tyrosine residue 489 (Y489) increases transcriptional activity of the β‐catenin/Tcf complex. To determine if Y489‐β‐catenin phosphorylation is involved in intestinal regeneration, normal and regenerating intestines of H. glaberrima specimens were dissected at different post‐evisceration stages. Tissues were processed for immunohistochemistry using anti‐PY489‐β‐catenin antibody and assessed by counting the temporal and spatial appearance of labeled cells in the distal, medial and proximal ends of the mesentery and gut rudiment. In normal non‐eviscerated animals, the antibody labeled about the 14% of cells in the coelomic lining and 31.2% of cells in the luminal epithelium. In regenerating specimens, PY489‐β‐catenin was expressed at all stages of regeneration from 3‐dpe up to 14‐dpe, with a peak increment of 40.6% of cells labeled in the mesothelium of the 7‐dpe intestinal rudiment. To determine the role of activating or inhibiting the WNT/β‐catenin pathway on the expression of the PY489 labeling, we treated tissue explants with the Wnt pathway activator LiCl and inhibitor iCRT14. When compared to controls there was no significant difference in the number of PY489‐β‐catenin immunoreactive cells observed in the LiCl‐treated explants, while there was a significant increase in immunoreactive cells in the iCRT14‐treated explants. Our results suggest that the Wnt/β‐catenin signaling is activated during intestinal regeneration in H. glaberrima and that phosphorylation in the Y489 residue of β‐catenin is important for the Wnt role in intestinal regeneration. In particular, the results suggest a possible role for Wnt pathway in the dedifferentiation status of the mesothelium once the initial intestinal blastema is formed. Our study might provide the basis for the role of the Wnt signaling pathway during organogenesis in holothurians and thus provide a better understanding of general regenerative processes.Support or Funding InformationFunded by NIH R15NS081686, NSF IOS‐1252679 and the University of Puerto Rico.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.