Mesentery AjFGF4–AjFGFR2–ERK pathway modulates intestinal regeneration via targeting cell cycle in echinoderms

Abstract

Objectives:The purpose of the study aims to understand the regeneration process and its cytology mechanism in economic echinoderms. Materials and Methods:The intestine regeneration process of Apostichopus japonicus was investigated by immunohistochemistry and the cell proliferation was detected by immunofluorescence and flow cytometry. Fibroblast growth factor 4 of A. japonicus (AjFGF4) was screened by RNA-seq analysis and validated to regulate cell proliferation by siAjFGF4 and recombinant-AjFGF4 treatment. The binding and co-localization of AjFGF4 and AjFGFR2 were verified by Co-IP, GST-pull down, and immunofluorescence. Then, the AjFGF4-AjFGFR2-ERK-cell cycle axis was examined by western blot, immunofluorescence, and flow cytometry techniques. Results:The mesentery was served as the epicenter of intestinal regeneration via activating cell proliferation and other cellular events. Mechanically, AjFGF4mediated cell proliferation was dependent on the binding to its receptor AjFGFR2, and then triggered the conserved ERK-MAPK pathway but not JNK and p38 pathway. The activated ERK-MAPK subsequently mediated the expression of cell cycle regulatory proteins of CDK2, Cyclin A, and Cyclin B to promote cell proliferation. Conclusions:We provide the first functional evidence that AjFGF4-AjFGFR2-ERKcell cycle axis mediated cell proliferation was the engine for mesentery-derived intestine regeneration in echinoderms. | INTRODUCTIONDamage to organs or tissues by infection, trauma, aging, diseases, congenital defects, and other injuries causes organ malfunction and is lifethreatening under serious conditions. 1 To maintain, improve, and restore organ functions after injury, one of the most exciting current biomedical research challenges is to decipher the molecular basis of organ regeneration, which is regulated by a series of dynamic and complex processes including the interplay among intracellular and extracellular signals, growth factors, cytokines, and other components. 2 Thus, the explorations of the basic principles and the molecular underpinnings of regeneration have provided a rich biological resource and tools for understanding, building, or repairing complex body parts, which could bring us a step closer to regenerating human organs. [3][4][5] However, the regeneration potentials present a heterogeneous distribution from the lowest to the highest phyla. 6 Adult mammals, in particular humans, are not categorized as regeneration-competent species, with a limited organ regenerative capacity following injury. 2,4 Whereas many lower vertebrates or invertebrates, such as amphibians, fish, and echinoderm possess extraordinary abilities to regenerate missing

Single-cell RNA sequencing of the holothurian regenerating intestine reveals the pluripotency of the coelomic epithelium

“…For instance, like the blastema cells of the amphibians, the cells of the holothurian anlage coelomic epithelium are proliferative undifferentiated cells and originated via a dedifferentiation process. Moreover, some of the genes expressed by the amphibian blastema cells or the overlying AEC, such as Wnt, Tgf-beta, and Fgf, are also known to be expressed during sea cucumber regeneration (Auger et al, 2023; Zeng et al, 2023). In amphibians, some of these factors are thought to be released by cells of the AEC, serving as a way of modulating the blastema cell activity.…”

“…This expression of Fgf and Wnt and their possible functions correlates with what has been found in sea cucumbers. Not only are the same growth factors expressed in C1 and C3, but a recent study highlighted the role of FGF4 as a modulator of cell proliferation during the intestinal regeneration of the sea cucumber A. japonicus (Zeng et al, 2023). This group demonstrated that inhibiting FGF4 and its receptor, FGFR2, negatively affected cell proliferation of the mesothelial layer during intestinal regeneration.…”

Bisphenol A (BPA) Directly Activates the G Protein-Coupled Estrogen Receptor 1 and Triggers the Metabolic Disruption in the Gonadal Tissue of Apostichopus japonicus

“…The sea cucumber, A. japonicus, as a nonmodel organism, is challenging to study with respect to its metabolic activity and signal transduction. Considering the high transfection efficiency, rapid proliferation, and evolutionarily conserved proteins in cell-signaling pathways in model cell lines [ 55 ], and the wide use of HEK293 cell lines in cell-signaling studies in invertebrates [ 56 , 57 , 58 ], we chose to use transfected HEK293 cells to determine the molecular and functional characteristics of AjGPER1. The limitations of studying sea cucumber GPER1 outside of its evolutionary context, to some extent, were complemented by in vitro experimental data from cultured A. japonicus ovarian tissues highly expressing this gene.…”

TMT-Based Quantitative Proteomic Analysis Reveals the Key Role of Cell Proliferation and Apoptosis in Intestine Regeneration of Apostichopus japonicus

“…With the development of high-throughput sequencing technology, a largescale gene expression profile related to the regeneration process of sea cucumbers has been constructed, enabling the study of this mechanism at the global transcriptome and proteome levels. The transcriptome of Apostichopus japonicus (A. japonicus) during intestinal regeneration has been well studied, while proteomic analysis only reported at the normal intestine and the early stage of regeneration (3 days post-evisceration (dpe)) [15,16]. Given that the process of intestinal regeneration is divided into multiple stages, and each process is crucial for regenerating a complete intestine and involves a series of cellular events, we investigated the differential proteins of the entire process of intestinal regeneration using tandem mass tag (TMT)-based proteomics.…”