Beta Cell Regeneration in Zebrafish : Investigating the Ductal Contribution

Diabetes is characterized by the loss of insulin producing beta cells. Although different therapeutic strategies do exist, they lack precise and dynamic control of glycemia as carried out by endogenous beta cells. One promising alternative is to replenish the pancreas with bona fide functional beta cells by triggering regeneration mechanisms. Previous studies have shown beta cell neogenesis originating from different pancreatic cell types (alpha, delta, acinar and ductal cells), depending on the used model. The ductal origin is supported by the fact that the embryonic duct epithelium gives rise to the endocrine lineage, and that in healthy and diabetic human adults, insulin positive cells could be found next to or in pancreatic ducts. Despite these observations, mammals show very limited regenerative capabilities, making it difficult to investigate those mechanisms. In contrast, zebrafish are extensively used for regeneration studies. The ability of adult zebrafish to regenerate its beta cells and restore normoglycemia after massive beta cell ablation has already been shown. We, and other groups, have previously shown that adult pancreatic duct cells act as progenitors, giving rise to beta cells in physiological and induced diabetic condition in vivo. To get insight into this process, we conducted comparative RNA-seq experiments on pancreatic duct cells from adult zebrafish. By this means, we identified regulated gene expression that can be linked to specific processes/pathways such as cell cycling and Notch. In order to confirm the involvement of identified candidate genes/pathways, we are setting up a screening method using chemical activators and inhibitors in old larvae, by looking at their ability to modify proliferation/differentiation of duct cells after beta cell ablation. In addition, we are also investigating the effect of mutations, generated by the CRISPR/Cas9 system within candidate genes, on the regeneration capabilities. Together, these strategies should provide new clues about regenerative processes triggered in duct cells that might be applied to overcome the poor regenerative capabilities of mammals