LAUSR

Strategies to promote β cell neogenesis could be used to restore functional β cell mass in both type 1 and type 2 diabetes. Here we examine the role of mitogen-inducible gene 6 ( mig6, a.k.a. erffi1 ) in the regulation of functional β cell mass. mig6 is evolutionarily conserved and encodes a protein that inhibits the epidermal growth factor receptor (EGFR) in a classic feedback mechanism, suggesting a potential role in cellular growth and development. Based on functional studies in mouse and human, we hypothesized that mig6 is required in pancreatic ducts for pancreatogenesis and β cell function. We used morpholino knockdown in zebrafish to define the role of mig6 in both exocrine pancreas and islet development. We established that mig6 knockdown ( mig6MO ) embryos have a disrupted pancreas morphogenesis, particularly, a truncated exocrine pancreas and fewer intra-pancreatic duct cells. Additionally, mig6 MO -injected animals had fewer β cells than controls. Together, our data lead us to hypothesize that mig6 may facilitate the expansion of the pancreas progenitor pool by blocking EGFR activation. We further investigated the role of mig6 in islet regeneration. Neogenic β cells may arise from two sources in the developing zebrafish, which can be distinguished by the retention of a fluorescent mark made at the one-cell stage. β cells derived via transdifferentiation from other postmitotic endocrine cells remain labeled whereas those derived from duct-associated progenitors lose their label via proliferation. We found that although the number of regenerated β cells was reduced overall in mig6MO -injected embryos, most new β cells were not labeled, suggesting that a significant progenitor pool remains in the knockdown embryos. Together, our data demonstrate that mig6 is essential for pancreas development and that it might be exploited as a switch between progenitor differentiation and endocrine transdifferentiation to increase β cell mass in diabetic patients. Disclosure K. El: None. P.T. Fueger: None. R.M. Anderson: None.