In vitro reprogramming of pancreatic alpha cells towards a beta cell phenotype following ectopic HNF4α expression

• In vitro ectopic expression of HNF4α in the murine alpha cell line (αTC1-9).
• HNF4α induces a change in morphology and suppression of glucagon.
• HNF4α induces key beta cell specific markers (insulin, GCK, C-peptide, GLUT2, Pax4).
• HNF4α over-expressing αTC1-9 cells secrete insulin in a glucose regulated manner.
• We report HNF4α promotes reprogramming of alpha cells to beta-like cells.

There is currently a shortage of organ donors available for pancreatic beta cell transplantation into diabetic patients. An alternative source of beta cells is pre-existing pancreatic cells. While we know that beta cells can arise directly from alpha cells during pancreatic regeneration we do not understand the molecular basis for the switch in phenotype. The aim of the present study was to investigate if hepatocyte nuclear factor 4 alpha (HNF4α), a transcription factor essential for a normal beta cell phenotype, could induce the reprogramming of alpha cells towards potential beta cells. We utilised an in vitro model of pancreatic alpha cells, the murine αTC1-9 cell line. We initially characterised the αTC1-9 cell line before and following adenovirus-mediated ectopic expression of HNF4α. We analysed the phenotype at transcript and protein level and assessed its glucose-responsiveness. Ectopic HNF4α expression in the αTC1-9 cell line induced a change in morphology (1.7-fold increase in size), suppressed glucagon expression, induced key beta cell-specific markers (insulin, C-peptide, glucokinase, GLUT2 and Pax4) and pancreatic polypeptide (PP) and enabled the cells to secrete insulin in a glucose-regulated manner. In conclusion, HNF4α reprograms alpha cells to beta-like cells.