New pancreas from old : microregulators of pancreas regeneration

MicroRNAs (miRNAs) are 18–22 nucleotide RNA molecules that mediate post-transcriptional gene silencing, primarily by binding to the 30 untranslated region of their target mRNA. Several studies have demonstrated the role ofmiRNAs in mouse pancreas development (miR124a, miR-503, miR-541, miR-214) as well as in insulin secretion (miR-375, miR-9). Pancreatic transcription factors that are temporally expressed during early pancreas development are re-expressed during pancreas regeneration following pancreatectomy in mice. The only exception to this is Neurogenin3 (NGN3). Here, we discuss recent evidence for miRNA-mediated silencing of ngn3, which inhibits endocrine cell development via the classical ‘stem cell pathway’ during mouse pancreatic regeneration, thereby favoring b-cell regeneration.