Multiple, temporal-specific roles for HNF6 in pancreatic endocrine and ductal differentiation

Abstract

Within the developing pancreas Hepatic Nuclear Factor 6 (HNF6) directly activates the pro-endocrine transcription factor, Ngn3. HNF6 and Ngn3 are each essential for endocrine differentiation and HNF6 is also required for embryonic duct development. Most HNF6 −/− animals die as neonates, making it difficult to study later aspects of HNF6 function. Here, we describe, using conditional gene inactivation, that HNF6 has specific functions at different developmental stages in different pancreatic lineages. Loss of HNF6 from Ngn3-expressing cells (HNF6 Δendo) resulted in fewer multipotent progenitor cells entering the endocrine lineage , but had no effect on β cell terminal differentiation. Early, pancreas-wide HNF6 inactivation (HNF6 Δpanc) resulted in endocrine and ductal defects similar to those described for HNF6 global inactivation. However, all HNF6 Δpanc animals survived to adulthood. HNF6 Δpanc pancreata displayed increased ductal cell proliferation and metaplasia, as well as characteristics of pancreatitis, including up-regulation of CTGF, MMP7, and p8/Nupr1. Pancreatitis was most likely caused by defects in ductal primary cilia. In addition, expression of Prox1, a known regulator of pancreas development, was decreased in HNF6 Δpanc pancreata. These data confirm that HNF6 has both early and late functions in the developing pancreas and is essential for maintenance of Ngn3 expression and proper pancreatic duct morphology.