Transcription Factor Hepatocyte Nuclear Factor 6 Regulates Pancreatic Endocrine Cell Differentiation and Controls Expression of the Proendocrine Gene ngn3

Abstract

Hepatocyte nuclear factor 6 (HNF-6) is the prototype of a new class of cut homeodomain transcription factors. During mouse development, HNF-6 is expressed in the epithelial cells that are precursors of the exocrine and endocrine pancreatic cells. We have investigated the role of HNF-6 in pancreas differentiation by inactivating its gene in the mouse. In hnf6^−/− embryos, the exocrine pancreas appeared to be normal but endocrine cell differentiation was impaired. The expression of neurogenin 3 (Ngn-3), a transcription factor that is essential for determination of endocrine cell precursors, was almost abolished. Consistent with this, we demonstrated that HNF-6 binds to and stimulates the ngn3 gene promoter. At birth, only a few endocrine cells were found and the islets of Langerhans were missing. Later, the number of endocrine cells increased and islets appeared. However, the architecture of the islets was perturbed, and their β cells were deficient in glucose transporter 2 expression. Adult hnf6^−/− mice were diabetic. Taken together, our data demonstrate that HNF-6 controls pancreatic endocrine differentiation at the precursor stage and identify HNF-6 as the first positive regulator of the proendocrine gene ngn3in the pancreas. They also suggest that HNF-6 is a candidate gene for diabetes mellitus in humans.

ACKNOWLEDGMENTS

We thank L. Hue, J. C. Henquin, and J. Rahier for discussions and C. Bouzin, S. Fierens, V. Lannoy, L. Maisin, Y. Peignois, E. Gils, T. Vancoetsem, and K. Wijnens for help. Anti-Pax-6 and anti-Glut-2 antibodies were from S. Saule and B. Thorens, respectively. The monoclonal antibodies against Isl-1 and Nkx2.2, developed by T. Jessel, were obtained from the DSHB developed under the auspices of NICHM and maintained at the University of Iowa.

This work was supported by grants from the Belgian State Program on Interuniversity Poles of Attraction, the D.G. Higher Education and Scientific Research of the French Community of Belgium, the Fund for Scientific Medical Research, and the National Fund for Scientific Research (Belgium). O.D.M. and J.J. were supported by grants from the National Institutes of Health and the Juvenile Diabetes Foundation. G.G. and F.G. were supported by a grant from the Association pour la Recherche sur le Cancer, by funds from the Institut National de la Recherche Scientifique, from the Centre National de la Recherche Scientifique, and from the Hôpital Universitaire de Strasbourg. F.P.L. is Senior Research Associate of the National Fund for Scientific Research (Belgium).