BADERC- Joel Habener

Joel Habener, M.D.

Pancreatic Islet Development and Function

The prevalence of the metabolic disease diabetes mellitus in the population world-wide is increasing at epidemic proportions. In the USA, 10% of individuals are afflicted and the health care costs incurred by the associated morbidity are in excess of $105B/year. Diabetes manifests in two distinct forms: type 1 (juvenile) and type 2 (adult onset), characterized by absolute or relative deficiency in the production of insulin by the pancreas. The studies we are pursuing are based on the premise that the fundamental morphological causation of both forms of diabetes is the occurrence of a reduction in the numbers of insulin-producing beta cells in the pancreas. As a consequence of this circumstance, there is an insufficient mass of beta cells available for the production of insulin in the amounts required to meet the metabolic needs of the body. The beta cell mass is determined by the balance between the rates of beta-cell death (apoptosis) and the birth of new beta-cells (neogenesis) to replace the dead beta-cells. In the rat and mouse pancreas the beta-cell mass turns over approximately every 40-50 days (2-3%/day) due to apoptosis and the formation (neogenesis) of new beta cells as they differentiate from progenitor cells located in the pancreatic ducts. We propose a "transcription factor hypothesis" as a cause of diabetes. This hypothesis states that specific transcriptional proteins, that regulate the expression of specific genes during pancreas development, are responsible for beta cell neogenesis and apoptosis and that malfunctioning of these proteins may curtail beta cell growth and function. We have identified two such proteins involved in neogenesis: the homeodomain protein IDX-1 (PDX-1) and the Pou-homeodomain protein Brain4 as key regulators of beta cell and alpha cell development, respectively. The intestinal incretin hormone glucagon-like peptide-1 (GLP-1) appears to stimulate the expression of IDX-1 (PDX-1) and the neogenesis of beta cells. We have also identified two bZIP (leucine zipper) proteins, C/EBP-beta and CHOP, that appear to participate in the apoptosis of beta cells in response to glucotoxic stress. Specifically we are investigating the regulation of the expression of these transcription factors during the differentiation of beta cells in cell culture models in vitro and by genetic manipulations of mice in vivo. We have discovered that rat and human pancreatic islets contain a distinct population of cells that express the neural stem cell-specific marker nestin, nestin-positive islet-derived stem/progenitor cells (NIPs). Focal regions of nestin-positive cells are also in large, small, and centrolobular ducts of the rat pancreas. Nestin-positive cells within pancreatic islets do not express islet hormones insulin, glucagon, somatostatin, or pancreatic polypeptide. After their isolation, nestin-positive cells have an indefinite proliferative capacity when cultured in vitro, are multipotential, and can be differentiated into islet-like clusters (ILCs) that produce glucagon and insulin. The discovery of NIPs within pancreatic islets has implications for the transplantation of islets into the livers of diabetic individuals.

We believe that an understanding of how the expression of IDX-1, Brn4, C/EBP-beta, and CHOP are regulated during pancreas development, islet cell neogenesis and apoptosis, as well as the properties of pancreatic stem cells, will provide opportunities for the development of future rational therapeutic approaches for the cure of diabetes.

References:

1. Stoffers DA, Ferrer J, Clarke WL and Habener JF. Early onset type 2 diabetes mellitus linked to IPF-1 (MODY4) Nature Genet 1997; 17:138-139.

2. Lu M, Seufert J and Habener JF. Pancreatic Beta-Cell Specific Repression of Insulin Gene Transcription by CCAAT/Enhancer-binding Protein C/EBP-beta: Inhibitory Interactions with basic Helix-Loop-Helix Factor E47. J Biol Chem 1997; 272: 28349-28359.

3. Stoffers DA, Stanojevic V and Habener JF. Insulin promoter factor-1 gene mutation linked to early-onset type 2 diabetes mellitus directs expression of a dominant negative isoform. J Clin Invest 1998;102: 232-241.

4. Seufert J, Weir GC, Habener JF. Differential expression of the insulin gene transcriptional repressor C/EBP-beta and transactivator IDX-1 in rat pancreatic beta-cells during the development of diabetes mellitus. J Clin Invest 1998;101: 2528-2539.

5. Stoffers DA, Kieffer TJ, Hussain MA, Drucker DJ, Bonner-Weir S, Habener JF, Egan JM. Insulinotropic glucagon-like peptide 1 agonists stimulate expression of homeodomain protein IDX-1 and increase islet size in mouse pancreas. Diabetes. 2000; 49(5):741-748.

6. Habener JF. Glucagon-like peptide-1 agonist stimulation of beta-cell growth and differentiation. Curr Opinion Endocrinol Diab. 2001;8:74-81.

7. Hussain MA, Habener JF, Eds. Series Editor, Shlomo Melmed. Molecular Basis of Pancreas Development and Function. Kluwer Academic Publishers, 2001.

8. Thomas MK, Devon ON, Lee JH, Peter A, Schlosser DA, Tenser MS, Habener JF. Development of diabetes mellitus in aging transgenic mice following suppression of pancreatic homeoprotein IDX-1. J Clin Invest 2001;108(2): 319-329.

9. Maytin EV, Ubeda M, Lin JC, Habener JF. Stress-inducible transcription factor CHOP/gadd153 induces apoptosis in mammalian cells via p38 kinase-dependent and independent mechanisms. Exp Cell Res. 2001:267(2):193-204.

10. Zulewski H, Abraham EJ, Gerlach MJ, Daniel PB, Moritz W, Muller B, Vallejo M, Thomas MK, Habener JF. Multipotential nestin-positive stem cells isolated from adult pancreatic islets differentiate ex vivo into pancreatic endocrine, exocrine, and hepatic phenotypes. Diabetes. 2001;50(3):521-533.

11. Abraham EJ, Leech CA, Lin JC, Zulewski H, Habener JF. Insulinotropic hormone glucagon-like peptide-1 differentiation of human pancreatic islet-derived progenitor cells into insulin-producing cells. Endocrinology. 2002;143(8):3152-3161.

12. Hussain MA, Miller CP, Habener JF. Brn-4 transcription factor expression targeted to the early developing mouse pancreas induces ectopic glucagon gene expression in insulin-producing beta cells. J Biol Chem. 2002;277(18):16028-16033.

13. Lechner A, Habener JF. Stem/progenitor cells derived from adult tissues: potential for the treatment of diabetes mellitus. Am J Physiol Endocrinol Metab 2003;284(2): E259-266.

14. Lechner A, Yang YG, Blacken RA, Wang L, Nolan AL, Habener JF. No evidence for significant transdifferentiation of bone marrow into pancreatic beta-cells in vivo.Diabetes. 2004;53:616-23.

15. Abraham EJ, Kodama S, Lin JC, Ubeda M, Faustman DL, Habener JF. Human pancreatic islet-derived progenitor cell engraftment in immunocompetent mice. Am J Pathol. 2004;164:817-30.






			Joel Habener, M.D. Pancreatic Islet Development and Function The prevalence of the metabolic disease diabetes mellitus in the population world-wide is increasing at epidemic proportions. In the USA, 10% of individuals are afflicted and the health care costs incurred by the associated morbidity are in excess of $105B/year. Diabetes manifests in two distinct forms: type 1 (juvenile) and type 2 (adult onset), characterized by absolute or relative deficiency in the production of insulin by the pancreas. The studies we are pursuing are based on the premise that the fundamental morphological causation of both forms of diabetes is the occurrence of a reduction in the numbers of insulin-producing beta cells in the pancreas. As a consequence of this circumstance, there is an insufficient mass of beta cells available for the production of insulin in the amounts required to meet the metabolic needs of the body. The beta cell mass is determined by the balance between the rates of beta-cell death (apoptosis) and the birth of new beta-cells (neogenesis) to replace the dead beta-cells. In the rat and mouse pancreas the beta-cell mass turns over approximately every 40-50 days (2-3%/day) due to apoptosis and the formation (neogenesis) of new beta cells as they differentiate from progenitor cells located in the pancreatic ducts. We propose a "transcription factor hypothesis" as a cause of diabetes. This hypothesis states that specific transcriptional proteins, that regulate the expression of specific genes during pancreas development, are responsible for beta cell neogenesis and apoptosis and that malfunctioning of these proteins may curtail beta cell growth and function. We have identified two such proteins involved in neogenesis: the homeodomain protein IDX-1 (PDX-1) and the Pou-homeodomain protein Brain4 as key regulators of beta cell and alpha cell development, respectively. The intestinal incretin hormone glucagon-like peptide-1 (GLP-1) appears to stimulate the expression of IDX-1 (PDX-1) and the neogenesis of beta cells. We have also identified two bZIP (leucine zipper) proteins, C/EBP-beta and CHOP, that appear to participate in the apoptosis of beta cells in response to glucotoxic stress. Specifically we are investigating the regulation of the expression of these transcription factors during the differentiation of beta cells in cell culture models in vitro and by genetic manipulations of mice in vivo. We have discovered that rat and human pancreatic islets contain a distinct population of cells that express the neural stem cell-specific marker nestin, nestin-positive islet-derived stem/progenitor cells (NIPs). Focal regions of nestin-positive cells are also in large, small, and centrolobular ducts of the rat pancreas. Nestin-positive cells within pancreatic islets do not express islet hormones insulin, glucagon, somatostatin, or pancreatic polypeptide. After their isolation, nestin-positive cells have an indefinite proliferative capacity when cultured in vitro, are multipotential, and can be differentiated into islet-like clusters (ILCs) that produce glucagon and insulin. The discovery of NIPs within pancreatic islets has implications for the transplantation of islets into the livers of diabetic individuals. We believe that an understanding of how the expression of IDX-1, Brn4, C/EBP-beta, and CHOP are regulated during pancreas development, islet cell neogenesis and apoptosis, as well as the properties of pancreatic stem cells, will provide opportunities for the development of future rational therapeutic approaches for the cure of diabetes. References: 1. Stoffers DA, Ferrer J, Clarke WL and Habener JF. Early onset type 2 diabetes mellitus linked to IPF-1 (MODY4) Nature Genet 1997; 17:138-139. 2. Lu M, Seufert J and Habener JF. Pancreatic Beta-Cell Specific Repression of Insulin Gene Transcription by CCAAT/Enhancer-binding Protein C/EBP-beta: Inhibitory Interactions with basic Helix-Loop-Helix Factor E47. J Biol Chem 1997; 272: 28349-28359. 3. Stoffers DA, Stanojevic V and Habener JF. Insulin promoter factor-1 gene mutation linked to early-onset type 2 diabetes mellitus directs expression of a dominant negative isoform. J Clin Invest 1998;102: 232-241. 4. Seufert J, Weir GC, Habener JF. Differential expression of the insulin gene transcriptional repressor C/EBP-beta and transactivator IDX-1 in rat pancreatic beta-cells during the development of diabetes mellitus. J Clin Invest 1998;101: 2528-2539. 5. Stoffers DA, Kieffer TJ, Hussain MA, Drucker DJ, Bonner-Weir S, Habener JF, Egan JM. Insulinotropic glucagon-like peptide 1 agonists stimulate expression of homeodomain protein IDX-1 and increase islet size in mouse pancreas. Diabetes. 2000; 49(5):741-748. 6. Habener JF. Glucagon-like peptide-1 agonist stimulation of beta-cell growth and differentiation. Curr Opinion Endocrinol Diab. 2001;8:74-81. 7. Hussain MA, Habener JF, Eds. Series Editor, Shlomo Melmed. Molecular Basis of Pancreas Development and Function. Kluwer Academic Publishers, 2001. 8. Thomas MK, Devon ON, Lee JH, Peter A, Schlosser DA, Tenser MS, Habener JF. Development of diabetes mellitus in aging transgenic mice following suppression of pancreatic homeoprotein IDX-1. J Clin Invest 2001;108(2): 319-329. 9. Maytin EV, Ubeda M, Lin JC, Habener JF. Stress-inducible transcription factor CHOP/gadd153 induces apoptosis in mammalian cells via p38 kinase-dependent and independent mechanisms. Exp Cell Res. 2001:267(2):193-204. 10. Zulewski H, Abraham EJ, Gerlach MJ, Daniel PB, Moritz W, Muller B, Vallejo M, Thomas MK, Habener JF. Multipotential nestin-positive stem cells isolated from adult pancreatic islets differentiate ex vivo into pancreatic endocrine, exocrine, and hepatic phenotypes. Diabetes. 2001;50(3):521-533. 11. Abraham EJ, Leech CA, Lin JC, Zulewski H, Habener JF. Insulinotropic hormone glucagon-like peptide-1 differentiation of human pancreatic islet-derived progenitor cells into insulin-producing cells. Endocrinology. 2002;143(8):3152-3161. 12. Hussain MA, Miller CP, Habener JF. Brn-4 transcription factor expression targeted to the early developing mouse pancreas induces ectopic glucagon gene expression in insulin-producing beta cells. J Biol Chem. 2002;277(18):16028-16033. 13. Lechner A, Habener JF. Stem/progenitor cells derived from adult tissues: potential for the treatment of diabetes mellitus. Am J Physiol Endocrinol Metab 2003;284(2): E259-266. 14. Lechner A, Yang YG, Blacken RA, Wang L, Nolan AL, Habener JF. No evidence for significant transdifferentiation of bone marrow into pancreatic beta-cells in vivo.Diabetes. 2004;53:616-23. 15. Abraham EJ, Kodama S, Lin JC, Ubeda M, Faustman DL, Habener JF. Human pancreatic islet-derived progenitor cell engraftment in immunocompetent mice. Am J Pathol. 2004;164:817-30.