Pancreatic β cell identity requires continual repression of non–β cell programs
Giselle Domínguez Gutiérrez, … , Klaus H. Kaestner, Lori Sussel
Giselle Domínguez Gutiérrez, … , Klaus H. Kaestner, Lori Sussel
Published December 12, 2016
Citation Information: J Clin Invest. 2017;127(1):244-259. https://doi.org/10.1172/JCI88017.
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Research Article Metabolism

Pancreatic β cell identity requires continual repression of non–β cell programs

Abstract

Loss of β cell identity, the presence of polyhormonal cells, and reprogramming are emerging as important features of β cell dysfunction in patients with type 1 and type 2 diabetes. In this study, we have demonstrated that the transcription factor NKX2.2 is essential for the active maintenance of adult β cell identity as well as function. Deletion of Nkx2.2 in β cells caused rapid onset of a diabetic phenotype in mice that was attributed to loss of insulin and downregulation of many β cell functional genes. Concomitantly, NKX2.2-deficient murine β cells acquired non–β cell endocrine features, resulting in populations of completely reprogrammed cells and bihormonal cells that displayed hybrid endocrine cell morphological characteristics. Molecular analysis in mouse and human islets revealed that NKX2.2 is a conserved master regulatory protein that controls the acquisition and maintenance of a functional, monohormonal β cell identity by directly activating critical β cell genes and actively repressing genes that specify the alternative islet endocrine cell lineages. This study demonstrates the highly volatile nature of the β cell, indicating that acquiring and sustaining β cell identity and function requires not only active maintaining of the expression of genes involved in β cell function, but also continual repression of closely related endocrine gene programs.

Authors

Giselle Domínguez Gutiérrez, Aaron S. Bender, Vincenzo Cirulli, Teresa L. Mastracci, Stephen M. Kelly, Aristotelis Tsirigos, Klaus H. Kaestner, Lori Sussel

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Figure 2

Lineage tracing in Nkx2.2ΔBeta mice indicates loss of insulin expression in Nkx2.2ΔBeta β cells.

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Lineage tracing in Nkx2.2ΔBeta mice indicates loss of insulin expression...
(A) qPCR analysis of insulin 1 (Ins1) and insulin 2 (Ins2) mRNA expression in islets from Nkx2.2ΔBeta 4-week-old mice (ΔBeta) compared with controls (n = 4). **P ≤ 0.01; 2-tailed Student’s t test. (B) Nkx2.2ΔBeta 4-week-old mice have an approximately 50% reduction in pancreas insulin content compared with controls (n = 3). **P ≤ 0.01; 2-tailed Student’s t test. (C) Loss of NKX2.2 results in decreased β cell mass at 4 weeks of age (n = 3). *P ≤ 0.05; 2-tailed Student’s t test. (D) Nkx2.2ΔBeta 4-week-old mice have no statistical difference in islet numbers compared with controls (n = 3); 2-tailed Student’s t test. (E) Islet size of Nkx2.2ΔBeta mice compared with controls was not statistically different at 4 weeks of age (n = 3); 2-tailed Student’s t test. There was a trend down in the number of largest islets, but the difference did not reach significance. (F and G) Immunofluorescence staining of insulin (green) and DAPI (blue) shows a decrease of insulin expression in islet cells from Nkx2.2ΔBeta 4-week-old mice compared with controls. (H and I) Immunofluorescence staining of insulin (green) and Tomato (red) shows a decrease or absence of insulin expression in Tomato-expressing β cell lineages. (J) Nkx2.2ΔBeta 4-week-old mice have fewer insulin-positive cells per islet area compared with controls (n = 3). ***P ≤ 0.001; 2-tailed Student’s t test. (K) qPCR analysis of chromogranin A (Chga) mRNA expression shows no statistical significance in pancreas from Nkx2.2ΔBeta mice compared with controls at P0 and 2 weeks of age (n = 4), as well as in islets from Nkx2.2ΔBeta 4-week-old mice compared with controls (n = 4–7). (L) Insulin levels are significantly lower in Nkx2.2ΔBeta mice after a glucose stimulus compared with controls (n = 3–4). **P ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test.