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 1

Deletion of Nkx2.2 in β cells results in diabetes.

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Deletion of Nkx2.2 in β cells results in diabetes. (A) Quantitative reve...
(A) Quantitative reverse transcriptase PCR (qRT-PCR) analysis of Nkx2.2 expression in islets isolated from Nkx2.2ΔBeta (ΔBeta) and control (Ctrl) mice at 4 weeks of age (n = 4). **P ≤ 0.01; 2-tailed Student’s t test. (B) Western Blot analysis of isolated islets from Nkx2.2ΔBeta and control mice confirms a reduction of NKX2.2 protein in islets isolated from 4 individual adult Nkx2.2ΔBeta mice. (C and D) Immunofluorescence staining of insulin (red) and NKX2.2 (green) demonstrates the loss of NKX2.2 expression in β cells from Nkx2.2ΔBeta compared with control mice at 4 weeks of age. The white boxes indicate regions of the islet that are shown in higher magnification in E and F. (G) Ad libitum blood glucose levels in 2-week-old male Nkx2.2ΔBeta mice compared with controls (n = 3–16), in 3-week-old mice (n = 5–22), and in 11-week-old mice (n = 6–18). **P ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test. Each control genotype was examined separately to ensure that the individual Cre and floxed alleles did not cause metabolic phenotypes. (H) Higher fasting blood glucose levels are evident in 11-week-old Nkx2.2ΔBeta mice compared with controls (3-week-old mice: n = 6–23; 11-week-old mice: n = 8–21). *P ≤ 0.05; 2-tailed Student’s t test. (I) Glucose intolerance is observed in Nkx2.2ΔBeta male mice compared with controls at 3 weeks of age (n = 6–23). *P ≤ 0.05, ***P ≤ 0.001; 2-tailed Student’s t test. (J) Glucose intolerance becomes more severe at 11 weeks of age in Nkx2.2ΔBeta male mice compared with control mice (n = 8–21). *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test.