Pancreatic β cell identity requires continual repression of non–β cell programs
Giselle Domínguez Gutiérrez, Aaron S. Bender, Vincenzo Cirulli, Teresa L. Mastracci, Stephen M. Kelly, Aristotelis Tsirigos, Klaus H. Kaestner, Lori Sussel
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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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 6

NKX2.2 is essential for the maintenance of β cell identity and function in adult β cells.

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NKX2.2 is essential for the maintenance of β cell identity and function ...
(A) Schematic of experimental design. (B) qRT-PCR analysis demonstrates significant deletion of Nkx2.2 in isolated islets from Nkx2.2ΔAdultBeta mice compared with controls 5 weeks after the last injection (n = 5–7). ***P ≤ 0.001; 2-tailed Student’s t test. (C) Deletion of Nkx2.2 increases ad libitum blood glucose in Nkx2.2ΔAdultBeta compared with controls starting at 1 week after the last injection (n = 16–20). *P ≤ 0.05, **P = ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test. (D) Fasting blood glucose levels become significantly increased 5 weeks after the last injection in Nkx2.2ΔAdultBeta compared with controls (n = 12–15). *P ≤ 0.05; 2-tailed Student’s t test. (E) Nkx2.2ΔAdultBeta mice are glucose intolerant at 3 weeks after the last injection compared with controls (n = 12–15). **P ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test. (F) Glucose intolerance becomes more severe 5 weeks after the last injection in Nkx2.2ΔAdultBeta compared with controls (n = 12–15). **P ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test. (G) Glucose intolerance continues to worsen with age; glucose tolerance test at 6–7 months after the last injection in Nkx2.2ΔAdultBeta compared with controls (n = 3–4). *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test. (H–N) Immunofluorescence staining of pancreata from Nkx2.2ΔAdultBeta and control mice 5 weeks after the last injection. Insets are magnifications of selected areas indicated by white boxes showing coexpression of insulin (INS) and somatostatin (SST) (J and K) and coexpression of SST and Tomato (TOM) (M and N). The images in I–N show the same islet that was costained with insulin, somatostatin, and Tomato. The channels were separated out and false-colored to more clearly indicate coexpressed cells. qRT-PCR analysis confirms the increase in somatostatin over time in Nkx2.2ΔAdultBeta compared with controls (n = 4–6). Asterisks indicate the location of insulin/somatostatin-copositive cells. (O) qRT-PCR analysis confirms the increase in somatostatin over time in Nkx2.2ΔAdultBeta compared to controls (n = 4-6). **P ≤ 0.01, ***P ≤ 0.001; 2-tailed Student’s t test.