PAX6 maintains β cell identity by repressing genes of alternative islet cell types
Avital Swisa, … , Ruth Ashery-Padan, Yuval Dor
Avital Swisa, … , Ruth Ashery-Padan, Yuval Dor
Published December 12, 2016
Citation Information: J Clin Invest. 2017;127(1):230-243. https://doi.org/10.1172/JCI88015.
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Research Article Endocrinology Genetics

PAX6 maintains β cell identity by repressing genes of alternative islet cell types

Abstract

Type 2 diabetes is thought to involve a compromised β cell differentiation state, but the mechanisms underlying this dysfunction remain unclear. Here, we report a key role for the TF PAX6 in the maintenance of adult β cell identity and function. PAX6 was downregulated in β cells of diabetic db/db mice and in WT mice treated with an insulin receptor antagonist, revealing metabolic control of expression. Deletion of Pax6 in β cells of adult mice led to lethal hyperglycemia and ketosis that were attributed to loss of β cell function and expansion of α cells. Lineage-tracing, transcriptome, and chromatin analyses showed that PAX6 is a direct activator of β cell genes, thus maintaining mature β cell function and identity. In parallel, we found that PAX6 binds promoters and enhancers to repress alternative islet cell genes including ghrelin, glucagon, and somatostatin. Chromatin analysis and shRNA-mediated gene suppression experiments indicated a similar function of PAX6 in human β cells. We conclude that reduced expression of PAX6 in metabolically stressed β cells may contribute to β cell failure and α cell dysfunction in diabetes.

Authors

Avital Swisa, Dana Avrahami, Noa Eden, Jia Zhang, Eseye Feleke, Tehila Dahan, Yamit Cohen-Tayar, Miri Stolovich-Rain, Klaus H. Kaestner, Benjamin Glaser, Ruth Ashery-Padan, Yuval Dor

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Figure 1

PAX6 expression in adult β cells from db/db mice and after treatment with an insulin receptor antagonist.

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PAX6 expression in adult β cells from db/db mice and after treatment wit...
(A) PAX6 protein levels in β cells from db/db mice and controls. Dissociated islet cells were costained for insulin and PAX6 and analyzed by flow cytometry. Graph shows the mean of PAX6 intensity in insulin+ cells isolated from 3 control and 5 db/db mice at 3 months of age. (B) Mean insulin intensity for the same samples as in A. (C) Representative plots of PAX6 versus insulin protein levels in the control and db/db mice depicted in A and B. PAX6 levels correlated with insulin levels in both control and db/db mice. db/db mice in panels A–C had, on average, glucose levels of 480 mg/dl. (D) Pax6 mRNA levels in 3-month-old control and db/db islets. n = 6 animals per group. (E) Negative correlation between Pax6 mRNA and blood glucose levels in db/db mice at different ages (4 weeks, 5–7 weeks, and 3 months, by Pearson’s correlation test, R = –0.9, P < 0.05). (F) mRNA levels of Pax6, Mafa, Nkx6.1, and Pdx1 in the same db/db (DB) mice as in E, averaged per blood glucose ranges (100–200, 200–400, and 400–600 mg/dl). n = 9, 7, 8, and 7 mice, respectively. (G) Pax6 mRNA levels of islets isolated from WT mice treated with the insulin receptor (IR) antagonist S961 for 4 days. Average blood glucose level was 434 mg/dl in the treated group. n = 3 per each group. *P < 0.05, **P < 0.01, and ***P < 0.001, by 2-tailed Student’s t test.