Fig. 3. Reduced Pdx1 expression in HFD beta-barr1-KO islets, Pdx1 rescue experiments, and reduced expression of cell cycle genes.

a Reduced expression of Pdx1 protein in the absence of beta-cell barr1. Lysates from pancreatic islets derived from HFD control (Con) and beta-barr1-KO (KO) mice were subjected to Western blotting studies (see Methods for details). Blots were probed with anti-Pdx1 and anti-β-actin antibodies. b Quantification of the Western blotting data shown in (a) (n = 4 per genotype). Pdx1 protein expression was normalized to the expression of β-actin. c Overexpression of Pdx1 in HFD beta-barr1-KO islets restores normal GSIS. Islets from HFD control and beta-barr1-KO mice were infected with either a control adenovirus (Ad-GFP) or an adenovirus coding for Pdx1 (Ad-Pdx1). GSIS was studied in static islet incubation assays. Islets were incubated for 1 h in Krebs solution containing 2.8 or 28 mM glucose. The amount of insulin secreted into the medium was normalized to the total insulin content of the islets in each well. Most notably, mutant islets treated with Ad-Pdx1 regained a similar degree of GSIS as Ad-Pdx1- or Ad-GFP-treated control islets (8–12 islet preparations from four mice per genotype). d Reduced expression of key cell cycle genes in HFD beta-barr1-KO islets, as determined by RNA-seq. See Methods for experimental details (mouse age: ~20 weeks; n = 6 mice/genotype). P values are indicated in the different panels (b: unpaired two-tailed t-test; c: two-way Anova followed by Sidak’s post hoc test). Source data are provided as a Source data file.