Fig. 1. The death receptor TMEM219 is expressed in islet beta cells.

a The transcriptome profile of genes encoding islet surface proteins was screened using RNA-seq of islets isolated from non-diabetic donors (n = 4). A full list of genes analyzed is reported in Supplementary Data 2. b Quantification of TMEM219 relative expression as compared to other relevant receptors in human islets by targeted qRT-PCR (n = 4). c Representative image of TMEM219 (green) and INS (red) co-expression in purified human islets of non-diabetic donors. Original magnification ×40, scale bar 25 μm. Merge is in the left panel. d Bar graph representing the expression of TMEM219 mRNA on flow-sorted insulin-positive and -negative cells obtained from purified human islets isolated from non-diabetic donors (n = 3). e Bar graphs comparing expression of TMEM219 and other IGFBP3 putative receptors (LRP1, TGF-β R1, and TGF-β R2) analyzed by qRT-PCR in purified human islets (n = 3). f Representative immunoblot of TMEM219 protein expression in human islets (with β-actin as a control). g, h Representative flow plot and a quantitative bar graph showing TMEM219 expression in insulin-positive and -negative cells detected using flow cytometry in healthy human islets (n = 3). Data are expressed as mean ± standard error of the mean (SEM) unless otherwise reported. **P < 0.01 by two-sided t test. mRNA expression was normalized to β-actin (ACTB). Experiments were performed in duplicate. The data shown in (c) and in (f) are the representative result from three independent experiments. Source data are provided as a Source Data file. RNAseq RNA sequencing analysis, RPKM reads per kilobase per million, INS insulin, qRT-PCR quantitative real-time polymerase chain reaction.