Epigenomic plasticity enables human pancreatic α to β cell reprogramming
Nuria C. Bramswig, … , Markus Grompe, Klaus H. Kaestner
Nuria C. Bramswig, … , Markus Grompe, Klaus H. Kaestner
Published February 22, 2013
Citation Information: J Clin Invest. 2013;123(3):1275-1284. https://doi.org/10.1172/JCI66514.
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Research Article

Epigenomic plasticity enables human pancreatic α to β cell reprogramming

Abstract

Insulin-secreting β cells and glucagon-secreting α cells maintain physiological blood glucose levels, and their malfunction drives diabetes development. Using ChIP sequencing and RNA sequencing analysis, we determined the epigenetic and transcriptional landscape of human pancreatic α, β, and exocrine cells. We found that, compared with exocrine and β cells, differentiated α cells exhibited many more genes bivalently marked by the activating H3K4me3 and repressing H3K27me3 histone modifications. This was particularly true for β cell signature genes involved in transcriptional regulation. Remarkably, thousands of these genes were in a monovalent state in β cells, carrying only the activating or repressing mark. Our epigenomic findings suggested that α to β cell reprogramming could be promoted by manipulating the histone methylation signature of human pancreatic islets. Indeed, we show that treatment of cultured pancreatic islets with a histone methyltransferase inhibitor leads to colocalization of both glucagon and insulin and glucagon and insulin promoter factor 1 (PDX1) in human islets and colocalization of both glucagon and insulin in mouse islets. Thus, mammalian pancreatic islet cells display cell-type–specific epigenomic plasticity, suggesting that epigenomic manipulation could provide a path to cell reprogramming and novel cell replacement-based therapies for diabetes.

Authors

Nuria C. Bramswig, Logan J. Everett, Jonathan Schug, Craig Dorrell, Chengyang Liu, Yanping Luo, Philip R. Streeter, Ali Naji, Markus Grompe, Klaus H. Kaestner

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Figure 1

Study design for determination of the transcriptome and differential histone marks in sorted human islet cells.

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Study design for determination of the transcriptome and differential his...
(A) Human islets were dispersed and subjected to FACS to obtain cell populations highly enriched for α, β, and exocrine (duct and acinar) cells. Chromatin was prepared and precipitated with antibodies for H3K4me3 and H3K27me3 followed by high-throughput sequencing (ChIP-Seq) (H3K4me3: n = 4 α, n = 4 β, n = 2 exocrine, H3K27me3: n = 3 α, n = 3 β, n = 2 exocrine). RNA-Seq analysis was performed to determine mRNA and lncRNA levels (n = 3 α, n = 3 β, n = 2 exocrine). (B) Sample purity assessment. Normalized insulin and glucagon expression levels of the individual α and β cell populations were obtained by qRT-PCR to calculate the contamination by the opposite cell population, revealing high sample purity (2.5%–10.3% contamination in the α and 2-13.1% contamination in the β cell populations; details in Supplemental Methods). (C) Analysis pipeline for H3K4me3 and H3K27me3 ChIP-Seq data. Peak calling (H3K4me3: GLITR; H3K27me3: STAR) on individual replicates, followed by signal pooling, was employed to assess histone modification profiles of α, β, and exocrine cells. Heat map analysis confirmed reproducibility of replicates. (D) Genome browser image of the PDX1 locus showing H3K4me3 enrichment in α, β, and exocrine cells and H3K27me3 enrichment only in α cells (defined as monovalent H3K4me3 enrichment in β and exocrine cells, bivalent mark in α cells; CpG islands: red bars).