Inhibition of histone methyltransferases leads to partial endocrine cell-fate conversion.
(A) H3K27me3 ChIP-Seq analysis of human islets shows decreased H3K27me3 levels at the ARX, MAFA, and PDX1 loci following treatment of human islets with the histone methyltransferase inhibitor Adox. (B) Adox-treatment of human islets results in colocalization of glucagon (red) and insulin (green) granules within the same cell (yellow arrows), suggesting partial endocrine cell fate conversion, which was not seen in vehicle-treated islets (control). Original magnification, ×63. For Z-stack confocal images see Supplemental Videos 1 and 2. (C) Treatment of human islets with Adox results in colocalization of the β cell–specific transcription factor Pdx1 (white) and glucagon (red), further indicating endocrine reprogramming (white arrows: glucagon-positive, Pdx1-negative cells; yellow arrows: glucagon-positive, Pdx1-positive cells). The images on the right correspond to the area within yellow box. Original magnification, ×63. (D) Quantification of glucagon-positive, Pdx1-positive cells in untreated and Adox-treated human islets reveals many double-positive cells after Adox treatment, indicating initiation of reprogramming events in α cells. (E) Adox treatment of human islets leads to a decrease in NKX6-1 and MAFA levels in β cells (n = 3 α, n = 3 β, n = 2 treated α, n = 2 treated β), an increase in PDX1-levels, and no change in INS and GCG levels. (F) In Adox-treated α cells, we observe no change in INS and GCG expression, a slight decrease in NKX6-1 and MAFA levels, and an increase of ARX and PDX1 expression.