REST Inhibits Direct Reprogramming of Pancreatic Exocrine to Endocrine Cells by Preventing PDX1-Mediated Activation of Endocrine Genes

Ofer Elhanani,Tomer Meir Salame,Jonathan Sobel,Dena Leshkowitz,Lital Povodovski,Itay Vaknin,Dror Kolodkin-Gal,Michael D Walker

doi:10.1016/j.celrep.2020.107591

Abstract

The emerging appreciation of plasticity among pancreatic lineages has created interest in harnessing cellular reprogramming for β cell replacement therapy of diabetes. Current reprogramming methodologies are inefficient, largely because of a limited understanding of the underlying mechanisms. Using an invitro reprogramming system, we reveal the transcriptional repressor RE-1 silencing transcription factor (REST) as a barrier for β cell gene expression in the reprogramming of pancreatic exocrine cells. We observe that REST-bound loci lie adjacent to the binding sites of multiple key β cell transcription factors, including PDX1. Accordingly, a loss of REST function combined with PDX1 expression results in the synergistic activation of endocrine genes. This is accompanied by increased histone acetylation and PDX1 binding at endocrine gene loci. Collectively, our data identify a mechanism for REST activity involving the prevention of PDX1-mediated activation of endocrine genes and uncover REST downregulation and the resulting chromatin alterations as key events in β cell reprogramming.

Highlights

Diabetes mellitus is a life-threatening metabolic disease currently affecting more than 415 million people worldwide (Zimmet, 2017)
We show that RE-1 silencing transcription factor (REST) serves as a negative regulator of exocrine cell reprogramming to the endocrine lineage and provide the detailed underlying mechanism
Our results suggest the following sequence of events: in acinar cells, REST binds cognate sites and recruits repressive chromatin-modifying enzymes, such as histone deacetylases (HDACs) (Naruse et al, 1999), that can block transcription factor binding to nearby enhancers of endocrine genes

Summary

Introduction

Diabetes mellitus is a life-threatening metabolic disease currently affecting more than 415 million people worldwide (Zimmet, 2017). An alternative approach is based on the recent appreciation that the mature pancreas possesses a surprising degree of plasticity: different pancreatic cells have been shown to possess the capacity to transdifferentiate or dedifferentiate (Al-Hasani et al, 2013; Furuyama et al, 2019; Pan et al, 2013; Talchai et al, 2012; Thorel et al, 2010). This has motivated researchers to develop protocols for direct reprogramming of various cell types into b cells. Most studies have focused on endoderm-derived tissues as the source of cells (Ariyachet et al, 2016; Baeyens et al, 2005; Chen et al, 2014; Ferber et al, 2000; Zhou et al, 2008) because developmentally related tissues share epigenetic signatures that may facilitate their conversion to b cells

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