c-Myc down-regulation is required for pre-acinar to acinar maturation in the pancreas (RNA-Seq)

Multipotent pancreatic progenitors (MPC) are defined as Ptf1a+, Mychigh, Cpa+ cells. During the transition from MPC to unipotent acinar progenitors, c-Myc is down-regulated whereas Ptf1a is up-regulated, leading to the deployment of the acinar program. Here, we show that c-Myc and Ptf1a interact directly and c-Myc binds to, and represses, the transcriptional activity of the PTF1 complex in vitro and in vivo. Using Ela1-Myc mice, in which c-Myc is overexpressed in acinar cells starting at E14.5, we find that acinar cells fail to undergo normal maturation at P1 and this is followed by a massive subsequent repression of the acinar programme. Lineage tracing with Ptf1aCreERT2;Rosa26YFP and Ela1-Myc;Ptf1aCreERT2;Rosa26YFP mice receiving TMX at E15.5 and analyzed at E18.5 revealed that c-Myc overexpression is associated with activation of a hepatic programme but not with pancreatic lineage misspecification At 8 weeks, the silencing of the acinar program is associated with increased expression of the PRC2 complex in a c-Myc dependent manner. Genome wide studies show that Ptf1a and c-Myc display partially overlapping chromatin occupancy patterns and DNA binding competition. We conclude that c-Myc down-regulation during development is crucial for the maturation of pre-acinar to acinar cells. c-Myc overexpression may contribute to pancreatic carcinogenesis by restraining cell differentiation and rendering cells susceptible to transformation. Overall design: Pancreas mRNA profiles of 8-week old wild type (WT) and ELA1-MYC mice were generated by deep sequencing, in triplicate, using Illumina GAIIx.

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Sánchez-Arévalo Lobo VJ, Fernández LC, Carrillo-de-Santa-Pau E, Richart L, Cobo I, Cendrowski J, Moreno U, Del Pozo N, Megías D, Bréant B, Wright CV, Magnuson M, Real FX