Genome‐wide analysis of gene transcription by EGR1 in response to TGF‐β2 stimulation of small intestinal cell differentiation (623.23)

Abstract

Human milk contains growth factors that maintain intestinal mucosal homeostasis. However, the molecular mechanisms behind how these growth factors regulate gene transcription are largely unknown. We used IEC‐6 (intestinal crypt cell) cells as a model and treated them with 10 ng/ml TGF‐β2, a milk growth factor known for its stimulatory effect on intestinal cell differentiation. Immunoblotting and immunofluorescent assays showed that EGR‐1 (early immediate gene, regulating cell survival, growth, differentiation and transformation) expression in the nucleus was stimulated, with maximum expression occurring at 1h and then a decrease with time. EGR1 was predicted to have binding sites in the promoters of Axin1 (‐248bp/258bp, the scaffold protein in Wnt signaling), LRP5 (‐78bp/113bp, interacting with Axin1), Notch1 (‐76bp/84bp, Notch signaling) and Hes1 (‐1158bp/1170bp, affecting differentiation of intestinal cells). Chromatin immunoprecipitation (CHIP) verified a binding site in the Axin1 promoter. To comprehensively explore the functions of EGR1 in intestinal cell growth, next‐generation sequencing (NGS) was used to examine the interaction between EGR1 and other genes under the stimulation of TGF‐β2 at 0h, 1h and 48h, respectively. In conclusion, our results for the first time show the genome‐wide interaction between EGR1, a TGF‐ β2 responsive factor, and active genes involved in intestinal crypt cell growth and differentiation.