The Myc 3' Wnt-responsive element regulates homeostasis and regeneration in the mouse intestinal tract.

The Wnt/β-catenin signaling pathway controls cellular proliferation in the intestines. In response to Wnt, β-catenin transits into the nucleus and associates with members of the T-cell factor (TCF) family of transcription factors. β-Catenin/TCF complexes bind Wnt responsive DNA elements (WREs) to activate target gene expression. The c-MYC proto-oncogene (MYC) is a direct target of β-catenin/TCF complexes. We recently identified the MYC 3' WRE, which maps 1.4-kb downstream from the MYC transcription stop site. To investigate the role of the Myc 3' WRE in the intestines, we generated a mouse model with a germ line deletion of this element. The intestinal architecture was largely preserved in knockout mice; however, removal of the Myc 3' WRE compromised the crypt microenvironment. In comparison to wild-type intestines, knockout intestines contained an increased number of proliferative cells and a reduced number of differentiated cells comprising both absorptive and secretory lineages. Using a model of colitis, we found that knockout colons repaired more rapidly during the recovery period of the protocol. These results indicate that regulation of MYC expression through the Myc 3' WRE contributes to intestinal homeostasis. Furthermore, our study implicates MYC as an important regulator of intestinal regeneration following injury.