Thumbnail Image

One-Carbon Metabolism Related B-Vitamins Alter The Expression Of MicroRNAS And Target Genes Within The Wnt Signaling Pathway In Mouse Colonic Epithelium

ABSTRACT It has been widely recognized that microRNAs are involved in nearly all cellular processes that have been investigated and contribute to a variety of diseases including cancer. Our prior studies demonstrated the depletion of one-carbon metabolism related B-vitamins, including folate, vitamin B2, B6 and B12, induced a genomic DNA hypomethylation and an elevation of the tumorigenic Wnt signaling in mouse colonic epithelium. The present study aimed to define whether microRNAs serve as mediators between these B-vitamins and the Wnt signaling, and thereby influence intestinal tumorigenesis. MicroRNA expression profiles were measured using miRNA microarray and real-time PCR on colonic epithelial cells from Apc1638N mice fed with diets deplete or sufficient in those B-vitamins. In silico bioinformatic analysis were performed to predict microRNA gene targets within the Wnt signaling cascade. Out of 609 microRNA examined, 18 microRNAs were found to be either significantly (p < 0.05) or mildly (p < 0.10) differentially expressed in the colonic epithelium of mice fed the depleted diet when compared to the counterpart. Bioinformatic prediction of microRNA gene targets identified 40 genes within the Wnt pathway to have homology with microRNA seed sequences within their 3’-UTR or protein coding sequence. Of the 6 genes tested for experimentally target validation, the expression of Sfrp1 was shown to be significantly inhibited (p < 0.05) whereas β-catenin was shown to be significantly elevated (p < 0.05) with alterations of others in a fashion indicating the activation of Wnt signaling. These findings indicate that microRNAs may constitute a mechanism by which one-carbon B-vitamin depletions regulate the Wnt signaling pathway and thereby inform intestinal tumorigenesis.