Abstract 138: Regulation of Mybl2 and miRNAs in differentiating colon epithelial cells in vitro and in vivo
Authors: Papetti Michael , Augenlicht Leonard H. 
Published: June 2012

Abstract
Intestinal homeostasis relies upon accurate reprogramming of highly proliferative, multipotent colon epithelial stem/progenitor cells into 3 specialized cell types (enterocytic, goblet, and enteroendocrine cells) that migrate along the crypt axis toward the lumen and another (Paneth cells) that partitions to the bottom of the crypt. This reprogramming is modeled in immortalized cell lines such as Caco-2 and HT29Cl.16E and Cl.19A that proliferate in an undifferentiated state in culture but acquire absorptive (Caco-2) or secretory (16E and 19A) phenotypes in response to contact inhibition of growth or treatment with the short chain fatty acid butyrate. These processes are dependent not only on tightly coordinated changes in gene expression but also posttranscriptional regulation. miRNA silencing is one mechanism of gene regulation by which 21bp oligonucleotides recruit a silencing complex to the 3’ untranslated regions (UTRs) of target genes. We have previously identified a functional miRNA target in the 3’ UTR of Mybl2, one of 14 genes downregulated during growth arrest- and butyrate- induced differentiation of Caco2, 16E, and 19A cells. We also demonstrated that overexpression of miR-365, a miRNA predicted to bind this target, downregulates Mybl2 protein in proliferating Caco2 cells. Although these cell lines are good models for colon epithelial cell maturation, demonstrating that these observations occur in vivo in differentiating cells along the crypt-luminal axis of the human colon is necessary to accurately define mechanisms that maintain intestinal homeostasis.
Here we have developed a technique to mechanically isolate intact, unamplified RNA from serial 10μ sections along the crypt-luminal axis of the human colon in vivo, from which we have determined the expression of several miRNAs. Expression of a subset of miRNAs is similar in both differentiating Caco2 cells in vitro and cells isolated form the human crypt-luminal axis in vivo : miR-365, 324-5p, 588, let-7a1, 331-3p, and 34a are significantly increased in differentiated versus proliferating colon epithelial cells in vitro and in vivo, though for the latter two the increases in vivo are more modest than those in vitro. On the other hand, miR-145, significantly upregulated in maturing Caco2 cells in vitro, is dowregulated in differentiated cells in vivo. Importantly, these results demonstrate that miR-365 likely plays an important part in Mybl2 regulation in differentiating human colon epithelial cells in vivo as we have shown in vitro, and they establish a method to determine the mechanisms of expression of critical proliferation and differentiation mediators, such as Mybl2, at a 10μ resolution along the human crypt-luminal axis in vivo.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 138. doi:10.1158/1538-7445.AM2011-138