| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000)
Fiscal Year 2011: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2010: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
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| Research Abstract |
The intestinal epithelium is the most rapidly self-renewing tissue in adult mammals. The self-renewing epithelium of the small intestine is ordered into crypts and villi.
In this study, we focused on the expression and role of tumor suppressor miRNA, Let-7, in mouse small intestine. As a result, we found expression of Let-7 family miRNAs were down-regulated in the crypt region. While expression of Lin28A, which is strong inhibitor of Pri-and Pre-let-7 processing, was only detected at crypt region, Lin28A-mediated inhibition of Let-7 was speculated.
To examine the processing of Let-7 in vivo, we use Let-7-GFP transgenic mice, in which processing of pri-miRNA were visualized by GFP expression. We found that processing of pri-let-7 was inhibited in crypt region. To examine the role of Lin28A-mediated down-regulation of Let-7 in intestinal stem cells, we use in vitro and in vivo analysis. Interestingly, we found that forced expression of Lin28A in rat crypt cell-derived cell line, IEC-6 cells, enhanced cell proliferation, migration activity and decreased contact inhibition of the cells. We observed that overexpression of Lin28 in IEC-6 cells potently depletes levels of multiple mature miRNAs in the let-7 family, leading to a concomitant increase in protein abundance of c-Myc, a let-7 target.
To investigate Lin28A function in vivo, we generated a transgenic mouse strain that expresses Lin28A in intestinal epithelium cells. Since some of the Lin28A transgenic mouse displays adenocarcinoma in small intestine, we are now examining the molecular mechanism of the phenotype.
Taken together, our results suggested that crypt specific Lin28A expression regulates cell proliferation of intestinal stem cells, and may contribute to malignant progression of intestinal tumors.
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