Systematic evaluation of microRNA processing patterns in tissues, cell lines, and tumors

  1. Eun Joo Lee1,
  2. Myungwon Baek1,
  3. Yuriy Gusev2,
  4. Daniel J. Brackett2,
  5. Gerard J. Nuovo3, and
  6. Thomas D. Schmittgen1
  1. 1College of Pharmacy, Ohio State University, Columbus, Ohio 43210, USA
  2. 2Department of Surgery, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104 USA
  3. 3Department of Pathology, Ohio State University, Columbus, Ohio 43210, USA

Abstract

Very little is known regarding regulation of microRNA (miRNA) biogenesis in normal tissues, tumors, and cell lines. Here, we profiled the expression of 225 precursor and mature miRNAs using real-time PCR and compared the expression levels to determine the processing patterns. RNA from 22 different human tissues, 37 human cancer cell lines, and 16 pancreas and liver tissues/tumors was profiled. The relationship between precursor and mature miRNA expression fell into the following four categories: (1) a direct correlation exists between the precursor and mature miRNA expression in all cells/tissues studied; (2) direct correlation of the precursor and mature miRNA exists, yet the expression is restricted to specific cell lines or tissues; (3) there is detectable expression of mature miRNA in certain cells and tissues while the precursor is expressed in all or most cells/tissues; or (4) both precursor and mature miRNA are not expressed. Pearson correlation between the precursor and mature miRNA expression was closer to one for the tissues but was closer to zero for the cell lines, suggesting that processing of precursor miRNAs is reduced in cancer cell lines. By using Northern blotting, we show that many of these miRNAs (e.g., miR-31, miR-105 and miR-128a) are processed to the precursor, but in situ hybridization analysis demonstrates that these miRNA precursors are retained in the nucleus. We provide a database of the levels of precursor and mature miRNA in a variety of cell types. Our data demonstrate that a large number of miRNAs are transcribed but are not processed to the mature miRNA.

Keywords

Footnotes

  • Reprints requests to: Thomas D. Schmittgen, College of Pharmacy, Ohio State University, Columbus, OH 43210, USA; e-mail: Schmittgen.2{at}osu.edu; fax: (614) 292-7766.

  • Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.804508.

    • Received August 30, 2007.
    • Accepted October 12, 2007.
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