Characterization of miRNA Expression in Normal Human Tissues
|Measuring the amount of naturally-occurring miRNAs in tissues of different physiological and pathological conditions is an important first step to investigate the functions of miRNAs. Applied Biosystems scientists examined the profiles of 345 human miRNAs in 40 normal tissues using TaqMan MicroRNA Assays. These profiles provide a baseline against which miRNA profiles in tissues can be compared.|
Normalizing RNA Input
miRNA Profiles Correlate with Anatomically and Physiologically Associated Tissues
Figure 1. Unsupervised Hierarchical Clustering of Normal Human Tissues Based on the Variation of miRNA Abundance. The pseudocolor scale outlines the CT values represented in the heat map. Reproduced with permission from BMC Genomics 2007, 8:166 .
Differentially Expressed Groups Clustered in Genome
Figure 2. An Enlarged View of the Eight Groups of Most Differentially Expressed miRNAs. Reproduced with permission from BMC Genomics 2007, 8:166 .
miR-129, miR-219, and miR-330, showed specific expression in brain. The computationally predicted targets for these miRNAs showed reduced expression in brain, while their expression in non-brain tissues was highly variable. miR-199a, miR-199b, and miR-214 showed low expression in brain and peripheral blood mononuclear cells (PBMC) relative to the other tissues. Computational predictions of brain and PBMC miRNA targets indicate expression in one or the other tissue, but not both.
These results indicate that miRNA expression may be controlled by a binary effect on expression of its targets: when miRNA expression is high, target gene expression is low; and when miRNA expression is low, expression of the target genes may be controlled by other elements such as transcription factors.
Yu Liang, Dana Ridzon, Linda Wong, Caifu Chen • Applied Biosystems, Foster City, CA