Human Genome as an RNA Machine
Fifteen years ago, no one had even heard of microRNAs. Not anymore: These small but abundant regulatory, non-coding RNAs - initially thought to be an oddity of nematode biology - appear to control gene expression in all animals, as well as in plants, some viruses, and at least one unicellular alga. So far, scientists have tracked their activity in all major organ systems, illustrated on the following pages.
Already, we see some general principles: Some animal micro-RNAs (miRNAs) are specific to a single tissue or cell type, others are expressed across multiple organs, and each organ seems to have a unique miRNA "profile" of characteristic expression levels among a set of miRNAs. These profiles change throughout development and during diseases such as cancer, suggesting that they may be useful diagnostic tools.
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