We are thrilled to share a pre-print describing a novel approach to interfere with global microRNA activity in cells and in living animals without affecting miRNA biogenesis or miRNA abundance.
The approach is based on a peptide (T6B) previously generated by Gunter Meister and Tom Tuschl that binds to Argonaute proteins and prevents the assembly of a functional miRISC complex, thus effectively blocking miRNA-mediated gene repression without impairing miRNA biogenesis.
To explore the consequences of miRNA-inhibition in vivo, we have generated a novel genetically engineered mouse strain that expresses the T6B peptide fused to YFP in a doxycycline-inducible manner. By crossing it with an appropriate rtTA expressing strain it is possible to block miRNA function in a tissue-restricted and temporally controlled manner.
The effect is fully reversible, and miRNA biogenesis (or endogenous siRNA function) are not affected. The entity of de-repression of predicted miRNA targets is roughly proportional to the corresponding miRNA family abundance.
Each “bubble” in the plot above is a set of predicted targets of a miRNA family. On the x axis we plotted the average log2 fold change compared to the background(reported as z-score) and on the y-axis is the miRNA family abundance. Using this novel mouse strain we show that although miRNA-mediated repression is required during embryonic development, in many adult tissues it seems largely dispensable under homeostatic conditions, and becomes essential only in after acute damage and during regeneration.
A notable exception is represented by the skeletal muscle and the heart, where even under physiologic conditions T6B induction results in tissue degeneration and death.
We have a ton of follow-up experiments planned and we hope our colleagues interested in the biology of miRNAs will find it useful. As always, the mouse strain will be freely available through @jacksonlab as soon as we have completed the donation process.
Dr. Gaspare La Rocca deserves a special mention as he was the main driver of this project. He came up with the idea, performed—together with Bryan King—most of the key experiments, and persisted through many ups and downs during the past few years.