Halo-enhanced Ago2 pulldown (HEAP) to identify miRNA targets in mouse embryonic stem cells (mESCs)

The identification of miRNA targets by Ago2-CLIP methods has provided major insights into the biology of this important class of non-coding RNAs. However, these methods are technically challenging and not easily translated to an in vivo setting. To overcome these limitations and to facilitate the investigation of miRNA functions in mice, we have developed a method (HEAP) to map miRNA-mRNA binding sites. This method uses a novel mouse strain harboring a conditional Halo-Ago2 allele expressed from the Ago2 locus. By using a resin conjugated to the HaloTag ligand, Ago2-miRNA-mRNA complexes can be efficiently purified from cells and tissues expressing Halo-Ago2. We demonstrate the reproducibility and sensitivity of this method in embryonic stem cells, in embryos, in adult tissues and in autochthonous mouse models of cancers. These tools and datasets are valuable resources to the scientific community and will facilitate the characterization of miRNA functions under physiological and pathological conditions. HEAP libraries generated from mESCs