A TALEN-based strategy for efficient bi-allelic miRNA ablation in human cells.

Significant progress in the functional understanding of microRNAs (miRNAs) has been made in mice, but a need remains to develop efficient tools for bi-allelic knockouts of miRNA in the human genome. Transcription activator-like effector nucleases (TALENs) provide an exciting platform for targeted gene ablation in cultured human cells, but bi-allelic modifications induced by TALENs alone occur at low frequency, making screening for double knockouts a tedious task. Here, we present an approach that is highly efficient in bi-allelic miRNA ablation in the human genome by combining TALENs targeting to the miRNA seed region with a homologous recombination donor vector and a positive selection strategy. A pilot test of this approach demonstrates bi-allelic miR-21 gene disruption at high frequency (∼87%) in cultured HEK293 cells. Analysis of three independent clones showed a total loss of miR-21 expression. Phenotypical analysis revealed increased miR-21 target gene expression, reduced cell proliferation, and alterations of global miRNA expression profiles. Taken together, our study reveals a feasible and efficient approach for bi-allelic miRNA ablation in cultured human cells and demonstrates its usefulness in elucidating miRNA function in human cells.

Integrated systems for exosome investigation.

Extracellular vesicles, including exosomes, are currently being investigated to better understand their biogenesis and biological functions. There is also a rapidly growing interest in utilizing exosomes present in patient biofluids for molecular diagnostics in the clinic. Exosomes are natural shuttles of RNA and protein cargo, making them attractive as potential therapeutic delivery vehicles. Here, we describe the methods for using the latest tools and technologies to study exosomes to better understand their roles in cell-to-cell communication, for discovery of clinical biomarkers and to engineer exosomes for therapeutic applications.