Stable knockdown of microRNA in vivo by lentiviral vectors

To study microRNA function in vivo, the authors optimize lentiviral-driven expression of microRNA target sequences in mice and show dose-dependent inhibition of microRNA-mediated regulation of reporter constructs as well as of natural microRNA targets. With the inhibition of a miR-223, they can phenocopy the knockout of this microRNA. Studying microRNA function in vivo requires genetic strategies to generate loss-of-function phenotypes. We used lentiviral vectors to stably and specifically knock down microRNA by overexpressing microRNA target sequences from polymerase II promoters. These vectors effectively inhibited regulation of reporter constructs and natural microRNA targets. We used bone marrow reconstitution with hematopoietic stem cells stably overexpressing miR-223 target sequence to phenocopy the genetic miR-223 knockout mouse, indicating robust interference of microRNA function in vivo.