TALEN-engineered human cell lines with microRNA-21 null mutations

Dysregulation of microRNA-21 (miR-21) is associated with many types of cancer as well as with kidney and cardiovascular diseases. Aberrant expression of miR-21 leads to multiple phenotypic alterations including cellular proliferation, invasiveness, apoptosis, and fibrosis. We recently used transcription activator-like effector nucleases to engineer human cell lines with miR-21 null mutations. As expected, loss of miR-21 resulted in decrease cell proliferation and reduced transforming activity in culture and in xenografts. Besides an increase of apoptotic gene expression, miR-21 knockout cells also had significantly increased expression of genes involved in extracellular matrix interaction. Results from small RNA sequencing suggest that miR-21 deletion changed the microRNA expression profile. These results raise intriguing possibilities that loss of miR-21 expression may influence cellular interactions and that cells with long term miR-21 deficiency may compensate for the loss of this highly expressed microRNA by changing the abundance of alternate microRNAs or the AGO2 protein in order to maintain the microRNA-AGO2 homeostasis. Further characterization and utilization of miR-21 knockout human cells will shed new light on this pathologically important microRNA.