Establishing embryonic stem cell lines with reduced expression of filamins A and B. (A) Schematic diagram of the targeting vector used to generate ESCs with reduced expression of both FlnA and FlnB. The vector is under the control of the CMV immediate early promoter, coexpresses GFP as a marker of shRNA expression, and renders cells resistant to Zeocin, allowing for enrichment of transfected cells. (B) shRNA sequence used to knock down both filamins A and B, with corresponding immunoblot of the ES cell line termed FlnAB_Low. Note that the expression of both filamin isoforms is reduced 70%-80%.