Depletion of septin 7 results in the formation of abnormal septin filaments. (A) Primary NK cells or NKL were nucleofected with the indicated siRNAs. 72 h after nucleofection, cells were lysed, clarified, and then subjected to SDS-PAGE followed by immunoblotting for the indicated proteins. (B) Primary NK cells nucleofected with the indicated siRNAs were plated onto fibronectin-coated coverslips 72 h after nucleofection. Cells were fixed and stained with antibodies against septin 1 and septin 2 and imaged using confocal microscopy. Representative images are shown. Scale bar, 10 µm; inset scale bar, 5 µm. Primary NK cells imaged in B were quantified for containing either normal septin 1 or septin 2 structures or abnormal septin structures. 50 cells were quantified for each condition over three independent experiments.