Defective spreading and actin remodeling of DKO MKs upon adhesion to Horm collagen. (A) Representative lowest plane images of spread BM-derived MKs analyzed by confocal microscopy (Leica TCS SP8) using a 40× objective. Scale bars, 25 µm. (B) Quantification of MK spreading area. At least 30 MKs were analyzed per animal. Values are mean ± SD (n = 3). (C-F) Analysis of F-actin distribution in WT and DKO MKs spread on Horm collagen. (B) Visualization of podosome-like structures by F-actin and Arp2 staining. Scale bars, 25 µm; insets, 10 µm. (C) Quantification of phalloidin fluorescence intensity (FI) normalized to α-tubulin (D), density of podosome-like structures (number per µm²) as well as total numbers in the Arp2- (E) and F-actin–channel (F) in control and DKO MKs spread on Horm collagen. Quantification was done using ImageJ Software. Unpaired, 2-tailed Student t test. ***P < .001. A.U., arbitrary unit; ns, nonsignificant.