MKs with Myh9-RD mutations have defective migration patterns in SDF-1 gradients. (A-F) Wind-rose plots of WT and Myh9-RD mutant MKs toward SDF-1. The length of each leaflet represents the migration trajectory as percentage of cells (WT^GFP+/−, n = 34; R702C^GFP+/−, n = 40; WT, n = 30; D1424N^+/−, n = 42; WT, n = 31; E1841K^+/−, n = 36). For cell migration assays, live-cell imaging was performed at 37°C and 5% CO₂ with an achromat ×10 (NA, 0.25) objective of a Nikon Eclipse TE200 microscope. Images were taken with a CoolSnap HQ2 camera with Metamorph software (Molecular Devices). (G) Scatterplots representing median and interquartile range of the distribution for forward migration indices of WT and mutant MKs up the SDF-1 gradient. Directional migration is indicated by values >0.1. (H) Scatterplots representing median distribution of MK velocities for WT and mutants. NS, not significant. (I-K) Representative histograms from 3 mice of each genotype showing the surface expression of CXCR4 on MKs by flow cytometry. **P ≤ .01; ***P ≤ .001; ****P ≤ .0001.