Stress-induced myosin-II localization and MK fragmentation altered by MYH9-RD. GFP-MIIA mutation associated with MYH9-RD, D1424N, or E1841K, specifically, were introduced into MEG-01 cells. (A) Introduction of a D1424N MIIA mutation in MEG-01 cells shows an increase in % pS1943 MIIA compared with WT by flow cytometry (*P < .005). (B) Representative fluorescent micrographs showing uniform GFP distribution from GFP-D1424N MIIA in MEG-01 (scale bar = 5 μm). (C) Upon application of stress by micropipette aspiration, GFP-MIIA is seen evenly distributed throughout the aspirated length in a manner similar to either S1943D MIIA or blebbistatin-treated cells (gray dotted line). E1841K: (y = 1.1*10⁻⁴x + 0.81, R² = 0.27, n = 10, ±SEM). (D) These cells showed an enhanced propensity to produce fragments similar to that of blebbistatin treatment (n > 8, ±SEM, *P < .05, significant from untransfected DMSO). (E) Quantification of MEG-01 size for each of the cell types used for micropipette aspiration. The MYH9-RD mutant cells, which produced fragments, show a higher distribution of larger cells compared with the WT and phosphomutants that did not fragment.