Finally, we performed a cytochalasin D (CytoD) washout study, which followed the re-assembly of actin filaments after forced depolymerization ( Figure 4H). The number of miR-142 −/− MKs that were able to create stress-fibers following treatment with CytoD was significantly lower, relative to control MKs ( Figure 4I). Collectively, these **data** reveal that miR-142 is pivotal for normal actin dynamics and architecture in MKs.