Punctuated MT filaments in RanBP10−/− MKs. For the quantitative evaluation of MK immunostained with an antibody against β-tubulin, 4 different MT network classifications were determined: reticular, cortical, bundled, and punctuated. The percentage of each subtype was determined individually. (A) The comparison of RanBP10-depleted, RanBP-overexpressing, and wild-type MKs indicated diverging effects on MT bundling and filament collapse. (B-C) Representative examples of immunostained MKs with reticular filamentous MT (B) and punctuated MT (C); scale bar 10 μm. (D) RanBP10-null MKs show a lack in filamentous MTs compared with wild-type cells but an increase in punctuated MT. (E) MK cultures were examined for proplatelet formation by light microscopy on day 5 of cultivation with TPO. RanBP10-null MKs have a slight decrease in proplatelet formation that is statistically significant (P < .05). Error bars represent SD. (F) Peripheral platelet counts did not differ between wild-type and mutant animals.