Differential effect of RhoAN19 and RhoAV14 overexpression on PPF. CD41⁺ MKs derived from CD34⁺ cells from leukapheresis or umbilical cord blood were infected either with Migr-GFP⁺ or Migr-RhoAV14-GFP⁺ or Migr-RhoAN19-GFP⁺. At 48 hours after infection GFP⁺ MKs were selected and then cultured. The effects of the constructs were studied on PPF. On the day indicated, the percentage of MKs exhibiting at least one PPT extension was determined by counting at least 300 MKs in each experimental group. Results are expressed as the mean ± SD of 3 independent experiments. (A) CD41⁺ MKs derived from leukapheresis CD34⁺ cells where PPF was scored every day from day 10 to day 13. Calculated percentages for each time point were 4.2%, 7.2%, 9.6%, and 4.2% for control Migr-GFP; 7.4%, 9.6%, 13.2%, and 6.4% for RhoAN19; and 3.1%, 3.9%, 4.4%, and 2.4% for RhoAV14 (t test; P < .05). (B) CD41⁺ MKs derived from umbilical cord blood CD34⁺ cells where PPF was scored every day from day 12 to day 15. Calculated percentages for each time point were 3%, 5.9%, 11.5%, and 8.3% for control Migr-GFP; 12.9%, 18.7%, 15.1%, and 13.7% for RhoAN19; and 1.1%, 3.5%, 4.3%, and 3% for RhoAV14 (t test; P < .03). (C) Representative micrographs of MKs derived from cord blood CD34⁺ at day 13: i, Migr-GFP⁺; ii, Migr-RhoAN19-GFP⁺; iii, Migr-RhoAV14-GFP⁺. Bars represent 20 μm.