Enhanced chemotaxis, F-actin assembly, and Rac activity in Rhoh^−/− HPCs. (A) In vitro migration of Lin⁻/c-kit⁺ cells in a transwell chamber assay in response to increasing concentration of SDF-1α for 4 hours. (B) Time course of migration of Lin⁻/c-kit⁺ cells in response to SDF-1α (100 ng/mL). (C) In vitro migration of Lin⁻/c-kit⁺ cells through FN-CH296–coated filters in a transwell chamber assay in response to SDF-1α for 4 hours. (D) Chemokinesis of Lin⁻/c-kit⁺ cells in uniform concentration of SDF-1α (100 ng/mL; 4 hours). Data represent the percentage of the migrated cells as the mean plus or minus SD; n = 3. (E) F-actin assembly. Lin⁻/c-kit⁺ cells were stimulated with SDF-1α (100 ng/mL) for 30 seconds before being stained with rhodamine-labeled phalloidin and 4′,6-diamidino-2-phenylindole. The percentage of cells with cortical F-actin is shown as the mean plus or minus SD; n = 3.