Homing to bone is defective in SrfKO^H cells. (A) Srf⁺ and SrfKO^H fetal liver LSK cells were mixed 1:1 and 10⁵ cells injected into the tail vein of C57Bl6 mice, with prior irradiation where indicated. The ratio of SrfKO^H to Srf⁺ cells present in the hind-limb long bones was evaluated at the indicated times. (B) Absolute numbers of cells homed to the long bones at different times after injection in the experiment shown in (A). (C) Proliferation of CFSE-labeled cells homed to long bones at different times after injection. (D) Homing to calvaria. Animals were injected with fetal liver LSK cells from Srf⁺ and SrfKO^H animals, labeled with CFSE and SNARF, respectively, to increase detection sensitivity, mixed 1:1. Left, relative proportions of Srf⁺ and SrfKO^H cells in calvaria 16 hours after injection. Right, distance of each homed LSK cell from the nearest bone or endothelial cell. Error bars = standard error of the mean.