Supplementation of Sbds-null monocytes with Rac2 TAT fusion proteins rescues migration but not OCG. (A) Migration of Sbds-null monocytes toward 100 ng/mL M-CSF was rescued by preincubating cells with WT or CA Rac2 TAT fusion proteins before the migration assay. Addition of the empty vector (pTAT-HA) had no effect on migration of WT or Sbds-null monocytes. Only Rac2-CA increased basal WT monocyte migration in the absence of M-CSF, and neither Rac2-CA nor Rac2-WT appreciably further increased WT monocyte migration in the presence of M-CSF. Rac2-CA mildly increased basal SBDS-null monocyte migration, and in the presence of M-CSF both Rac2-CA and Rac2-WT increased Sbds-null monocyte migration to nearly WT levels. Cosupplementation of cells with equimolar Rac1-CA and Rac2-CA (Rac1/2-CA) did not further increase migration of WT or Sbds-null monocytes in the presence or absence of M-CSF over and above levels achieved by Rac2-CA alone. Statistical significance was measured by comparing the number of monocytes that migrated in the presence of M-CSF to resting values within each treatment group (n ≥ 3): *P < .005; **P < .01. (B) OCG was not rescued in Sbds-null cultures treated with Rac2-CA or Rac1/2-CA at concentrations that increased migration. Small (3 or 4 nuclei/OC), medium (5-7 nuclei/OC), and large (≥ 8 nuclei/OC) osteoclasts were quantified after TRACP staining. In both genotypes, there was no difference in the number of osteoclasts in each size category after treatments by pTAT-HA, Rac2-CA, or Rac1/2-CA versus vehicle alone (n = 4): P > .05.