Defective Adhesion, Migration and Homing Are Associated with Altered Rho GTPase Activity in Cells from Fanconi Anemia Patients.

Fanconi anemia (FA) is a genetic disorder characterized by bone marrow failure and predisposition to malignancy. One of the potential therapeutic options for patients with FA is collection of autologous multipotent hematopoietic progenitors prior to the development of severe pancytopenia for autologous transplantation and gene therapy. However, poor engraftment of FA hematopoietic cells represents a major obstacle for effective transplantation. Our current study attempted to investigate the mechanism underlying defective engraftment of FA bone marrow (BM) cells. Using BM cells from patients carrying mutations in the FA complementation group A (FA-A), we demonstrate that SDF (Stromal cell-derived factor)-1alpha – and integrin-mediated migration and adhesion, respectively, is defective in FA primary BM cells compared to those from normal donors (more than 2-fold decrease in both migration and adhesion compared to normal BM cells). Complementation of the FA-A defect by retrovirus gene transfer of FANCA gene almost completely restores the ability of the BM cells to migrate towards the chemokine SDF-1alpha. Similar results are obtained with primary fibroblast cells derived from a FA-A patient, which show 3-fold and 35% decrease in adhesion and migration, respectively, compared to FANCA -corrected cells. Furthermore, when transplanted into immunodeficient Nod/scid recipient mice, the FA-A BM cells exhibited significantly impaired homing function whereas normal cells were efficiently homed in the bone marrow. A significant decrease in the activity of the Rho GTPase Cdc42 in FA-A cells is found associated with the patient cell defective functions. Taken together, these data suggest that the FA proteins play a role in the regulation of cell adhesion and migration in addition to maintaining genomic stability, influencing homing and engraftment, possibly via the small GTPase signaling pathway. These findings may have implications in development of strategies for restoring engraftment function of FA hematopoietic cells.