Decreased chemotactic migration of WASp-deficient CD41⁺MKs. Lin^- bone marrow cells harvested from wild-type 129Sv and WASp-deficient mice were grown for 72 hours in the presence of TPO. Migration experiments were carried out for 4 hours in bare, matrigel-coated (A) or CI-coated (B) transwells as described in “Materials and methods.” SDF-1 was added to the lower compartment at the indicated concentrations. The percentage of migrated CD41⁺ cells was determined by flow cytometry and showed reduced migratory potential of CD41⁺ WASp-deficient MKs compared with CD41⁺ wild-type MKs in the presence of SDF-1. The data represent the percentage of migrated CD41⁺ cells compared with total CD41⁺ input cells. The graphs show the mean and SD of 2 independent experiments performed in triplicate.