Reduction in SCF-induced tritiated thymidine incorporation of Lyn-deficient mast cells can be reconstituted by ectopic expression of wild-type Lyn.

(A) Transfection with wild-type Lyn restores SCF-induced proliferation of Lyn-deficient mast cells to normal. Wild-type (WT) and Lyn-deficient mast cells (KO) were transfected with Lyn wild-type (WT) or vector control DNA. Transfected mast cells were incubated for 24 hours in QBSF-58 media containing the indicated concentration of SCF and then assessed for [³H]-thymidine incorporation as described in “Materials and methods.” All data represent the mean and standard deviation of quadruplicate samples. (B) Reconstitution of SCF-induced proliferation of Lyn-deficient cells is dependent on Lyn kinase activity. Lyn-deficient mast cells (KO) were transfected with wild-type Lyn (WT), kinase-inactive Lyn (KI), or vector control DNA. Transfected mast cells were incubated for 24 hours in the indicated concentration of SCF and then assessed for [³H]-thymidine incorporation, as described in “Materials and methods.” All data represent the mean and standard deviation of quadruplicate samples.