Leucine treatment of SBDS-deficient cells. (A) Translation in S-3 cells and SCR cells was studied by measuring incorporation of 35S-methionine/cysteine into equal amounts of newly synthesized trichloroacetic acid-precipitable peptides. Data are the mean ± SE of 3 experiments. *P < .05, statistically significant results (t test). (B) SBDS-knockdown and control K562 cells were induced to undergo erythroid differentiation by plating 2 × 104 cells/35-mm dishes with hemin. Replicate cultures were either treated or not treated with 600 μg/mL of leucine and assessed daily for cell numbers by trypan blue exclusion. The cell growth of the SBDS-knockdown K562 cells after 5 days was significantly improved with leucine treatment (P < .05). (C) SDS patients and healthy control bone marrow CD34+ cells were plated in duplicates at a density of 1 × 103 cells/1 mL dish with serum-free containing methylcellulose and a cytokine cocktail (SCF, GM-CSF, IL-3, IL-6, G-CSF, and erythropoietin). Additional duplicate cultures were plated in the same conditions, but with leucine. BFU-E colonies containing 50 cells or more were scored after 14 days under an inverted microscope.
