Decreased HSC-supporting ability of niche cells in the ATF4^−/− FL. (A) Schematic illustration of the experimental designused to determine the effect of endothelial cells (ECs) or stromal cells (SCs) on WT HSCs (SLAM cells). (B) Representative flow cytometric analysis of the endothelial and stromal cells detected in the FL. (C-F) Representative flow cytometric analysis and statistical data of WT HSCs cocultured with endothelial or stromal cells for 3 to 4 days (n = 3 for each group). (G-H) Donor chimerism of the WT HSCs cocultured with endothelial or stromal cells of different genotypes for 3 to 4 days at 16 weeks after transplantation (n ≥ 7). Student t test *P < .05 and **P < .01.