CD41 expression correlates with a quiescent state of HSCs. (A) Bar diagrams showing in vivo BrdU incorporation in CD41+ and CD41− LSK fractions in 2-month-old (n = 10) and 16-month-old (n = 3) mice. (B) Scatter plots showing in vivo BrdU incorporation of CD41+ (dark gray) and CD41− (light gray) LT-HSC (LSKCD34−) and ST-HSC+LMPP (LSKCD34+) cell fractions in individual 2-month-old mice. White symbols indicate total cell fraction (n = 10). (C) Size distribution of 224 single CD41− and CD41+ LT-HSC (LSKCD48−CD150+) derived colonies after 14 days in methylcellulose culture (n = 3). Error bars, SEM. (D) Bar diagram showing expression of CD41 within the LSKCD150+ (LT-HSC) fraction in control (-5FU) or mice 7 days after 5-FU treatment (n = 3). (E) Bar diagram showing the proportion of cells with the LT-HSC phenotype (LSKCD150+CD48−) expressing CD41 after 2 to 3, 5, and 7 days of ex vivo culture of sorted CD41+ or CD41− LSKCD150+CD48− LT-HSCs. *P < .05, ***P < .001 by Student t test.