CD41 expression increases with age to mark the majority of LT-HSCs. (A) Representative FACS plots of CD41 expression within LSK cells in 2-month-old, adult 6-month-old, and 16-month-old mice. (B) Top panel shows gating strategies for analysis of the LSK compartment according to the 34F (CD34/flt3) or SLAM (CD150/CD48) stain codes. Bottom panel shows a bar diagram depicting the proportion of cells expressing CD41 within each population shown gated in the top panel. The LSKCD34+Flt3+ (LSK34+F+) gate contains LMPPs (n = 3). Error bars, SEM. (C) Representative FACS plots showing the expression of CD41 plotted against either CD34 (top) or CD150 (bottom) in mice of different ages. Quadrant statistics are frequency of parent, whereas statistics in bold text (%) correspond to the proportion of CD41+ cells within the LT-HSC subset defined as CD34− (top) or CD150+ (bottom). Note that in addition to the increase in the proportion of phenotypical LT-HSCs with age, the proportion of LT-HSCs expressing CD41+ increases as well. HSC, hematopoietic stem cell; LT, long-term; ST, short-term.