Time-lapse imaging reveals CSF-1R Y559 to be sufficient for CSF-1–mediated lineage choice. (A) Csf1r^−/− preGMPs were FACS purified and transduced with lentiviruses encoding different CSF-1R mutants (supplemental Figure 3B-C). Transduced cells were purified, time-lapse imaged during CSF-1–mediated differentiation (Video 1), and tracked. (B) Percentage of surviving colonies. Dying colonies were defined as those with <2 cell divisions of undifferentiated cells. (C) Percentage of differentiating colonies (colonies with CD11b^pos F4/80^pos adherent cells at any timepoint) of all starting cells. Displayed Ywt and YEF data were pooled from all experiments. Total movies/colonies analyzed: Ywt (9/247), Y544F (3/55), Y559F (4/75), Y697F (3/45), Y706F (3/52), Y721F (3/81), Y807F (3/141), Y921F (4/114), Y974F (2/51), YEF (4/140), Y544AB (2/64), Y559AB (3/138), Y721AB (2/67), Y559/721AB (4/99), Y807AB (2/72), and Y559/807AB (4/115). For pairwise comparison, see supplemental Figures 6 and 7. Red bars represent single tyrosine mutants and controls, blue bars represent AB mutants. P values (calculated for data pairs) are shown as follows: *P < .05; **P < .01; ***P < .001 compared with Ywt (single tyrosine mutants) or YEF (AB mutants). AB, add back.