ARNT KO LT-HSCs exhibit diminished viability. (A) Representative cell-cycle FACS plot of LT-HSCs from control and KO animals. (B) No significant differences in cell cycle were observed in any hematopoietic progenitors from KO animals (n = 6 ctrl, n = 6 KO). (C) Quantification of BrdU proliferation assay in HSC subsets. (D) qRT-PCR analysis of p16 and p19 in FACS-sorted LT-HSCs. (E) Representative Annexin V FACS plot of LT-HSC shows enhanced apoptosis in KO LT-HSCs. (F) LT-HSCs, but not MPPs or LSK cells, display enhanced apoptosis (n = 6 ctrl, n = 6 KO). (G) Histogram of representative ROS analysis and (H) quantification of mean fluorescence intensity for LT-HSCs and MPPs. No differences were observed. (I) qRT-PCR analysis of FACS-sorted LT-HSCs for cell survival factors. *P < .05, **P < .01.