Hematopoietic stem and progenitors were equally radiation sensitive in R4^KO vs Wt mice, but stromal and endothelial cells were more significantly impacted in R4^KO mice.

A. Representative flow cytometry plots for the BM HSC, MPP and Myeloid Progenitor (MyPro) populations with and without radiation preconditioning. B. Representative flow cytometry plots for the collagenase-released fraction of the BM for total live, stroma, and VEC (CD45-/Ter119-/CD31+/Sca1+) populations with and without radiation preconditioning. C. Radiation preconditioning significantly impacted the levels of Wt and R4KO HSC, MPP, and MyPro in the bone marrow. However, the levels were not significantly different between Wt or R4KO radiation preconditioned cohorts. Data represent n = 2 independent experiments with n = 6 Wt at 0 rads, n = 8 Wt at 450 rads, n = 6 R4KO at 0 rads, and n = 8 R4KO 450 rads. Statistics: Unpaired two tailed student’s t-test. * p≤ 0.05, ** p≤ 0.01, and **** p≤0.0001. One-way Anova: HSC p KO total live cells, stromal cells, and VECs were significantly more radiation sensitive than the Wt equivalent cell types. Data represent n = 2 independent experiments with n = 6 Wt at 0 rads, n = 8 Wt at 450 rads, n = 6 R4KO at 0 rads, and n = 8 R4KO at 450 rads. Statistics: Unpaired two tailed student’s t-test. * p≤ 0.05, ** p≤ 0.01, and **** p≤0.0001. One-way Anova: Live p = 0.0049, stroma p = 0.0028, and VEC p = 0.1315.