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Exposure to 20 mGy radiation decreases HSC functions
A
B
C
D
Figure 4. Low doses (LD) of ionizing radiations (IR) do not induce DNA dou- ble strand breaks nor activate ATM- dependent/p53-dependent DNA repair pathway in human hematopoietic stem progenitor cells (HSPC). CD34+ CD38low CD45RA– CD90+ HSPC were purified by cell sorting and exposed to different doses of IR as indicated. (A) γΗ2AX and 53BP1 foci were examined by confocal microscopy 30 minutes (min) post IR (at least 100 cells by condition were ana- lyzed. (B) Number (Nb) of 53BP1 (left panel) and γH2AX (right panel) foci by positive HSPC. (C and D) CD34+ cells were irradiated, cultured 10 min (C) or 3 hours (h) (D) at 37°C, stained for cell surface markers then fixed. (C) Analysis of ATM-phosphorylation on Ser1981 by FACS in CD34+ CD38low CD45RA– CD90+ HSPC (one representative experiment out of 4). (D) Analysis of p53-phosphory- lation on Ser15 (left) and p53 protein expression (right) in CD34+ CD38low CD45RA– CD90+ HSPC by FACS 3 h post IR (one representative experiment out of 5). Results are shown as mean±stan-
mean. *P<0.05,
dard error of
****P<0.0001 (Mann and Whitney sta- tistics).
haematologica | 2020; 105(8)
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