Fig. 1

A Schematic illustration of the spatiotemporal location of hematopoietic niche sites in zebrafish. Corresponding dosing windows (hours post fertilization (hpf)) for chemical or genetic modulation are defined by colored bars and text and used to mark treatment schemes in subsequent figures. Created in BioRender. Walcheck, M. (2026) https://BioRender.com/umy6s89. B ROS level measured by flow cytometry using CellROX Orange^TM fluorescent ROS-dye in total live cells (*P = 0.0097, ****P < 0.0001) and in CD41:GFP+ HSPCs (***P = 0.0002, ****P < 0.0001) from 72 hpf Tg(−6.0itga2b:EGFP) embryos. MFI of CellROX is displayed relative to the average of the control for each experiment (NAC treatment (Tx): 10 µM, 48-72 hpf) [two-tailed unpaired t test with Welch’s correction: Mean ± SEM, n = 6 embryos/condition, 13 replicate clutches for prdx1-MO, 10 for NAC]. C Representative WISH images showing combined expression of runx1/cmyb following pdrx1 knockdown or NAC treatment in the VDA at 36 hpf (NAC Tx: 10 µM, 24–36 hpf; top row) and CHT at 72 hpf (NAC Tx: 10 µM, 48–72 hpf, middle row) compared to stage-matched wild-type (WT; AB strain) controls. Scale bar, 100 µM. D Phenotypic distribution plot of runx1/cmyb expression scored in embryos from (C) as high (Hi), medium (Med) and low (Lo) relative to WT sibling controls at 36 hpf (*P = 0.0416, top row) and 72 hpf (*P = 0.0309, middle row) [Pearson’s chi-square (two-sided), n = 20/condition, 4 clutches]. ETg(−6.0itga2b:EGFP) embryos treated as above (C) and imaged at 72 hpf. Scale bar, 200 µM. F Frequency of CD41^lo HSPCs in Tg(−6.0itga2b:EGFP) embryos by flow cytometry at 72 hpf after prdx1 knockdown (****P < 0.0001) or NAC (**P = 0.0036) (Tx: 10 µM, 48–72 hpf; two-tailed unpaired t test with Welch’s correction: Mean ± SEM, n = 12/condition, 10 clutches for prdx1 MO, 8 clutches for NAC). G Confocal imaging of Tg(−6.0itga2b:EGFP) embryos at 120 hpf treated with prdx1-MO or NAC (Tx: 10 µM, 48–120 hpf). CHT: top row; Scale bar, 100 µM. Kidney marrow (KM, region highlighted by white box): bottom row; Scale bar, 50 µM. H Frequency of CD41^lo HSPCs in Tg(−6.0itga2b:EGFP) embryos by flow cytometry at 120 hpf after prdx1-MO (*P = 0.0037) or NAC treatment (P = 0.6858), as shown in (G) (NAC Tx: 10 µM, 48–120 hpf [two-tailed unpaired t test with Welch’s correction: mean ± SEM, n = 8 whole embryos/ condition, 6 clutches]. I Representative WISH images of rag1 expression in the thymus at 120 hpf following prdx1 knockdown. Scale bar, 100 µM. J Phenotypic distribution of rag1 expression from (I) scored as Hi, Med, and Lo (****P < 0.0001) [Pearson’s chi-square (two-sided): n = 15/condition, 3 clutches]. K Frequency of Rag2+ lymphoid progenitor cells in Tg(rag2:GFP) embryos by flow cytometry at 120 hpf after prdx1 knockdown (*P = 0.0399) [two-tailed unpaired t test with Welch’s correction: mean ± SEM, n = 8/condition, 3 clutches]. B, D, F, H, J, K Source data are provided as a Source Data file.