Fig. 1: Screening of FKBP-EPOR chimeras to facilitate EPO-free erythroid differentiation.

A Schematic of chimeric FKBP-EPOR transgenes integrated at the CCR5 locus via CRISPR/AAV-mediated editing. Red boxes represent the location of FKBP within the EPOR. Expected functional ligands are displayed above each construct. B Schematic of HSPC editing and subsequent erythroid differentiation in the presence or absence of BB. Created in BioRender. Lesch, B. (2025) https://BioRender.com/k36m210. C Percentage of edited HSPCs that acquired erythroid markers (CD34-APC^-/CD45-V450^-/CD71-PE-Cy7⁺/GPA-PE⁺) +/−BB normalized to unedited cells +EPO at d14 of differentiation. Bars represent median +/−SEM; *p = 0.0196 by unpaired two-tailed t test across distinct samples. N = 5 biological replicates for all 1.5 conditions; N = 3 biological replicates for all 1.1, 1.2, 1.3, 1.4, 1.6, and 1.7 conditions; N = 1 biological replicate for all Mock conditions. D Fold change of edited allele frequencies over the course of differentiation +/−BB and +/−EPO. Bars represent median +/−SEM. N = 5 biological replicates for −BB/−EPO and +BB/−EPO conditions; N = 3 biological replicates for −BB/+EPO and +BB/+EPO conditions. Source data are provided as a Source Data file. E Representative flow cytometry staining and gating scheme for synEPOR 1.5-edited HSPCs at d14 of differentiation −EPO and +/−BB. Arrows indicate that only gated cells are displayed on the subsequent plot.