Childhood cancer treatment with radiotherapy and DNA-damaging chemotherapy can cause severe hematological toxicity, including prolonged bone marrow suppression, infection and treatment delays. Patients differ substantially in their response to similar treatment, but the biological mechanisms underlying this variation are incompletely understood. The aim of this project is to identify cellular pathways and candidate biomarkers associated with susceptibility to treatment-induced hematological toxicity. We have established two complementary human hematopoietic model systems: hematopoietic cells differentiated from induced pluripotent stem cells (iPSCs) and cord-blood-derived hematopoietic stem and progenitor cells. Using multiparameter flow cytometry, we distinguish defined populations including hematopoietic stem/multipotent progenitor cells (HSC/MPP), lymphoid progenitors (LMPP/MLP) and myeloid progenitors (GMP/CMP). These populations are exposed to clinically relevant DNA-damaging treatments, including ionizing radiation. Single-cell RNA-sequencing data have now been generated from radiation-treated hematopoietic populations. The next stage of the project is computational analysis of these data to identify cell-type-specific transcriptional responses and signaling pathways activated after treatment. Analyses will include quality control, normalization, dimensionality reduction, clustering, cell-population annotation, differential expression, pathway analysis and comparisons between treatment conditions and hematopoietic populations. The transcriptomic findings will subsequently be integrated with functional measurements of DNA damage and repair and, in later experiments, phosphoproteomic data. Candidate pathways and biomarkers will be prioritized based on reproducibility, cell-type specificity and association with treatment response. The long-term goal is to identify robust biomarkers suitable for future evaluation in pediatric cancer patients at risk of severe hematological toxicity.