Diagnosing recipient- vs. donor-derived posttransplant myelodysplastic neoplasm via targeted single-cell mutational profiling

Distinguishing donor- vs. recipient-derived myelodysplastic neoplasm (MDS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is challenging and has direct therapeutical implications. Here, we took a translational approach that we used in addition to conventional diagnostic techniques to resolve the origin of MDS in a 38-year-old patient with acquired aplastic anemia and evolving MDS after first allo-HSCT. Specifically, we used single-cell transcriptional profiling to differentiate between donor- and recipient-derived bone marrow cells and established a strategy that additionally allows identification of cells carrying the MDS-associated U2AF1S34Y variant. The patient exhibited mixed donor chimerism combined with severely reduced erythropoiesis and dysplastic morphology within the granulocytic and megakaryocytic lineage along with the MDS-associated U2AF1S34Y mutation in the bone marrow. Single-cell transcriptional profiling together with targeted enrichment of the U2AF1S34Y-specific locus further revealed that, while the immune compartment was mainly populated by donor-derived cells, myelopoiesis was predominantly driven by the recipient. Additionally, concordant with recipient-derived MDS, we found that U2AF1S34Y-mutated cells were exclusively recipient derived with X but not Y chromosome-specific gene expression. Our study highlights the clinical potential of integrating high-resolution single-cell techniques to resolve complex cases for personalized treatment decisions. The study was funded by intramural resources of the Charité – Universitätsmedizin Berlin and the Berlin Institute of Health. [Display omitted] •Distinguishing recipient- from donor-derived MDS post allo-HSCT is critical•The latter can currently not be addressed with conventional methods•Single-cell profiling of the U2AF1S34Y mutation unravels the origin of MDS•Targeted single-cell sequencing may serve as an additional pillar for MDS diagnostics Myelodysplastic neoplasms (MDS) are characterized by malignant transformation of blood-forming cells and can occur after allogeneic hematopoietic stem cell transplantation. Determining whether this is caused by the patient’s own cells (recipient derived) or cells received from the transplant (donor derived) is therefore critical. However, conventional methods fail to adequately address this question. Here, the authors solve the origin of MDS in a 38-year-old patient affected by this scenario. Using a customized single-cell-based