Single-cell analyses reveal aberrant pathways for megakaryocyte-biased hematopoiesis in myelofibrosis and identify mutant clone-specific targets

Myelofibrosis is a severe myeloproliferative neoplasm characterised by increased numbers of abnormal bone marrow megakaryocytes that induce progressive fibrosis, destroying the hematopoietic microenvironment. To determine the cellular and molecular basis for aberrant megakaryopoiesis in myelofibrosis, we performed high-throughput single-cell transcriptome profiling of 50,702 hematopoietic stem/progenitor cells (HSPCs), and single-cell proteomics, genomics and functional assays. We identified an aberrant pathway for direct megakaryocyte differentiation from the earliest stages of hematopoiesis in myelofibrosis and associated aberrant molecular signatures, including surface antigens selectively expressed by JAK2-mutant HSPCs. Myelofibrosis megakaryocyte progenitors were heterogeneous, with distinct expression of fibrosis and proliferation-associated genes and putative therapy targets. We validated the integrin G6B as a promising JAK2-mutant clone-specific surface antigen, warranting further development as an immunotherapeutic target. Our study paves the way for selective immunotherapeutic targeting in myelofibrosis and more broadly illustrates the power of single-cell multi-omics to discover tumor-specific therapeutic targets and mediators of tissue fibrosis. Overall design: Examination of 3 human myelofibrosis tissue samples and 2 controls