HMGA1 Chromatin Regulators Drive MPN Progression [scRNA-Seq]

Myeloproliferative neoplasms (MPN) transform to myelofibrosis (MF) and highly lethal acute myeloid leukemia (AML), although actionable mechanisms driving progression remain elusive. The HMGA1 chromatin regulator is up-regulated during MPN progression with highest levels after transformation. HMGA1 depletion in JAK2V617F MPN AML cell lines disrupts proliferation, clonogenicity, and leukemic engraftment. Surprisingly, loss of just a single Hmga1 allele prevents progression to MF in JAK2V617F transgenic mice, decreasing blood counts and expansion in stem and myeloid progenitors while preventing splenomegaly and fibrosis within the spleen and bone marrow. RNA sequencing revealed HMGA1-dependent transcriptional networks that govern proliferation (E2F, G2M, mitosis, MYC targets) and cell fate, including the GATA2 master regulatory gene. Silencing GATA2 recapitulates phenotypes observed with HMGA1 depletion whereas GATA2 re-expression partially rescues leukemogenesis. HMGA1 transactivates GATA2 through sequences near the developmental enhancer (+9.5), increasing chromatin accessibility and recruiting active histone marks. Further, HMGA1 transcriptional networks, including GATA2, are activated in human MF after leukemic transformation. Further, HMGA1 depletion synergizes with the JAK2 inhibitor, ruxolitinib, to prolong survival in murine MPN AML. These findings illuminate HMGA1 as a key epigenetic switch required for MPN transformation and promising therapeutic target to treat or prevent disease progression. We used 10x genomics platform to profile single-cell transcriptome of LSK (Lineage-/Sca1+/Ckit+) hematopoietic stem/progenitor cells (HSPCs) derived from 2 JAK2V617F/V617F and 2 JAK2V617F/V617F-Hmga1+/- mice