Fetal Liver-Restricted Leukemic Proliferation Via GATA1s-CSF2RB-MPL Axis In Down Syndrome
Description
Transient abnormal myelopoiesis (TAM) is a human fetal liver leukemia driven by GATA1s mutations and a rare exemplar of a spontaneously resolving cancer when blood formation shifts from liver to bone marrow (BM) during development. We report that upregulated cytokine receptor CSF2RB marks TAM cells because it is a GATA2 target that escapes repression by GATA1s. Pathologically expressed CSF2RB unexpectedly interacts with the TPO receptor (MPL) to prolong JAK-STAT signaling by fetal-liver produced TPO, driving GATA1s-mutant cell expansion. TAM can transform into myeloid leukemia of Down syndrome (ML-DS) upon acquisition of additional mutations. The ML-DS driver CSF2RB A455D forces MPL dimerization resulting in constitutive JAK-STAT activation, bypassing TPO dependence in the fetal-liver niche, thereby enabling proliferation in the BM. Base-editing reversion of another ML-DS JAK-STAT-activating mutation, JAK3 A572V, restores TPO dependence. Collectively, we define a cytokine gate that developmentally restricts GATA1s oncogenic competence, highlighting a therapeutically targetable niche-specific tumor dependency.
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Raw FASTQ files generated from the 10x Genomics platform were processed using Cell Ranger v6.0.1. Reads were aligned to the human reference genome (GRCh38), and gene–cell count matrices were generated for each sample. Downstream analysis was performed using the Seurat package v4.1.072. Low-quality cells with high mitochondrial gene content were filtered using the miQC package73 v3.20 with a posterior cutoff of 0.99. Doublets were identified and removed using scDblFinder74 with default parameters. Cells expressing more than 500 genes were retained for further analysis. Gene expression matrices were log-normalized using the NormalizeData function with method = "vst" to identify 3,000 variable genes per sample. A set of 2,000 shared variable genes across samples was selected using SelectIntegrationFeatures function for principal component analysis (PCA). Disomic samples were integrated using Harmony with 30 principal components. The resulting 35 Harmony-corrected PCs were used for Uniform Manifold Approximation and Projection (UMAP) and Louvain clustering to generate a transcriptional reference map of disomic haematopoiesis. T21 and TAM samples were projected onto the disomic reference using Symphony. Cell type annotations were assigned based on expression of lineage-specific marker genes, positive enrichment of published gene signatures and AUCcell scores derived from curated hematopoietic lineage gene sets. Single cell genotyping of TAM samples was performed by GoT or imputed with scPred.
Institutions
- University of OxfordOxfordshire, Oxford