Low-input proteomics identifies vWF as a negative regulator of Tet2 mutant hematopoietic stem cell expansion.

Despite rapid advances in mapping genetic drivers and gene expression changes in hematopoietic stem cells (HSCs), few studies exist at the protein level. We perform a deep, multi-omics characterization (epigenome, transcriptome, and proteome) of HSCs in a mouse model carrying a loss-of-function mutation in Tet2, a driver of increased self-renewal in blood cancers. Using state-of-the-art, multiplexed, low-input mass spectrometry (MS)-based proteomics, we profile TET2-deficient (Tet2(-/-)) HSCs, revealing previously unrecognized molecular processes that define the pre-leukemic HSC molecular landscape. Specifically, we obtain more accurate stratification of wild-type and Tet2(-/-) HSCs than transcriptomic approaches and identify extracellular matrix (ECM) molecules as being dysregulated upon TET2 loss. HSC expansion assays using ECM-functionalized hydrogels confirm a selective effect on the expansion of Tet2-mutant HSCs. Taken together, our study represents a comprehensive molecular characterization of Tet2-mutant HSCs and identifies a previously unanticipated role of ECM molecules in regulating self-renewal of disease-driving HSCs.