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

## TL;DR

This study uses proteomics to discover that ECM molecules regulate the expansion of blood cancer-linked stem cells with Tet2 mutations.

## Contribution

The study reveals a new role for extracellular matrix molecules in controlling Tet2-mutant hematopoietic stem cell self-renewal.

## Key findings

- Low-input proteomics provides a detailed molecular map of TET2-deficient hematopoietic stem cells.
- ECM molecules are dysregulated in Tet2−/− HSCs and influence their expansion.
- ECM-functionalized hydrogels confirm selective expansion of Tet2-mutant HSCs.

## Abstract

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.

•A comprehensive molecular map of TET2 deficiency in hematopoietic stem cells (HSCs)•Global mass spectrometry-based proteomics approach for 10,000 primary HSCs•Application of 2D functionalized hydrogel to test ECM molecules in primary HSCs•Physical and mechanical modulators impact Tet2-mutant HSC fate

A comprehensive molecular map of TET2 deficiency in hematopoietic stem cells (HSCs)

Global mass spectrometry-based proteomics approach for 10,000 primary HSCs

Application of 2D functionalized hydrogel to test ECM molecules in primary HSCs

Physical and mechanical modulators impact Tet2-mutant HSC fate

Jassinskaja, Bode et al. provide a multi-omics characterization of Tet2-mutated cells, including global proteomics revealing novel roles for extracellular matrix (ECM) molecules in selectively modifying self-renewal divisions. These findings point more broadly to physical and mechanical mediators of self-renewal, implicating integrins and cytokine signaling as extracellular drivers of clonal expansion.