a-western-blotting-protocol-for-small-numbers-hematopoietic-stem

A Western Blotting Protocol for Small Numbers of Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) are rare cells, with the mouse bone marrow containing only ~25,000 phenotypic long term repopulating HSCs. A Western ...

Cincinnati Children's Hospital Medical Center

Perelman School of Medicine, University of Pennsylvania

Third Military Medical University

The transcription factor RUNX1 is frequently mutated in myelodysplastic syndrome and leukemia. RUNX1 mutations can be early events, creating preleukemic stem cells that expand in the bone marrow. Here we show, counterintuitively, that Runx1-deficient hematopoietic stem and progenitor cells (HSPCs) have a slow growth, low biosynthetic, small cell phenotype and markedly reduced ribosome biogenesis (Ribi). The reduced Ribi involved decreased levels of rRNA and many mRNAs encoding ribosome proteins. Runx1 appears to directly regulate Ribi; Runx1 is enriched on the promoters of genes encoding ribosome proteins and binds the rDNA repeats. Runx1-deficient HSPCs have lower p53 levels, reduced apoptosis, an attenuated unfolded protein response, and accordingly are resistant to genotoxic and ER stress. The low biosynthetic activity and corresponding stress resistance provides a selective advantage to Runx1-deficient HSPCs, allowing them to expand in the bone marrow and outcompete normal HSPCs.

Xiongwei Cai

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