Many aspects of cellular physiology remain unstudied in somatic stem cells. For example, there are almost no data on protein synthesis in any somatic stem cell. We found that the amount of protein synthesized per hour in haematopoietic stem cells (HSCs) in vivo was lower than in most other haematopoietic cells, even if we controlled for differences in cell cycle status or forced HSCs to undergo self-renewing divisions. Reduced ribosome function in Rpl24Bst/+ mice further reduced protein synthesis in HSCs and impaired HSC function. Pten deletion increased protein synthesis in HSCs but also reduced HSC function. Rpl24Bst/+ cell-autonomously rescued the effects of Pten deletion in HSCs, blocking the increase in protein synthesis, restoring HSC function, and delaying leukaemogenesis. Pten deficiency thus depletes HSCs and promotes leukaemia partly by increasing protein synthesis. Either increased or decreased protein synthesis impairs HSC function
