Little is known about the regulation of translation in somatic stem cells, although mutations affecting ribosomal functions and translation in humans have been associated with haematopoietic defects, including cancers. Morrison and colleagues (Nature http://doi.org/rt9; 2014) have monitored protein synthesis in haematopoietic stem cells (HSCs) and progenitors in vivo, taking advantage of the incorporation of a fluorescently labelled O-propargyl-puromycin in nascent polypeptides. By analysing mouse haematopoietic cells one hour after injection of the analogue, they find that HSCs synthesize less protein per hour than other cells in the bone marrow. When induced to undergo self-renewing divisions, HSCs also produced less protein. A mutation in the Rpl24 ribosome subunit decreases protein synthesis in multiple cell types, and the authors show this mutation further reduces protein synthesis in HSCs, without any apparent adverse effect on the bone marrow per se. However, these HSCs have impaired proliferative potential in vitro and in transplantation assays, indicating a requirement for a specific level of protein synthesis in these cells. Authors have previously found that deletion of Pten in mice caused depletion of HSCs and leukaemia. They now show that protein synthesis is increased in HSCs from Pten-deficient mice. Combining the Rpl24 mutation and the Pten deletion restored protein synthesis to low levels and suppressed leukaemic development. How the tight control of protein translation level is maintained in HSCs is a question for future studies.
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Le Bot, N. Tight control of HSC protein synthesis. Nat Cell Biol 16, 307 (2014). https://doi.org/10.1038/ncb2949