Protein Lnk Keeps Hematopoietic Stem Cells Silent

Wei Tong and colleagues, at Children’s Hospital of Philadelphia, have provided new insight into the molecular control of hematopoietic stem cells (HSCs), the cells that give rise to all types of blood cell, by explaining why mice lacking an inhibitory protein known as Lnk have more HSCs than normal mice.

In the study, it was observed that a greater proportion of HSCs in mice lacking Lnk were not undergoing cell division and were said to be quiescent (i.e., in a state of inactivity or in silent mode).  Lnk was found to regulate HSC quiescence by binding a signaling protein known as JAK2 after it was activated following binding of the soluble factor TPO to its receptor Mpl.  The authors therefore hypothesize that in the absence of the inhibitory molecule Lnk, TPO-initiated signaling from Mpl to JAK2 goes unchecked and the number of HSCs produced is increased to a level at which they do not need to undergo cell division as often to maintain their population.

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