Distinct hematopoietic cell fates regulated by graded expression of HOXA10

The homeobox (Hox) transcription factor HOXA10 has been implicated in regulation of hematopoietic cell fate. Here, using a transgenic mouse model where expression of HOXA10 is tightly regulated in a graded, doxycyclin-dependent manner we demonstrate that several key commitment steps in hematopoietic differentiation have distinctly different outcomes depending on the expression level of HOXA10. Similarly, HOXA10 regulates hematopoietic stem cell (HSC) proliferation in a dose dependent manner, since intermediate levels of HOXA10 generated a 4.5-fold increase in long-term repopulating capacity after 13 days of liquid culture, whereas high levels reduced proliferation of HSCs. Interestingly, the effects on HSC proliferation were associated with altered expression of several known regulators of stem cell self-renewal. Taken together, our findings reveal entirely novel functional and molecular aspects of HOXA10 in regulation of hematopoiesis and emphasize the need for tightly regulated production of HOX proteins in possible future applications of stem cell expansion.

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