In addition, lethally irradiated WT mice, which were reconstituted with miR-142 −/− bone marrow (BM) cells and analyzed 6 weeks following transfer, showed platelet paucity relative to controls that were reconstituted with WT BM cells (Figure 1-figure supplement 1). However, the decrease in platelet numbers in this model was less significant compared to that demonstrated in germline miR-142-deficient mice ( Figure 1F), plausibly due to contribution of WT cells. Taken together, these **data** demonstrate that hematopoietic-specific miR-142 activity is required for normal platelet production.