NAAA and essential thrombocythemia: MgPs may partially overlap pMKPs which have been reported to be expanded in the mouse essential thrombocythemia model.38 MgPs appeared to be more immature than MkPs11,13 because MgPs generated on average 8 cells per cell, significantly more Mks than did MkPs in vitro, also supported by in vivo Plt reconstitution activity (Figs. 2, 4).