In vitro colony assay for a new class of megakaryocyte precursor: colony-forming unit megakaryocyte (CFU-M).

A plasma culture system has been used successfully to grow and quantitate megakaryocyte colonies from mouse bone marrow following their staining for acetylcholinesterase activity in situ. Colonies averaging about six acetylcholinesterase-positive cells appear with a peak incidence after 4 days in culture with a plating efficiency of one colony formed for every 10(4) nucleated cells plated.