Human erythroid colony formation in vitro: evidence for clonal origin.

Human marrow cells, suspended in methylcellulose medium containing erythropoietin, give rise to discrete colonies of hemoglobin synthesizing cells. The presumption that such colonies originate from single progenitor cells has been tested directly in females with X-chromosome inactivation mosaicism using glucose-6-phosphate dehydrogenase (G-6-PD) as a marker. When individual colonies were grown from marrow cells obtained from two black females heterozygous for G-6-PD, only one or the other isoenzyme type was observed, but not both. These results are most consistent with the interpretation that human erythroid colonies arise from single cells.