Expression of HOX B6 from in vitro erythropoietic progenitor cell colonies (CFU-E after 48 hours and BFU-E after 10 days incubation) and in colonies derived from HPP-CFC (after 14 days of incubation). (A) Ethidium bromide gel for HOX B6. (B) Southern blot for HOX B6. (C) HPRT control. Lane 1, markers; lane 2, erythroid colonies from 8.5-day embryos; lane 3, erythroid burst colonies from 8.5-day embryos; lane 4, erythroid colonies from 13.5-day fetal liver; lane 5, erythroid burst colonies from 13.5-day fetal liver; lane 6, erythroid colonies from adult bone marrow; lane 7, erythroid burst colonies from adult bone marrow; lane 8, colonies from 13.5-day fetal liver HPP-CFC; and lane 9, colonies from adult bone marrow HPP-CFC.