Expression of thecretransresponder gene in bone marrow progenitors response to the human CD34tTA transgene. Multicolor FACS¹¹  was used to separate bone marrow of human CD34tTA × tet-O-cre double transgenic mice (tg) into (A) hematopoietic stem cells (HSC), (B) common myeloid progenitors (CMP), (C) granulocyte/macrophage progenitors (GMP), and (D) megakaryocyte/erythrocyte progenitors (MEP). (E) HSCs and (F) mixed progenitor cells (including CMP, GMP, and MEP) from a wild-type animal (wt) were isolated and used as control. The expression of cre protein was demonstrated by immunohistochemistry with a polyclonal antiserum directed against the protein. Expression was found in HSCs, CMPs, and MEPs, whereas GMPs and cells from wild-type animals were negative. Original magnification, × 100.