Pbx expression in embryonic hematopoietic tissues.

(A) Immunoperoxidase staining of AGM (left panel) and FL (2 right panels) with a Pbx1b-specific mAb. Nuclear staining includes mesonephric mesenchyme and some cells lining the dorsal aorta in the AGM, as well as endothelial cells (ECs) lining hepatic sinusoids (S) and rare intraparenchymal (IP) cells in the fetal liver. (B) Western blotting with Pbx1b and Pbx long-form–specific mAbs. Lanes 1 and 2, whole cell extract from wild-type (wt) andPbx1^−/−E14 FL, respectively; lanes 3 through 8, whole cell extracts from populations of cells enriched for the indicated progenitors by immunomagnetic beads or flow cytometry; lanes 9 and 10, nuclear and cytoplasmic extracts from wt FL at E14, respectively. (C) Schematic depiction of myeloid differentiation from HSCs to CMPs to granulocyte/monocyte progenitors (GMPs) and megakaryocyte/erythrocyte progenitors (MEPs) as described by Akashi et al.24