The contribution of the Tie2 + lineage to primitive and definitive hematopoietic cells

The regulatory elements of the Tie2 / Tek promoter are commonly used in mouse models to direct transgene expression to endothelial cells. Tunica intima endothelial kinase 2 ( Tie2 ) is also expressed in hematopoietic cells, although this has not been fully characterized. We determine the lineages of adult hematopoietic cells derived from Tie2 ‐expressing populations using Tie2‐Cre;Rosa26R‐EYFP mice. In Tie2‐Cre;Rosa26R‐EYFP mice, analysis of bone marrow cells showed Cre‐mediated recombination in 85% of the population. In adult bone marrow and spleen, we analyzed subclasses of early hematopoietic progenitors, T cells, monocytes, granulocytes, and B cells. We found that ∼ 84% of each lineage was EYFP + , and nearly all cells that come from Tie2‐expressing lineages are CD45 + , confirming widespread contribution to definitive hematopoietic cells. In addition, more than 82% of blood cells within the embryonic yolk sac were of Tie2 + origin. Our findings of high levels of Tie2‐Cre recombination in the hematopoietic lineage have implications for the use of the Tie2‐Cre mouse as a lineage‐restricted driver strain. genesis 48:563–567, 2010. © 2010 Wiley‐Liss, Inc.