Genetic Cre-loxP assessment of epicardial cell fate using Wt1-driven Cre alleles.

RATIONALE Wt1-Cre-based tools are important reagents for studying epicardial cell fate and gene function. OBJECTIVE To better describe the properties of Wt1-Cre-based tools to enhance their use in Cre-loxP-based experiments. METHODS AND RESULTS In contrast to recently reported results, we show that constitutive Wt1(GFPCre) in combination with certain Cre-activated reporters can be used to trace (pro) epicardial cell fate. Wt1(CreERT2) can be efficiently induced by tamoxifen administration. We show substantial labeling of coronary endothelial cells when induction is performed at late but not early stages of heart development. CONCLUSIONS Wt1-based Cre alleles are useful tools for genetic lineage tracing of epicardial cells and mesothelium of other organs. Using these tools with proper understanding of their properties and limitations enables genetic labeling of epicardial cells and their derivatives.