extent these factors correlate with cell fate in EPDCs is unknown. We hypothesize that the localized expression of NFATc1, WT1 and Tbx18 inPE cells andEPDCs influences EPDC cell fate.Chick embryonic day 4 (E4)PE andE7 epicardiumwere explanted to compareNFATc1,WT1and Tbx18 function in PE cells and EPDCs. NFATc1, WT1 and Tbx18 are expressed in subsets of cultured PE cells and EPDCs. Therefore, these cultures will be used to investigate cell type diversity in PE cells versus EPDCs. In a subset of cultured PE cells, NFATc1 colocalizes with the endothelial marker Flk1, which suggests that NFATc1marks endothelial precursors in vitro. Tbx18 and WT1 are expressed in subsets of EPDCs, but the fate of these cells is unknown. Also, loss of Tbx18 function using Tbx18 specific siRNA significantly decreases EPDC proliferation, as detected by BrdU incorporation assay. These data suggest that NFATc1, WT1andTbx18mark different cell lineages in PE and EPDC cultures, and that Tbx18 regulates EPDC proliferation. Our long-term goal is to define the molecular mechanisms that regulate PE and EPDC proliferation and cell lineage specification.
Jessica Jemmett, Arielle Woznica, Ella Starobinska