sentence: EPDC fate mapping and genetic lineage tracing experiments in different animal models , including mouse Cre lines for Wilm ’ s tumor 1 ( WT1 ) , Tbx18 , Tcf21 , Scleraxis and Semaphorin3D , indicate that the PE and epicardium are composed of a heterogeneous cell population , making it difficult , if not impossible , to trace the fate of all EPDCs simultaneously [ 10,11 ] .