“To analyze epicardial cell development and raldh2 expression in epi-KO hearts, we crossed tcf21:CreER; shhact/+with shhact/+fish carrying the epicardium-specific DsRed2 reporter transgene Tg(tcf21;DsRed2) (tcf21:DsRed2) (Kikuchi et al., 2011) and obtained tcf21:DsRed2; tcf21:CreER; shhact/ctembryos after PCR genotyping of individual embryos.”