A BAC transgenic Hes1-EGFP reporter reveals novel expression domains in mouse embryos

► We have generated a transgenic Hes1-EGFP reporter mouse line, Tg(Hes1-EGFP)1Hri. ► We present a characterisation of Hes1 expression in whole embryos from e7.0-e10.5. ► Detection of Hes1 expression in the definitive endoderm before gut tube closure. ► We provide an analysis of Hes1 expression in selected organs during development.