The transgene is a bacterial artificial chromosome (BAC), RPCI-428P2, bearing a 305 kb mouse genomic segment that contains the Ascl1 locus(98 kb of 5' and 206 kb of 3' of the start codon), in which the coding sequence of the gene has been replaced with an EGFP-IRES-CRE cassette. The GFP reporter expression is low but reflects the Ascl1 pattern throughout multiple stages and in multiple regions, including the caudal neural tube, the telencephalon and diencephalon, and sympathetic and enteric nervous systems.