Bacterial artificial chromosome (BAC) library (Source BioScience) was used to obtain a 160 kb BAC (BMQ-305H2) containing the entire mouse Neurod1 gene. This BAC was modified to replace the coding region with a creERT2 fusion gene (a Cre recombinase fused to a human estrogen receptor ligand-binding domain) followed by a frt-flanked neomycin (neo) selection cassette. Four lines were generated: L (low expression), M1 (intermediate expression), M2, H (high expression). This is a representative record for all lines. Transgene expression patterns are consistent with endogenous gene expression.