A 5 kb genomic fragment of Hoxa5 (containing the temporal (T) control region, the brachial spinal cord (BSC) enhancer, proximal Hoxa5 promoter, both exons and the intron of Hoxa5) drives cre epxression in this transgene. An IRES-EGFPcre cassette was inserted into exon 1 of Hoxa5 downstream of the translation initiation codon. A 2.1 kb fragment containing the mesodermal (MES) enhancer and an additional 7.4-kb of downstream sequences including an enhancer driving lung and gut (L/G) expression were added at the 3' end of the construct to produce the 14.5 Hoxa5/Cre transgene. Eight founder lines were obtained and line 447B was established. This line has 6 copies of the transgene.