For the transgene insert, genomic sequence from approximately -308 bp (relative to Gata3 transcription start site in CD-1 strain) to the 5' end of intron 2 (which includes upstream regulatory sequences, exon 1b, intron 1b, exon 2 and part of intron 2) was modified by the insertion of a beta-galactosidase reporter gene cassette (which includes poly(A) signal sequence) in place of the Gata3 ATG start site. The reporter is expressed in embryo limb bud muscle and intercostal muscle. (J:332297)