A 7.8-kb BALB/c genomic DNA fragment extending downstream from exon 3 of paired box gene 4 (Pax4) was ligated in-frame to the 5' end of the beta-galactosidase (lacZ) gene. Transgenic embryos express beta-galactosidase in the endocrine pancreas in recapitulation of the cell type- and developmental stage-specific expression of paired box gene 4 (Pax4). The genomic fragment includes a 407 base pair segment that in the genome resides approximately 1.3 kb upstream of the Pax4 transcription start site and that is 88% identical to the orthologous segment from Homo sapiens. This highly conserved region contains target sequences for four transcription factors that regulate pancreatic beta and delta cell-specific gene expression. (J:66530)