Fig. 1. Schematic representation of the Gata4 locus and the Gata4 G2-lacZ transgene. The top line represents a 103 kb region of the mouse Gata4 locus, including its seven exons (black vertical lines). The arrow represents the transcriptional start; exon 2 is the first coding exon of the Gata4 gene. The red boxes (G1-G5) represent five regions of strong conservation between human and mouse Gata4 within noncoding sequences. The lower line depicts the transgene construct G2-lacZ, which contains the 4368 bp G2 fragment of Gata4 subcloned into the transgenic reporter plasmid HSP68-lacZ.