This transgene contains two copies of the Hhex B6 intronic enhancer, one upstream of the Hspa1b promoter and the second downstream of an IRES-GFP construct. Cre (from the pturbo cre construct) was inserted between the Hspa1b promoter and the IRES. Cre activity is detected in a mosaic pattern in medial and lateral prospective hepatic endoderm cells in embryos between E7.5 and E9.5. (J:112804)