Fig. 3. Expression directed by the Gata4 lateral mesoderm enhancer becomes restricted to the mesenchyme surrounding the liver. Representative X-gal-stained transgenic embryos (A-C) and dissected livers from transgenic animals (E-H) are shown. (A-C) Expression directed by the Gata4 enhancer is present exclusively in the liver (L) of transgenic embryos at 11.5 dpc (A), and this expression is restricted to the mesenchyme surrounding the liver, as observed in sagittal (B) and transverse (C) sections. The liver mesenchyme expression directed by the enhancer is identical to the expression of endogenous Gata4 in the liver, which was evident in transverse sections at 11.5 dpc (D). (E-G) Expression directed by the Gata4 enhancer in the liver mesenchyme was strong at 11.5 dpc (E) but began to diminish by 13.5 dpc (F) and 16.5 dpc (G). No transgene expression was observed in the adult liver (H). NT, neural tube. The arrows in C and D denote expression of G2-lacZ and endogenous Gata4 in the mesenchyme surrounding the liver at 11.5 dpc. Scale bars: in B-D, 100 µm; in H, 1 cm.