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Fig. 4. Deletional analysis of the Gata4 lateral mesoderm enhancer
identifies a highly conserved element that is necessary and sufficient for
enhancer function in vivo. (A) Schematic diagram of the deletion constructs of
the Gata4 lateral mesoderm enhancer. The genomic organization of the
G2 region of Gata4 is depicted at the top. Red boxes represent three
regions of high sequence homology between the opossum and mouse Gata4
genes, denoted as CR1, CR2 and CR3. The nucleotide positions of each deletion
construct, relative to G2, are denoted on the left, and mesoderm expression
directed by each construct is summarized by a plus (mesodermal expression) or
a minus (no detectable mesodermal expression) to the right of the line
representing each construct. The column on the far right indicates the number
of independent transgenic lines or F0 embryos that expressed lacZ in
the septum transversum and lateral mesoderm as a fraction of the total number
of transgene-positive F0 embryos or lines examined. (B-H) Representative
transgenic embryos for each of the deletion constructs depicted in A were
collected at 9.5 dpc and X-gal stained. G2, G2
2 and G24 directed
strong expression in the septum transversum (ST) and visceral mesoderm
(B,D,F). G24 encompasses only the region surrounding the highly
conserved CR2. G25 contains only 308 bp of CR2 and was sufficient to
direct only very weak expression in septum transversum and gut mesoderm (G).
Deletion of CR2 (2495-3738) from G2 to generate G26 completely
ablated transgene activity (H). Arrowheads indicate visceral mesoderm.
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