Sites of β-galactosidase activity in transgenic mouse embryos.

<p>All sites showed only selective cells positive for enhancer activation. DRGs = dorsal root ganglia; E = embryonic day of gestation; MN = motoneurons; OFT = cardiac outflow tract; PA = pharyngeal arch; PSM = pre-somitic mesoderm.</p

Bioinformatics analyses of the human <i>FGF10</i> locus surrounding the first exon.

<p><b>A</b>: Alignment of genomic regions around and within the human [hg18] <i>FGF10</i> locus to those of frog [xenTro2], chicken [galGal3], opossum [monDom4], mouse [mm9], dog [canFam2] and rhesus macaque [rheMac2] with colored regions >90% identical and the vertical scale ranging from 50% (bottom) to 100% (top). Color code for genomic features at <a href="http://ecrbrowser.dcode.org/ecrInstructions/ecrInstructions.html" target="_blank">http://ecrbrowser.dcode.org/ecrInstructions/ecrInstructions.html</a>. The <i>FGF10</i>-Pr1, <i>FGF10</i>-Pr2 and FGF10-Int1 regions examined in this study are boxed. <b>B</b>: A non-canonical predicted site for GATA-type transcription factors is 52 nucleotides 5′ to the ISL1 cognate sequence in <i>FGF10</i>-Int1 in the direction of transcription on the – strand in humans, mice and (not shown) macaque and opossum. <b>C</b>: Nucleotide sequence of the <i>FGF10</i>-Int1 enhancer module and position of conserved putative transcription factor binding sites as predicted by rVista (<a href="http://rvista.dcode.org" target="_blank">http://rvista.dcode.org</a>). All indicated human sites are identical to those of the macaque and mouse except for the SMAD prediction, only found in mouse; the ISL1, GATA and HOXA7 sites are also identical to the opossum, and the ISL1, NKX2-5 and TBX sites are also identical to the dog.</p

Expression of <i>ISL1</i> and <i>GATA4</i> transcripts in the human heart between 26 and 38 days of gestation.

<p><b>A–H</b>: <i>ISL1 in situ</i> at Carnegie stages (CS)12 (26–28 days post fertilization [dpf]), CS13 (28–31 dpf), CS14 (32–33 dpf) and CS15 (34–36 dpf) respectively. <b>E–H</b> are magnifications of <b>A–D</b> respectively. <b>I–K</b> show <i>GATA4</i> expression in adjacent sections to <b>B–D</b>. <b>A</b>: <i>ISL1</i> is expressed at CS12 in foregut endoderm, splanchnic mesoderm, and early motoneurons. <b>B, F</b>: At CS13, <i>ISL1</i> is transcribed by mesenchyme around the cardiac OFT and pharyngeal arches. <i>ISL1</i> expression continues in the splanchnic mesoderm between the trachea and OFT, and is visible in dorsal root ganglia, at CS14 (<b>C, G</b>) and CS15 (<b>D, H</b>). <b>I–K</b>: <i>GATA4</i> is expressed in the endocardium and myocardium of the arterial pole at CS13, CS14 and CS15 (<b>I, J, K</b> respectively). <b>Inset</b>: RT-PCR of <i>ISL1</i>, <i>GATA4</i>, <i>GATA5</i>, <i>GATA6</i>, <i>FGF10</i> and positive control <i>ACTB</i> mRNAs in embryonic human hearts at stages CS13-16 (to 40 dpf). Abbreviations: drg, dorsal root ganglia; es, esophagus; fb, forebrain; fg, foregut; ph, pharynx; nt, neural tube; oft, OFT; ra, right atrium; t, trachea. Arrows, motoneurons. Bar: 110 µm (A–D, I) and 55 µm (E–H, J, K).</p

<i>In vitro</i> reporter assays support an additive combinatorial effect of transcription factors upon the FGF10 intronic enhancer.

<p>LUC-<i>FGF10</i>-Int1, which construct placed the luciferase gene under the control of the FGF10-Int1 element, was transfected alone or together with <i>ISL1</i>, <i>GATA4</i> and <i>TBX20</i> expression vectors into 10T1/2 cells. Each factor alone potentiated luciferase expression and these effects were additive in combination.</p