Regulation of <i>cyp1a1</i> by AHR.

<p><b>(A)</b> Overview pictures of <i>cyp1a1</i> expression at 52 hpf in DMSO or BNF-treated WT (<b>A</b>), <i>ahr1a -/-</i> (<b>B</b>), <i>ahr2 -/-</i> (<b>C</b>), <i>ahr1b</i>,<i>2 -/-</i> <b>(D</b>) and triple AHR mutants (<b>E</b>). <i>ahr1a -/-</i> are indistinguishable from WT. (*) indicates expression in the eye in DMSO and BNF-treated embryos, which is lost only in <i>ahr1b</i>,<i>2 -/-</i> and triple AHR mutants. Note reduction of endogenous vascular <i>cyp1a1</i> expression in <i>ahr2</i> mutants (<b>C,</b> upper panels) that is lost in <i>ahr1b</i>,<i>2 -/-</i> and triple AHR mutants (<b>D, E</b> upper panels). <i>ahr2 -/-</i> embryos treated with BNF do not induce <i>cyp1a1</i> expression in the skin, revealing staining in blood vessels underneath (<b>C</b>, lower panel), which is abolished in <i>ahr1b</i>,<i>2 -/-</i> and triple AHR mutants (<b>D, E</b>, lower panels). Scale bar is 500 um. (<b>F-T)</b> High magnification images of blood vessels of 3 different planes of the head vasculature: the LDA (<b>F-J</b>), the hindbrain blood vessels (<b>K-O</b>) and the hindbrain capillaries (<b>P-T</b>) in all genetic combinations with DMSO and BNF treatment. Note strong dependence of LDA (but not hindbrain arteries, PHBC or CtAs) on <i>ahr2</i> for full <i>cyp1a1</i> expression. White asterisk denotes liver. Yellow arrowheads label individual CtAs. Numbers indicate embryos with indicated expression pattern/total embryos of that genotype analyzed. Scale bar is 100 um. Abbreviations–AHR: aryl hydrocarbon receptor, BNF: beta-naphthoflavone, CtA: central artery, CYP: cytochrome p450, DMSO: dimethylsulfoxide, hpf: hours post fertilization, LDA: lateral dorsal aortae, PHBC: primordial hindbrain channel, WT: wildtype.