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Fig. 4 Expression patterns and domains of bmp7b and bmpr1ba in inner-embryonic domains and structures after induction of bmp4 and in controls (lateral and dorsal views, the prospective head facing left). Scalebars indicate 200 µm. Scheme of experimental procedure (top): Heat shock of outcrossed transgenes tg(hsp:bmp4/cmlc2:GFP) at 8.5 hpf and fixation for whmish at 11 hpf. Genotyping and separation of recorded expression patterns (A–B′) specimens with typical expression patterns, genotyped cmlc2:GFP/bleeding heart (BH) negative. (C–D′) Specimens with typical expression patterns genotyped cmlc2:GFP/BH positive. (E–H′) Schematic drawing of the respective patterns. (A, A′, E and E′) Expression pattern of bmp7b without bmp4 induction (3 embryos, 3 embryos with pattern). Note the broad expression domain, at the anterior midline, likely corresponding to the anterior neuroectoderm. (B, B′, F and F′) Expression domain of the bmpr1ba without bmp4 induction (5 embryos, 5 embryos with pattern). Please note the two distinct and separate expression domains. The anterior domain, likely corresponds to the anterior ANP. The posterior domain likely corresponds to the region of the midbrain-hindbrain boundary. (C, C′, G and G′) Expression domain of bmp7b after induction of bmp4 (8 embryos, 6 embryos with pattern). The expression domain remains similar to the uninduced one, albeit with a slight smaller projection dorsally, seen in the lateral perspective (please note the arrow in (C)). (D, D′, H and H′) Expression domain of bmpr1ba after induction of bmp4 (16 embryos, 16 embryos with pattern). Please note the single expression domain, which mostly includes the domains seen in the control. No gap is seen separating an anterior and a posterior expression domain as seen in the control. The anterior margin of the ANP lacks expression (arrow in (D)), please see (B) as control.