Figure 5: Enhancer activity of the MACS1 and Block-2 orthologues in mouse embryos.

The LacZ reporter expression driven by orthologues of MACS1 (a) and Block-2 (b) in mouse embryos. Black and white arrowheads depict presence and absence of the reporter expression specifically in the ventral laryngeal epithelium or dorsal esophageal epithelium, respectively. The MACS1 orthologues of coelacanth, paddlefish and spotted gar drove reporter expression in the laryngeal epithelia (Le) and laryngotracheal groove (Lt), which was indistinguishable from that driven by the mouse MACS1 (a). They did not induce reporter expression in the dorsal epithelia of pharynx. The MACS1 orthologues of Japanese eel and medaka did not induce reporter expression in the laryngeal epithelia or laryngotracheal groove (a). They did not induce reporter expression in the dorsal epithelia of pharynx, although expression was sometimes observed in the ventral epithelia of pharynx (a). The Block-2 orthologue of spotted gar did not drive any reporter expression, despite its sequence similarity to those of Japanese eel and euteleosts (b). Block-2 orthologue of Japanese eel and medaka Block-2 drove reporter expression in the dorsal epithelia of pharynx and oesophagus (b). The number of LacZ positive embryos over total number of transgenic embryos is shown in right bottom of each caudal section. Scale bars, 200 μm. Pe, pharyngeal epithelia.