Figure 4.

RA cannot promote notochord sheath mineralization when BMP signaling is blocked during initiation phases of mineralization. (A–D’) RA fails to induce hyper-mineralization of the notochord sheath while BMP signaling is blocked. (E–H’) BMP induced ectopic entpd5a activation cannot be hindered by interfering with the intra-cellular signal transduction of the RA pathway. (A–H’) Lateral views of transgenic zebrafish larvae shown in merged transmitted and fluorescent light channels with tissue stainings, genotypes and treatments as indicated at an age of 7dpf (A–D’) or 6dpf (E–H’). Heat-shocks were performed once a day for 45 minutes at 40°C. Arrowheads in (G’) point to faintly EGFP-positive chordoblasts in areas of presumably segmented Tg(entpd5a:egfp) expression. Image-pairs X/X’ show identical specimens. Scale bar (shown in A, applying to all panels): 100 µm.