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Fig. 4. Retinoic acid and median clefts. (A,B) Frontal views of the stage 43–44 face of (A) control embryo and (B) an embryo treated with a retinoic acid receptor inhibitor(from stage 24–32). The mouth is outlined with red dots. scale bars = 225 m. (C, D) Transverse sections through the face at stage 43–44 where E-cadherin is labeled (red)and F-actin is labeled using phalloidin (green). E-cadherin marks epithelium of the oral cavity and phalloidin shows outlines of cells and muscle for context (see Ref. [40] fordetails on this labeling). scale bars = 120 m. (E) Schematic showing our hypothesis of the role of RA signaling in regulating primary palate and midface development. RAR is expressed in the early face and regulates homeobox genes, cell cycle regulators and transcriptional regulators to modulate both growth and differentiation. |
