Expression of Cyp26A1. A. Dorsal view of Cyp26A1 expression in the rhombic lip at e3.5. B. Dorsal view of Cyp26A1 expression in the rhombic lip and roofplate (*) at e5. C. Transverse section through an e3.5 hindbrain (dashed line in A) showing Cyp26A1 expression at the rhombic lip (arrow) D. Transverse section through an e5 hindbrain (dashed line in B), showing punctate expression of Cyp26A1 extending into the roofplate (arrow). E. Ventral view of the hindbrain at e5 shows Cyp26A1 within a discrete population of neurons. F. Tlx3 expression at e5 identifies the noradrenergic area postrema (arrow). G. In section (dashed line in F), the area postrema (arrow) overlies the nucleus ambiguus (white arrow). H. Transverse section through caudal hindbrain (dashed line in E) shows Cyp26A1 expression approximately mapping to neurons that express Tlx3 (arrow). I. Ventral view of hindbrain at e6 shows columnar Cyp26A1 expression. J and K. Transverse sections through rostral and caudal parts of the hindbrain expression domain (dashed black and white lines in I), respectively. L. Lateral view of e6 embryo showing relative positions of hindbrain and midbrain label (arrow). M. Dorsal view of e8 embryo; discrete expression at the caudal margin of the optic tectum (arrow). N. Transverse section through midbrain expression domains (dashed line in M).