Continued foxj1 expression and ciliogenesis in the premetamorphic and adult brain of Xenopus. In situ hybridization and scanning electron microscopy (SEM) on explanted brains at stage 53 and SEM on adult brains. (A) Explant shown in dorsal (d) and ventral (v) view. Expression in the ventral midline, subcommissural organ (SCO, arrowhead), choroid plexus (cp; outlined arrowhead), and ventricular regions. Inset in (A) focuses on expression in rhombomere boundaries (rhb) after removal of the pigmented rhombencephalon (rhomb) roof. (B) SEM picture of brain explant dissected sagittally with view onto the ventricular surface, the zona limitans intrathalamica (ZLI) is delimited with orange dashed line and boundaries between brain regions are indicated by white dashed lines. Bar represents 500 μm. (A’-A””) Transversal histological sections as indicated in (A), dorsal side up. (C-I) SEM pictures corresponding to regions indicated in (A’-A””), respectively. (C) Close-up view of third ventricle cp; inset showing enlarged view of MCCs. (D) Top view onto ventricular surface of SCO of a frontally bisected specimen. (E) Overview of the diencephalon (di) region; inset showing MCCs emerging at the di-/mesencephalic boundary, similar to those of the ZLI. (F-I) Frontally bisected specimens. (F) View into the dorsal ventricular lumen of the mesencephalon (mes) with Reissner’s fiber (RF, arrowhead) spanning the ventricle. Left inset: enlargement of mes MCCs. Right inset: enlargement of RF. (G) View onto the ventral midline (ml). (H) Ventral part of the rhomb with rhombomeres (rh) and rhb as indicated. (I) cp of the rhomb roof with MCCs. (J-L) SEM pictures of sagittally bisected adult brain in the telencephalon (tel; (J)) and di region (K, L) showing a multiciliated ependymal monolayer. Arrows indicate sites of ependyma detachment due to mechanical stress during processing. a = anterior; hy = hypophysis; l = left; p = posterior; r = right.