Fig. 7

Cyp26 Promotes Hypophyseal Permeability by Repressing Claudin-5 Expression (A) Pituicytes are enriched with genes related with retinoic acid (RA) homeostasis. The genes encoding the proteins associated in each step of the RA homeostasis pathway are shown. Pituicytes can import blood-borne retinol reaching hypophysis and degrade it using Cyp26b1. The relative expression levels of the genes in pituicyte transcriptome are shown in brackets (log2FC units). (B–E) Talarozole inhibits the Cyp26b-mediated catabolism of retinoic acid (A). Measurement of hypophyseal permeability using the transgenic biosensor Tg(l-fabp:DBP-EGFP;kdrl:mCherry-caax) was performed as described in Figure 4. Larvae were treated with DMSO (C) or Cyp26 inhibitor Talarozole at 10 μM (D) between 4 and 5 dpf, and extravasation of DBP-EGFP protein was quantified (E). Talarozole treatment led to reduced extravasation of DBP-EGFP from the hypophyseal loop (E; ∗p < 0.05; Mann-Whitney test; n = 13, 16 for each treatment). A.U., arbitrary units. Scale bar: 10 μm. (F–H) Measurement of tight junction Marker Claudin-5 (Cldn5) expression on immunohistochemistry using anti-Cldn5 in Tg(fli1:nuc-EGFP). Transgenic larvae were treated with DMSO (F) or talarozole at 10 μM (G) between 4 and 5 dpf, followed by anti-Cldn5 immunostaining. Scale bar: 10 μm. Talarozole treatment led to increased anti-Cldn5 immunofluorescence in the hypophyseal vascular loop (H; ∗p < 0.05; Student’s t test; n = 16, 18 for each treatment). A.U., arbitrary units. Data are presented as mean ± SEM (E and H). See related Figure S7.