Fig. 4. Histological analysis and T4 immunostaining in wild-type and noi^tu29–/– mutant zebrafish larvae at 7-8 dpf. (A,B) Haematoxylin and Eosin staining: selected section of a wild-type sibling (A) showing a thyroid follicle and noi^tu29–/– larva (B), in the area where normally follicles would form. (C,D) PAS staining: selected section of a wild-type sibling (C) and noi^tu29–/– larva (D), in the area where normally follicles would form. (E-L) T4 immunostaining. (E,G,I,K) Selected sections of a wild-type sibling with the anterior domain of T4 localisation (E,G) and three follicles out of a total of seven follicles present in this specimen (I,K). The follicles are distributed along the ventral aorta, ventral to the basibranchial cartilage (compare with Fig. 2J). (F,H,J,L) Four selected sections of a 7 dpf noi^tu29–/– larva, showing the presence of the anterior domain of T4 localisation (F,H). No follicles were found in any of the noi^–/– mutants (J,L). Arrows point to follicles and/or T4 immunostaining, the asterisks mark the heard oedema that is forming in noi^tu29–/–. bb, basibranchial cartilage; ch, ceratohyale.