Thyroglobulin (TG) immunostaining labels the apical and some lateral membranes of thyroid follicle cells. Ventral views (A-D,H-J), anterior always to the left, and cross-sections (E-G). Stage and probe/staining are indicated as in Figure 1. A-D: TG immunostaining labels thyroid follicles from approximately 55 hours postfertilization (hpf). The ceratohyal cartilage (the ventral portion of the hyoid arch) and the heart (out of focus) are highlighted by dotted lines. E-G: In situ hybridization combined with TG immunostaining. At 55 hpf, immunostaining labels clearly only the lumen of a first follicle when combined with nk2.1a (E). Later, the follicle has grown (E and F show same magnification). F: ctsb is not exclusively expressed in thyroid follicle cells, but also in subepidermal cells (arrowheads) and in pharyngeal mesenchyme. G: slc5a5 and tg are exclusively expressed in the cytoplasm of follicle cells (tg staining is identical to slc5a5, not shown). H: Close-up of T4 immunostaining, showing follicle cells (arrows) around the follicle lumen in Nomarski optics, same magnification as in G. I,J: In lia mutants, a row of distinct follicles is visualized with T4 immunostaining. In the strongly affected pharynx, most cartilaginous structures are missing. The dotted line in I demarcates the ceratohyal cartilage that is still present in this mutant (Herzog et al.,[2004a]). Note that the overall length of the pharyngeal area is reduced. In a wild-type sibling, the ceratohyal cartilage is marked for comparison (J, dotted line). h, heart; ch, ceratohyal.
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