FIG. 6.

Evidence for defective iodide organification in Vps34^cKO thyroid: follicular lumina with Tg but devoid of I-Tg. (A) Thyroid sections from control (left) and Vps34^cKO (right) labeled for E-cadherin (green) and Tg (red), recognized either for a core protein epitope (Tg), or a hormonogenic peptide (I-Tg). Control follicular lumina are round and uniformly labeled for both Tg and I-Tg. In Vps34^cKO, follicular structures are less regular, with the majority containing Tg, but not the hormonogenic peptide. In Vps34^cKO, two serial (tilted) sections are shown. (B) Comparison of Tg labeling in control and Vps34^cKO thyrocytes. In control follicles, Tg is essentially restricted to lumen, with little or no signal inside thyrocytes. In Vps34^cKO, Tg is readily detected within thyrocytes as collections of submicrometric dots or larger spheres (arrowheads). Of note, some luminal cells (broken line in middle panel) also contain Tg-labeled spheres, indicating active endocytosis (arrow). I-Tg, iodinated thyroglobulin; Tg, thyroglobulin.