FIG. 1.

Genetic and histopathological characterization. (A) Extensive genetic excision of Vps34 exon 21. Compared with control (black boxes), Vps34^cKO thyroid (red boxes) shows ∼70% reduction in exon 21 mRNA level at P14. The unchanged mRNA level spanning exons 22–24 serves as control. Boxes with median and percentiles of 10 WT and 11 cKO samples; ***p < 0.0001 by Mann–Whitney nonparametric test. (B) Increased thyroid weight. Compared with control (black boxes), Vps34^cKO thyroid (red boxes) shows a twofold increase in thyroid weight. Boxes with median and percentiles of 8 WT and 6 cKO samples; **p < 0.01 by Mann–Whitney nonparametric test. (C) Histopathological evidence for colloid exhaustion. As compared with control thyroid tissues (n = 3) where all follicles show regular lumen filling with homogeneous and intense PAS staining, Vps34^cKO thyroids (n = 3) present fewer, mostly centrally located, PAS-stained follicles and with weaker staining intensity, and other follicles that appear empty (for further quantification; Supplementary Fig. S1). (D) Vps34^cKO thyrocytes are altered and follicles contain abundant nonepithelial cells. Nuclei are labeled by Hoechst (shown in white); thyrocyte basolateral contours are labeled for E-cadherin (red); two lumen boundaries are delineated by broken lines. As compared with control thyroid follicles, Vps34^cKO follicular structures are frequently irregular and contain additional cells inside the lumen (arrowheads). These cells are not labeled for E-cadherin. cKO, conditional knockout; mRNA, messenger RNA; PAS, Periodic-Acid–Shiff; WT, wild type.