Figure 2.

Improvement by HSC transplantation of biosynthetic and lysosomal overload in Ctns^−/− thyroid. Eight-month-old/6-month posttransplant Ctns^−/− mice were compared with age-matched WT and Ctns^−/− mice. Samples were analyzed by double immunofluorescence for E-cadherin (red, thyrocyte structure) and either (green) KDEL, as generic marker of endoplasmic reticulum residents (A), or LAMP-1, as lysosomal membrane marker (B). A, ER expansion. In WT follicles (a), thyrocytes are flat or cuboidal, and the ER mostly occupies the basal cytoplasm. In nongrafted Ctns^−/− mice (b), thyrocytes are columnar (hypertrophic, reaching ∼20 μm in height), and KDEL labeling fills the lumen of dilated ER (arrows), which is spread over the entire cytoplasm. Upon grafting (c), Ctns^−/− thyrocyte height is generally decreased and the ER is overall reduced as compared with panel b. However, KDEL antibodies occasionally delineate larger structures devoid of luminal signal (arrow). B, Lysosome abnormalities. In WT thyrocytes (a), LAMP-1-labeled structures are dotty and sparse along the cytoplasm. In nongrafted Ctns^−/− thyrocytes (b), many lysosomes are dilated and concentrated at the apical pole (arrows and enlarged in insert). LAMP-1 also labels cell remnants in the follicular lumen. Panels c and d show two distinct patterns of grafted Ctns^−/− thyrocytes. In panel c, the aspect is comparable with WT (ie, preserved). In panel d, enlarged lysosomes are obvious, even frequently larger than in panel b. For electron microscopy, see Supplemental Figure 2 (crystals were detected only in nongrafted Ctns^−/− thyrocytes).