http://repub.eur.nl/res/aut/54695/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/34606/ 2011-12-01T00:00:00Z Adenomatous polyposis coli (APC) is a multifunctional protein as well as a tumor suppressor. To determine the functions of the C-terminal domain of Apc, we have investigated Apc1638T/1638Tmice, which express a truncated Apc that lacks the C-terminal domain. Apc1638T/1638Tmice are tumor free and exhibit growth retardation. In the present study, we analyzed the morphology and functions of the thyroid gland in Apc1638T/1638Tmice. There was no significant difference in the basal concentration of serum thyroid hormones between Apc1638T/1638Tand Apc+/+mice. Thyroid follicle size was significantly larger in Apc1638T/1638Tmice than in Apc+/+mice. The extent of serum T4 elevation following exogenous thyroid-stimulating hormone (TSH) injection was lower in Apc1638T/1638Tmice than in Apc+/+mice. TSH also induced a greater reduction in thyroid follicle size in Apc1638T/1638Tmice than in Apc+/+mice. Analyses using immunohistochemistry and electron microscopy indicated that follicular epithelial cells in Apc1638T/1638Tmice had an enlarged rough endoplasmic reticulum of irregular shape. These results suggest that the C-terminal domain of Apc is involved in thyroid morphology and function.