Fig. 6. ß-catenin is increased in postnatal TgALK3^QD/QD mouse kidney tissue. (A) Immunohistochemistry of kidney tissue from control and TgALK3^QD/QD mice at P10, using rabbit anti-human ß-catenin and HRP-conjugated anti-rabbit antibodies. Top left panels: Hematoxylin-stained kidney tissue from control mouse demonstrates absence of detectable ß-catenin protein in the medulla. Hematoxylin-stained kidney tissue from TgALK3^QD/QD mouse demonstrates marked upregulation of ß-catenin expression in a subset of tubules and epithelial cysts in the medulla. Bottom left panels: higher power view of kidney cortex of a TgALK3^QD/QD mouse. Low levels of ß-catenin were detected. By contrast, ß-catenin levels in the medulla of a TgALK3^QD/QD mouse kidney are greatly increased in dilated tubules (cysts). Right panel: ß-catenin expression in whole kidney lysate was increased by 46% in TgALK3^QD (gray) versus control (white) mice, and by a further 60% in TgALK3^QD/QD (black) mice. A representative blot is shown above. (B) Activation of ALK3 signaling increases the activity of a ß-catenin/TCF reporter gene in vivo. ß-galactosidase activity was assayed in the kidneys of newborn QD/QD, Tcf-gal and QD/QD; Tcf-gal mice. Top panels demonstrate ß-gal expression in Eosin-stained cross-sections of the entire kidney (composite image). Lower panels demonstrate ß-gal expression in representative corresponding tissue sections. No ß-galexpression was detected in QD/QD kidneys. Weak expression was detected in Tcf-gal mice. By contrast, ß-gal expression was markedly increased in QD/QD; Tcf-gal mouse kidney, with localization in tubular epithelium. Data are mean±s.d. from three independent experiments.

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