Mice that lack activity of alphavbeta6- and alphavbeta8-integrins reproduce the abnormalities of Tgfb1- and Tgfb3-null mice

Abstract

The arginine-glycine-aspartate (RGD)-binding integrins alphavbeta6 and alphavbeta8 activate latent TGFbeta1 and TGFbeta3 in vivo, but it is uncertain whether other RGD-binding integrins such as integrins alphavbeta5 and alphavbeta3 activate these TGFbeta isoforms. To define the combined role of alphavbeta6- and alphavbeta8-integrin in TGFbeta activation, we analyzed mice lacking function of both integrins by means of gene deletion and/or pharmacologic inhibition. Most Itgb6-/-;Itgb8-/- embryos die at mid-gestation; those that survive develop cleft palate-as observed in Tgfb3-/- mice. Itgb8-/- mice treated with an anti-alphavbeta6-integrin antibody develop severe autoimmunity and lack Langerhans cells-similar to Tgfb1-null mice. These results support a model in which TGFbeta3-mediated palate fusion and TGFbeta1-mediated suppression of autoimmunity and generation of Langerhans cells require integrins alphavbeta6 and alphavbeta8 but not other RGD-binding integrins as TGFbeta activators.

Fig. 1.

Phenotype of adult Itgb8^–/– mice. (A) Itgb8^–/– mice are smaller than control mice. White bars show control weights (n=13), black bars show Itgb8^–/– weights (n=14). Error bars represent the s.e.m. (B) Representative hematoxylin- and eosin-stained sections of liver and colon of Itgb8^–/– mice (9 weeks of age, original magnification 400×) demonstrate lack of inflammation. Scale bar: 100 μm.

Fig. 2.

Cleft palate in Itgb6^–/–;Itgb8^–/– neonates. The control sample shows normally fused palatal shelves, whereas the Itgb6^–/–;Itgb8^–/– sample demonstrates a cleft of the secondary palate. Arrows indicate cleft palate.

Fig. 3.

(A) Kaplan-Meier survival curves for Itgb8^–/– mice (n=17), Itgb8^–/– mice with 6.3G9 treatment starting at P3 (n=4), Itgb8^–/– mice with 6.3G9 treatment starting at P0 (n=8), and Itgb8^–/– mice with 6.3G9 treatment starting at E16.5 (n=12). (B) Hematoxylin and eosin staining of liver, lung, stomach and heart of representative Itgb8^–/– and littermate non-KO control mice treated with 6.3G9 starting at E16.5 and sacrificed at 19 days. (C) Itgb8^–/– mice treated with 6.3G9 starting at E16.5 lack Langerhans cells (LCs). Representative examples of epidermal sheets stained with an antibody that recognizes LCs. (D) Tregs isolated from thymus and spleen were identified by staining for FOXP3. Cells are from control mice, Itgb8^–/– mice, and control and Itgb8^–/– mice treated with 6.3G9 starting at E16.5. (n=3-4 for thymus, n=3 for spleen). Error bars represent the s.e.m. Scale bar: 100 μm.