Studies of mesenchymal cell function during development and disease using transgenic techniques.

Cells interact with collagens using specific cell surface protein receptors belonging to a family called integrins. We have identified one collagen-binding integrin (alpha11beta1), characterized its structure and are studying its function using genetical ly modified mice lacking alpha 11 integrin. 1. Alpha 11 integrin-deficient mice form normally but do not grow properly. We have found that the smaller size of these mice is due to a defect in incisors. At the molecular level, embryonic fibroblasts lacki ng alpha11 show reduced cell attachment, reduced proliferation and a reduced ability to reorganize collagen lattices. Our most immediate goal is to understand the molecular mechanisms underlying the tooth defect more in detail but also to try and underst and how the defects at the molecular level translates into a tissue phenotype. We are currently testing the hypothesis that reduced FGF-10 production by the tooth mesenchyme, through autocrine and paracrine mechanisms, contributes to the tooth phenotype. We are also creating mice that lack multiple collagen receptors to determine what effect this will have on tissue formation and integrity. 2. We are characterizing the integrin alpha 11 promoter in detail. We have identified transcription factors Sp1/Ets 1 as being important for fibroblasts-specific expression of integrin alpha 11, and we are now trying to identify fibroblast specific enhancer elements. We are in a position to generate transgenic reporter mice with different parts of the promoter. 3. We have cloned a zebrafish orthologue of alpha 11 integrin and are now developing reagents to study its expression and function during ectomesenchyme formation. 4. We have initiated collaborations with international groups to learn what role collagen-bindi ng integrins play in human teeth and periodontitis, in muscle fibrosis and in lung cancer. In all these conditions it is assumed that the stromal compartment plays a central role in the pathological conditions.