FBN-1/TGF-β relationships and fibrillopathies

Fibrillin-1(FBN-1) is the main component of the 10-12 nm microfibrils found in the extracellular matrix (ECM). ECM dysplays a structural role in the tissue-specific organization and takes part in the regulation of various cytokines and growth factors. A growing body of evidences supports a narrow relationship between FBN-1 and TGF-beta. Homology between FBN-1 and latent TGF-beta (LTGF) allows microfibrills to be a reservoir for this cytokine. The Marfan syndrome (MFS), a prototypic fibrillinopathy, highlights these relationships as it relates to 2 major genes that are FBN1 and TGF-beta type II receptor (TGFBR2) genes. In a mouse model of MFS, an up-regulation of the TGF-beta pathway is partly responsible for the phenotype. This FBN-1/TGF-beta relationship may play also a role in systemic sclerosis (SSc), a multigenic disease characterized by excessive generalised ECM deposit. Indeed, two related animal models results from both gene mutations: the Tight Skin 1 mouse is due to a partial in-frame duplication of the Fbn1 gene and another model conditionally overexpresses TGF-beta type 1 receptor. A better understanding of FBN-1/TGF-beta relationship appears of great importance in fibrillinopathies: it may allow reconsidering the nosologic framework of these diseases including the TGF-beta signalopathies and could lead to innovative therapeutic strategies.