Fibronectin splice variants: understanding their multiple roles in health and disease using engineered mouse models.

The extracellular matrix (ECM) is a highly dynamic network of proteins, glycoproteins, and proteoglycans. Numerous diseases result from mutation in genes coding for ECM proteins, but only recently it has been reported that mutations in the fibronectin (FN) gene were associated with a human disorder. FN is one of the main components of the ECM. It generates protein diversity through alternative splicing of a single pre-mRNA, having at least 20 different isoforms in humans. The precise function of these protein isoforms has remained obscure in most cases. Only in the recent few years, it was possible to shed light on the multiple roles of the alternatively spliced FN isoforms. This substantial progress was achieved basically with the knowledge derived from engineered mouse models bearing subtle mutations in specific FN domains. These data, together with a recent report associating mutations in the FN gene to a form of glomerulopathy, clearly show that mutations in constitutive exons or misregulation of alternatively spliced domains of the FN gene may have nonlethal pathological consequences. In this review, we focus on the pathological consequences of mutations in the FN gene, by connecting the function of alternatively spliced isoforms of fibronectin to human diseases.