A Review of the Type-1 Fibrillinopathies: Pathophysiology, Diagnosis and Novel Therapeutic Strategies

Abstract

Type-1 fibrillinopathies are a family of connective tissue disorders with major clinical manifestations in the skeletal, ocular and cardiovascular systems. The type-1 fibrillinopathies are caused by mutations in the fibrillin-1 gene (FBN1), which encodes fibrillin-1, a large glycoprotein and a major component of the extracellular matrix microfibrils, providing both structural and regulatory support to connective tissues. The type-1 fibrillinopathies have been associated with over 1800 unique mutations within the FBN1 and demonstrate a wide range of phenotypic variability. This, in conjunction with a number of other factors has impacted on the identification of genotypephenotype correlations, pathogenesis and diagnostic tests for this family of diseases, leaving many open-ended theories. Current standard of care relies heavily on surgical intervention and lifelong use of β-blockers to slow disease progression, with research focused heavily on antagonism of transforming growth factor β, which is known to be dysregulated in patients with FBN1 mutations. Antisense oligonucleotides present a novel therapeutic strategy for the type-1 fibrillinopathies, by mediating the alteration of exon arrangement of both the normal and disease-causing mRNA transcripts, to re-establish the periodicity of fibrillin-1. The induced proteins, while internally truncated, should be homologous and thus be able to form multimer units. This treatment alone or in association with isoform switching, TGF-β antagonism or enhanced/inhibited protein degradation could facilitate the assembly of fibrillin-1 monomers into multimers and consequently a decrease in phenotypic severity. This review presents a basic overview of the past and current knowledge about the spectrum of type-1 fibrillinopathies with a particular focus on Marfan syndrome, as well as presenting novel potential therapeutic strategies.