Molecular analysis of eight mutations in FBN1

Mutations in the gene encoding extracellular glycoprotein fibrillin-1 (FBN1 ) cause Marfan syndrome (MFS) and other related connective tissue disorders . In this study, eight mutations have been detected in MFS patients by hete roduplex analysis. These comprise two mis sense mutations, C1835Y and C2258 Y in calcium-binding epidermal growth factor-like domains, two nonsense mut ations, R1541X and R2394X in transforming growth factor pi-binding protein- like domains, one splice site mutation, which has been detected previously, and three small insertions or deletions resulting in a frameshift. Fibrobl ast cells have been established from seven of the MFS patients and the bioc hemical effects of the mutations on fibrillin-1 synthesis and secretion ass essed by pulse-chase analysis. Each cysteine mutation resulted in the delay ed secretion of fibrillin-1 and both nonsense and frameshift mutations caus ed reduced levels of synthesis and/or deposition of fibrillin-1. Indirect i mmunofluorescence and rotary shadowing electron microscopy analysis of fibr illin microfibrils revealed no major differences between normal and patient samples. We discuss the relative merits of the biochemical techniques used in this study.