In marfan syndrome the defect is in

In Marfan syndrome, a connective tissue disorder of autosomal dominant inheritance, the basic biochemical abnormality is a mutation affecting fibrillin. This glycoprotein, secreted by fibroblasts, is the major component of microfibrils found in the extracellular matrix. Microfibrils serve as scaffolding for the deposition of tropoelastin, an integral component of elastic fibers. Fibrillin is encoded by the FBN1 gene, which maps to chromosomal locus 15q21. Mutations in the FBN1 gene are found in all patients with Marfan syndrome. Although microfibrils are widely distributed in the body, they are paicularly abundant in the aoa, ligaments, and the ciliary zonules that suppo the ocular lens; these tissues are prominently affected in Marfan syndrome. (Robbins Basic Pathology, 9 th edition. page : 220)