title: A microfibril assembly assay identifies different mechanisms of dominance underlying Marfan syndrome, stiff skin syndrome and acromelic dysplasias.
abstract: Fibrillin-1 is the major component of the 10-12 nm diameter extracellular matrix microfibrils. The majority of mutations affecting the human fibrillin-1 gene, FBN1, result in Marfan syndrome (MFS), a common connective tissue disorder characterised by tall stature, ocular and cardiovascular defects. Recently, stiff skin syndrome (SSS) and a group of syndromes known collectively as the acromelic dysplasias, which typically result in short stature, skin thickening and joint stiffness, have been linked to FBN1 mutations that affect specific domains of the fibrillin-1 protein. Despite their apparent phenotypic differences, dysregulation of transforming growth factor β (TGFβ) is a common factor in all of these disorders. Using a newly developed assay to track the secretion and incorporation of full-length, GFP-tagged fibrillin-1 into the extracellular matrix, we investigated whether or not there were differences in the secretion and microfibril assembly profiles of fibrillin-1 variants containing substitutions associated with MFS, SSS or the acromelic dysplasias. We show that substitutions in fibrillin-1 domains TB4 and TB5 that cause SSS and the acromelic dysplasias do not prevent fibrillin-1 from being secreted or assembled into microfibrils, whereas MFS-associated substitutions in these domains result in a loss of recombinant protein in the culture medium and no association with microfibrils. These results suggest fundamental differences in the dominant pathogenic mechanisms underlying MFS, SSS and the acromelic dysplasias, which give rise to TGFβ dysregulation associated with these diseases.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK sacha.jensen@bioch.ox.ac.uk.
authors.forename: Sacha A
authors.initials: SA
authors.lastname: Jensen
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Iqbal
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK.
authors.forename: Alicja
authors.initials: A
authors.lastname: Bulsiewicz
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK.
authors.forename: Penny A
authors.initials: PA
authors.lastname: Handford
mesh_terms: D003286:Contracture / Q000235:genetics* / Q000473:pathology; D004392:Dwarfism / Q000235:genetics / Q000473:pathology; D005109:Extracellular Matrix / Q000235:genetics / Q000473:pathology; D000071838:Fibrillin-1; D000071837:Fibrillins; D006801:Humans; D008382:Marfan Syndrome / Q000235:genetics* / Q000473:pathology; D020894:Microfibrils / Q000235:genetics / Q000473:pathology; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D012873:Skin Diseases, Genetic / Q000235:genetics* / Q000473:pathology; D053773:Transforming Growth Factor beta1 / Q000235:genetics* / Q000378:metabolism; D054392:Adipokines
chemical_list: D000071838:Fibrillin-1; D000071837:Fibrillins; D008840:Microfilament Proteins; D053773:Transforming Growth Factor beta1; C000605722:FBN1 protein, human; D054392:Adipokines; C508960:TGFB1 protein, human