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A microfibril assembly assay identifies different mechanisms of dominance underlying Marfan syndrome, stiff skin syndrome and acromelic dysplasias.

Jensen SA, Iqbal S, Bulsiewicz A, Handford PA - Hum. Mol. Genet. (2015)

Bottom Line: 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.Despite their apparent phenotypic differences, dysregulation of transforming growth factor β (TGFβ) is a common factor in all of these disorders.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK sacha.jensen@bioch.ox.ac.uk.

No MeSH data available.


Related in: MedlinePlus

Fibrillin-1 domain organisation and mutation sites in domains TB4 and TB5. (A) The fibrillin-1 domain organisation is dominated by calcium-binding EGF-like domains (white) interspersed with transforming growth factor β-binding protein-like (TB; blue) and hybrid (diagonal stripes) domains. Other regions include the fibrillin unique N-terminal (FUN; purple) and non-calcium-binding EGF-like (grey) domains, a proline-rich region (orange) and a conserved 2Cys domain (yellow). N- and C-terminal propeptides (black) are processed by furin before microfibril assembly. (B) Structure of the cbEGF22-TB4-cbEGF23 fragment of fibrillin-1 (pdb 1UZJ) (6), with RGD integrin binding site indicated, showing the sites affected by SSS substitutions C1564S and W1570C (cyan spheres, left panel) and MFS substitution C1564Y (magenta spheres, right panel). In essence, residues important for stabilising TB domain fold are affected. (C) Homology model of the cbEGF24-TB5-cbEGF25 region of fibrillin-1, showing sites affected by geleophysic and acromicric dysplasias (light orange and dark orange spheres, respectively, left panel) and MFS substitutions (magenta spheres, right panel). All are predicted to affect the fold of the domain. The cbEGF24-TB5-cbEGF25 model was created with Modeller software using the cbEGF22-TB4-cbEGF23 structure as a template (10). Figures were rendered using PyMOL (Schrödinger, LLC) to show cbEGF domains (green), TB domains (blue), calcium ions (red) and disulphide bonds (yellow).
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DDV181F1: Fibrillin-1 domain organisation and mutation sites in domains TB4 and TB5. (A) The fibrillin-1 domain organisation is dominated by calcium-binding EGF-like domains (white) interspersed with transforming growth factor β-binding protein-like (TB; blue) and hybrid (diagonal stripes) domains. Other regions include the fibrillin unique N-terminal (FUN; purple) and non-calcium-binding EGF-like (grey) domains, a proline-rich region (orange) and a conserved 2Cys domain (yellow). N- and C-terminal propeptides (black) are processed by furin before microfibril assembly. (B) Structure of the cbEGF22-TB4-cbEGF23 fragment of fibrillin-1 (pdb 1UZJ) (6), with RGD integrin binding site indicated, showing the sites affected by SSS substitutions C1564S and W1570C (cyan spheres, left panel) and MFS substitution C1564Y (magenta spheres, right panel). In essence, residues important for stabilising TB domain fold are affected. (C) Homology model of the cbEGF24-TB5-cbEGF25 region of fibrillin-1, showing sites affected by geleophysic and acromicric dysplasias (light orange and dark orange spheres, respectively, left panel) and MFS substitutions (magenta spheres, right panel). All are predicted to affect the fold of the domain. The cbEGF24-TB5-cbEGF25 model was created with Modeller software using the cbEGF22-TB4-cbEGF23 structure as a template (10). Figures were rendered using PyMOL (Schrödinger, LLC) to show cbEGF domains (green), TB domains (blue), calcium ions (red) and disulphide bonds (yellow).

Mentions: The structure of fibrillin-1 is dominated by 43 calcium-binding epidermal growth factor-like (cbEGF) domains interspersed with 7 transforming growth factor β-binding protein-like (TB) domains (Fig. 1A). TB domains are found only in the fibrillin/LTBP superfamily of proteins (11). Their structure is characterised by eight cysteine residues, disulphide bonded in a C1-C3, C2-C6, C4-C7, C5-C8 arrangement, with a small hydrophobic core that in most cases is formed by a conserved tryptophan (6,12,13). The majority of mutations affecting the gene encoding human fibrillin-1, FBN1, result in Marfan syndrome (MFS), a common (1:5000 incidence), autosomal dominant disorder of the fibrous connective tissue with highly variable clinical manifestations characterised by skeletal, ocular and cardiovascular defects. MFS-associated mutations affect all domains of fibrillin-1 and, until recently, few genotype–phenotype correlations have been established. An exception was the ‘neonatal’ region, spanning from domains cbEGF11-18, which is associated with a severe, early onset form of MFS (14).Figure 1.


A microfibril assembly assay identifies different mechanisms of dominance underlying Marfan syndrome, stiff skin syndrome and acromelic dysplasias.

Jensen SA, Iqbal S, Bulsiewicz A, Handford PA - Hum. Mol. Genet. (2015)

Fibrillin-1 domain organisation and mutation sites in domains TB4 and TB5. (A) The fibrillin-1 domain organisation is dominated by calcium-binding EGF-like domains (white) interspersed with transforming growth factor β-binding protein-like (TB; blue) and hybrid (diagonal stripes) domains. Other regions include the fibrillin unique N-terminal (FUN; purple) and non-calcium-binding EGF-like (grey) domains, a proline-rich region (orange) and a conserved 2Cys domain (yellow). N- and C-terminal propeptides (black) are processed by furin before microfibril assembly. (B) Structure of the cbEGF22-TB4-cbEGF23 fragment of fibrillin-1 (pdb 1UZJ) (6), with RGD integrin binding site indicated, showing the sites affected by SSS substitutions C1564S and W1570C (cyan spheres, left panel) and MFS substitution C1564Y (magenta spheres, right panel). In essence, residues important for stabilising TB domain fold are affected. (C) Homology model of the cbEGF24-TB5-cbEGF25 region of fibrillin-1, showing sites affected by geleophysic and acromicric dysplasias (light orange and dark orange spheres, respectively, left panel) and MFS substitutions (magenta spheres, right panel). All are predicted to affect the fold of the domain. The cbEGF24-TB5-cbEGF25 model was created with Modeller software using the cbEGF22-TB4-cbEGF23 structure as a template (10). Figures were rendered using PyMOL (Schrödinger, LLC) to show cbEGF domains (green), TB domains (blue), calcium ions (red) and disulphide bonds (yellow).
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DDV181F1: Fibrillin-1 domain organisation and mutation sites in domains TB4 and TB5. (A) The fibrillin-1 domain organisation is dominated by calcium-binding EGF-like domains (white) interspersed with transforming growth factor β-binding protein-like (TB; blue) and hybrid (diagonal stripes) domains. Other regions include the fibrillin unique N-terminal (FUN; purple) and non-calcium-binding EGF-like (grey) domains, a proline-rich region (orange) and a conserved 2Cys domain (yellow). N- and C-terminal propeptides (black) are processed by furin before microfibril assembly. (B) Structure of the cbEGF22-TB4-cbEGF23 fragment of fibrillin-1 (pdb 1UZJ) (6), with RGD integrin binding site indicated, showing the sites affected by SSS substitutions C1564S and W1570C (cyan spheres, left panel) and MFS substitution C1564Y (magenta spheres, right panel). In essence, residues important for stabilising TB domain fold are affected. (C) Homology model of the cbEGF24-TB5-cbEGF25 region of fibrillin-1, showing sites affected by geleophysic and acromicric dysplasias (light orange and dark orange spheres, respectively, left panel) and MFS substitutions (magenta spheres, right panel). All are predicted to affect the fold of the domain. The cbEGF24-TB5-cbEGF25 model was created with Modeller software using the cbEGF22-TB4-cbEGF23 structure as a template (10). Figures were rendered using PyMOL (Schrödinger, LLC) to show cbEGF domains (green), TB domains (blue), calcium ions (red) and disulphide bonds (yellow).
Mentions: The structure of fibrillin-1 is dominated by 43 calcium-binding epidermal growth factor-like (cbEGF) domains interspersed with 7 transforming growth factor β-binding protein-like (TB) domains (Fig. 1A). TB domains are found only in the fibrillin/LTBP superfamily of proteins (11). Their structure is characterised by eight cysteine residues, disulphide bonded in a C1-C3, C2-C6, C4-C7, C5-C8 arrangement, with a small hydrophobic core that in most cases is formed by a conserved tryptophan (6,12,13). The majority of mutations affecting the gene encoding human fibrillin-1, FBN1, result in Marfan syndrome (MFS), a common (1:5000 incidence), autosomal dominant disorder of the fibrous connective tissue with highly variable clinical manifestations characterised by skeletal, ocular and cardiovascular defects. MFS-associated mutations affect all domains of fibrillin-1 and, until recently, few genotype–phenotype correlations have been established. An exception was the ‘neonatal’ region, spanning from domains cbEGF11-18, which is associated with a severe, early onset form of MFS (14).Figure 1.

Bottom Line: 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.Despite their apparent phenotypic differences, dysregulation of transforming growth factor β (TGFβ) is a common factor in all of these disorders.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK sacha.jensen@bioch.ox.ac.uk.

No MeSH data available.


Related in: MedlinePlus