Comparison of two phenotypically distinct lattice corneal dystrophies caused by mutations in the transforming growth factor beta induced (TGFBI) gene

Authors

  • Ebbe Toftgaard Poulsen,

    1. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
    3. Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark
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  • Kasper Runager,

    1. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
    3. Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark
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  • Michael W. Risør,

    1. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
    3. Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark
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  • Thomas F. Dyrlund,

    1. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
    3. Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark
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  • Carsten Scavenius,

    1. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
    3. Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark
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  • Henrik Karring,

    1. Department of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, University of Southern Denmark, Odense, Denmark
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  • Jeppe Praetorius,

    1. Department of Biomedicine, Aarhus University, Aarhus, Denmark
    2. Membranes, Aarhus University, Aarhus, Denmark
    3. InterPrET, Aarhus University, Aarhus, Denmark
    4. Department of Health, Aarhus University, Aarhus, Denmark
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  • Henrik Vorum,

    1. Department of Ophthalmology, Aalborg University Hospital, Aalborg, Denmark
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  • Daniel E. Otzen,

    1. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
    3. Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark
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  • Gordon K. Klintworth,

    1. Department of Pathology, Duke University Medical Center, Durham, NC, USA
    2. Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA
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  • Jan J. Enghild

    Corresponding author
    1. Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
    2. Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
    3. Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark
    • Correspondence: Dr. Jan J. Enghild, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark

      E-mail: jje@mb.au.dk

      Fax: +45-86-12-31-78

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Abstract

Purpose

In this study, we investigated whether the phenotypic difference observed between two lattice corneal dystrophy type 1 (LCD type 1) cases caused by either a single A546D substitution or an A546D/P551Q double substitution in TGFBIp (transforming growth factor beta induced protein) can be ascribed to (i) a difference in the proteomes of corneal amyloid deposits, (ii) altered proteolysis of TGFBIp, or (iii) structural changes of TGFBIp introduced by the P551Q amino acid substitution.

Experimental design

Amyloid deposits were isolated from the corneas of two siblings with LCD type 1 resulting from A546D/P551Q mutations in the TGFBI gene using laser capture microdissection and subsequently analyzed by LC-MS/MS. Proteolytic processing of TGFBIp was addressed by counting peptide spectra. Lastly, to study the possible effect of the P551Q substitution, recombinant FAS1–4 domain variants were subjected to in vitro stability assays.

Results

The amyloid proteomes and TGFBIp processing of the two A546D/P551Q LCD type 1 cases were similar to each other as well as to the A546D amyloid proteome previously reported by us. The stability assays revealed a minor destabilization of the FAS1–4 domain upon the addition of the P551Q mutation, moreover, it resulted in different accessibility to tryptic cleavage sites between the A546D and A546D/P551Q mutant FAS1–4 domain variants.

Conclusion and clinical relevance

The difference in A546D and A546D/P551Q LCD type 1 phenotypes cannot be ascribed to altered corneal amyloid composition or altered in vivo proteolytic processing of TGFBIp. Instead, a small difference in thermodynamic stability introduced by the P551Q mutation most likely causes structural changes of TGFBIp. The MS proteomics data have been deposited to the ProteomeXchange with identifier PXD000307 (http://proteomecentral.proteomexchange.org/dataset/PXD000307).

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