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Invest Ophthalmol Vis Sci. 2015 Jul;56(8):4653-61. doi: 10.1167/iovs.15-16922.

Protein Composition of TGFBI-R124C- and TGFBI-R555W-Associated Aggregates Suggests Multiple Mechanisms Leading to Lattice and Granular Corneal Dystrophy.

Author information

1
School of Biomedical Sciences, Centre for Molecular Biosciences (CMB), University of Ulster, Coleraine, Northern Ireland, United Kingdom 2Department of Molecular Biology and Genetics, Science Park, Aarhus University, Aarhus, Denmark.
2
Department of Molecular Biology and Genetics, Science Park, Aarhus University, Aarhus, Denmark 3Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Aarhus, Denmark.
3
Department of Histopathology, Royal Victoria Eye and Ear Hospital, Dublin 2, Ireland.
4
School of Biomedical Sciences, Centre for Molecular Biosciences (CMB), University of Ulster, Coleraine, Northern Ireland, United Kingdom 5Cathedral Eye Clinic, Belfast, Northern Ireland, United Kingdom.
5
School of Biomedical Sciences, Centre for Molecular Biosciences (CMB), University of Ulster, Coleraine, Northern Ireland, United Kingdom.

Abstract

PURPOSE:

Transforming growth factor beta-induced (TGFBI)-related dystrophies constitute the most common heritable forms of corneal dystrophy worldwide. However, other than the underlying genotypes of these conditions, a limited knowledge exists of the exact pathomechanisms of these disorders. This study expands on our previous research investigating dystrophic stromal aggregates, with the aim of better elucidating the pathomechanism of two conditions arising from the most common TGFBI mutations: granular corneal dystrophy type 1 (GCD1; R555W) and lattice corneal dystrophy type 1 (LCD1; R124C).

METHODS:

Patient corneas with GCD1 and LCD1 were stained with hematoxylin and eosin and Congo red to visualize stromal nonamyloid and amyloid deposits, respectively. Laser capture microdissection was used to isolate aggregates and extracted protein was analyzed by mass spectrometry. Proteins were identified and their approximate abundances were determined. Spectra of TGFBIp peptides were also recorded and quantified.

RESULTS:

In total, three proteins were found within GCD1 aggregates that were absent in the healthy control corneal tissue. In comparison, an additional 18 and 24 proteins within stromal LCD1 and Bowman's LCD1 deposits, respectively, were identified. Variances surrounding the endogenous cleavage sites of TGFBIp were also noted. An increase in the number of residues experiencing cleavage was observed in both GCD1 aggregates and LCD1 deposits.

CONCLUSIONS:

The study reveals previously unknown differences between the protein composition of GCD1 and LCD1 aggregates, and confirms the presence of the HtrA1 protease in LCD1-amyloid aggregates. In addition, we find mutation-specific differences in the processing of mutant TGFBIp species, which may contribute to the variable phenotypes noted in TGFBI-related dystrophies.

PMID:
26207300
DOI:
10.1167/iovs.15-16922
[Indexed for MEDLINE]

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