BIGH3 Wild-Type and Mutant Proteins

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DESCRIPTION (provided by applicant): The cornea contains an abundant poorly understood clinically relevant protein important for the preservation of corneal transparency. Mutations in the TGFBI (BIGH3) gene are responsible for several phenotypically different inherited corneal diseases that have no apparent non-ocular manifestations. These disorders include several varieties of lattice corneal dystrophy and corneal amyloidoses, granular corneal dystrophy, Reis- B|cklers corneal dystrophy, Thiel-Behnke dystrophy, and several atypical corneal disorders. The particular clinical and histopathologic phenotypes are dependent upon the precise mutation in TGFBI, but a molecular explanation for the different phenotypes remains to be determined. The mutated extracellular transforming growth factor beta induced protein (TGFBIp) encoded by TGFBI accumulates in the corneal stroma in these disorders which are apparently limited to the cornea. The long-term objectives are to understand the properties of this unique protein and to investigate the molecular mechanisms responsible for the specific deposits that accumulate within the cornea in patients with mutated TGFBI. The Specific Aims of this proposal are: (1) to screen subjects with inherited corneal diseases for TGFBI mutations, (2) to analyze abnormal deposits isolated from surgically excised corneal tissue by laser capture micro-dissection and liquid chromatography/tandem mass spectrometry (LC MS/MS) to determine whether part or all of the mutated TGFBIp accumulates in the cornea and what other protein(s) are closely linked to it, (3) to determine the biochemical and biophysical properties of the FAS4 domain of purified recombinant wild-type and disease producing TGFBIp and (4) to solve the three-dimensional structure at atomic resolution of recombinant wild- type TGFBIp and the FAS4 domains of recombinant wild-type and disease producing mutants using X-ray crystallography and nuclear magnetic resonance spectroscopy (NMR). PUBLIC HEALTH RELEVANCE. This is a study of an important poorly understood protein (TGFBIp). Mutations in the gene (TGFBI) encoding for this protein cause several corneal diseases (dystrophies) and a better understanding of TGFBIp will lead to better methods of treating the resulting impaired vision and debilitating symptoms.