| Structural highlights
Disease
[BGH3_HUMAN] Defects in TGFBI are the cause of epithelial basement membrane corneal dystrophy (EBMD) [MIM:121820]; also known as Cogan corneal dystrophy or map-dot-fingerprint type corneal dystrophy. EBMD is a bilateral anterior corneal dystrophy characterized by grayish epithelial fingerprint lines, geographic map-like lines, and dots (or microcysts) on slit-lamp examination. Pathologic studies show abnormal, redundant basement membrane and intraepithelial lacunae filled with cellular debris. Although this disorder usually is not considered to be inherited, families with autosomal dominant inheritance have been identified.[1] Defects in TGFBI are the cause of corneal dystrophy Groenouw type 1 (CDGG1) [MIM:121900]; also known as corneal dystrophy granular type. Inheritance is autosomal dominant. Corneal dystrophies show progressive opacification of the cornea leading to severe visual handicap.[2] Defects in TGFBI are the cause of corneal dystrophy lattice type 1 (CDL1) [MIM:122200]. Inheritance is autosomal dominant. Defects in TGFBI are a cause of corneal dystrophy Thiel-Behnke type (CDTB) [MIM:602082]; also known as corneal dystrophy of Bowman layer type 2 (CDB2). Defects in TGFBI are the cause of Reis-Buecklers corneal dystrophy (CDRB) [MIM:608470]; also known as corneal dystrophy of Bowman layer type 1 (CDB1).[3] [4] [5] Defects in TGFBI are the cause of lattice corneal dystrophy type 3A (CDL3A) [MIM:608471]. CDL3A clinically resembles to lattice corneal dystrophy type 3, but differs in that its age of onset is 70 to 90 years. It has an autosomal dominant inheritance pattern.[6] [7] Defects in TGFBI are the cause of Avellino corneal dystrophy (ACD) [MIM:607541]. ACD could be considered a variant of granular dystrophy with a significant amyloidogenic tendency. Inheritance is autosomal dominant.
Function
[BGH3_HUMAN] Binds to type I, II, and IV collagens. This adhesion protein may play an important role in cell-collagen interactions. In cartilage, may be involved in endochondral bone formation.
Publication Abstract from PubMed
Hereditary mutations in the transforming growth factor beta induced (TGFBI) gene cause phenotypically distinct corneal dystrophies characterized by protein deposition in cornea. We show here that the Arg555Trp mutant of the fourth fasciclin 1 (FAS1-4) domain of the protein (TGFBIp/keratoepithelin/betaig-h3), associated with granular corneal dystrophy type 1, is significantly less susceptible to proteolysis by thermolysin and trypsin than the WT domain. High-resolution liquid-state NMR of the WT and Arg555Trp mutant FAS1-4 domains revealed very similar structures except for the region around position 555. The Arg555Trp substitution causes Trp555 to be buried in an otherwise empty hydrophobic cavity of the FAS1-4 domain. The first thermolysin cleavage in the core of the FAS1-4 domain occurs on the N-terminal side of Leu558 adjacent to the Arg555 mutation. MD simulations indicated that the C-terminal end of helix alpha3' containing this cleavage site is less flexible in the mutant domain, explaining the observed proteolytic resistance. This structural change also alters the electrostatic properties, which may explain increased propensity of the mutant to aggregate in vitro with 2,2,2-trifluoroethanol. Based on our results we propose that the Arg555Trp mutation disrupts the normal degradation/turnover of corneal TGFBIp, leading to accumulation and increased propensity to aggregate through electrostatic interactions.
Mutation in transforming growth factor beta induced protein associated with granular corneal dystrophy type 1 reduces the proteolytic susceptibility through local structural stabilization.,Underhaug J, Koldso H, Runager K, Nielsen JT, Sorensen CS, Kristensen T, Otzen DE, Karring H, Malmendal A, Schiott B, Enghild JJ, Nielsen NC Biochim Biophys Acta. 2013 Oct 12. pii: S1570-9639(13)00366-X. doi:, 10.1016/j.bbapap.2013.10.008. PMID:24129074[8]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Boutboul S, Black GC, Moore JE, Sinton J, Menasche M, Munier FL, Laroche L, Abitbol M, Schorderet DF. A subset of patients with epithelial basement membrane corneal dystrophy have mutations in TGFBI/BIGH3. Hum Mutat. 2006 Jun;27(6):553-7. PMID:16652336 doi:10.1002/humu.20331
- ↑ Chakravarthi SV, Kannabiran C, Sridhar MS, Vemuganti GK. TGFBI gene mutations causing lattice and granular corneal dystrophies in Indian patients. Invest Ophthalmol Vis Sci. 2005 Jan;46(1):121-5. PMID:15623763 doi:46/1/121
- ↑ Chakravarthi SV, Kannabiran C, Sridhar MS, Vemuganti GK. TGFBI gene mutations causing lattice and granular corneal dystrophies in Indian patients. Invest Ophthalmol Vis Sci. 2005 Jan;46(1):121-5. PMID:15623763 doi:46/1/121
- ↑ Okada M, Yamamoto S, Tsujikawa M, Watanabe H, Inoue Y, Maeda N, Shimomura Y, Nishida K, Quantock AJ, Kinoshita S, Tano Y. Two distinct kerato-epithelin mutations in Reis-Bucklers corneal dystrophy. Am J Ophthalmol. 1998 Oct;126(4):535-42. PMID:9780098
- ↑ Rozzo C, Fossarello M, Galleri G, Sole G, Serru A, Orzalesi N, Serra A, Pirastu M. A common beta ig-h3 gene mutation (delta f540) in a large cohort of Sardinian Reis Bucklers corneal dystrophy patients. Mutations in brief no. 180. Online. Hum Mutat. 1998;12(3):215-6. PMID:10660331
- ↑ Yamamoto S, Okada M, Tsujikawa M, Shimomura Y, Nishida K, Inoue Y, Watanabe H, Maeda N, Kurahashi H, Kinoshita S, Nakamura Y, Tano Y. A kerato-epithelin (betaig-h3) mutation in lattice corneal dystrophy type IIIA. Am J Hum Genet. 1998 Mar;62(3):719-22. PMID:9497262 doi:10.1086/301765
- ↑ Stix B, Leber M, Bingemer P, Gross C, Ruschoff J, Fandrich M, Schorderet DF, Vorwerk CK, Zacharias M, Roessner A, Rocken C. Hereditary lattice corneal dystrophy is associated with corneal amyloid deposits enclosing C-terminal fragments of keratoepithelin. Invest Ophthalmol Vis Sci. 2005 Apr;46(4):1133-9. PMID:15790870 doi:46/4/1133
- ↑ Underhaug J, Koldso H, Runager K, Nielsen JT, Sorensen CS, Kristensen T, Otzen DE, Karring H, Malmendal A, Schiott B, Enghild JJ, Nielsen NC. Mutation in transforming growth factor beta induced protein associated with granular corneal dystrophy type 1 reduces the proteolytic susceptibility through local structural stabilization. Biochim Biophys Acta. 2013 Oct 12. pii: S1570-9639(13)00366-X. doi:, 10.1016/j.bbapap.2013.10.008. PMID:24129074 doi:http://dx.doi.org/10.1016/j.bbapap.2013.10.008
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