To identify the types of <i>TGFBI</i> (transforming growth factor, beta-induced) gene mutations in three Chinese families with Reis-Bücklers corneal dystrophy (RBCD), lattice corneal dystrophy type I (LCDI), or Avellino corneal dystrophy (ACD) and to investigate the relationship between the phenotypes and genotypes of corneal dystrophy.
It is our intention to demonstrate that the pre-operative genetic screening for TGFBI mutations should be mandatory for refractive surgery candidates.Patients and MethodsIn this study, we reviewed the proband's post-LASIK slit-lamp and in vivo confocal microscopy images and genetic testing results, and performed genetic testing on eleven additional members of the family to investigate the penetrance of corneal dystrophy in asymptomatic members who carry the mutation.ResultsThe proband demonstrated a post-LASIK exacerbation of Granular Corneal Dystrophy type 2 (GCD2), identified as a TGFBIR124H mutation.
In granular corneal dystrophy type 2 (GCD2), corneal deposits containing fragments of transforming growth factor-β-induced protein appear in sequence as granular lesions (GLs), linear lesions (LLs), and diffuse haze (DH).
LASIK surgery of granular corneal dystrophy type 2 patients leads to accumulation and differential proteolytic processing of transforming growth factor beta-induced protein (TGFBIp).
Treatment with 4-PBA considerably reduced the levels of BiP, IRE1α, and XBP1 in GCD2 cells; notably, 4-PBA treatment significantly reduced the levels of TGFBIp without change in TGFBI mRNA levels.
From the results, we conclude that our toehold-mediated, DNA displacement-based, SERS sensor allows a rapid and sensitive detection of a BIGH3 gene point mutation associated with Avellino corneal dystrophy, indicating the practical ability of the method to diagnose genetic diseases caused by point mutations.
We review our current understanding of the molecular mechanisms of granular corneal dystrophy type 2 (GCD2) and studies of other TGFBI corneal dystrophies.
TGFβ1-induced expression of transforming growth factor β-induced protein (TGFBIp) and extracellular matrix (ECM) genes plays a major role in the development of granular corneal dystrophy type 2 (GCD2: also called Avellino corneal dystrophy).
Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant disease caused by a R124H point mutation in the transforming growth factor-β-induced gene (TGFBI).
We describe the phenotypic range of GCD2 heterozygotes for the common R124H mutation in TGFBI; seven with an extremely mild phenotype and six with an extremely severe phenotype.
Primary culture corneal fibroblasts were isolated from the corneas of healthy subjects and patients with granular corneal dystrophy type 2 (GCD2) with a homozygous mutation in TGFBIR124H.
In our study, thirty patients from five pedigrees and ten sporadic patients were diagnosed as four TGFBI gene-linked corneal dystrophies of granular corneal dystrophy type I (GGCD I), Avellino corneal dystrophy (ACD), lattice corneal dystrophy type I (LCD I), and lattice corneal dystrophy type IIIA (LCD IIIA), and in total, seven disease-causing mutations, namely R555W, A546D, A546T, and T538P mutations in exon 12, R124H and R124C mutations in exon 4, and P501T mutation in exon 11, were identified, while four polymorphisms of V327V, L472L, F540F, and 1665-1666insC were screened in exons 8, 11, and 12.
Genetic examination identified that two ACD subjects were associated with homozygous R124H mutation of TGFBI, and four LCD I subjects were all associated with R124C heterozygous mutation.
Point mutations of the BIGH3 gene are associated with the most common corneal dystrophies (CDs), such as Avellino corneal dystrophy, Reis-Bucklers corneal dystrophy, and lattice corneal dystrophy.
An additional feature of nonhyaline, nonamyloid, TGFBIp subepithelial deposits might substantiate the categorization of such cases as a variant form of ACD.
Granular corneal dystrophy type II (GCD II) is an autosomal dominant disorder characterized by age-dependent progressive accumulation of transforming growth factor-beta-induced protein (TGFBIp) deposits in the corneal stroma.
We also find that the periostin-TGFBI interaction is disrupted in corneal fibroblasts cultured from granular corneal dystrophy type II patients and that periostin accumulates in TGFBI-positive corneal deposits in granular corneal dystrophy type II (also known as Avellino corneal dystrophy).