Keratoepithelin Gene Research Articles

Recurrence of anterior corneal dystrophies after keratoplasty

AbstractPurpose To describe the rates of simple recurrence (SR) and clinically significant recurrence (CSR) of anterior dystrophies in donor corneas after penetrating or lamellar keratoplasty.Methods Retrospective case series of patients who underwent keratoplasty for anterior dystrophies from 1954 to 2008 with a minimum follow‐up time of three years. Kaplan Meier survival curves were calculated for both parameters (SR and CR) to demonstrate recurrence of the different dystrophies thru time.Results A total of 109 eyes of 66 patients were included: 8 cases of Bowman´s dystrophy (6 eyes with CDRB/Reis Bucklers and 2 eyes with CDTB/Thiel Bhenke), 19 cases of CDG/Granular, 53 cases of CDL/Lattice and 29 cases of CDM/Macular. The median follow‐up time for each kind of dystrophy varied from 75 months (6.25 years) to 180 months (15 years). The survival function for simple recurrence was significantly higher (376.2 months/31 years) for cases of CDM, as compared to those dystrophies related to the keratoepithelin gene : CDRB =177.6 months, CDL=168 months and CDG =89.2 months. Clinically significant recurrence (CR) was noted predominantly in cases of CDL and CDGConclusion Keratoplasty (whether penetrating or lamellar) is an effective treatment for cases of anterior dystrophies, when visual axis is affected or when other less invasive treatment modalities fail. The statistically significant difference in survival time of recurrence after keratoplasty for the different kinds of anterior dystrophies coincides with literature and may help us in prognosticating the best treatment option for each individual case. Theme: DALK and PK Does one or more of the authors have any financial interest in the subject matter of this presentation?: No

Clinical Findings and Treatments of Granular Corneal Dystrophy Type 2 (Avellino Corneal Dystrophy): A Review of the Literature

To review the literature about clinical findings and treatments of granular corneal dystrophy type 2 (GCD2). Various literatures on clinical findings, exacerbations after refractive corneal surgery, and treatment modalities of GCD2 were reviewed. GCD2 is an autosomal dominant disease. Mutation of transforming growth factor beta-induced gene, TGFBI, or keratoepithelin gene in human chromosome 5 (5q31) is the key pathogenic process in patient with GCD2. Corneal trauma activates TGFBI and then it overproduces transforming growth factor beta-induced gene protein (TGFBIp), which is main component of the corneal opacity. Refractive corneal surgery is a popular procedure to correct refractive error worldwide. However, several cases about exacerbation of GCD2 after corneal refractive surgery such as photorefractive keratectomy, laser in situ keratomileusis, and laser epithelial keratomileusis have been reported. The opacities deteriorate patient's best-corrected visual acuity. Recurrence-free interval varies many factors such as the type of procedure the patient had received and the genotype of the patient. To treat the opacities in GCD2, phototherapeutic keratectomy, lamellar keratoplasty, deep lamellar keratoplasty, and penetrating keratoplasty (PKP) were used. However, the recurrence is still an unsolved problem. Perfect treatment of exacerbation after corneal surface ablation does not exist until now. To prevent exacerbation, refractive surgeons must do a careful preoperative examination of candidates in refractive surgeries.

Identification of an amyloidogenic region on keratoepithelin via synthetic peptides

Mutations of keratoepithelin (KE) gene in human chromosome 5q31 have been linked with corneal epithelial or stromal dystrophies characterized by the abnormal deposits of amyloid fibrils and/or non-amyloid aggregations in corneal tissue. We report herein that synthetic peptide containing amino acid (a.a.) residues of 515–532 of native KE protein can readily form β-sheet-containing amyloid fibrils in vitro. Amyloid fibrils formed in various conditions from short synthetic peptides (containing a.a. 515–532 and 515–525, respectively) were characterized by thioflavin T (ThT) fluorescence assay, Congo red staining, electron microscopy (EM) and circular dichroism (CD). Triple-N-methylation of the synthetic peptides prevented the β-sheet polymerization and related amyloid fibril formation. Comparison study with ThT fluorescence further demonstrated that synthetic peptides containing corneal dystrophy-related mutations within this region formed amyloid fibrils to various extents. Our results suggest that each individual dystrophy-related mutation by itself does not necessarily potentiate amyloid fibril formation of KE. Roles of these intrinsically amyloidogenic foci in abnormal KE aggregations and amyloid deposits of stromal corneal dystrophies await further investigation.

Delayed Corneal Epithelial Wound Healing After Penetrating Keratoplasty in Individuals With Lattice Corneal Dystrophy

To investigate whether corneal epithelial cells of individuals with lattice corneal dystrophy (LCD) possess an intrinsic defect. Retrospective case-control study. The medical charts of nine individuals with LCD and those of 14 patients with keratoconus and 11 patients with corneal leukoma (controls), all of whom underwent penetrating keratoplasty (PKP) in one eye at Yamaguchi University Hospital between February 1998 and November 2001, were examined for the time for epithelial resurfacing after surgery. The time required for resurfacing of the corneal epithelium after PKP was significantly greater in LCD patients (8.56 +/- 4.95 days, mean +/- SD) than in patients with either keratoconus (1.71 +/- 0.91 days, P = .006) or corneal leukoma (3.00 +/- 1.95 days, P = .03). Corneal epithelial wound healing was delayed in LCD patients after PKP, suggesting that the keratoepithelin gene mutations responsible for this condition affect corneal epithelial cells.

Optimized expression and refolding of human keratoepithelin in BL21 (DE3)

Keratoepithelin (KE) is an extracellular protein participating in cell adhesion and differentiation. Mutations of the KE gene (on 5q31 in humans) cause deposition of abnormal proteins (amyloid and non-amyloid) in corneal stroma and lead to several corneal dystrophies in humans. However, further studies on the KE protein have been limited by the intrinsic difficulty of purifying this protein. A high-expression plasmid containing human KE gene was constructed to generate recombinant KE proteins in Escherichia coli. The plasmid was transformed into E. coli BL21 (DE3) and the recombinant protein was expressed as an insoluble His-tagged fusion protein and purified by nickel chelation affinity chromatography under denaturing conditions. On average, 12 mg of purified KE was routinely obtained from 1 L of culture media. The recombinant KE was refolded in arginine-containing dialysis solutions and the recovery of bioactive KE typically was ∼70%. The procedures developed in this report should enable reproducible production of KE and related mutant proteins in large quantities and facilitate future studies on biochemical and biophysical properties of KE and the pathogenesis of related corneal dystrophies.

Kerato-Epithelin Mutation (R 555 Q) in a Case of Reis-Bücklers Corneal Dystrophy

Background: Mutations in the kerato-epithelin gene on chromosome 5 q 31 are known to cause four distinct autosomal dominant diseases of the human cornea: Reis-Bücklers, granular, lattice, and Avellino corneal dystrophy. Mutation of arginin to glutamine in codon 555 (R 555 Q) in kerato-epithelin was recently reported in four blood-related patients with Reis-Bücklers corneal dystrophy. Case: A 42-year-old female has had photophobia with decreasing vison since the age of 20 years. Her corrected visual acuity was 0.5 in both eyes. She showed subepithelial opacities in both corneas characteristic of Reis-Bücklers corneal dystrophy. Method: The DNA was extracted from leukocytes according to standard protocols. The keratoepithelin gene was examined for a mutation by the polymerase chain reaction and direct sequencing. Findings: We identified kerato-epithelin mutation R 555 Q. The patient's two children and 50 controls did not show missense mutation. Conclusion: Kerato-epithelin mutation R 555 Q was present in a Japanese patient with Reis-Bücklers corneal dystrophy.

Lattice corneal dystrophy. Detection of a point mutation in the kerato-epithelin gene

Lattice dystrophy is an autosomal-dominantly inherited disease. A mutation of the gene coding for kerato-epithelin has been found in patients with this stromal dystrophy. In codon 124 a Guanine to Adenine mutation of the nucleotide 417 has been described. We looked for this mutation in a family with lattice dystrophy treated in our clinic. Using primers specific for kerato-epithelin gene, we amplified the cDNA extracted from lymphocytes of two patients suffering from lattice dystrophy. The polymerase chain reaction (PCR) products were subcloned and sequenced. Guanine to Adenine mutations, as published were detected in both of our patients at codon 124. We found the published mutation in both of our patients, indicating that this Guanine to Adenine exchange is pathognomonic for lattice dystrophy.

Severe form of juvenile corneal stromal dystrophy with homozygous R124H mutation in the keratoepithelin gene in five Japanese patients

AIMTo confirm the mutation of the keratoepithelin gene in patients with a severe form of superficial juvenile granular corneal dystrophy (GCD).METHODSFive Japanese probands in whom GCD was diagnosed after histopathological...

Granular corneal dystrophy with homozygous mutations in the kerato-epithelin gene

PURPOSE: To report a family with several members affected with granular corneal dystrophy Groenouw type 1. Three members of the family were affected with a severe placoid type of corneal dystrophy. To determine the relationship between gene mutations and phenotypic variations of the disease, we analyzed the kerato-epithelin gene. METHODS: The pedigree included a consanguineous marriage of two affected individuals. The three family members affected with a severe form of corneal dystrophy were offspring of these parents. However, the phenotype of other affected family members was typical granular corneal dystrophy. We isolated genomic DNA from leukocytes of the family members. Exons of the kerato-epithelin gene were amplified by the polymerase chain reaction and were analyzed using the single-strand conformation polymorphism technique. Mutations were identified by direct sequencing method and restriction digestion analysis. RESULTS: The three severely affected family members exhibited homozygous mutations at codon 555 (arginine to tryptophan) in the kerato-epithelin gene, whereas those with typical granular corneal dystrophy had the heterozygous mutation at the same codon. Unaffected family members did not have the mutation. CONCLUSIONS: We determined that the severe phenotype of granular corneal dystrophy is caused by homozygous mutations in the kerato-epithelin gene. Clinical manifestation of the severe phenotype is a placoid type of corneal dystrophy and early recurrence after surgery. Granular corneal dystrophy appears to be the first ophthalmic disease in which homozygosity for a dominant allele has been genetically identified.

Lattice corneal dystrophy type 1 in a Canadian kindred is associated with the Arg 124 → Cys mutation in the kerato-epithelin gene

To identify the mutation responsible for lattice corneal dystrophy type 1 in an extended Canadian kindred. A search for a mutation in the candidate gene, kerato-epithelin, was carried out by single-strand conformation polymorphism and sequencing analyses. AC --> T mutation at position 417 was detected in exon 4 of the kerato-epithelin gene, which is expected to cause an Arg124 --> Cys change. This is the same nucleotide change described previously in two Swiss families with lattice corneal dystrophy type 1. Although the possibility that the three families (two previously described Swiss families and this Canadian kindred) are related has not been excluded, it appears that the unique phenotype of lattice corneal dystrophy type 1 is caused by this particular amino acid change.