Novel mutations of CHST6 in Iranian patients with macular corneal dystrophy

PURPOSE

To characterize mutations within the carbohydrate sulfotransferase 6 (CHST6) gene in Iranian subjects from 12 families with macular corneal dystrophy (MCD).

METHODS

Genomic DNA was extracted from peripheral blood of 20 affected patients and 60 healthy volunteers followed by polymerase chain reaction (PCR) and direct sequencing of the CHST6 coding region. The observed nucleotide sequences were then compared with those found by investigators in other populations with MCD and in the controls.

RESULTS

Analysis of CHST6 revealed 11 different mutations. These mutations were comprised of six novel missense mutations (p.F55L, p.P132L, p.S136G, p.C149Y, p.D203Y, and p.H249R), one novel nonsense mutation (p.S48X), one novel frame shift (after P297), and three previously reported missense mutations (p.P31L, p.C165Y, and p.R127C). The majority of the detected MCD mutations are located in the binding sites or the binding pocket, except the p.P31L and p.H249R mutations.

CONCLUSIONS

Nucleotide changes within the coding region of CHST6 are predicted to significantly alter the encoded sulfotransferase within the evolutionary conserved sequences. Our findings show that CHST6 mutations are responsible for the pathogenesis of MCD in Iranian patients. Moreover, the observation that some cases of MCD cannot be explained by mutations in the coding region of CHST6 suggests that MCD may result from possible upstream rearrangements in the CHST6 genomic region.

Immunophenotypes of macular corneal dystrophy in India and correlation with mutations in CHST6

PURPOSE

To determine the immunophenotypes of macular corneal dystrophy (MCD) in Indian patients and to correlate them with mutations in the carbohydrate 6-sulfotransferase (CHST6) gene.

METHODS

Sixty-four patients from 53 families with MCD that were previously screened for mutations in CHST6 were included in an immunophenotype analysis. Antigenic keratan sulfate (AgKS) in serum as well as corneal tissue was evaluated in 31 families. Only cornea was evaluated in 11 families, and only serum was evaluated in 11 families. AgKS was detected in formalin-fixed, paraffin-embedded corneal sections by immunohistochemistry and in serum by ELISA using a monoclonal antibody against sulfated forms of KS in patients with MCD as well as normal controls.

RESULTS

Analysis of corneal and/or serum AgKS disclosed MCD type I (27 families), MCD type IA (5 families), and MCD type II (3 families) in the cases studied. An additional 10 families were either MCD type I or MCD type IA since only serum AgKS data were available. Seven families manifested atypical immunophenotypes since the corneal AgKS expression was either of MCD type I or MCD type IA, but serum AgKS levels ranged from 19 ng/ml to 388 ng/ml. More than one immunophenotype was detected amongst siblings in two families. Each immunophenotype was associated with mutational heterogeneity in CHST6.

CONCLUSIONS

MCD type I was the predominant immunophenotype in the Indian population studied followed by MCD type IA and then MCD type II. We detected further immunophenotypic heterogeneity by finding atypical patterns of AgKS reactivity in a subset of families. There were no simple correlations between immunophenotypes and specific mutations in CHST6, suggesting that factors other than CHST6 mutations may be contributing to the immunophenotypes in MCD.

[Posterior polymorphous corneal dystrophy--case report]

Posterior polymorphous corneal dystrophy (PPCD) is a rare, bilateral, congenital disorder. It affects endothelial cells and Descemet's membrane. Slit lamp examination of PPCD shows characteristic bilateral endothelial bands, vesicles, and polymorphous opacities at the level of Descemet's membrane and endothelium, which can be accompanied by iridocorneal peripheral adhesions, iris atrophy, and corectopia. The clinical phenotype of PPCD can vary from relatively benign Descemet's thickening to severe progression towards vision loss from corneal edema or consecutive glaucoma. We present a case report of a 7-years old male patient with left eye corneal edema. Diagnosis of PPCD is made by slit-lam examination accompanied by anterior segment optical coherence tomography (AS OCT), and specular microscopy examination. Examination also revealed corneal changes in left eye of 32-years old patient's mother.

The IC3D classification of the corneal dystrophies

BACKGROUND

The recent availability of genetic analyses has demonstrated the shortcomings of the current phenotypic method of corneal dystrophy classification. Abnormalities in different genes can cause a single phenotype, whereas different defects in a single gene can cause different phenotypes. Some disorders termed corneal dystrophies do not appear to have a genetic basis.

PURPOSE

The purpose of this study was to develop a new classification system for corneal dystrophies, integrating up-to-date information on phenotypic description, pathologic examination, and genetic analysis.

METHODS

The International Committee for Classification of Corneal Dystrophies (IC3D) was created to devise a current and accurate nomenclature.

RESULTS

This anatomic classification continues to organize dystrophies according to the level chiefly affected. Each dystrophy has a template summarizing genetic, clinical, and pathologic information. A category number from 1 through 4 is assigned, reflecting the level of evidence supporting the existence of a given dystrophy. The most defined dystrophies belong to category 1 (a well-defined corneal dystrophy in which a gene has been mapped and identified and specific mutations are known) and the least defined belong to category 4 (a suspected dystrophy where the clinical and genetic evidence is not yet convincing). The nomenclature may be updated over time as new information regarding the dystrophies becomes available.

CONCLUSIONS

The IC3D Classification of Corneal Dystrophies is a new classification system that incorporates many aspects of the traditional definitions of corneal dystrophies with new genetic, clinical, and pathologic information. Standardized templates provide key information that includes a level of evidence for there being a corneal dystrophy. The system is user-friendly and upgradeable and can be retrieved on the website www.corneasociety.org/ic3d.

A new corneal disease with recurrent erosive episodes and autosomal-dominant inheritance

PURPOSE

The aim of this study was to characterize the phenotype in a large family with autosomal-dominant recurrent corneal erosions, and also to exclude genetic linkage to known autosomal-dominant inherited corneal dystrophies with clinical resemblance.

METHODS

We describe the medical history and clinical findings in patients from a six-generation family with recurrent corneal erosions. A total of 28 individuals were evaluated by ophthalmological examination. Genomic DNA was prepared from peripheral blood and analysed with polymorphic microsatellite markers close to known genes causing autosomal-dominant corneal dystrophies.

RESULTS

The patients had erosive symptoms that usually lasted from 1 to 7 days. The symptoms were described as early as at 8 months of age, and by the age of 5 the majority of the affected individuals suffered from recurrent corneal erosions. The attacks generally declined in frequency and intensity with age, and 52% of the patients developed central keloid-like corneal opacities. Nine patients received corneal grafts, and recurrences were seen in all grafts. The affected patients did not share haplotypes for genetic microsatellite markers surrounding known genes causing autosomal-dominant corneal dystrophies.

CONCLUSION

We describe a new hereditary disease with recurrent corneal erosions. Attacks of symptoms similar to recurrent erosions dominate the phenotype, but half of those affected also developed corneal, keloid-like, central opacities. This disorder was not genetically linked to any clinically resembling corneal dystrophies with autosomal-dominant inheritance.

[TGFBI gene mutations in the Ukrainian patients with inherited corneal stromal dystrophies]

Mutations Arg124Cys, Thr538Arg, Arg555Thr, Arg555Gln, Leu558Pro, and His626Arg in TGFBI gene were analyzed by polymerase chain reaction and restriction in 84 patients with various forms of corneal stromal dystrophies from 49 unrelated families and 29 clinically healthy relatives of these patients. A new mutation in TGFBI gene, Leu558Pro, was identified in the patients with atypical lattice dystrophy. The haplotypes of four microsatellite markers surrounding TGFBI gene region were analyzed in 22 families. The data on association of genotype and phenotype suggest that the analysis of TGFBI gene mutations is important for differential diagnostics of corneal dystrophies.

Macular corneal dystrophy: mutational spectrum in German patients, novel mutations and therapeutic options

INTRODUCTION

The objective of this study was to investigate genotype-phenotype correlations, the consequences for surgical treatment, and the therapeutical options in patients with macular corneal dystrophy (MCD).

MATERIAL AND METHODS

We investigated MCD genotype by using polymerase chain reaction followed by direct sequencing in one family and four patients with MCD. Results were confirmed by restriction analysis. Clinical phenotypes, histopathological findings, and therapeutical proceedings of each patient were reported and compared with the molecular genetic results.

RESULTS

Five mutations, four missense mutations, and one frameshift mutation, from which three were novel, and one single-nucleotide polymorphism, were identified within the coding region of the CHST6 gene. In three patients, two with a homozygous mutation within the start codon (Met1Leu) and one with a heterozygous mutation (Leu200Arg) and a polymorphism (Arg162Gly), with irregular corneal surface and recurrent erosions a phototherapeutic keratectomy lead to a transient success. An additional fitting of rigid gas permeable contact lenses in one patient could further improve irregular astigmatism. In two patients, one with a frameshift mutation (1734_1735delTG; Arg211Gln) and one with two compound heterozygous mutations (Leu200Arg; Leu173Phe) and an additional polymorphism (Arg162Gly) a penetrating keratoplasty improved BCVA without any recurrence of the opacities within the follow-up time.

DISCUSSION

Different genotypes imply several phenotypes, which influence therapeutical proceedings in MCD patients. Our study shows the wide range of diagnostic findings and therapeutical options in patients suffering from macular corneal dystrophy depending on the genotype.

Clinical features, diagnosis and management of maternally inherited diabetes and deafness (MIDD) associated with the 3243A>G mitochondrial point mutation

Maternally inherited diabetes and deafness (MIDD) affects up to 1% of patients with diabetes but is often unrecognized by physicians. It is important to make an accurate genetic diagnosis, as there are implications for clinical investigation, diagnosis, management and genetic counselling. This review summarizes the range of clinical phenotypes associated with MIDD; outlines the advances in genetic diagnosis and pathogenesis of MIDD; summarizes the published prevalence data and provides guidance on the clinical management of these patients and their families.

Genetic analysis of 14 families with Schnyder crystalline corneal dystrophy reveals clues to UBIAD1 protein function

Schnyder crystalline corneal dystrophy (SCCD) is a rare autosomal dominant disease characterized by progressive corneal opacification resulting from abnormal deposition of cholesterol and phospholipids. Recently, six different mutations on the UBIAD1 gene on chromosome 1p36 were found to result in SCCD. The purpose of this article is to further characterize the mutation spectrum of SCCD and identify structural and functional consequences for UBIAD1 protein activity. DNA sequencing was performed on samples from 36 individuals from 14 SCCD families. One affected individual was African American and SCCD has not been previously reported in this ethnic group. We identified UBIAD1 mutations in all 14 families which had 30 affected and 6 unaffected individuals. Eight different UBIAD1 mutations, 5 novel (L121F, D118G, and S171P in exon 1, G186R and D236E in exon 2) were identified. In four families with DNA samples from both affected and unaffected individuals, the D118G, G186R, T175I, and G177R mutations cosegregated with SCCD. In combination with our previous report, we have identified the genetic mutation in UBIAD1 in 20 unrelated families with 10 (including 5 reported here), having the N102S mutation. The results suggest that N102S may be a mutation hot spot because the affected families were unrelated including Caucasian and Asian individuals. There was no genotype phenotype correlation except for the T175I mutation which demonstrated prominent diffuse corneal haze, typically without corneal crystals. Protein analysis revealed structural and functional implications of SCCD mutations which may affect UBIAD1 function, ligand binding and interaction with binding partners, like apo E.

Sequencing of the CHST6 gene in Czech macular corneal dystrophy patients supports the evidence of a founder mutation

AIMS

To characterise the role of the carbohydrate sulfotransferase gene (CHST6) in macular corneal dystrophy (MCD) in Czech patients.

METHODS

The coding region of the CHST6 gene was directly sequenced in 10 affected and five unaffected members from eight apparently unrelated MCD families. The type of MCD was determined by enzyme-linked immunosorbent assay of antigenic keratan sulfate (KS) in serum and by immunohistochemical staining of corneas with monoclonal anti-KS antibody.

RESULTS

The following changes in the coding sequence of the CHST6 gene were observed; homozygous mutation of c.1A>T (p.M1?); homozygous mutation c.599T>G (p.L200R); compound heterozygosity for c.599T>G and c.614G>A (p.R205Q); compound heterozygosity for c.494G>A (p.C165Y) and c.599T>G; heterozygous c.599T>G mutation and no other change in the coding sequence. One proband exhibited no changes. The pathogenic mutation c.599T>G (p.L200R) was in allelic association with the c.484C>G (p.R162G) polymorphism. Nine patients from seven families were of MCD type I including the subtype IA.

CONCLUSION

Four different CHST6 missense mutations, of which p.C165Y is novel, were identified. Allelic association of the c.[484C>G; 599T>G] in six probands out of eight, as well as occurrence of this particular allele in a heterozygous state in one healthy control individual, supports a common founder effect for MCD in the Czech Republic.

Homozygous granular corneal dystrophy type II (Avellino corneal dystrophy): natural history and progression after treatment

PURPOSE

To describe the clinical features of homozygous granular corneal dystrophy type II (GCDII) with age and with several kinds of treatment in 18 homozygous patients in several different conditions.

METHODS

Eighteen homozygous GCDII patients, confirmed with DNA analysis, of 13 families were enrolled. Their clinical features that include age at detection by parents, visual acuity, and disease progression were evaluated. We also studied the recurrence patterns for the 13 patients who underwent phototherapeutic keratectomy, penetrating keratoplasty, lamellar keratoplasty, or deep lamellar keratoplasty.

RESULTS

The age at detection by the parents ranged from 3 to 5 years; visual loss begins in childhood with progression into the 20s. All of the patients who had undergone surgeries acquired better vision immediately after surgery. Corneal deposits reappeared soon after treatments. Recurrences became progressively more rapid and severe with treatments.

CONCLUSIONS

The clinical features of homozygous GCDII are characterized by a severe granular type of corneal dystrophy with an early onset and rapid progression. After surgical treatment, recurrence is rapid and severe.

[Association between macular corneal dystrophy and high myopia in two sisters]

PURPOSE OF THE PAPER: To report a rare association between Groenow type II macular corneal dystrophy and degree myopia, as encountered in two non-twin sisters. We conducted a clinical surveillance of the morbid ophthalmological manifestations presented by two non-twin sisters. These manifestations occurred in an almost identical manner over time. An isolated case of this pathological coexistence would have been dismissed as a morbid coincidence without any particular significance. However, its presence at the only daughters of a family made us look for further reports of such cases in scientific literature, but our search ended without any similar findings. The lack of similar reports of coexistence between macular corneal dystrophy and high degree myopia at members of the same family could indicate the possibility of this being the description of a rare syndrome.

Spontaneous and inheritable R555Q mutation in the TGFBI/BIGH3 gene in two unrelated families exhibiting Bowman's layer corneal dystrophy

PURPOSE

Bowman's layer corneal dystrophies (CDBs) include 2 distinct types: CDB1, or Reis-Bücklers (RBCD), and CDB2, or Thiel-Behnke (TBCD). We studied the genetic basis of 2 cases of apparent spontaneous CDB mutations and attempted to determine if these are sporadic and inheritable mutations.

DESIGN

Retrospective molecular genetic study and case report.

PARTICIPANTS

Twelve patients were recruited from 2 unrelated families for this study, including 2 affected individuals from one family (family A) and 1 affected individual from another (family B).

METHODS

Slit-lamp examination was performed for each patient to determine the disease phenotype. Histological analysis of affected cornea specimens was used for identification of pathogenic corneal opacities in 2 affected patients from family A.

MAIN OUTCOME MEASURES

Genomic DNA was isolated from the blood samples and used for mutation screening of the TGFBI/BIGH3 gene. Sixteen polymorphic DNA markers from 9 different chromosomes were used to establish the maternity and paternity of the 2 probands.

RESULTS

The 2 families were confirmed to be unrelated. The age onset of ocular symptoms was <2 years for all 3 affected patients. Clinical diagnoses of CDB1 (RBCD) and CDB2 (TBCD) were made for probands A and B, respectively. The affected corneas showed epithelial haze with diffuse, irregular, patchy opacities in a honeycomb and geographic pattern. Subepithelial plaques, increased trichome staining of anterior stroma, and irregular Bowman's layer were observed. An R555Q mutation was found in TGFBI/BIGH3 in the 2 probands but not in their parents. The son of proband A was also affected and apparently inherited his disease allele from his father.

CONCLUSION

The R555Q mutation occurred spontaneously and independently in the 2 unrelated CDB families and was confirmed to be transmitted to the next generation in 1 of the 2 families. These findings strongly support the notion that a genetic diagnosis should be determined for CDB and other dystrophies associated with mutations in TGFBI/BIGH3. The discovery of a spontaneous mutation should alert clinicians to be aware of the existence of genetic alterations for their patients without apparent family history of the disease.

Four mutations (three novel, one founder) in TACSTD2 among Iranian GDLD patients

PURPOSE

To perform a mutation screening of TACSTD2 in 13 Iranian Gelatinous Drop-like Corneal Dystrophy (GDLD) pedigrees. To assess genotype-phenotype correlations. To determine intragenic SNP haplotypes associated with the mutations, so as to gain information on their origin.

METHODS

The coding region of TACSTD2 was sequenced in the probands of 13 unrelated Iranian GDLD pedigrees. Variations were assessed in other available affected and unaffected family members and in unrelated normal control subjects by restriction fragment length polymorphism (RFLP). The variations were classified as being associated with disease if they segregated with the disease phenotype in the families, were not observed in 100 control individuals, disrupted protein expression, or affected conserved positions in the coded protein. Three intragenic single-nucleotide polymorphisms (SNPs) were used to define haplotypes associated with putative disease-causing mutations.

RESULTS

The probands were each homozygous for one of four putative disease-causing variations observed in TACSTD2: C66X, F114C, L186P, and E227K. Three of these are novel. E227K was found in 10 of the Iranian patients. There were some phenotypic differences among different patients carrying this mutation-for example, with respect to age at onset. Genotyping of intragenic SNPs identified four haplotypes. C66X, F114C, and L186P were each associated with a haplotype common among control chromosomes, whereas all E227K alleles were associated with a haplotype not found among the control chromosomes.

CONCLUSIONS

Although mutations in TACSTD2 among Iranian patients with GDLD were heterogeneous, E227K was found to be a common mutation. It is suggested that E227K may be a founder mutation in this population. Based on positions of known mutations in TACSTD2, significance of the thyroglobulin domain of the TACSTD2 protein in the pathogenesis of GDLD is suggested.

TGFBI (BIGH3) gene mutations in Hungary--report of the novel F547S mutation associated with polymorphic corneal amyloidosis

PURPOSE

To identify mutations in the Transforming Growth Factor Beta Induced (TGFBI) gene in Hungarian patients with corneal dystrophy and to characterize histological features of their corneal buttons excised during penetrating keratoplasty.

METHODS

Exons of TGFBI were sequenced in 38 members of 15 unrelated families with corneal dystrophy and exon 12 was also sequenced in 100 healthy controls from the same population. Immunohistological analysis of available corneal buttons excised during penetrating keratoplasty was also performed.

RESULTS

Molecular genetic analysis revealed a heterozygous R124C mutation in 18 patients with lattice type I dystrophy. A R555W heterozygous mutation was detected in five patients with granular Groenouw type I corneal dystrophy and a R555Q heterozygous mutation was found in four patients clinically diagnosed with Reis-Bücklers (one patient) and Thiel-Behnke (three patients) dystrophy. Three patients with "atypical granular" dystrophy later diagnosed as Avellino dystrophy were heterozygous for the R124H mutation. A novel heterozygous mutation (T1640C) causing a F547S amino acid exchange was detected in a patient with polymorphic corneal amyloidosis. Immunohistochemistry showed the presence of BIGH3 protein deposits in all examined corneal buttons. Electron microscopy confirmed the presence of amyloid fibrils in the case of the novel mutation.

CONCLUSIONS

Our results indicate that molecular genetic analysis is required to confirm the diagnosis of corneal dystrophies. We report the first cases of Avellino dystrophy from Central-Eastern Europe. We conclude that the novel F547S mutation causes polymorphic corneal amyloidosis since no other mutations were detected in the TGFBI gene of this patient and the novel mutation could not be found in healthy controls.

Autosomal recessive CHED associated with novel compound heterozygous mutations in SLC4A11

PURPOSE

To determine the genetic basis of autosomal recessive congenital hereditary endothelial dystrophy (CHED2) in an American patient of Chinese ancestry.

METHODS

Slit-lamp examination of the proband and his parents, as well as histopathologic examination of excised corneal specimens from the proband, were performed to confirm the diagnosis of autosomal recessive CHED. DNA was collected from the proband and his parents, and all 19 exons of the SLC4A11 gene were amplified and screened.

RESULTS

The proband showed diffuse bilateral corneal edema, which was not present in either of his parents. After the performance of bilateral penetrating keratoplasties, histopathologic examination of the excised corneal specimens showed marked corneal stromal edema and an absence of corneal endothelial cells. Screening of SLC4A11 showed 2 heterozygous mutations: c.743G>A (Ser232Asn) and c.1033A>T (Arg329X). The proband's mother was found to be heterozygous for the Ser232Asn missense mutation, and his father was heterozygous for the Arg329X nonsense mutation. No other coding region sequence variants were identified in the proband or his parents, and neither of the identified mutations was identified in 100 control individuals.

CONCLUSIONS

CHED2 is associated with mutations in SLC4A11, a member of the SLC4 family of base transporters. Although the majority of affected individuals reported to date have shown homozygous mutations, associated with consanguinity in the Burmese, Indian, and Pakistani populations, we report 2 novel, independently sorting SLC4A11 mutations in an affected individual of Chinese ancestry.

Is the lattice dystrophy of the cornea due to developmental anomalies of neural crest cells during embryogenesis (neurocristopathies)?

With the present paper authors try to give an embryological approach in understanding etiopathogenesis of lattice corneal dystrophy (LCD). The case of a 41-years-old man affected by isolated LCD has been examined at the Ophtalmologic Clinic of the University of Catania, Italy. Sore cornea has been excised during cornea transplantation, and it has been examined by transmission electron microscopy (TEM). Results confirm classic submicroscopic findings described in literature. However these findings offer possibility to consider an embryological interpretation of LCD pathogenesis. Our findings with those of literature put forward hypothesis of a hereditary etiopathogenetical role exerted by keratocytes, direct derivatives of neural crest cells during embryogenesis, probably via an abnormal gene expression in producing proteinaceous precursor of amyloid substance (APP). LCD could be considered a neurocristopathy.

[Analysis of mutation in KRT12 gene in a Chinese family with Meesmann's corneal dystrophy]

OBJECTIVE

To investigate the mutation of KRT12 gene in a large Chinese family with Meesmann's corneal dystrophy by molecular genetic study and linkage analysis.

METHODS

Mode of inheritance was determined in a family with Meesmann's corneal dystrophy provided by Xingtai Eye Hospital. The blood samples were obtained from members of this family, including both affected and unaffected members. The genome-DNA was extracted from the samples. Linkage analysis was conducted in the selected markers (D17S800, D17S930, D12S390, D12S96) in the locus around KRT12 and KRT3 genes. The exons of linked genes were sequenced directly. All of the members in this family were examined with slit lamp biomicroscope and photographed. Blood samples were collected from 100 normal subjects and analyzed as the controls.

RESULTS

The mode of inheritance of corneal dystrophy in this family was identified as autosomal dominant inheritance. The clinical diagnosis was Meesmann's corneal dystrophy. Linkage analysis revealed a lod score of 2.41 with theta = 0.00 at markers D17S800 and D17S930. Linkage was revealed between corneal dystrophy and KRT12 gene. Sequences of KRT12 gene in affected members showed the mutant in exon 1, T419A and L132H. All affected members in this family were heterozygotes of this mutation. No mutation of this type was identified in all unaffected member of this family and in the 100 normal controls.

CONCLUSION

Mutation of KRT12 gene in exon 1, T419A and L132H is the molecular genetic change leading to the occurrence of Meesmann's corneal dystrophy in this Chinese family.

Deep Anterior Lamellar Keratoplasty in Korean Patients With Avellino Dystrophy

PURPOSE

To evaluate the surgical outcome of deep anterior lamellar keratoplasty (DALK) in Korean patients with Avellino dystrophy.

METHODS

A retrospective study was performed in 4 eyes (4 patients) with recurrent Avellino dystrophy after phototherapeutic keratectomy (PTK). Genetic study was performed on 2 patients to confirm the diagnosis. Partial-thickness donor cornea (devoid of endothelium and Descemet membrane) was transplanted onto a recipient bed after deep lamellar dissection and removal of recipient stroma. Visual acuity, refractive error, keratometry values, topographic astigmatism, and complications were evaluated after a follow-up period of at least 14 months.

RESULTS

The mean age of the patients was 52.5 +/- 3.32 years, and the mean follow-up period was 17.5 +/- 3.11 months. Visual acuity was improved to > or = 20/25 in all cases. Postoperative topographic astigmatism ranged from 1.2 to 4.9 D. In 1 case, double anterior chamber developed after the operation, which resolved after gas injection into the anterior chamber. During the follow-up period, there were no signs of graft rejection, and all grafts were transparent except one, in which small opacity recurred in the peripheral corneal stroma 13 months postoperatively.

CONCLUSIONS

DALK is considered a good primary surgical option in patients with recurrent Avellino dystrophy after PTK.

Identification of mutations in UBIAD1 following exclusion of coding mutations in the chromosome 1p36 locus for Schnyder crystalline corneal dystrophy

PURPOSE

To identify the genetic basis of Schnyder crystalline corneal dystrophy (SCCD) through screening positional candidate genes and UBIAD1, in which mutations have been associated with SCCD, in affected families.

METHODS

The coding region of each of the 16 positional candidate genes for which mutation screening has not been previously reported was screened with polymerase chain reaction (PCR) amplification and automated sequencing in four affected individuals from two families with SCCD. In addition, the coding region of UBIAD1, located just outside of the originally described SCCD candidate interval on chromosome 1p36, was directly sequenced in affected and unaffected individuals from three families with SCCD.

RESULTS

Eighteen novel and 15 previously reported sequence variants were identified in 10 of the 16 positional candidate genes. Only two of the sequence variants segregated with the affected phenotype in either of the families screened. Both were novel single nucleotide polymorphisms (SNPs) predicted to result in synonymous amino acid substitutions in different predicted genes. However, one of these SNPs was also identified in control individuals, and the other SNP was not predicted to alter splicing. Screening of UBIAD1 revealed a different missense mutation in each of the three unrelated probands that was screened: p.Asn102Ser, p.Arg119Gly, and p.Leu121Val. Screening of the affected and unaffected relatives of the probands in whom the p.Asn102Ser and p.Leu121Val mutations were identified demonstrated that each mutation segregated with the affected phenotype. None of the three missense mutations was identified in 110 control individuals.

CONCLUSIONS

No presumed pathogenic coding region mutations were identified in the genes mapped to the candidate region for SCCD. However, missense mutations in UBIAD1, located just outside of the originally described SCCD fine mapped region, were identified in each of the three families with SCCD, confirming that mutations in UBIAD1 are associated with SCCD.

The TGFBI A546D mutation causes an atypical type of lattice corneal dystrophy

PURPOSE

To report the clinical, molecular, and histopathological features of a distinct transforming growth factor-beta-induced (TGFBI) gene-linked amyloidotic corneal dystrophy exhibiting an unusual lattice pattern.

METHODS

A complete ophthalmologic examination was performed in 10 individuals of a Mexican family in which autosomal dominant transmission of the disease was observed. DNA was obtained from peripheral blood leukocytes of each participating subject. Genetic analyses included TGFBI polymerase chain reaction (PCR) amplification and automated nucleotidic sequencing of exons 4, 11, 12, 13, and 14 from genomic DNA. Histological analysis of corneal tissue from an affected individual who underwent a penetrating keratoplasty was also performed.

RESULTS

The corneal phenotype in this pedigree was characterized by multiple bilateral round opacities in the central part of the cornea combined with a conspicuous central and peripheral lattice pattern. TGFBI analysis revealed a heterozygous point mutation at exon 12 (1637 C>A) in all affected individuals, predicting an A546D missense change.

CONCLUSIONS

The lattice phenotype resulting from the TGFBI A546D mutation in this family is distinct from that observed in a previously described pedigree carrying the A546D mutation and exhibiting a phenotype designated "polymorphic corneal amyloidosis". We propose this particular disorder to be classified as an atypical type of lattice stromal corneal dystrophy.

An unusual presentation of macular corneal dystrophy associated with uniparental isodisomy and a novel Leu173Pro mutation

PURPOSE

To report an unusual phenotype of macular corneal dystrophy (MCDC1) associated with a novel CHST6 mutation transmitted via maternal isodisomy.

METHODS

Slit lamp examination of the patient and his parents was performed. DNA was collected from each individual for amplification and sequencing of the CHST6 coding region, as well as exons 4 and 12 of TGFBI. Serum antigenic keratan sulfate (AgKS) levels were measured for confirmation of the diagnosis and subtyping of MCDC1. Quantitative real-time PCR (qPCR) was performed to differentiate between homozygous and hemizygous sequence variants. Genotyping at 12 single nucleotide polymorphisms (SNPs) within and surrounding CHST6 was performed to determine the pattern of inheritance of mutations identified in CHST6.

RESULTS

Examination of the proband revealed bilateral, discrete, axially distributed, gray-white deposits at the level of Bowman's layer, with diffuse fine corneal stromal haze. Screening of TGFBI exons 4 and 12 in the proband did not reveal any allelic variants. However, screening of CHST6 in the proband demonstrated a novel homozygous missense mutation involving a highly conserved amino acid (c.518T > C; Leu173Pro) and undetectable serum AgKS levels in the proband confirmed the diagnosis of type I MCDC1. Quantitative PCR confirmed that both copies of CHST6 were present in the patient, excluding the possibility that the mutation was present in the hemizygous state. The results of genotyping were consistent with maternal isodisomy, as the patient was homozygous for an allele possessed by his mother at each SNP, two of which were informative and demonstrated nonpaternal inheritance.

CONCLUSION

A phenotypically unusual variant of MCDC1 was found to be associated with the novel Leu173Pro mutation in CHST6, transmitted via uniparental isodisomy, a previously unreported pattern of inheritance in the corneal dystrophies.

In vivo laser confocal microscopic findings of corneal stromal dystrophies

OBJECTIVE

To investigate in vivo laser confocal microscopic findings of genetically mapped corneal stromal dystrophies and their relationship to histopathologic findings.

METHODS

Seven patients with Avellino corneal dystrophy, 2 patients with lattice corneal dystrophy, and 2 patients with macular corneal dystrophy were examined genetically and using slitlamp biomicroscopy and in vivo laser confocal microscopy. Corneal specimens obtained after surgery in selected patients were histopathologically studied.

RESULTS

In Avellino corneal dystrophy (Arg124His mutation of human transforming growth factor beta-induced gene [TGFBI]), highly reflective granular materials with irregular edges were observed in the superficial stroma. In lattice corneal dystrophy (Arg124Cys and Leu527Arg mutations of TGFBI), highly reflective branching filaments of variable width were observed in the stroma. In macular corneal dystrophy (Ala217Thr mutation of the carbohydrate sulfotransferase gene [CHST6]), homogeneous reflective materials with dark striaelike images were observed throughout the stroma. All confocal findings correlated well with histopathologic findings.

CONCLUSIONS

In vivo laser confocal microscopy is capable of high-resolution visualization of characteristic corneal microstructural changes related to 3 types of genetically mapped corneal stromal dystrophies. The use of laser confocal microscopy may be valuable in the differential diagnosis of corneal stromal dystrophies, especially when diagnosis is otherwise uncertain.

A novel variant lattice corneal dystrophy caused by association of mutation (V625D) in TGFBI gene

PURPOSE

To characterize the molecular defect in the TGFBI gene in a Chinese family affected with an atypical lattice corneal dystrophy.

DESIGN

Case report and experimental study.

METHODS

Molecular genetic analysis was performed on the DNA extracted from peripheral leucocytes from a Chinese family with atypical lattice corneal dystrophy. Fifty normal unrelated subjects of Chinese origin were used as controls. All exons of the TGFBI gene were amplified by polymerase chain reaction and directly sequenced.

RESULTS

Bilateral, symmetrical, ridgy round pattern of opacities with uneven surfaces and thin lattice lines were noted in the proband. Analysis of exon 14 revealed a heterozygous T to A transition on codon 625. The mutation was not detected in the unaffected family member and 50 unaffected individuals.

CONCLUSIONS

The novel TGFBI gene mutation (V625D) is associated with an early-onset variant of lattice corneal dystrophy. This case highlights the utility of molecular genetic analysis in differentiating corneal dystrophies associated with an atypical phenotype from nondystrophic conditions.

A missense mutation in the M1S1 gene found in a turkish patient with gelatinous droplike corneal dystrophy

PURPOSE

To report a missense mutation in the M1S1 gene found in a Turkish patient with gelatinous droplike corneal dystrophy (GDLD).

METHODS

A Turkish patient with GDLD was examined. Keratoplasty was performed and a diagnosis of GDLD was made by histopathologic and electron microscopic studies. Genomic DNA was extracted from peripheral blood and the paraffin-embedded tissue of the corneal button. A 248-bp DNA fragment of the M1S1 gene was amplified, and sequencing reactions were analyzed. The results were compared with those of 30 healthy, nonrelated individuals.

RESULTS

On light microscopic examination, sheets of amorphous amyloid deposits were observed in subepithelial regions and in the anterior and midcorneal stroma. Electron microscopy revealed dense collagen fibrils and entrapped filamentous amyloid fibrils in the corneal stroma. A substitution of T-->C at nucleotide 557 was found in the peripheral blood DNA sequence analysis, which resulted in an amino acid substitution of L-->P (L186P). Results were confirmed by direct DNA sequencing analysis of the paraffin-embedded corneal button. The patient with GDLD was homozygous for the mutation, resulting in amino acid substitution L186P.

CONCLUSIONS

This is the first report, to our knowledge, of a homozygous mutation (L186P) in the M1S1 gene found in a Turkish patient. The clinical examination may be insufficient in sporadic cases, and histopathologic examination and molecular genetic analysis can accelerate and improve the accuracy of diagnosis in patients with GDLD.

Exclusion of TACSTD2 in an Iranian GDLD pedigree

PURPOSE

To perform a mutation screen of TACSTD2 in an Iranian Gelatinous Drop-like Corneal Dystrophy (GDLD) pedigree.

METHODS

In addition to the coding region of TACSTD2, for the first time the promoter, the entire 5'-noncoding region, and the entire 3'-untranslated region of the gene were sequenced from an affected member of the pedigree. Phenotypic features of affected individuals were assessed.

RESULTS

The proband carried six sequence variations in TACSTD2. One of the variations was homozygous and caused a synonymous codon change. The remaining five were heterozygous variations in the 3'-untranslated region. None of the variations were assessed to be associated with GDLD. Fibroblastic scars were evident in in corneal histology sections of two affected members of the pedigree.

CONCLUSIONS

It is concluded that GDLD in the pedigree is probably not caused by mutations in TACSTD2, supporting evidence for the existence of at least one other locus for GDLD. Phenotypic features of the Iranian patients, including the existence of fibroblastic scars in the corneas, were similar to those of a previously reported GDLD patient without TACSTD2 mutations. This suggests the disease in these individuals may be due to mutations in the same gene.

R124C and R555W TGFBI mutations in Spanish families with autosomal-dominant corneal dystrophies

PURPOSE

Mutations in the transforming growth factor beta I (TGFBI) gene cause several types of autosomal-dominant corneal dystrophies. We investigated the role of this gene in two Spanish families affected by lattice type I or granular type I corneal dystrophies.

METHODS

We recruited 13 subjects from two unrelated families diagnosed with autosomal dominant lattice type I or granular type I corneal dystrophies. Corneal phenotypes were assessed by slit lamp examination. Genomic DNA was obtained from blood samples, and exons 4, 11, 12, and 14, which contained mutation hot spots of the TGFBI gene, were screened for mutations by PCR DNA sequencing.

RESULTS

We identified two TGFBI mutations: R124C (exon 4), which segregated with lattice type I corneal dystrophy, and R555W (exon 12), which segregated granular type I corneal dystrophy. Two single-nucleotide polymorphisms were also found, of which H428H was novel and F540F was previously reported.

CONCLUSIONS

This is the first report of mutations in the TGFBI gene in Spanish families affected by corneal dystrophy. R124C and R555W TGFBI mutations cause lattice and granular type I corneal dystrophies in the studied families. Our results indicate that the genetic defects underlying corneal dystrophies in Spanish patients are similar to those found in other populations.

Mutations in the UBIAD1 gene, encoding a potential prenyltransferase, are causal for Schnyder crystalline corneal dystrophy

Schnyder crystalline corneal dystrophy (SCCD, MIM 121800) is a rare autosomal dominant disease characterized by progressive opacification of the cornea resulting from the local accumulation of lipids, and associated in some cases with systemic dyslipidemia. Although previous studies of the genetics of SCCD have localized the defective gene to a 1.58 Mbp interval on chromosome 1p, exhaustive sequencing of positional candidate genes has thus far failed to reveal causal mutations. We have ascertained a large multigenerational family in Nova Scotia affected with SCCD in which we have confirmed linkage to the same general area of chromosome 1. Intensive fine mapping in our family revealed a 1.3 Mbp candidate interval overlapping that previously reported. Sequencing of genes in our interval led to the identification of five putative causal mutations in gene UBIAD1, in our family as well as in four other small families of various geographic origins. UBIAD1 encodes a potential prenyltransferase, and is reported to interact physically with apolipoprotein E. UBIAD1 may play a direct role in intracellular cholesterol biochemistry, or may prenylate other proteins regulating cholesterol transport and storage.

[TGFBI gene mutation analysis in a Chinese family with Thiel-Behnke corneal dystrophy]

OBJECTIVE

To identify the gene mutation in autosomal dominant Thiel-Behnke corneal dystrophy affecting a five-generation Chinese family. To study the TGFBI gene mutation in Chinese patients with Thiel-Behnke corneal dystrophy by molecular genetic analysis.

METHODS

Ophthalmologic examinations were performed in 10 patients and two normal family members in an autosomal dominant Thiel-Behnke corneal dystrophy family. Five ml peripheral blood was collected and Genomic DNA was extracted using salt fractionation. The exons 4, 7, 8, 11 and 12 of the TGFBI gene were amplified by PCR and mutation analysis was performed by direct sequencing.

RESULTS

Mutation analysis of the exons 4, 7, 8, 11 and 12 of the TGFBI gene identified a G-->A missense mutation in the exon 12 by bidirectional sequencing. This mutation resulted in a substitution of glutamine for arginine at amino acid 555 (R555Q) of the protein. This mutation existed in all of the patients, but not in unaffected individuals.

CONCLUSION

Thiel-Behnke corneal dystrophy in this family is caused by R555Q mutation of the TGFBI gene, the phenotypes of this corneal dystrophy are closely correlated with TGFBI mutation.

Novel CDH3 mutations in hypotrichosis with juvenile macular dystrophy

BACKGROUND

Hypotrichosis with juvenile macular dystrophy (HJMD) is a rare autosomal recessive disorder characterized by sparse and short hair, heralding progressive degeneration of the retinal pigment epithelium, which leads to blindness by the second decade of life. The disorder is caused by mutations in CDH3, a gene encoding P-cadherin, a major component of adherens junctions. Most HJMD cases reported to date have been shown to be caused by homozygous CDH3 mutations segregating in consanguineous families.

AIM AND METHODS

To elucidate the genetic basis of HJMD in two nonconsanguineous families, we established the coding sequence of CDH3 in four patients and their healthy siblings.

RESULTS

The four patients demonstrated markedly variable degrees of visual acuity impairment. Novel biallelic recessive mutations were identified in all affected individuals. One patient in the first family was found to carry two heterozygous mutations, IVS2 + 1G-->A and p.E504K; the other three patients in the second family were compound heterozygous for a missense mutation, p.H575R, and a nonsense mutation, p.R221X.

CONCLUSION

This paper expands the spectrum of known mutations in CDH3 and points to the existence of clinical heterogeneity in this syndrome.

Mutational spectrum of the SLC4A11 gene in autosomal recessive congenital hereditary endothelial dystrophy

PURPOSE

Autosomal recessive congenital hereditary endothelial dystrophy (AR-CHED or CHED2) is a bilateral corneal disorder manifesting at birth or in early childhood. CHED2 is caused by mutations in the sodium bicarbonate transporter-like solute carrier family 4 member 11 (SLC4A11) gene on chromosome 20p13. We screened 42 unrelated families with CHED2 in order to establish the spectrum of mutations in SLC4A11 and to look for genotype-phenotype correlations.

METHODS

Forty-two families (49 affected and 73 unaffected members) with recessive CHED were recruited according to predefined diagnostic criteria. Clinical data including age at onset and presentation, pre- and post-operative visual acuities, and presence of nystagmus were taken from patient records. Histopathologic parameters such as corneal thickness, Descemet membrane thickness, and endothelial cell counts were assessed on corneal sections. DNA from patients was screened for sequence changes by polymerase chain reaction (PCR)-amplification of coding regions of SLC4A11 and single strand conformation polymorphism analysis followed by sequencing. Sequence changes found were tested in 50 unrelated normal controls.

RESULTS

Twenty-seven different mutations were identified in 35 unrelated families, 19 of which were not previously reported. The mutations identified consisted of 13 missense, 5 nonsense, 7 deletions, 1 complex (deletion plus insertion) mutation, and 1 splice site mutation. Both mutant alleles were identified in 33 families and only one mutant allele in two families. No correlations were evident between clinical or histopathologic parameters and SLC4A11 mutations.

CONCLUSIONS

These data add to the mutational repertoire of SLC4A11 and establish the high degree of mutational heterogeneity in autosomal recessive CHED.

Replication and refinement of linkage of posterior polymorphous corneal dystrophy to the posterior polymorphous corneal dystrophy 1 locus on chromosome 20

PURPOSE

The study purpose was to identify the genetic basis of posterior polymorphous corneal dystrophy, an autosomal dominant disorder of the corneal endothelium that is associated with the development of corneal edema, necessitating corneal transplantation for visual rehabilitation. Glaucoma also develops in up to 40% of patients with posterior polymorphous corneal dystrophy.

METHODS

Linkage analysis, using microsatellite markers previously used to demonstrate linkage of posterior polymorphous corneal dystrophy to the chromosome 20 candidate region known as posterior polymorphous corneal dystrophy 1, was performed in 29 members of a family with posterior polymorphous corneal dystrophy. Thirty-four microsatellite markers were used to refine the posterior polymorphous corneal dystrophy 1 interval. TCF8, located on chromosome 10, was screened in an affected family member to exclude posterior polymorphous corneal dystrophy 3.

RESULTS

Significant evidence of linkage to the posterior polymorphous corneal dystrophy 1 interval was obtained with both single-point and multipoint analyses. The largest single-point log odds ratio score obtained was 4.38 (theta=0) at marker D20S471; within 4.7 Mbp (7.2 cM) of D20S471 eight markers provided single-point log odds ratio scores of greater than 3.00 and three markers provided single-point log odds ratio scores greater than 4.00. The largest multipoint log odds ratio score obtained was 4.83, found across the adjacent markers D20S844, D20S191, D20S484, and D20S111. The support interval for posterior polymorphous corneal dystrophy 1 in the family we report is approximately 13.5 Mbp (10 cM) long and lies between the markers D20S182 and D20S195. Eleven markers have multipoint log odds ratio scores greater than 4.0 within this region. No coding region mutations were identified in TCF8 in an affected member of the family, effectively excluding posterior polymorphous corneal dystrophy 3.

CONCLUSIONS

The originally described 19.8 cM posterior polymorphous corneal dystrophy 1 candidate disease interval has been refined to a 10 cM interval between markers D20S182 and D20S195. A portion of this refined interval overlaps a more recently reported posterior polymorphous corneal dystrophy 1 interval, with only 20 known and predicted genes mapped to the 2.4 cM common interval.

A new mutation in TP63 is associated with age-related pathology

Increases in the number of allelic malformation syndromes have led to their classification according to their pathogenesis rather than their clinical specific phenotype. TP63 (also known as TP73L) mutations have been identified in several such syndromes characterized by autosomal dominant transmission and various combinations of ectodermal dysplasia, limb malformations and orofacial clefting. TP63 has not yet been implicated in early aging phenotype in humans, even though p63 activates a program of cellular senescence and p63-compromised mice display features of accelerated aging. We report on a family with four affected adult females presenting with Rapp-Hodgkin syndrome (RHS), an autosomal dominant clinical entity that associates anhidrotic ectodermal dysplasia with cleft lip and palate. Features between RHS and EEC syndrome (ectrodactyly, ectodermal dysplasia and cleft lip/palate) have led to the recent identification of mutations in the TP63 gene, located on 3q27, in this condition. Our patients present typical clinical features of RHS, but also ophthalmic anomalies such as corneal dystrophy and premature menopause (around 30 years). The latter findings have never been reported in this condition, and could be secondary to a new TP63 deletion that has been identified in this family.

TGFBIp/betaig-h3 protein: a versatile matrix molecule induced by TGF-beta

TGFBIp/betaig-h3 protein is an extracellular matrix molecule initially cloned from human adenocarcinoma cells treated with TGF-beta. Its precise function remains obscure but a number of studies have demonstrated it to be an intriguingly versatile molecule role in a wide range of physiological and pathological conditions. To date, the most extensively studied and reported action of TGFBIp/betaig-h3 protein is in corneal dystrophy and several excellent reviews are available on this. Work from various laboratories on this molecule has compiled a tremendous amount of information over the past decade and a half. Here we review the current understanding on TGFBIp/betaig-h3 protein and its functions in morphogenesis, extracellular matrix interactions, adhesion/migration, corneal dystrophy, tumorigenesis, angiogenesis, nephropathies, osteogenesis, wound healing and inflammation.

Two novel mutations identified in two Chinese gelatinous drop-like corneal dystrophy families

PURPOSE

To identify the genetic defect in the TACSTD2 gene that causes gelatinous drop-like corneal dystrophy (GDLD) in two unrelated consanguineous Chinese families.

METHODS

Genomic DNA was prepared from leukocytes of peripheral venous blood. The coding region of the TACSTD2 gene was evaluated by means of polymerase chain reaction and direct sequencing.

RESULTS

Sequencing of the TACSTD2 gene of the two probands revealed two novel homozygous frameshift mutations: c.84insG and c.480delC. The identified molecular defect cosegregates with the disease among affected members of the families and is not found in 50 unaffected controls.

CONCLUSIONS

This study reports two novel mutations in two GDLD families and expands the spectrum of mutations in TACSTD2 gene that may cause pathological corneal amyloidosis.

Novel mutations in the ZEB1 gene identified in Czech and British patients with posterior polymorphous corneal dystrophy

We describe the search for mutations in six unrelated Czech and four unrelated British families with posterior polymorphous corneal dystrophy (PPCD); a relatively rare eye disorder. Coding exons and intron/exon boundaries of all three genes (VSX1, COL8A2, and ZEB1/TCF8) previously reported to be implicated in the pathogenesis of this disorder were screened by DNA sequencing. Four novel pathogenic mutations were identified in four families; two deletions, one nonsense, and one duplication within exon 7 in the ZEB1 gene located at 10p11.2. We also genotyped the Czech patients to test for a founder haplotype and lack of disease segregation with the 20p11.2 locus we previously described. Although a systematic clinical examination was not performed, our investigation does not support an association between ZEB1 changes and self reported non-ocular anomalies. In the remaining six families no disease causing mutations were identified thereby indicating that as yet unidentified gene(s) are likely to be responsible for PPCD.