Recessive Congenital Hereditary Endothelial Dystrophy Research Articles

Exome Sequencing Reveals SLC4A11 Variant Underlying Congenital Hereditary Endothelial Dystrophy (CHED2) Misdiagnosed as Congenital Glaucoma.

Autosomal recessive congenital hereditary endothelial dystrophy (CHED2) may be misdiagnosed as primary congenital glaucoma (PCG) due to similar clinical phenotypes during early infancy. In this study, we identified a family with CHED2, which was previously misdiagnosed as having PCG, and followed up for 9 years. Linkage analysis was first completed in eight PCG-affected families, followed by whole-exome sequencing (WES) in family PKGM3. The following in silico tools were used to predict the pathogenic effects of identified variants: I-Mutant 2.0, SIFT, Polyphen-2, PROVEAN, mutation taster and PhD-SNP. After detecting an SLC4A11 variant in one family, detailed ophthalmic examinations were performed again to confirm the diagnosis. Six out of eight families had CYP1B1 gene variants responsible for PCG. However, in family PKGM3, no variants in the known PCG genes were identified. WES identified a homozygous missense variant c.2024A>C, p.(Glu675Ala) in SLC4A11. Based on the WES findings, the affected individuals underwent detailed ophthalmic examinations and were re-diagnosed with CHED2 leading to secondary glaucoma. Our results expand the genetic spectrum of CHED2. This is the first report from Pakistan of a Glu675Ala variant with CHED2 leading to secondary glaucoma. The p.Glu675Ala variant is likely a founder mutation in the Pakistani population. Our findings suggest that genome-wide neonatal screening is worthwhile to avoid the misdiagnosis of phenotypically similar diseases such as CHED2 and PCG.

Molecular Mechanisms of Fuchs and Congenital Hereditary Endothelial Corneal Dystrophies.

The cornea, the eye's outermost layer, protects the eye from the environment. The cornea's innermost layer is an endothelium separating the stromal layer from the aqueous humor. A central role of the endothelium is to maintain stromal hydration state. Defects in maintaining this hydration can impair corneal clarity and thus visual acuity. Two endothelial corneal dystrophies, Fuchs Endothelial Corneal Dystrophy (FECD) and Congenital Hereditary Endothelial Dystrophy (CHED), are blinding corneal diseases with varied clinical presentation in patients across different age demographics. Recessive CHED with an early onset (typically age: 0-3years) and dominantly inherited FECD with a late onset (age: 40-50years) have similar phenotypes, although caused by defects in several different genes. A range of molecular mechanisms have been proposed to explain FECD and CHED pathology given the involvement of multiple causative genes. This critical review provides insight into the proposed molecular mechanisms underlying FECD and CHED pathology along with common pathways that may explain the link between the defective gene products and provide a new perspective to view these genetic blinding diseases.

Coexistence of Congenital Hereditary Endothelial Dystrophy and Fuchs Endothelial Corneal Dystrophy Associated With SLC4A11 Mutations in Affected Families.

To evaluate parents of probands affected with autosomal recessive congenital hereditary endothelial dystrophy (CHED) for clinical signs of Fuchs endothelial corneal dystrophy (FECD) and to determine the genotypes of the SLC4A11 gene in the probands and their parents. This study involved 9 patients affected with CHED from 8 families. The parents of such probands were examined to investigate for possible signs of FECD although they did not present with any visual complaints. Blood samples were collected after obtaining consent, from all 9 cases and the parents of each proband, for genetic analysis. Genomic DNA isolated from blood leukocytes was used for genetic analysis. Screening of the coding regions of the SLC4A11 gene for mutations was carried out by standard procedures using polymerase chain reaction (PCR) amplification and sequencing. Sequences were checked against the human SLC4A11 reference sequence to detect alterations and in normal control samples available in the laboratory. The probands had characteristic signs of CHED, whereas one of the parents of each of the probands showed early signs of FECD, characterized by the presence of guttae in the central cornea corroborative with the diagnosis of FECD, and were otherwise asymptomatic at that time. The CHED-affected probands were homozygous for various SLC4A11 mutations, and their parents were heterozygous for the same. The mutations included missense mutations in 6 probands and nonsense mutations in 2 cases. Heterozygosity for SLC4A11 mutations in the parents of children with autosomal recessive CHED appears to be a risk factor for the development of FECD in these cases.

Missense mutation in SLC4A11 in two Pakistani families affected with congenital hereditary endothelial dystrophy (CHED2)

BackgroundAutosomal recessive congenital hereditary endothelial dystrophy (CHED2) is a recessively inherited eye disorder that is more common in consanguineous populations.MethodsTwo families affected with CHED2 were recruited from the Punjab province of Pakistan to identify the underlying genetic defect. Blood samples from both the families, designated as CH01 and CH02, were collected. Genomic DNA was isolated. Initially, linkage analysis using microsatellite markers was carried out to confirm the linkage to the SLC4A11 gene, previously reported to be implicated in the pathology of the disease. Later on, sequencing was carried out to find the pathogenic mutation in the enrolled families. Identified variation was further confirmed by typing 50 ethnically matched normal control samples.ResultsThe results of linkage analysis indicated the putative linkage to SLAC4A11 gene, located at the CHED2 locus on chromosome 20p13‐p12 in both families. Mutational analysis revealed an unidentified homozygous mutation c.2024A>C (p.E675A) in the affected members of both the families. Haplotype analysis of both the families showed that the affected members carry the same haplotype, thereby indicating a possibility of a common ancestral mutation. Use of bioinformatic tools including PolyPhen and SIFT suggested that a single amino acid change of E to A at position 675 affected the function of the protein.ConclusionThis study reports a newly identified mutation (c.2024A>C) in the SLC4A11 gene segregating with the diseased haplotype in two consanguineous Pakistani families.

Posterior corneal dystrophies

AbstractPosterior corneal dystrophies represent a clinically and genetically heterogeneous group of disorders. The International Committee for Classification of Corneal Dystrophies (IC3D) lists autosomal dominant congenital hereditary endothelial dystrophy (CHED1), autosomal recessive congenital hereditary endothelial dystrophy (CHED2), posterior polymorphous corneal dystrophy (PPCD) and Fuchs endothelial corneal dystrophy (FECD) as separate clinical entities​. The course will provide an overview of posterior corneal dystrophies with a focus on recent clinical and genetic findings and their possible implications for future classification.

A Novel Nonsense Mutation of the SLC4A11 Gene in a Korean Patient With Autosomal Recessive Congenital Hereditary Endothelial Dystrophy

A Novel Nonsense Mutation of the SLC4A11 Gene in a Korean Patient With Autosomal Recessive Congenital Hereditary Endothelial Dystrophy

Oligomerization of SLC4A11 protein and the severity of FECD and CHED2 corneal dystrophies caused bySLC4A11mutations

Mutations in the SLC4A11 gene, which encodes a plasma membrane borate transporter, cause recessive congenital hereditary endothelial corneal dystrophy type 2 (CHED2), corneal dystrophy and perceptive deafness (Harboyan syndrome), and dominant late-onset Fuchs endothelial corneal dystrophy (FECD). We analyzed missense SLC4A11 mutations identified in FECD and CHED2 patients and expressed in transfected HEK 293 cells. Chemical cross-linking and migration in nondenaturing gels showed that SLC4A11 exists as a dimer. Furthermore, co-immunoprecipitation of epitope-tagged proteins revealed heteromeric interactions between wild-type (WT) and mutant SLC4A11 proteins. When expressed alone, FECD- and CHED2-causing mutant SLC4A11 proteins are primarily retained intracellularly. Co-expression with WT SLC4A11 partially rescued the cell surface trafficking of CHED2 mutants, but not FECD mutants. CHED2 alleles of SLC4A11 did not affect cell surface processing of WT SLC4A11. In contrast, FECD mutants reduced WT cell surface processing efficiency, consistent with dominant inheritance of FECD. The reduction in movement of WT protein to the cell surface caused by FECD SLC4A11 helps to explain the dominant inheritance of this disorder. Similarly, the failure of CHED2 mutant SLC4A11 to affect the processing of WT protein, explains the lack of symptoms found in CHED2 carriers and the recessive inheritance of the disorder.

Amyloid corneal deposition in corneal buttons of congenital hereditary endothelial dystrophy (CHED) – A clinical and histopathological case series

Purpose To determine the frequency, pathology and clinical relevance of amyloid deposited in corneas of CHED. Methods Clinical and histopathological case series. Results Amyloid subepithelial deposition was found in 5 (6.6%) corneal buttons of 75 patients with histopathologically confirmed CHED diagnosis. Clinical findings included history of parental consanguinity, poor vision (ranging from counting fingers from one foot to 3/200), corneal edema, and central whitish subepithelial corneal nodules in all the five cases and positive family history in 4 of 5 cases. The patients underwent PKP at a mean age of 15 years (range 3–22 years). Histological findings included attenuated endothelium (6/6) thickened Descemet’s membrane (6/6), stromal edema (2/6), and subepithelial amyloid deposits (6/6). All patients improved from vision point of view. To date, no recurrence of the amyloid has been seen in the grafts. Conclusion Considering the consanguinity, family history, early onset, and bilaterality, this study supports our hypothesis that the amyloid is primary in nature in our patients and indicates a new subtype of autosomal recessive CHED that require further chemical and genetic analysis. This subtype has the same prognosis for PKP as all CHED patients, if not better.

High Measured Intraocular Pressure in Children With Recessive Congenital Hereditary Endothelial Dystrophy

To report the phenomenon of high measured intraocular pressure in recessive congenital hereditary endothelial dystrophy. A case series was retrospectively reviewed. Five infants with significant congenital corneal haze had increased measured intraocular pressure that remained high despite drug treatment and surgery to decrease intraocular pressure. The clinical diagnosis of recessive congenital hereditary endothelial dystrophy without glaucoma was made based on the absence of buphthalmos, a distinct pattern of mosaic corneal haze with significant corneal thickness, and absence of cupping in healthy-appearing optic nerve heads. Intraocular pressure can be falsely elevated in some children with recessive congenital hereditary endothelial dystrophy, leading to confusion with congenital glaucoma.

Congenital hereditary endothelial dystrophy with progressive sensorineural deafness (Harboyan syndrome)

Harboyan syndrome is a degenerative corneal disorder defined as congenital hereditary endothelial dystrophy (CHED) accompanied by progressive, postlingual sensorineural hearing loss. To date, 24 cases from 11 families of various origin (Asian Indian, South American Indian, Sephardi Jewish, Brazilian Portuguese, Dutch, Gypsy, Moroccan, Dominican) have been reported. More than 50% of the reported cases have been associated with parental consanguinity. The ocular manifestations in Harboyan syndrome include diffuse bilateral corneal edema occurring with severe corneal clouding, blurred vision, visual loss and nystagmus. They are apparent at birth or within the neonatal period and are indistinguishable from those characteristic of the autosomal recessive CHED (CHED2). Hearing deficit in Harboyan is slowly progressive and typically found in patients 10–25 years old. There are no reported cases with prelinglual deafness, however, a significant hearing loss in children as young as 4 years old has been detected by audiometry, suggesting that hearing may be affected earlier, even at birth. Harboyan syndrome is caused by mutations in the SLC4A11 gene located at the CHED2 locus on chromosome 20p13-p12, indicating that CHED2 and Harboyan syndrome are allelic disorders. A total of 62 different SLC4A11 mutations have been reported in 98 families (92 CHED2 and 6 Harboyan). All reported cases have been consistent with autosomal recessive transmission. Diagnosis is based on clinical criteria, detailed ophthalmological assessment and audiometry. A molecular confirmation of the clinical diagnosis is feasible. A variety of genetic, metabolic, developmental and acquired diseases presenting with clouding of the cornea should be considered in the differential diagnosis (Peters anomaly, sclerocornea, limbal dermoids, congenital glaucoma). Audiometry must be performed to differentiate Harboyan syndrome from CHED2. Autosomal recessive types of CHED (CHED2 and Harboyan syndrome) should carefully be distinguished from the less severe autosomal dominant type CHED1. The ocular abnormalities in patients with Harboyan syndrome may be treated with topical hyperosmolar solutions. However, corneal transplantation (penetrating keratoplasty) represents definitive treatment. Corneal transplantation produces a substantial visual gain and has a relatively good surgical prognosis. Audiometric monitoring should be offered to all patients with CHED2. Hearing aids may be necessary in adolescence.

Identification of Mutations in the SLC4A11 Gene in Patients With Recessive Congenital Hereditary Endothelial Dystrophy

To identify Solute Carrier family 4 (sodium borate cotransporter) member 11 (SLC4A11) gene mutations associated with autosomal recessive congenital hereditary endothelial dystrophy (CHED2). DNA extraction from blood, polymerase chain reaction amplification, and direct sequencing of all the exons of the SLC4A11 gene were performed for 26 affected members of 20 unrelated families with CHED2. Of 10 mutations observed, 6 were novel, 1 of which involves a complete deletion of exon 6, identified for the first time, to our knowledge, in SLC4A11. The mutations cosegregated with the disease phenotype and were absent in 200 ethnically matched control chromosomes analyzed. This study increases the number of SLC4A11 gene mutations and confirms the role of this gene in causing CHED2. Clinical examination did not reveal any considerable variability in disease expressivity in patients carrying SLC4A11 mutations. Extensive linkage analysis may reveal the modifier genes involved in causing CHED2 in the SLC4A11 mutations unidentified in 9 families. In India, there is a high frequency of CHED2, possibly related to consanguineous marriages. Counseling could be provided to explain the drawbacks of consanguineous marriages to assist in reducing this devastating disorder.

Mutation in the SLC4A11 Gene Associated with Autosomal Recessive Congenital Hereditary Endothelial Dystrophy in a Large Saudi Family

Objective: To determine the role of the SLC4A11 gene in two pedigrees affected with autosomal recessive congenital hereditary endothelial dystrophy (CHED). Methods: Nine members of a pedigree from the Kingdom of Saudi Arabia (pedigree 971G) and 2 twins in a pedigree from Bosnia (pedigree GGO413) were diagnosed with autosomal recessive CHED and contributed DNA samples for genetic studies. The proband of each pedigree was tested for disease-causing mutations in the SLC4A11 gene with bi-directional DNA sequencing. Screening assays using restriction enzyme digests were developed to test a cohort of 99 normal control subjects for the presence of SLC4A11 mutations. Results: A novel, homozygous mutation in the SLC4A11 gene (Thr271Met) was detected in the proband of pedigree 971G. Homozygous Thr271Met mutations were detected in all affected members of pedigree 971G. The Thr271Met mutation was not detected in a cohort of 99 normal control subjects. This mutation alters a highly conserved amino acid in the encoded SLC4A11 protein. No SLC4A11 mutations were detected in pedigree GGO413. Conclusion: A novel SLC4A11 mutation (Thr271Met) is associated with autosomal recessive CHED in a pedigree from the Kingdom of Saudi Arabia and provides additional support that mutations in this gene cause disease.

SLC4A11 mutations in Fuchs endothelial corneal dystrophy

The endothelial (posterior) corneal dystrophies, which result from primary endothelial dysfunction, include Fuchs endothelial corneal dystrophy (FECD), posterior polymorphous corneal dystrophy (PPCD) and congenital hereditary endothelial dystrophy (CHED). Mutations in SLC4A11 gene have been recently identified in patients with recessive CHED (CHED2). In this study, we show that heterozygous mutations in the SLC4A11 gene also cause late-onset FECD. Four heterozygous mutations [three missense mutations (E399K, G709E and T754M) and one deletion mutation (c.99-100delTC)] absent in ethnically matched controls were identified in a screen of 89 FECD patients. Missense mutations involved amino acid residues showing high interspecies conservation, indicating that mutations at these sites would be deleterious. Accordingly, immunoblot analysis, biochemical assay of cell surface localization and confocal immunolocalization showed that missense proteins encoded by the mutants were defective in localization to the cell surface. Our data suggests that SLC4A11 haploinsufficiency and gradual accumulation of the aberrant misfolded protein may play a role in FECD pathology and that reduced levels of SLC4A11 influence the long-term viability of the neural crest derived corneal endothelial cells.

Genetics of corneal endothelial dystropies

Abstract Purpose: Purpose‐ To determine whether mutations in genes SLC4A11 and TCF8 causative of recessive CHED and PPCD, respectively, may also play a pathogenic role in the more common Fuchs corneal endothelial dystrophy. The endothelial (posterior) corneal dystrophies, which result from primary endothelial dysfunction, include Fuchs endothelial dystrophy (FECD), posterior polymorphism dystrophy (PPCD) and congenital hereditary endothelial dystrophy (CHED). As they share common features of disease it is possible that a proportion of them could be clinical manifestations of different mutations of the same gene. Methods: Method‐Exons SLC4A11 and TCF8 gene were PCR amplified in 64 Chinese FECD cases and then subjected to bi‐directional sequencing. Eighty Chinese samples were used as normal age matched controls. To characterise SLC4A11 mutations wild type and mutant cDNA constructs were transfected in to HEK293 cells and protein extracts used for immunoblot analysis and cell surface processing assays. Confocal immunolocalization were also performed using established protocols. Results: Results‐Three heterozygous mutations were identified in this screen of 64 FECD patients. These were two missense mutations (G709E and T754M) and one deletion mutation (99‐100delTC). Missense mutations involved amino acid residues showing high interspecies conservation indicating that mutations at these sites would be deleterious. Accordingly, immunoblot analysis, biochemical assay of cell surface localization and confocal immunolocalization showed that missense mutants were defective in localization to the cell surface. No convincing pathogenic mutations were identified in the TCF8 gene. Conclusions: Conclusion‐ Our data suggests that 4.7% (95% CI=0.98% to 13.1%) of FECD in the Chinese can be attributable to SLC4A11 mutations.

Autosomal Recessive CHED Associated With Novel Compound Heterozygous Mutations in SLC4A11

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

NovelSLC4A11mutations in patients with recessive congenital hereditary endothelial dystrophy (CHED2)

Autosomal recessive congenital hereditary endothelial dystrophy (CHED2) is a severe and rare corneal disorder that presents at birth or shortly thereafter, characterized by corneal opacification and nystagmus. Recently the gene for CHED2 was identified and seven different mutations in the SLC4A11 gene were reported. Here, we report seven novel mutations and two previously identified mutations in families from India and the United Kingdom with recessive CHED. The novel changes include two nonsense (p.Trp240X; p.Gln800X) three missense (p.Glu143Lys; p.Cys386Arg; p.Arg755Trp) and two splice site mutations (c.2240+1G>A; c.2437-1G>A). Interestingly, the c.2398C>T (p.Gln800X) and c.2437-1G>A identified in two affected siblings represent the first compound heterozygous mutations in the SLC4A11 gene.

Mutations in sodium-borate cotransporter SLC4A11 cause recessive congenital hereditary endothelial dystrophy (CHED2)

Congenital hereditary endothelial dystrophy (CHED) is a heritable, bilateral corneal dystrophy characterized by corneal opacification and nystagmus. We describe seven different mutations in the SLC4A11 gene in ten families with autosomal recessive CHED. Mutations in SLC4A11, which encodes a membrane-bound sodium-borate cotransporter, cause loss of function of the protein either by blocking its membrane targeting or nonsense-mediated decay.

Localization of the Gene for Autosomal Recessive Congenital Hereditary Endothelial Dystrophy (CHED2) to Chromosome 20 by Homozygosity Mapping

Congenital hereditary endothelial dystrophy (CHED) is a corneal disorder that presents with diffuse bilateral corneal clouding. Vision may be severely impaired, and many patients require corneal transplantation. Both autosomal dominant (AD) and autosomal recessive (AR) forms of the disorder have been described. The gene responsible for AD CHED (HGMW-approved symbol CHED1) has been mapped to the pericentromeric region of chromosome 20. Investigating a large, consanguineous Irish pedigree with autosomal recessive CHED, we have previously excluded linkage to this AD CHED locus. We now describe a genome-wide search using homozygosity mapping and DNA pooling. Evidence of linkage to chromosome 20p was demonstrated with a maximum lod score of 9.30 at a recombination fraction of 0.0 using microsatellite marker D20S482. A region of homozygosity in all affected individuals was identified, narrowing the disease gene locus to an 8-cM region flanked by markers D20S113 and D20S882. This AR CHED (HGMW-approved symbol CHED2) disease gene locus is physically and genetically distinct from the AD CHED locus.

Homozygosity mapping and linkage analysis demonstrate that autosomal recessive congenital hereditary endothelial dystrophy (CHED) and autosomal dominant CHED are genetically distinct

BACKGROUNDCongenital hereditary endothelial dystrophy (CHED) is a corneal dystrophy characterised by diffuse bilateral corneal clouding resulting in impaired vision. It is inherited in either an autosomal dominant (AD) or autosomal...

Clinical Differentiation of Recessive Congenital Hereditary Endothelial Dystrophy and Dominant Hereditary Endothelial Dystrophy

Our review of previously published reports and familial cases revealed that corneal clouding in autosomal recessive congenital hereditary endothelial dystrophy was present at birth or within the neonatal period. Further, corneal changes with time were minimal, nystagmus was often present, and there were no other signs or symptoms. Patients with autosomal dominant endothelial dystrophy usually had clear corneas early in life; corneal opacification was slowly progressive, nystagmus was infrequent, and photophobia, as well as epiphora, may have been the first indications of the dystrophy. As there is usually little or no congenital evidence of the dominant type, "infantile" or "autosomal dominant" hereditary endothelial dystrophy would be more appropriate names for the dominant variant.