Congenital Hereditary Endothelial Dystrophy Research Articles

Mutational Analysis of the SLC4A11 Gene in a (Filipino) Family with Congenital Hereditary Endothelial Dystrophy

Aim: The study aims to identify if mutations in the SLC4A11 gene are present in Filipino families affected with congenital hereditary endothelial dystrophy (CHED). Methods: This is a family cohort study that investigated the genetic profile of a selected family in northern Luzon, Philippines, whose members were diagnosed with congenital hereditary endothelial dystrophy (CHED). A patient who was diagnosed with CHED prior to this study served as the proband for this family. A detailed family history was obtained and a complete ophthalmologic examination was performed on each of the family members. A total of six affected members and three unaffected members were included in this study. DNA was isolated from peripheral blood samples of the family members, polymerase chain reaction (PCR) was used to amplify the gene’s entire coding region (19 exons and 2 putative promoter regions), and finally, the amplified regions were analyzed using DNA sequencing. Results: Consanguinity was not present in the family. Corneal haze was reported to have been present since birth or shortly thereafter in all the affected patients. Slit-lamp examination showed edematous corneas. Molecular studies of the SLC4A11 gene revealed four novel homozygous point mutations variably presenting in the six affected members, as well as the three unaffected members. One unaffected family member (I-1) had a novel sense mutation absent in the other family members. All affected siblings showed little phenotypic variability. Conclusions: This is the first report that gives us a genetic profile of a northern Luzon family with members affected by CHED. This study supports earlier findings that mutations in the SLC4A11 gene are not consistently the same among different ethnic groups worldwide, probably due to the disease’s genetic heterogeneity. Our study documented five novel mutations, adding to the growing list of mutations probably responsible for acquiring the CHED phenotype. It is possible that there are more novel mutations waiting to be discovered in this hereditary disease. Screening for these specific mutations in other families may prove useful for genetic counseling, prenatal diagnosis, and the future development of gene therapy.

Investigation of the functional impact of CHED- and FECD4-associated SLC4A11 mutations in human corneal endothelial cells.

Mutations in the solute linked carrier family 4 member 11 (SLC4A11) gene are associated with congenital hereditary endothelial dystrophy (CHED) and Fuchs corneal endothelial dystrophy type 4 (FECD4), both characterized by corneal endothelial cell (CEnC) dysfunction and/or cell loss leading to corneal edema and visual impairment. In this study, we characterize the impact of CHED-/FECD4-associated SLC4A11 mutations on CEnC function and SLC4A11 protein localization by generating and comparing human CEnC (hCEnC) lines expressing wild type SLC4A11 (SLC4A11WT) or mutant SLC4A11 harboring CHED-/FECD4-associated SLC4A11 mutations (SLC4A11MU). SLC4A11WT and SLC4A11MU hCEnC lines were generated to express either SLC4A11 variant 2 (V2WT and V2MU) or variant 3 (V3WT and V3MU), the two major variants expressed in ex vivo hCEnC. Functional assays were performed to assess cell barrier, proliferation, viability, migration, and NH3-induced membrane conductance. We demonstrate SLC4A11-/- and SLC4A11MU hCEnC lines exhibited increased migration rates, altered proliferation and decreased cell viability compared to SLC4A11WT hCEnC. Additionally, SLC4A11-/- hCEnC demonstrated decreased cell-substrate adhesion and membrane capacitances compared to SLC4A11WT hCEnC. Induction with 10mM NH4Cl led SLC4A11WT hCEnC to depolarize; conversely, SLC4A11-/- hCEnC hyperpolarized and the majority of SLC4A11MU hCEnC either hyperpolarized or had minimal membrane potential changes following NH4Cl induction. Immunostaining of primary hCEnC and SLC4A11WT hCEnC lines for SLC4A11 demonstrated predominately plasma membrane staining with poor or partial colocalization with mitochondrial marker COX4 within a subset of punctate subcellular structures. Overall, our findings suggest CHED-associated SLC4A11 mutations likely lead to hCEnC dysfunction, and ultimately CHED, by interfering with cell migration, proliferation, viability, membrane conductance, barrier function, and/or cell surface localization of the SLC4A11 protein in hCEnC. Additionally, based on their similar subcellular localization and exhibiting similar cell functional profiles, protein isoforms encoded by SLC4A11 variant 2 and variant 3 likely have highly overlapping functional roles in hCEnC.

The newest IC3D classification of corneal dystrophies

In the year 2015, the International Committee for the Classification of Corneal Dystrophies (IC3D) incorporated new clinical, histopathologic, and genetic information into the former 2008 classification. To this end, the IC3D sighted and evaluated worldwide peer‐reviewed articles for new information on corneal dystrophies published between 2008 and 2014. Using this information, corneal dystrophy templates including categories 1 to 4 and anatomic classification were updated. New clinical, histopathologic, and confocal photographs were added.On the basis of revisiting the cellular origin of corneal dystrophies, a modified anatomic classification was proposed consisting of (1) epithelial and subepithelial dystrophies, (2) epithelial‐stromal TGFBI dystrophies, (3) stromal dystrophies, and (4) endothelial dystrophies. The entity “Epithelial recurrent erosion dystrophies ERED” actually includes a number of potentially distinct epithelial dystrophies (Franceschetti corneal dystrophy, Dystrophia Smolandiensis, and Dystrophia Helsinglandica) but must be differentiated from dystrophies such as TGFBI‐induced dystrophies, which are also often associated with recurrent epithelial erosions. The chromosome locus of Thiel‐Behnke corneal dystrophy is only located on 5q31. The entity previously designated as a variant of Thiel‐Behnke corneal dystrophy on chromosome 10q24 may represent a novel corneal dystrophy. Congenital hereditary endothelial dystrophy (CHED, formerly CHED2) is most likely only an autosomal recessive disorder. The so‐called autosomal dominant inherited CHED (formerly CHED1) is insufficiently distinct to continue to be considered a unique corneal dystrophy. On review of almost all of the published cases, the description appeared most similar to a type of posterior polymorphous corneal dystrophy linked to the same chromosome 20 locus (PPCD1). Anterior segment OCT has emerged as a helpful tool to reveal in vivo features of several corneal dystrophies that previously required histopathologic examination in order to definitively diagnose them.This revision of the IC3D classification includes an updated anatomic classification of corneal dystrophies that more accurately classifies TGFBI dystrophies affecting multiple layers rather than being confined to one corneal layer. At this time, a 3rd edition of the IC3D classification of corneal dystrophies is under way.

Corneal opacities in children

The corneal opacities in childhood could be either, congenital or acquired. The congenital could either localized/non‐systemic disease, like the congenital hereditary endothelial dystrophy, posterior polymorphous corneal dystrophy, congenital hereditary stromal dystrophy, peters anomaly, congenital anterior staphyloma, sclerocornea, cornea plana, cornea tumours, epibulbar dermoid, or related to systemic/metabolic Disorders like mucopolysaccharidoses, cystinosis, tyrosinemia, schnyder crystalline dystrophy, fetal alcohol syndrome. The acquired corneal opacities could be either traumatic, like traumatic breaks in descemet membrane, corneal blood staining, corneal keloids, or non traumatic like keratoconus, posterior corneal depression, keratoglobus, congenital or infantile glaucoma, Corneal ulcers, Familial dysautonomia (Riley‐Day syndrome), Stevens‐Johnson syndrome and toxic epidermal necrolysis. We will discuss these cases, their clinical picture, work up and management.

Clinical features and results of surgical treatment of congenital corneal opacities in infants and children under 3 years of age

Congenital corneal opacities (CCO) are rare eye anomalies of various etiological causes. Given the heterogeneity of the clinical and morphological manifestations of CCO, its functional disorders are of the same type and significant, leading to visual disability. This anomaly occurs in 6 per 100,000 newborns.
 AIM: To study the clinical and anatomical features and treatment results of CCO in children aged under 3 years old, who were treated in the Department of Eye Pathology in Children of Helmholtz National Medical Research Center of Eye Diseases for the period from January 1, 2010, to December 31, 2022 (12 years).
 MATERIAL AND METHODS: The clinical and anatomical features and results of surgical treatment of 142 patients (172 eyes) with CCO aged 0–3 years were analyzed in the period from January 1, 2010, to December 31, 2022. According to the clinical picture, all CCOs were classified as congenital glaucoma, sclerocornea, Peters anomaly, anterior staphyloma, endothelial corneal dystrophy, dermoid, and Axenfeld–Rieger syndrome, and were idiopathic. Surgical methods included end-to-end keratoplasty, layered keratoplasty, limbokeratoplasty, and end-to-end reconstructive keratoplasty, including synechial excision, cataract removal, pupil formation, and anterior vitrectomy. The treatment results were evaluated based on the biological and functional results. The biological results of the operation (graft engraftment) were evaluated in the Kaplan–Meier model.
 RESULTS: Congenital glaucoma dominates among clinical diagnoses of CCO (40% of all cases), followed by Peters anomaly, sclerocornea, congenital hereditary endothelial corneal dystrophy, other hereditary corneal dystrophies and anterior staphyloma, Axenfeld–Rieger syndrome, and corneal dermoid. In 5 (3%) cases, the CCO was defined as idiopathic. Surgical treatment was performed on 78 (86 eyes) out of 142 (54.9%) patients. The 1-year survival rate following transplants in patients with high blood pressure was 75%; with Peters anomaly, 67%; and with sclerocornea, 54%, and the 2-year survival rates were 70%, 63%, and 36%, respectively. The 1 and 2 years urvival rates following transplants in patients with congenital endothelial hereditary dystrophy were 88 and 82%, respectively.
 CONCLUSION: The results show that CCO manifest heterogeneously in children aged under 3 years old. Careful anamnesis collection, thorough clinical examination, and additional studies such as UBM are crucial in obtaining accurate diagnosis and classification of CCO and provide recommendations on treatment strategies.

12-year follow-up of the first endothelial keratoplasty without Descemet stripping in a 3-month newborn with Congenital Hereditary Endothelial Dystrophy (CHED)

BackgroundEndothelial Keratoplasty (EK) is now considered as the standard treatment for Congenital Hereditary Endothelial Dystrophy (CHED) by many surgeons. We present the 12-year clinical outcome of the youngest operated patient with CHED in which we successfully performed a bilateral EK procedure without removing the recipient endothelium-Descemet complex.Case presentationIn November 2010 we performed EK without Descemet Stripping in a 3-month female newborn, thinking that the lower manipulation obtained by leaving the recipient endothelium–Descemet complex could be the key factor for the success of our surgery. Such a particular technique was new in newborns. The surgery was a success, but the long-term visual result was not predictable at that time. We followed the patient at 4 months, and then yearly. At the latest visit in October 2022 the visual, cognitive, and motorial developments were normal, with Best-corrected Distance Visual Acuity of 0.4 LogMAR with − 0.75 D sf + 2.75 D cyl @ 105° in the right eye (RE) and 0.4 LogMAR with + 1.50 D sf + 2.50 D cyl @ 60° in the left eye (LE). The endothelial microscope showed an unexpected healthy endothelium, with a cell count of 2383 cells/mm2 in the RE and of 2547 cells/mm2 in the LE from a starting donor count of 2900 cells/mm2. No secondary procedures were performed during the 12-year follow-up.ConclusionEK without Descemet stripping has proved to be a successful procedure over time in our newborn. The unexpected healthy endothelium suggests a role of the Descemet membrane in CHED.

Pathogenicity and Function Analysis of Two Novel SLC4A11 Variants in Patients With Congenital Hereditary Endothelial Dystrophy.

The purpose of this study was to explore the pathogenicity and function of two novel SLC4A11 variants associated with congenital hereditary endothelial dystrophy (CHED) and to study the function of a SLC4A11 (K263R) mutant in vitro. Ophthalmic examinations were performed on a 28-year-old male proband with CHED. Whole-exome and Sanger sequencing were applied for mutation screening. Bioinformatics and pathogenicity analysis were performed. HEK293T cells were transfected with the plasmids of empty vector, wild-type SLC4A11, and SLC4A11 (K263R) mutant. The transfected cells were treated with SkQ1. Oxygen consumption, cellular reactive oxygen species (ROS) level, mitochondrial membrane potential, and apoptosis rate were measured. The proband had poor visual acuity with nystagmus since childhood. Corneal foggy opacity was evident in both eyes. Two novel SLC4A11 variants were detected. Sanger sequencing showed that the proband's father and sister carried c.1464-1G>T variant, and the proband's mother and sister carried c.788A>G (p.Lys263Arg) variant. Based on the American College of Medical Genetics (ACMG) guidelines, SLC4A11 c.1464-1G>T was pathogenic, whereas c.788A>G, p.K263R was a variant of undetermined significance. In vitro, SLC4A11 (K263R) variant increased ROS level and apoptosis rate. Decrease in mitochondrial membrane potential and oxygen consumption rate were remarkable. Furthermore, SkQ1 decreased ROS levels and apoptosis rate but increased mitochondrial membrane potential in the transfected cells. Two novel heterozygous pathogenic variants of the SLC4A11 gene were identified in a family with CHED. The missense variant SLC4A11 (K263R) caused mitochondrial dysfunction and increased apoptosis in mutant transfected cells. In addition, SkQ1 presented a protective effect suggesting the anti-oxidant might be a novel therapeutic drug. This study verified the pathogenicity of 2 novel variants in the SLC4A11 gene in a CHED family and found an anti-oxidant might be a new drug.

Structural insights into the conformational changes of BTR1/SLC4A11 in complex with PIP2

BTR1 (SLC4A11) is a NH3 stimulated H+ (OH-) transporter belonging to the SLC4 family. Dysfunction of BTR1 leads to diseases such as congenital hereditary endothelial dystrophy (CHED) and Fuchs endothelial corneal dystrophy (FECD). However, the mechanistic basis of BTR1 activation by alkaline pH, transport activity regulation and pathogenic mutations remains elusive. Here, we present cryo-EM structures of human BTR1 in the outward-facing state in complex with its activating ligands PIP2 and the inward-facing state with the pathogenic R125H mutation. We reveal that PIP2 binds at the interface between the transmembrane domain and the N-terminal cytosolic domain of BTR1. Disruption of either the PIP2 binding site or protonation of PIP2 phosphate groups by acidic pH can transform BTR1 into an inward-facing conformation. Our results provide insights into the mechanisms of how the transport activity and conformation changes of BTR1 are regulated by PIP2 binding and interaction of TMD and NTD.

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.

Updates on congenital hereditary endothelial dystrophy.

Congenital hereditary endothelial dystrophy (CHED) is a rare genetic corneal disorder causing progressive cornea clouding and significant visual impairment. CHED remains a leading indication for pediatric corneal transplantation despite its infrequency, particularly in regions with high consanguinity rates like Southeast Asia. Identifying the Solute Carrier Family 4 Member 11 (SLC4A11) gene as the genetic basis of CHED has led to the discovery of it's various genetic variations. However, a comprehensive understanding of its clinical-genetic correlation, pathophysiology, and optimal management is ongoing. This review aims to consolidate current knowledge about CHED, covering its genetic origins, pathophysiological mechanisms, clinical presentation, and management strategies. Surgical intervention, such as penetrating keratoplasty (PK), Descemet stripping automated endothelial keratoplasty (DSAEK), and Descemet membrane endothelial keratoplasty (DMEK), remains the primary treatment. DSAEK and DMEK offer advantages over PK, including quicker visual recovery, reduced complications, and longer graft survival, especially in the pediatric age group. The timing of surgical interventions depends on disease severity, age at presentation, comorbidities, and visual potential. Elevated oxidative stress in CHED corneal tissue suggests potential benefits from anti-inflammatory drugs to rescue mutated endothelial cells. Considering the limitations of corneal graft surgeries, exploring novel gene-based molecular therapies are essential for future management. Early diagnosis, appropriate surgical interventions, amblyopia control, and genetic counseling for predictive analysis are pivotal for optimizing CHED management. A multidisciplinary approach involving ophthalmologists, researchers, and genetic counselors is essential for precise diagnosis and optimal care for CHED patients.

Clinical and diagnostic imaging profile of three anterior segment dysgenesis disorders presenting with infantile corneal opacities.

To describe three anterior segment dysgenesis disorders with infantile corneal opacities, namely, congenital hereditary endothelial dystrophy (CHED), primary congenital glaucoma (PCG), and Peters anomaly (PA) in terms of clinical characteristics, histopathology, genetic association, and diagnostic imaging profiles using imaging modalities such as ultrasound biomicroscopy (UBM) and microscope-integrated intraoperative optical coherence tomography (i-OCT). Seventy-four eyes with 22 eyes of CHED, 28 eyes of PA, and 24 eyes of PCG were clinically evaluated and underwent imaging using UBM and i-OCT. Corneal buttons of 16 operated patients underwent histopathological analysis, while genetic analysis was done in 23 patients using whole-exome sequencing. Corneal diameters (CD) and UBM parameters like anterior chamber depth (ACD), iris thickness (IT), and ciliary body (CB) thickness revealed a statistically significant difference between the three categories. In PA, 9 eyes had a third rare phenotype with only a posterior corneal defect with no iris adhesions. Genetic mutations were seen in all tested patients with CHED, in 83.3% of patients with PCG, and in 80% of patients with the third type of PA. i-OCT helped in the characterization of corneal opacity, identification of posterior corneal defects, iridocorneal adhesions, and contour of Descemet's membrane. Overlapping phenotypes of the above disorders cause a diagnostic dilemma and parameters like CDs, UBM ACD, IT, and CB thickness help differentiate between them. i-OCT can help in classifying the diseases in a high resolution, non-contact manner, and can better delineate corneal characteristics. The rare third type of PA phenotype may have a genetic association.

Commentary: Endothelial keratoplasty in congenital hereditary endothelial dystrophy - Benefits and challenges.

Commentary: Endothelial keratoplasty in congenital hereditary endothelial dystrophy - Benefits and challenges.

A review of techniques and outcomes of endothelial keratoplasty in congenital hereditary endothelial dystrophy.

Congenital hereditary endothelial dystrophy affects the Descemet membrane and endothelium, resulting in corneal decompensation. Penetrating keratoplasty (PKP) has been the gold-standard surgical management until recently; however, at present, endothelial keratoplasty (DSEK/DSAEK/n-DSEK: Descemet-stripping or non-Descemet stripping endothelial keratoplasty and DMEK/n-DMEK: Descemet membrane endothelial keratoplasty) is being preferred due to lesser intraoperative and postoperative complications, early visual recovery, and comparable visual outcomes. Endothelial keratoplasty (EK) can be challenging, especially in pediatric eyes with CHED due to smaller eyeballs, shallow anterior chambers, phakic status, and poor intraoperative visibility due to thick and hazy corneas. A total of 198 articles matched our search strategy. After screening for duplication and going through the titles and abstracts, 12 relevant original articles, one case series, and six case reports were included in this review. Various surgical modifications have to be adopted in comparison to adult eyes to overcome the aforementioned difficulties. Regardless, studies have shown favorable visual outcomes with better graft survival and fewer complications in eyes that underwent EK compared to PKP. Hence, timely surgical intervention and strict amblyopia management can result in better final visual outcomes. The purpose of this review is to summarize various intraoperative difficulties and the surgical modifications required, different surgical techniques, visual and graft-related outcomes, and various complications of EK in CHED eyes.

Penetrating Keratoplasty Versus Descemet Stripping Automated Endothelial Keratoplasty in Children With Congenital Hereditary Endothelial Dystrophy: Long-Term Results.

The purpose of this study was to compare the outcomes of Descemet stripping automated endothelial keratoplasty (DSAEK) and penetrating keratoplasty (PKP) in patients with congenital hereditary endothelial dystrophy (CHED). This was a retrospective, comparative study of all the patients with a histopathological diagnosis of CHED who underwent PKP or DSAEK between January 1, 1990, and December 31, 2016. All the cases were included except those patients who had clear grafts but did not complete 2 years of postoperative follow-up. The main outcome measure was graft clarity 2 years after surgery. There were 111 eyes of 63 patients. Seventy-six eyes underwent PKP, and 35 eyes underwent DSAEK. The median age at surgery was 6.8 years in the PKP group and 10.32 years in the DSAEK group. At 2 years postoperatively, clear grafts were noted in 66 of 76 (86.8%) eyes in the PKP group and 30 of 35 (85.7%) eyes in the DSAEK group. At the last follow-up, 80.3% of PKP grafts and 82.8% of DSAEK grafts were clear ( P =0.5). The type and timing of complications differed between the 2 groups. The PKP group had a statistically significant higher rate of graft rejection (19.5%) versus the DSAEK group (0%) ( P =0.01). DSAEK complications were mainly lenticule detachment that developed within one month postoperatively. There was no statistically significant difference in the visual outcomes at the last follow-up between the groups. Endothelial keratoplasty is a safe alternative to conventional PKP in CHED. The visual outcome and survival rates were comparable, but DSAEK had a lower rejection rate and fewer suture-related complications.

Identification and in silico analysis of a spectrum of SLC4A11 variations in Indian familial and sporadic cases of congenital hereditary endothelial dystrophy

BackgroundCongenital hereditary endothelial dystrophy (CHED) is a rare form of corneal dystrophy caused by SLC4A11 gene variations. This study aims to find the genetic alterations in SLC4A11, in two Indian familial CHED cases with affected members n = 3 and n = 2 respectively and five sporadic CHED cases using direct sequencing, followed by in silico analysis and characterization of the identified variants.ResultsAll three affected members of the first CHED family were identified with a novel homozygous c.1514C > G (p.Ser489Trp) variation while second family showed presence of a compound heterozygous variation c.529A > C (p.Arg161Arg) + c.2461insT (p.Val805fs). Among five sporadic cases, two showed novel changes, homozygous c.1487G > T (p.Ser480Ile) and c.620-2A > G, while the other one had previously reported homozygous c.2653C > T (p.Arg869Cys) variation. The remaining two cases did not reveal the presence of SLC4A11-related pathogenic variations. The identified variations were excluded from the Indian control (n = 80). In silico analysis using homology-based protein modeling and pathogenicity prediction tools, which revealed these alterations as pathogenic, changing their protein stability, local flexibility, residue contact clashes, and the hydrogen bond interactions.ConclusionsThis study contributed to the CHED mutational spectrum, adding four novel variations and confirming a previously reported one. It demonstrates different type of variations in CHED cases, including coding, non-coding, homozygous, synonymous, and compound heterozygous variations. The identified variations revealed different degrees of pathogenic effects in silico. Moreover, two sporadic cases could not be identified with pathogenic variation emphasizing the involvement of other genes or genetic mechanisms.

Mutational analysis in sodium-borate cotransporter SLC4A11 in consanguineous families from Punjab, Pakistan.

AimTo identify the molecular basis of Congenital Hereditary Endothelial Dystrophy CHED caused by mutations in SLC4A11, in the consanguineous Pakistani families.MethodsA total of 7 consanguineous families affected with Congenital Hereditary Endothelial Dystrophy were diagnosed and registered with the help of ophthalmologists. Blood samples were collected from affected and unaffected members of the enrolled families. Mutational analysis was carried out by DNA sequencing using both Sanger and Whole Exome Sequencing (WES). Probands of each pedigree from the 7 families were used for WES. Results were analyzed with the help of different bioinformatics tools.ResultsThe sequencing results demonstrated three known homozygous mutations in gene SLC4A11 in probands of 7 families. These mutations p.Glu675Ala, p.Val824Met, and p.Arg158fs include 2 missense and 1 frameshift mutation. The mutations result in amino acids that were highly conserved in SLC4A11 across different species. The mutations were segregated with the disease phenotype in the families.ConclusionThis study reports 3 mutations in 7 families. One of the pathogenic mutations (p.R158fs) was identified for the first time in the Pakistani population. However, two mutations (p.Glu675Ala, p.Val824Met) were previously reported in two and one Pakistani family respectively. As these mutations segregate with the disease phenotype and bioinformatics tool also liable them as pathogenic, they are deemed as probable cause of underlying disease.

Mitochondrial ROS in Slc4a11 KO Corneal Endothelial Cells Lead to ER Stress.

Recent studies from Slc4a11 −/− mice have identified glutamine-induced mitochondrial dysfunction as a significant contributor toward oxidative stress, impaired lysosomal function, aberrant autophagy, and cell death in this Congenital Hereditary Endothelial Dystrophy (CHED) model. Because lysosomes are derived from endoplasmic reticulum (ER)—Golgi, we asked whether ER function is affected by mitochondrial ROS in Slc4a11 KO corneal endothelial cells. In mouse Slc4a11 −/− corneal endothelial tissue, we observed the presence of dilated ER and elevated expression of ER stress markers BIP and CHOP. Slc4a11 KO mouse corneal endothelial cells incubated with glutamine showed increased aggresome formation, BIP and GADD153, as well as reduced ER Ca2+ release as compared to WT. Induction of mitoROS by ETC inhibition also led to ER stress in WT cells. Treatment with the mitochondrial ROS quencher MitoQ, restored ER Ca2+ release and relieved ER stress markers in Slc4a11 KO cells in vitro. Systemic MitoQ also reduced BIP expression in Slc4a11 KO endothelium. We conclude that mitochondrial ROS can induce ER stress in corneal endothelial cells.

Update on the genetics of corneal endothelial dystrophies.

Corneal endothelial dystrophies are a heterogeneous group of diseases with different modes of inheritance and genetic basis for each dystrophy. The genes associated with these diseases encode transcription factors, structural components of the stroma and Descemet membrane, cell transport proteins, and others. Congenital hereditary endothelial dystrophy (CHED) is associated with mutations in two genes, OVOL2 and SLC4A11, for dominant and recessive forms of CHED, respectively. Mutations in three genes are known to cause posterior polymorphous corneal dystrophy (PPCD). They are OVOL2 (PPCD1), ZEB1 (PPCD3), and GRHL1 (PPCD4). The PPCD2 locus involving the collagen gene COL8A2 on chromosome 1 is disputed due to insufficient evidence. Mutations in the COL8A2 gene are associated with early-onset Fuchs’ endothelial corneal dystrophy (FECD). Several genes have been associated with the more common, late-onset FECD. Alterations in each of these genes occur in a fraction of patients, and the most prevalent genetic alteration in FECD patients across the world is a triplet repeat expansion in the TCF4 gene. Knowledge of the genetics of corneal endothelial dystrophies has considerably advanced within the last decade and has contributed to better diagnosis of these dystrophies as well as opened up the possibility of novel therapeutic approaches based on the molecular mechanisms involved. The functions of genes identified to date provide insights into the pathogenic mechanisms involved in each disorder.

Consanguinity and ocular disorders in India: Electronic medical records driven big data analytics.

Purpose: To describe the distribution of ocular disorders in patients with a family history of consanguinity presenting to a multi-tier ophthalmology hospital network in India.Methods: This cross-sectional hospital-based study included 2,805,267 new patients presenting between August 2010 and April 2021. Patients with a family history of consanguinity were included as cases. The sociodemographic and clinical data were collected using an electronic medical record system.Results: Overall, 20,445 (0.73%) new patients were documented to have a family history of consanguinity. The prevalence rates were 4.04% in children (age: <16 years) and 0.21% in adults. The mean age of the patients was 11.87 ± 11.06 years. The majority of the patients were males (56.48%) and students (54.43%) by profession. The majority (93.05%) of the patients were in the 0–30-years age bracket, with over half of them (53.71%) presenting in the first decade of life. A significant number of patients were from higher socioeconomic status (73.48%) and the rural region (47.62%). The most common degree of consanguinity documented was second degree (3.95%). The most common ocular disorders associated with a high proportion of consanguinity were congenital hereditary endothelial dystrophy (CHED) (100%), corneal macular dystrophy (83.78%), xeroderma pigmentosum (80.95%), and ocular albinism (73.59%). A tenth of the patients (9.8%) reported a similar history of ocular disorders among the family members and more commonly among the siblings (70.4%).Conclusion: Consanguineous marriages are not uncommon in India. They cause ocular disorders that cause visual impairment in a significant majority of those affected in their early decades of life. Genetic counseling plays a role in prevention.

Human SLC4A11 does not complement BOR1 or support borate transport in Saccharomyces cerevisiae.

Borate is an essential micronutrient in plants regulated by borate transporters, which also protect both yeast and plants from toxically high levels of borate and share homology with the human SLC4 transporters. SLC4A11 is linked to congenital hereditary endothelial dystrophy and was initially reported to transport borate before subsequent studies rebutted this conclusion. To better understand the transport activities of purported borate transporters, we tested the ability of SLC4A11 and eleven borate transporters from A. thaliana and O. sativa to complement a BOR1 deletion in S. cerevisiae . We show that AtBOR4 , AtBOR5 , AtBOR7 , OsBOR2 , and OsBOR3 can each complement ScBOR1 , while the rest of the transporters tested do not rescue growth. Additionally, quantification of intracellular borate content demonstrates that SLC4A11 does not export borate in yeast, supporting studies that its transported substrate is not borate.