Kerato-epithelin mutations in four 5q31-linked corneal dystrophies

[The latest IC3D classification of corneal dystrophies-Overview and changes of the 3rd edition]

The International Committee on Classification of Corneal Dystrophies (IC3D) was founded in 2005 to address difficulties arising from the outdated nomenclature for corneal dystrophies (CD) and to correct misconceptions in the literature. For each of the 22 CDs, a separate template was created to represent the current clinical, pathological and genetic knowledge of the disease. In addition, each template contains representative clinical photographs as well as light and electron microscopic images and, if available, confocal microscopic and coherence tomographic images of the respective CD. After the first edition was published in 2008, the revised version followed in 2015. The third edition of the IC3D was published as open access in February 2024. The latest edition is intended to serve as a reference work in everyday clinical practice and facilitate the diagnosis of CD, which might sometimes be difficult. This article provides an overview of the diagnostic and treatment principles of CD and presents the IC3D and its changes over time.

Improving the Yield of Genetic Diagnosis through Additional Genetic Panel Testing in Hereditary Ophthalmic Diseases

Numerous hereditary ophthalmic diseases display significant genetic diversity. Consequently, the utilization of gene panel sequencing allows a greater number of patients to receive a genetic diagnosis for their clinical manifestations. We investigated how to improve the yield of genetic diagnosis through additional gene panel sequencing in hereditary ophthalmic diseases. A gene panel sequencing consisting of a customized hereditary retinopathy panel or hereditary retinitis pigmentosa (RP) panel was prescribed and referred to a CAP-accredited clinical laboratory. If no significant mutations associated with hereditary retinopathy and RP were detected in either panel, additional gene panel sequencing was requested for research use, utilizing the remaining panel. After additional gene panel sequencing, a total of 16 heterozygous or homozygous variants were identified in 15 different genes associated with hereditary ophthalmic diseases. Of 15 patients carrying any candidate variants, the clinical symptoms could be tentatively accounted for by genetic mutations in seven patients. However, in the remaining eight patients, given the in silico mutation predictive analysis, variant allele frequency in gnomAD, inheritance pattern, and genotype-phenotype correlation, fully elucidating the clinical manifestations with the identified rare variant was challenging. Our study highlights the utility of gene panel sequencing in achieving accurate diagnoses for hereditary ophthalmic diseases and enhancing the diagnostic yield through additional gene panel sequencing. Thus, gene panel sequencing can serve as a primary tool for the genetic diagnosis of hereditary ophthalmic diseases, even in cases where a single genetic cause is suspected. With a deeper comprehension of the genetic mechanisms underlying these diseases, it becomes feasible.

Recurrence Characteristics on Optical Coherence Tomography and Treatments of Reis-Bücklers Corneal Dystrophy After Phototherapeutic Keratectomy or Penetrating Keratoplasty

PURPOSE

To evaluate the recurrence characteristics on optical coherence tomography and clinical outcomes after phototherapeutic keratectomy (PTK) or penetrating keratoplasty (PKP) in patients with Reis-Bücklers corneal dystrophy (RBCD).

DESIGN

Retrospective interventional case series.

METHODS

Seventeen patients with RBCD (31 eyes, including 6 surgery-naïve eyes and 25 surgical eyes) received 44 surgical interventions from 1996 through 2022. PTK or PKP was performed as the initial surgical procedure. Significant recurrence was determined when best spectacle-corrected visual acuity decreased at least 2 lines with increased opacity in the superficial cornea. Repeated PTK or PTK on the corneal graft (CG-PTK) was considered if patients could not endure poor vision due to significant recurrence. Recurrence depth and annual increase in thickness of the central cornea and subepithelial deposits were assessed by anterior segment optical coherence tomography.

RESULTS

The mean follow-up time was 12.8 ± 8.5 years (range, 2.0-25.5 years). The mean logMAR best spectacle-corrected visual acuity improved from 1.24 ± 0.48 preoperatively to 0.27 ± 0.09 postoperatively in the initial PTK group (13 eyes, P < .001), from 1.84 ± 0.69 to 0.40 ± 0.13 in the PKP group (12 eyes, P < .001), from 1.04 ± 0.46 to 0.30 ± 0.07 in the repeated PTK group (12 times in 7 eyes, P < .001), and from 1.29 ± 0.43 to 0.39 ± 0.11 in the CG-PTK group (7 times in 5 eyes, P = .001). The median significant recurrence time was 27 months (95% confidence interval 23.9-30.1), 96 months (84.1-107.9), 31 months (28.8-33.1), and 24 months (19.8-28.2), respectively (P < .001). The depth of superficial deposits located between the epithelium and the anterior stroma was approximately 115 µm (85-159 µm). The annual thickening of subepithelial deposits was 14 ± 2 µm after initial PTK, 7 ± 3 µm after PKP, 14 ± 3 µm after repeated PTK, and 30 ± 11 µm after CG-PTK, compared to 4 ± 2 µm in surgery-naïve eyes (P = .002, .515, .002, <.001). The thickness of the central cornea increased by 15 ± 2 µm, 7 ± 2 µm, 15 ± 3 µm, and 31 ± 10 µm per year in the 4 surgery groups, respectively, compared to 5 ± 2 µm in surgery-naïve eyes (P = .001, .469, .001, <.001).

CONCLUSIONS

Better visual acuity can be achieved after PTK than PKP for treatment of RBCD. The annual thickening of subepithelial deposits may approximate an increase in central corneal thickness. The superficial distribution of subepithelial deposits makes it feasible to perform repeated PTK, even on the corneal allograft, for recurrent RBCD.

Mimicking TGFBI Hot-Spot Mutation Did Not Result in Any Deposit Formation in the Zebrafish Cornea

PURPOSE

Mutations in transforming growth factor beta-induced (TGFBI) protein are associated with a group of corneal dystrophies (CDs), classified as TGFBI-associated CDs, characterized by deposits in the cornea. Mouse models were not proper in several aspects for modelling human disease. The goal of this study was to generate zebrafish mutants to investigate the corneal phenotype and to decide whether zebrafish could be a potential model for TGFBI-associated CDs.

METHODS

The conserved arginine residue, codon 117, in zebrafish tgfbi gene was targeted with Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 method. Cas9 VQR variant was used with two target-specific sgRNAs to generate mutations. The presence of mutations was evaluated by T7 Endonuclease Enzyme (T7EI) assay and the type of the mutations were evaluated by Sanger sequencing. The mutant zebrafish at 3 months and 1 year of age were investigated under the microscope for corneal opacity and eye sections were evaluated histopathologically with hematoxylin-eosin, masson-trichrome and congo red stains for corneal deposits.

RESULTS

We achieved indel variation at the target sequence that resulted in p.Ser115_Arg117delinsLeu (c. 347_353delinsT) by nonhomology mediated repair in F1. This zebrafish mutation had the potential to mimic two disease-causing mutations reported in human cases previously: R124L and R124L + del125-126. Mutant zebrafish did not show any corneal opacity or corneal deposits at 3 months and 1 year of age.

CONCLUSION

This study generated the first zebrafish model mimicking the R124 hot spot mutation in TGFBI-associated CDs. However, evaluations even at 1 year of age did not reveal any deposits in the cornea histopathologically. This study increased the cautions for modelling TGFBI-associated CDs in zebrafish in addition to differences in the corneal structure between zebrafish and humans.

Endothelial Overexpression of TGF-β-Induced Protein Impairs Venous Thrombus Resolution: Possible Role in CTEPH

Endothelial cells play a critical role during venous thrombus remodeling, and unresolved, fibrotic thrombi with irregular vessels obstruct the pulmonary artery in patients with chronic thromboembolic pulmonary hypertension (CTEPH). This study sought to identify endothelial mediators of impaired venous thrombus resolution and to determine their role in the pathogenesis of the vascular obstructions in patients with CTEPH. Endothelial cells outgrown from pulmonary endarterectomy specimens (PEA) were processed for mRNA profiling, and nCounter gene expression and immunohistochemistry analysis of PEA tissue microarrays and immunoassays of plasma were used to validate the expression in CTEPH. Lentiviral overexpression in human pulmonary artery endothelial cells (HPAECs) and exogenous administration of the recombinant protein into C57BL/6J mice after inferior Vena cava ligation were employed to assess their role for venous thrombus resolution. RT2 PCR profiler analysis demonstrated the significant overexpression of factors downstream of transforming growth factor beta (TGFβ), that is TGFβ-Induced Protein (TGFBI or BIGH3) and transgelin (TAGLN), or involved in TGFβ signaling, that is follistatin-like 3 (FSTL3) and stanniocalcin-2 (STC2). Gene expression and immunohistochemistry analysis of tissue microarrays localized potential disease candidates to vessel-rich regions. Lentiviral overexpression of TGFBI in HPAECs increased fibrotic remodeling of human blood clots in vitro, and exogenous administration of recombinant TGFBI in mice delayed venous thrombus resolution. Significantly elevated plasma TGFBI levels were observed in patients with CTEPH and decreased after PEA. Our findings suggest that overexpression of TGFBI in endothelial promotes venous thrombus non-resolution and fibrosis and is causally involved in the pathophysiology of CTEPH.

Mini-Review: Clinical Features and Management of Granular Corneal Dystrophy Type 2

Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant corneal stromal dystrophy that is caused by p.Arg124His mutation of transforming growth factor β induced (TGFBI) gene. It is characterized by well demarcated granular shaped opacities in central anterior stroma and as the disease progresses, extrusion of the deposits results in ocular pain due to corneal epithelial erosion. Also, diffuse corneal haze which appears late, causes decrease in visual acuity. The prevalence of GCD2 is high in East Asia including Korea. Homozygous patients show a severe phenotype from an early age, and the heterozygote phenotype varies among patients, depending on several types of compound heterozygous TGFBI mutations. In the initial stage, conservative treatments such as artificial tears, antibiotic eye drops, and bandage contact lenses are used to treat corneal erosion. Different surgical methods are used depending on the depth and extent of the stromal deposits. Phototherapeutic keratectomy removes anterior opacities and is advantageous in terms of its applicability and repeatability. For deeper lesions, deep anterior lamellar keratoplasty can be used as the endothelial layer is not always affected. Recurrence following these treatments are reported within a wide range of rates in different studies due to varying definition of recurrence and follow-up period. In patients who have undergone corneal laser vision-correction surgeries such as photorefractive keratectomy, LASEK, or LASIK including SMILE surgery, corneal opacity exacerbates rapidly with severe deterioration of visual acuity. Further investigations on new treatments of GCD2 are necessary.

Genome editing in the treatment of ocular diseases

Genome-editing technologies have ushered in a new era in gene therapy, providing novel therapeutic strategies for a wide range of diseases, including both genetic and nongenetic ocular diseases. These technologies offer new hope for patients suffering from previously untreatable conditions. The unique anatomical and physiological features of the eye, including its immune-privileged status, size, and compartmentalized structure, provide an optimal environment for the application of these cutting-edge technologies. Moreover, the development of various delivery methods has facilitated the efficient and targeted administration of genome engineering tools designed to correct specific ocular tissues. Additionally, advancements in noninvasive ocular imaging techniques and electroretinography have enabled real-time monitoring of therapeutic efficacy and safety. Herein, we discuss the discovery and development of genome-editing technologies, their application to ocular diseases from the anterior segment to the posterior segment, current limitations encountered in translating these technologies into clinical practice, and ongoing research endeavors aimed at overcoming these challenges.

Release of frustration drives corneal amyloid disaggregation by brain chaperone

TGFBI-related corneal dystrophy (CD) is characterized by the accumulation of insoluble protein deposits in the corneal tissues, eventually leading to progressive corneal opacity. Here we show that ATP-independent amyloid-β chaperone L-PGDS can effectively disaggregate corneal amyloids in surgically excised human cornea of TGFBI-CD patients and release trapped amyloid hallmark proteins. Since the mechanism of amyloid disassembly by ATP-independent chaperones is unknown, we reconstructed atomic models of the amyloids self-assembled from TGFBIp-derived peptides and their complex with L-PGDS using cryo-EM and NMR. We show that L-PGDS specifically recognizes structurally frustrated regions in the amyloids and releases those frustrations. The released free energy increases the chaperone's binding affinity to amyloids, resulting in local restructuring and breakage of amyloids to protofibrils. Our mechanistic model provides insights into the alternative source of energy utilized by ATP-independent disaggregases and highlights the possibility of using these chaperones as treatment strategies for different types of amyloid-related diseases.

Management of Stromal Corneal Dystrophies; Review of the Literature with a Focus on Phototherapeutic Keratectomy and Keratoplasty

Corneal dystrophies are a group of non-inflammatory inherited disorders of the cornea. This review considers treatment options for epithelial-stromal and stromal corneal dystrophies: namely Reis–Bücklers, Thiel–Behnke, lattice, Avellino, granular, macular and Schnyder corneal dystrophies. Where there is visual reduction, treatment options may include either phototherapeutic keratectomy (PTK) or corneal transplantation. Due to the anterior location of the deposits in Reis-Bücklers and Thiel–Behnke dystrophies, PTK is considered the treatment of choice. For lattice, Avellino, granular and macular corneal dystrophies, PTK provides temporary visual improvement; however, with recurrences, repeat PTK or a corneal transplant would be needed. For Schnyder dystrophy, should treatment be required, PTK may be the preferred option due to the potential for recurrence of the disease in corneal transplantation. This review discusses the literature and evidence base for the treatment of corneal dystrophies in terms of visual outcomes and recurrence rate.

Variant Landscape of 15 Genes Involved in Corneal Dystrophies: Report of 30 Families and Comprehensive Analysis of the Literature

Corneal dystrophies (CDs) represent a group of inherited diseases characterized by the progressive deposit of abnormal materials in the cornea. This study aimed to describe the variant landscape of 15 genes responsible for CDs based on a cohort of Chinese families and a comparative analysis of literature reports. Families with CDs were recruited from our eye clinic. Their genomic DNA was analyzed using exome sequencing. The detected variants were filtered using multi-step bioinformatics and confirmed using Sanger sequencing. Previously reported variants in the literature were summarized and evaluated based on the gnomAD database and in-house exome data. In 30 of 37 families with CDs, 17 pathogenic or likely pathogenic variants were detected in 4 of the 15 genes, including TGFBI, CHST6, SLC4A11, and ZEB1. A comparative analysis of large datasets revealed that 12 of the 586 reported variants are unlikely causative of CDs in monogenic mode, accounting for 61 of 2933 families in the literature. Of the 15 genes, the gene most frequently implicated in CDs was TGFBI (1823/2902, 62.82% of families), followed by CHST6 (483/2902, 16.64%) and SLC4A11 (201/2902, 6.93%). This study presents, for the first time, the landscape of pathogenic and likely pathogenic variants in the 15 genes responsible for CDs. Awareness of frequently misinterpreted variants, such as c.1501C>A, p.(Pro501Thr) in TGFBI, is crucial in the era of genomic medicine.

Assessment of the corneal biomechanical features of granular corneal dystrophy type 2 using dynamic ultra-high-speed Scheimpflug imaging

PURPOSE

To evaluate the corneal biomechanical features of eyes with granular corneal dystrophy type 2 (GCD2) by analyzing corneal biomechanical indices obtained using a Corvis ST (CST) dynamic ultra-high-speed Scheimpflug imaging device.

METHODS

In this retrospective case-control study, 35 CST parameters were compared in normal eyes (control) and eyes of patients with GCD2 treated at Osaka University Hospital, Osaka, Japan. The parameters included the Corvis Biomechanical Index (CBI), which is important in differentiating eyes with keratoconus from normal eyes. We measured the deposition rates of lesions in the central 7-mm region of the eye and assessed the correlation between the deposition rate and the CBI.

RESULTS

Twenty-one eyes with GCD2 and 23 control eyes were analyzed. Eyes with GCD2 showed significantly less corneal stiffness in 15 CST parameters than did control eyes. In particular, the CBI was remarkably higher in eyes with GCD2 than in control eyes (P = 0.000006). Additionally, the deposition rate and the CBI were positively correlated.

CONCLUSIONS

GCD2 eyes had softer corneas than did control eyes in most biomechanical CST parameters, and one of the parameters (the CBI) was linked to the rate of deposited lesions. Since IOP may be underestimated in GCD2 eyes, management should be especially careful in GCD2 cases complicated by glaucoma.

Reduced OPA1, Mitochondrial Fragmentation and Increased Susceptibility to Apoptosis in Granular Corneal Dystrophy Type 2 Corneal Fibroblasts

The progressive degeneration of granular corneal dystrophy type 2 (GCD2) corneal fibroblasts is associated with altered mitochondrial function, but the underlying mechanisms are incompletely understood. We investigated whether an imbalance of mitochondrial dynamics contributes to mitochondrial dysfunction of GCD2 corneal fibroblasts. Transmission electron microscopy revealed several small, structurally abnormal mitochondria with altered cristae morphology in GCD2 corneal fibroblasts. Confocal microscopy showed enhanced mitochondrial fission and fragmented mitochondrial tubular networks. Western blotting revealed higher levels of MFN1, MFN2, and pDRP1 and decreased levels of OPA1 and FIS1 in GCD2. OPA1 reduction by short hairpin RNA (shRNA) resulted in fragmented mitochondrial tubular networks and increased susceptibility to mitochondrial stress-induced apoptosis. A decrease in the mitochondrial biogenesis-related transcription factors NRF1 and PGC1α was observed, while there was an increase in the mitochondrial membrane proteins TOM20 and TIM23. Additionally, reduced levels of mitochondrial DNA (mtDNA) were exhibited in GCD2 corneal fibroblasts. These observations suggest that altered mitochondrial fission/fusion and biogenesis are the critical molecular mechanisms that cause mitochondrial dysfunction contributing to the degeneration of GCD2 corneal fibroblasts.

A new electrochemical method that mimics phosphorylation of the core tau peptide K18 enables kinetic and structural analysis of intermediates and assembly

Tau protein's reversible assembly and binding of microtubules in brain neurons are regulated by charge-neutralizing phosphorylation, while its hyperphosphorylation drives the irreversible formation of cytotoxic filaments associated with neurodegenerative diseases. However, the structural changes that facilitate these diverse functions are unclear. Here, we analyzed K18, a core peptide of tau, using newly developed spectroelectrochemical instrumentation that enables electroreduction as a surrogate for charge neutralization by phosphorylation, with simultaneous, real-time quantitative analyses of the resulting conformational transitions and assembly. We observed a tipping point between behaviors that paralleled the transition between tau's physiologically required, reversible folding and assembly and the irreversibility of assemblies. The resulting rapidly electroassembled structures represent the first fibrillar tangles of K18 that have been formed in vitro at room temperature without using heparin or other charge-complementary anionic partners. These methods make it possible to (i) trigger and analyze in real time the early stages of conformational transitions and assembly without the need for preformed seeds, heterogenous coacervation, or crowding; (ii) kinetically resolve and potentially isolate never-before-seen early intermediates in these processes; and (iii) develop assays for additional factors and mechanisms that can direct the trajectory of assembly from physiologically benign and reversible to potentially pathological and irreversible structures. We anticipate wide applicability of these methods to other amyloidogenic systems and beyond.

Clinical and Histopathologic Characteristics and Template of the TGFBI p.(His626Arg) Missense Variant Lattice Corneal Dystrophy

PURPOSE

The aim of this study was to define, following the IC3D template format, the clinical and histopathologic phenotype of the p.(His626Arg) missense variant lattice corneal dystrophy (LCDV-H626R), the most common variant lattice dystrophy, and to record long-term outcome of corneal transplantation in this dystrophy.

METHODS

A database search and a meta-analysis of published data on LCDV-H626R were conducted. A patient diagnosed with LCDV-H626R who underwent bilateral lamellar keratoplasty followed by rekeratoplasty of 1 eye is described, including histopathologic examination of the 3 keratoplasty specimens.

RESULTS

One hundred forty-five patients from at least 61 families and 11 countries diagnosed with LCDV-H626R were found. This dystrophy is characterized by recurrent erosions, asymmetric progression, and thick lattice lines that extend to corneal periphery. The median age is 37 (range, 25-59) years at the onset of symptoms, 45 (range, 26-62) years at the time of diagnosis, and 50 (range, 41-78) years at the time of the first keratoplasty, suggesting a median interval from the first symptoms to diagnosis and to keratoplasty of 7 and 12 years, respectively. Clinically unaffected carriers have been of age 6 to 45 years. Central anterior stromal haze and centrally thick, peripherally thinner branching lattice lines in the anterior to midstroma of the cornea were noted preoperatively. Histopathology of the host anterior corneal lamella showed a subepithelial fibrous pannus, a destroyed Bowman layer, and amyloid deposits extending to the deep stroma. In the rekeratoplasty specimen, amyloid localized to scarring along the Bowman membrane and to the margins of the graft.

CONCLUSIONS

The IC3D-type template for LCDV-H626R should help diagnose and manage variant carriers. The histopathologic spectrum of findings is broader and more nuanced than what has been reported.

A case of lattice corneal dystrophy type 1 with bilateral Mooren's ulcer

Purpose

To report a rare case of lattice corneal dystrophy type 1 (LCD1) with bilateral Mooren's ulcer.

Observations

This case involved a 62-year-old male patient with LCD1 who presented with the primary complaint of experiencing pain and photophobia in both eyes for 2 months prior to his initial visit. Upon examination, a peripheral corneal ulcer was observed in both eyes covering more than 3 of the 4 quadrants, accompanied with ciliary injection and severe corneal infiltration. He was diagnosed with Mooren's ulcer, and treatment with 0.1% betamethasone and 0.5% levofloxacin eye drops and systemic cyclosporine and betamethasone was initiated. At 1-month post treatment initiation, a remaining ulceration ridge was observed on the corneal surface in his left eye, which was subsequently resected. Complete epithelialization was achieved at 1-month postoperative in the left eye and after 6-months of conservative topical treatment in the right eye. At 8-9 years post onset of Mooren's ulcer, the patient underwent penetrating keratoplasty in both eyes while undergoing treatment with oral cyclosporine administration for severe corneal opacity due to progression of lattice dystrophy. Post treatment, there has been no recurrence of ulcerations, even though more that 10 years has passed since the onset of Mooren's ulcer.

Conclusions and importance

To the best of our knowledge, this is the first reported case of LCD1 with bilateral Mooren's ulcer, and in this rare case, the patient was successfully treated with a combination of steroid, cyclosporine, and peripheral superficial keratectomy, and a good visual outcome was achieved after penetrating keratoplasty (PK) under the use of systemic cyclosporine.

Phenotypes of Granular Corneal Dystrophy Type 2 among Koreans in Their Twenties

Purpose: Granular corneal dystrophy type 2 (GCD2) is a hereditary disease that features granular and lattice stromal deposits in the cornea. There are homozygotes and heterozygotes and the opacities are exacerbated by corneal trauma or surgery, such as laser in situ keratomileusis (LASIK). As there is individual variability in GCD2 phenotypes, we investigated various corneal features of GCD2 patients in their twenties, the main age group for refractive surgery.Methods: From genetically confirmed GCD2 patients who had an R124H mutation of the transforming growth factor β induced (<i>TGFBI</i>) gene at age 20 to 29 years, we chose representative patients: one homozygote; one compound heterozygote; one simple heterozygote with a severe phenotype with many granular deposits; one common heterozygote; and four heterozygotes with normal corneas. The corneas of all patients were subject to slit-lamp examination and photographed.Results: The homozygote had confluent granular deposits covering the cornea. The compound heterozygote had granular and lattice deposits covering the center of the cornea. The patient with a severe phenotype had more than 30 granular deposits in one eye, but was a simple GCD2 heterozygote, verified by full-sequencing of the <i>TGFBI</i> gene. In the four patients with normal corneas, a single small lesion was subsequently detected during follow-up in two, at 3 weeks and 6 months, respectively. Both corneas were judged clear at chance examinations.Conclusions: Among Koreans in their twenties, GCD2 patients have various phenotypes, from clear corneas to severe confluent opacities. There are GCD2 heterozygotes with nearly clear corneas, so caution must be taken when choosing patients for refractive surgery.

Targeting of Scavenger Receptors Stabilin-1 and Stabilin-2 Ameliorates Atherosclerosis by a Plasma Proteome Switch Mediating Monocyte/Macrophage Suppression

BACKGROUND

Scavenger receptors Stabilin-1 (Stab1) and Stabilin-2 (Stab2) are preferentially expressed by liver sinusoidal endothelial cells. They mediate the clearance of circulating plasma molecules controlling distant organ homeostasis. Studies suggest that Stab1 and Stab2 may affect atherosclerosis. Although subsets of tissue macrophages also express Stab1, hematopoietic Stab1 deficiency does not modulate atherogenesis. Here, we comprehensively studied how targeting Stab1 and Stab2 affects atherosclerosis.

METHODS

ApoE-KO mice were interbred with Stab1-KO and Stab2-KO mice and fed a Western diet. For antibody targeting, Ldlr-KO mice were also used. Unbiased plasma proteomics were performed and independently confirmed. Ligand binding studies comprised glutathione-S-transferase-pulldown and endocytosis assays. Plasma proteome effects on monocytes were studied by single-cell RNA sequencing in vivo, and by gene expression analyses of Stabilin ligand-stimulated and plasma-stimulated bone marrow-derived monocytes/macrophages in vitro.

RESULTS

Spontaneous and Western diet-associated atherogenesis was significantly reduced in ApoE-Stab1-KO and ApoE-Stab2-KO mice. Similarly, inhibition of Stab1 or Stab2 by monoclonal antibodies significantly reduced Western diet-associated atherosclerosis in ApoE-KO and Ldlr-KO mice. Although neither plasma lipid levels nor circulating immune cell numbers were decisively altered, plasma proteomics revealed a switch in the plasma proteome, consisting of 231 dysregulated proteins comparing wildtype with Stab1/2-single and Stab1/2-double KO, and of 41 proteins comparing ApoE-, ApoE-Stab1-, and ApoE-Stab2-KO. Among this broad spectrum of common, but also disparate scavenger receptor ligand candidates, periostin, reelin, and TGFBi (transforming growth factor, β-induced), known to modulate atherosclerosis, were independently confirmed as novel circulating ligands of Stab1/2. Single-cell RNA sequencing of circulating myeloid cells of ApoE-, ApoE-Stab1-, and ApoE-Stab2-KO mice showed transcriptomic alterations in patrolling (Ccr2^-/Cx3cr1⁺⁺/Ly6C^lo) and inflammatory (Ccr2⁺/Cx3cr1⁺/Ly6C^hi) monocytes, including downregulation of proatherogenic transcription factor Egr1. In wildtype bone marrow-derived monocytes/macrophages, ligand exposure alone did not alter Egr1 expression in vitro. However, exposure to plasma from ApoE-Stab1-KO and ApoE-Stab2-KO mice showed a reverted proatherogenic macrophage activation compared with ApoE-KO plasma, including downregulation of Egr1 in vitro.

CONCLUSIONS

Inhibition of Stab1/Stab2 mediates an anti-inflammatory switch in the plasma proteome, including direct Stabilin ligands. The altered plasma proteome suppresses both patrolling and inflammatory monocytes and, thus, systemically protects against atherogenesis. Altogether, anti-Stab1- and anti-Stab2-targeted therapies provide a novel approach for the future treatment of atherosclerosis.

Periostin: biology and function in cancer

Periostin (POSTN), a member of the matricellular protein family, is a secreted adhesion-related protein produced in the periosteum and periodontal ligaments. Matricellular proteins are a nonstructural family of extracellular matrix (ECM) proteins that regulate a wide range of biological processes in both normal and pathological conditions. Recent studies have demonstrated the key roles of these ECM proteins in the tumor microenvironment. Furthermore, periostin is an essential regulator of bone and tooth formation and maintenance, as well as cardiac development. Also, periostin interacts with multiple cell-surface receptors, especially integrins, and triggers signals that promote tumor growth. According to recent studies, these signals are implicated in cancer cell survival, epithelial-mesenchymal transition (EMT), invasion, and metastasis. In this review, we will summarize the most current data regarding periostin, its structure and isoforms, expressions, functions, and regulation in normal and cancerous tissues. Emphasis is placed on its association with cancer progression, and also future potential for periostin-targeted therapeutic approaches will be explored.

Identification of genetic variants in five chinese families with keratoconus: Pathogenicity analysis and characteristics of parental corneal topography

Purpose: The study aims to identify genetic variants in five Chinese families with Keratoconus (KC) and describe the characteristics of parental corneal topography.

Methods: Fifteen participants, including five probands and ten parents from five Chinese families with KC, were recruited for genetic and clinical analyses. Targeted next-generation sequencing using a custom-designed panel for KC was applied on the probands for variant identification. Sanger sequencing and cosegregation analysis of the suspected pathogenic variants were performed on the family members. The pathogenicities of variants were evaluated according to the American College of Medical Genetics and Genomics guidelines (ACMG). Pentacam 3D anterior segment analysis system was applied for keratectasia detection and the Corvis ST for corneal biomechanics measurement. Fifteen parameters were recorded, including nine keratectasia indicators (BAD-D, TP, Kmax, Df, Db, Dp, Dt, Da, ARTH), six corneal biomechanical indicators (CBI, DA ratio, SP-A1, IR, bIOP, TBI).

Results: A total of six novel variants, including five missense variants and one frameshift variant, were detected in the HMX1, SLC4A11, TGFBI, PIKFYVE, and ZEB1 genes in five probands, all of which showed co-segregation of genotype and clinical phenotype and were determined to be pathogenic. The genetic model was autosomal dominant (AD) in four families and autosomal recessive (AR) in 1 family. The analysis of keratectasia and corneal biomechanical indicators of the proband’s parents (first-generation relatives) in AD families revealed that there were several abnormal indexes in BAD-D, TP, Kmax, Df, Db, Dp, Dt, Da, CBI, DA ratio, SP-A1, IR, bIOP and TBI test indexes, showing clinical characteristics of incipient KC.

Conclusion: Our study shows that variants in HMX1, SLC4A11, TGFBI, PIKFYVE, and ZEB1 were associated with KC. Our study extends the gene spectrum associated with KC, provides novel insights into KC phenotypic assessments, and contributes to early diagnosis for these patients.

TMAO to the rescue of pathogenic protein variants

Trimethylamine N-oxide (TMAO) is a chemical chaperone found in various organisms including humans. Various studies unveiled that it is an excellent protein-stabilizing agent, and induces folding of unstructured proteins. It is also well established that it can counteract the deleterious effects of urea, salt, and hydrostatic pressure on macromolecular integrity. There is also existence of large body of data regarding its ability to restore functional deficiency of various mutant proteins or pathogenic variants by correcting misfolding defects and inhibiting the formation of high-order toxic protein oligomers. Since an important class of human disease called "protein conformational disorders" is due to protein misfolding and/or formation of high-order oligomers, TMAO stands as a promising molecule for the therapeutic intervention of such diseases. The present review has been designed to gather a comprehensive knowledge of the TMAO's effect on the functional restoration of various mutants, identify its shortcomings and explore its potentiality as a lead molecule. Future prospects have also been suitably incorporated.

Superficial Keratectomy: A Review of Literature

Superficial keratectomy (SK) is the manual dissection of the superficial corneal layers (epithelium, Bowman's layer, and sometimes superficial stroma). SK is done using a surgical blade or diamond burr. Some surgeons use intraoperative mitomycin C 0.02% or amniotic membrane transplantation to improve surgical outcomes. This literature review shows that SK remains an effective method for different indications, including tissue diagnosis, excision of corneal degenerations, dystrophies, scarring, recurrent corneal erosions, and retained corneal foreign body.

Mutation analysis of the TGFBI gene in pedigrees of lattice corneal dystrophy in Eastern China

BACKGROUND

To delineate the mutations of the TGFBI gene in Eastern China by whole-exome sequencing (WES) in eight Chinese families with lattice corneal dystrophy (LCD).

MATERIALS AND METHODS

This retrospective study included eight families with LCD from Eastern China. Clinical features were examined using slit-lamp examination, anterior segment optical coherence tomography, and in vivo confocal microscopy. Peripheral blood samples of probands were collected for WES, and saliva samples from family members were collected for TGFBI screening using Sanger sequencing. The physicochemical effects of mutations were investigated using bioinformatics tools.

RESULTS

Family 1 presented a classic LCD I with a p.R124C mutation of the TGFBI gene, while the other seven families were diagnosed with LCD IIIA. Six of the seven LCD IIIA families had heterozygous single-gene mutations (p.A546D, p.L565 H, p.T621P), and one had a compound heterozygous (cis) mutation (p.P501T and p.N622 H). The mutation of p.L565 H was the first time of integrated family report in contrast to the cases reported in 2019, and the p.T621P mutation was first reported in a Chinese population. Notably, the family with the compound mutation was associated with an obvious early-onset (in the 2nd decade of life) compared to the LCD IIIA patients with each single mutation (p.P501T or p.N622 H) showing late-onset (in the 7th decade of life).

CONCLUSIONS

WES is efficient for the genomic testing of LCD and genetic relationship identification in different families with the same mutated gene. We identified a compound heterozygous mutation (p.P501T and p.N622 H) and two mutations (p.T621P and p.L565 H) uncommon in China.

Genetic screening of TGFBI in Iranian patients with TGFBI-associated corneal dystrophies and a meta-analysis of global variation frequencies

PURPOSE

Transforming growth factor beta-induced (TGFBI)-associated corneal dystrophies (CDs) are a clinically heterogeneous group of CDs caused by mutations in the TGFBI gene. Nucleotide sequences encoding two arginine residues at positions 124 and 555 in TGFBI protein are mutation hotspots. We screened regions of TGFBI that include the hotspots in a cohort of Iranian patients with TGFBI-associated CDs. We also performed a meta-analysis for frequencies of all reported TGFBI mutations.

METHODS

Twenty-four TGFBI-associated CD-diagnosed patients were recruited. Exons 4 and 12 of TGFBI were amplified by the polymerase chain reaction and sequenced by Sanger protocol. A meta-analysis on reported TGFBI sequence data was done by reviewing all published relevant articles available in NCBI.

RESULTS

Twenty-two out of 24 patients had mutations in exons 4 or 12 of TGFBI. The most frequent mutations were p.Arg124Cys, p.Arg124His, and p.Arg555Trp; each of these was found in six families. Three other missense mutations including p.Arg555Gln, p.Ile522Asn, and p.Ala546Thr were also identified. The data suggested a fairly tight genotype/phenotype correlation for the most common CDs. Literature review evidenced that the reported mutations affected less than 30% of the amino acids of the TGFBI protein and that p.Arg124His, p.Arg124Cys, p.Arg555Trp, p.Arg124Leu, p.Arg555Gln, and p.His626Arg were the most frequent mutations.

CONCLUSION

TGFBI mutation profile of Iranian patients is very similar to that of the rest of the world. The meta-analysis confirmed the worldwide prevalence of p.Arg124 and p.Arg555, showed that p.His626Arg is also relatively frequent, and evidenced the value of screening exons 4 and 12 of TGFBI.

Torin 1 alleviates impairment of TFEB-mediated lysosomal biogenesis and autophagy in TGFBI (p.G623_H626del)-linked Thiel-Behnke corneal dystrophy

Thiel-Behnke corneal dystrophy (TBCD) is an epithelial-stromal TGFBI dystrophy caused by mutations in the TGFBI (transforming growth factor beta induced) gene, though the underlying mechanisms and pathogenesis of TBCD are still obscure. The study identifies a novel mutation in the TGFBI gene (p.Gly623_His626del) in a TBCD pedigree. Characteristics of the typical vacuole formation, irregular corneal epithelial thickening and thinning, deposition of eosinophilic substances beneath the epithelium, and involvement of the anterior stroma were observed in this pedigree via transmission electron microscopy (TEM) and histological staining. Tgfbi-p.Gly623_Tyr626del mouse models of TBCD were subsequently generated via CRISPR/Cas9 technology, and the above characteristics were further verified via TEM and histological staining. Lysosomal dysfunction and downregulation of differential expression protein CTSD (cathepsin D) were observed using LysoTracker Green DND-26 and proteomic analysis, respectively. Hence, lysosomal dysfunction probably leads to autophagic flux obstruction in TBCD; this was supported by enhanced LC3-II and SQSTM1 levels and decreased CTSD. TFEB (transcription factor EB) was prominently decreased in TBCD corneal fibroblasts and administration of ATP-competitive MTOR inhibitor torin 1 reversed this decline, resulting in the degradation of accumulated mut-TGFBI (mutant TGFBI protein) via the ameliorative lysosomal function and autophagic flux owing to elevated TFEB activity as measured by western blot, confocal microscopy, and flow cytometry. Transfected HEK 293 cells overexpressing human full-length WT-TGFBI and mut-TGFBI were generated to further verify the results obtained in human corneal fibroblasts. Amelioration of lysosome dysfunction may therefore have therapeutic efficacy in the treatment of TBCD.Abbreviations AS-OCT: anterior segment optical coherence tomography; ATP: adenosine triphosphate; Cas9: CRISPR-associated protein 9; CLEAR: coordinated lysosomal expression and regulation; CRISPR: clustered regularly interspaced short palindromic repeats; CTSB: cathepsin B; CTSD: cathepsin D; CTSF: cathepsin F; CTSL: cathepsin L; DNA: deoxyribonucleic acid; ECM: extracellular matrix; Fas1: fasciclin 1; FC: flow cytometry; GAPDH: glyceraldeyde-3-phosphate dehydrogenase; GCD2: granular corneal dystrophy type 2; HE: hematoxylin and eosin; LAMP2: lysosomal-associated membrane protein; MT: mutation type; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; mut-TGFBI: mutant TGFBI protein; SD: standard deviation; TBCD: Thiel-Behnke corneal dystrophy; TEM: transmission electron microscopy; TFEB: transcription factor EB; TGFBI: transforming growth factor beta induced; WT: wild type.

Mutation effects on FAS1 domain 4 based on structure and solubility

Mutations in the fasciclin 1 domain 4 (FAS1-4) of transforming growth factor β-induced protein (TGFBIp) are associated with insoluble extracellular deposits and corneal dystrophies (CDs). The decrease in solubility upon mutation has been implicated in CD; however, the exact molecular mechanisms are not well understood. Here, we performed molecular dynamics simulations followed by solvation thermodynamic analyses of the FAS1-4 domain and its three mutants-R555W, R555Q, and A546T-linked to granular corneal dystrophy type 1, Thiel-Behnke corneal dystrophy and lattice corneal dystrophy, respectively. We found that both R555W and R555Q mutants have less affinity toward solvent water relative to the wild-type protein. In the R555W mutant, a remarkable increase in solvation free energy was observed because of the structural changes near the mutation site. The mutation site W555 is buried in other hydrophobic residues, and R557 simultaneously forms salt bridges with E554 and D561. In the R555Q mutant, the increase in solvation free energy is caused by structural rearrangements far from the mutation site. R558 separately forms salt bridges with D575, E576, and E598. Thus, we thus identified the relationship between the decrease in solubility and conformational changes caused by mutations, which may be useful in designing potential therapeutics and in blocking FAS1 aggregation related to CD.

An Arg124Cys mutation in transforming growth factor β-induced gene associated with lattice corneal dystrophy type I in a Chinese pedigree

Purpose:

To identify a clinical and genetic form of a large Chinese family with an autosomal-dominant lattice corneal dystrophy type I (LCD I).

Methods:

The patients’ eyes were examined on the basis of slit-lamp microscopy, and other clinical records were also collected. Genomic DNA was extracted from peripheral leukocytes of the affected patients and their unaffected family members. Each previous reported mutation of the transforming growth factor β-induced gene (TGFBI) gene was amplified by touch-down polymerase chain reaction and directly sequenced to verify the disease-causing mutation.

Results:

Typical clinical features of LCD I were found by slit-lamp photography in these affected Chinese pedigrees. A heterozygous single base-pair transition from C to T (c.418 C > T), leading to amino acid substitution Arg124Cys (R124C) in the encoded TGFBI protein, was detected in all of the eighteen affected patients. The same mutation was not found in unaffected family members.

Conclusion:

The R124C mutation hot spot, which was relatively rare in China, was responsible for LCD I in the large family. Molecular genetic analysis of TGFBI gene can offer an accurate diagnosis of patients with lattice corneal dystrophies in the clinical treatment.

The role of the extracellular matrix protein TGFBI in cancer

The secreted extracellular protein, transforming growth factor beta induced (TGFBI or βIGH3), has roles in regulating numerous biological functions, including cell adhesion and bone formation, both during embryonic development and during the pathogenesis of human disease. TGFBI has been most studied in the context of hereditary corneal dystrophies, where mutations in TGFBI result in accumulation of TGFBI in the cornea. In cancer, early studies focused on TGFBI as a tumor suppressor, in part by promoting chemotherapy sensitivity. However, in established tumors, TGFBI largely has a role in promoting tumor progression, with elevated levels correlating to poorer clinical outcomes. As an important regulator of cancer progression, TGFBI expression and function is tightly regulated by numerous mechanisms including epigenetic silencing through promoter methylation and microRNAs. Mechanisms to target TGFBI have potential clinical utility in treating advanced cancers, while assessing TGFBI levels could be a biomarker for chemotherapy resistance and tumor progression.

Evaluation of the Genetic Variation Spectrum Related to Corneal Dystrophy in a Large Cohort

AIMS

To characterize the genetic landscape and mutation spectrum of patients with corneal dystrophies (CDs) in a large Han ethnic Chinese Cohort with inherited eye diseases (IEDs).

METHODS

Retrospective study. A large IED cohort was recruited in this study, including 69 clinically diagnosed CD patients, as well as other types of eye diseases patients and healthy family members as controls. The 792 genes on the Target_Eye_792_V2 chip were used to screen all common IEDs in our studies, including 22 CD-related genes.

RESULTS

We identified 2334 distinct high-quality variants on 22 CD-related genes in a large IEDs cohort. A total of 21 distinct pathogenic or likely pathogenic mutations were identified, and the remaining 2313 variants in our IED cohort had no evidence of CD-related pathogenicity. Overall, 81.16% (n = 56/69) of CD patients received definite molecular diagnoses, and transforming growth factor-beta-induced protein (TGFBI), CHTS6, and SLC4A11 genes covered 91.07, 7.14, and 1.79% of the diagnosed cases, respectively. Twelve distinct disease-associated mutations in the TGFBI gene were identified, 11 of which were previously reported and one is novel. Four of these TGFBI mutations (p.D123H, p.M502V, p.P501T, and p.P501A) were redefined as likely benign in our Han ethnic Chinese IED cohort after performing clinical variant interpretation. These four TGFBI mutations were detected in asymptomatic individuals but not in CD patients, especially the previously reported disease-causing mutation p.P501T. Among 56 CD patients with positive detected mutations, the recurrent TGFBI mutations were p.R124H, p.R555W, p.R124C, p.R555Q, and p.R124L, and the proportions were 32.14, 19.64, 14.29, 10.71, and 3.57%, respectively. Twelve distinct pathogenic or likely pathogenic mutations of CHTS6 were detected in 28 individuals. The recurrent mutations were p.Y358H, p.R140X, and p.R205W, and the proportions were 25.00, 21.43, and 14.29%, respectively. All individuals associated with TGFBI were missense mutations; 74.19% associated with CHTS6 mutations were missense mutations, and 25.81% were non-sense mutations. Hot regions were located in exons 4 and 12 of TGFBI individuals and located in exon 3 of CHTS6 individuals. No de novo mutations were identified.

CONCLUSION

For the first time, our large cohort study systematically described the variation spectrum of 22 CD-related genes and evaluated the frequency and pathogenicity of all 2334 distinct high-quality variants in our IED cohort. Our research will provide East Asia and other populations with baseline data from a Han ethnic population-specific level.

Genotypic Homogeneity in Distinctive Transforming Growth Factor-Beta Induced (TGFBI) Protein Phenotypes

Background: To evaluate the distribution of the transforming growth factor-beta induced (TGFBI) corneal dystrophies in a multi-ethnic population in Singapore, and to present the different phenotypes with the same genotype. Methods: This study included 32 patients. Slit lamp biomicroscopy was performed for each patient to determine the disease phenotype. Genomic DNA was extracted from the blood samples and the 17 exons of the TGFBI gene were amplified by PCR and sequenced bi-directionally for genotype analysis. Results: Regarding phenotypes, the study patients comprised 11 (34.4%; 8 with R555W and 3 with R124H mutation) patients with granular corneal dystrophy type 1 (GCD1), 6 (18.8%; 5 with R124H and 1 with R124C mutation) patients with GCD2, 13 (40.6%; 7 with R124C, 2 with H626R, 2 with L550P, 1 with A620D and 1 with H572R) patients with lattice corneal dystrophy (LCD) and 2 (6.3%; 1 with R124L and 1 with R124C) patients with Reis–Bückler corneal dystrophy. Regarding genotype, R124H mutation was associated with GCD2 (5 cases; 62.5%) and GCD1 (3 cases; 37.5%). R124C mutation was associated with LCD (7 cases; 87.5%) and GCD2 (1 case; 12.5%). All the 8 cases (100%) of R555W mutation were associated with GCD1. Conclusions: Although the association between genotype and phenotype was good in most cases (65.7%; 21 of 32 patients), genotype/phenotype discrepancy was observed in a significant number.

A recognition survey of granular corneal dystrophy type 2 genetic detection in China

AIM

To evaluate the feasibility of promoting genetic detection for granular corneal dystrophy type 2 (GCD₂) by a questionnaire conducted among citizens in five cities in China.

METHODS

The data were collected by questionnaire, and analyzed by Chi-square test and one-tailed t test in IBM SPSS statistics.

RESULTS

Based on the survey data on the awareness of GCD₂ genetic detection in this study and the positive predictive analysis report of the citizens in five cities in China, the vast majority (84.2%) of respondents had never heard of it and did not know that GCD₂ patients have been prohibited from performing excimer surgery that can deteriorate GCD₂ patients' condition even leading to blindness. Though 3.4% of patients understood GCD₂ very much, they have no idea that GCD₂ could not be 100% accuracy diagnosed by the conventional inspection methods.

CONCLUSION

It is feasible and necessary to use GCD₂ genetic detection as an excimer preoperative examination project. In order to promote the development of detection project, a few improvements should be carried out in terms of the promoting efforts, costs, and research progress.

Molecular diagnosis based on comprehensive genetic testing in 800 Chinese families with non-syndromic inherited retinal dystrophies

IMPORTANCE

Inherited retinal dystrophies (IRDs) are a group of monogenic diseases, one of the leading causes of blindness.

BACKGROUND

Introducing a comprehensive genetic testing strategy by combining single gene Sanger sequencing, next-generation sequencing (NGS) including whole exome sequencing (WES), and a specific hereditary eye disease enrichment panel (HEDEP) sequencing, to identify the disease-causing variants of 800 Chinese probands affected with non-syndromic IRDs.

DESIGN

Retrospective analysis.

PARTICIPANTS

Eight hundred Chinese non-syndromic IRDs probands and their families.

METHODS

A total of 149 patients were subjected to Sanger sequencing. Of the 651 patients subjected to NGS, 86 patients underwent WES and 565 underwent HEDEP. Patients that likely carried copy number variations (CNVs) detected by HEDEP were further validated by multiplex ligation-dependent probe amplification (MLPA) or quantitative fluorescence PCR (QF-PCR).

MAIN OUTCOME MEASURES

The diagnostic rate.

RESULTS

(Likely) pathogenic variants were determined in 481 cases (60.13% detection rate). The detection rates of single gene Sanger sequencing, WES and HEDEP were 86.58%, 31.40% and 56.99%, respectively. Approximately 11.64% of 481 cases carried autosomal dominant variants, 72.97% carried AR variants and 15.39% were found to be X-linked. CNVs were confirmed by MLPA or QF-PCR in 17 families. Fourteen genes that each caused disease in 1% or more of the cohort were detected, and these genes were collectively responsible for disease in almost one half (46.38%) of the families.

CONCLUSIONS AND RELEVANCE

Sanger sequencing is ideal to detect pathogenic variants of clinical homogeneous diseases, whereas NGS is more appropriate for patients without an explicit clinical diagnosis.

Clinical Evaluation of Electrolysis for Reis-Bücklers Corneal Dystrophies and In Vivo Histological Analysis Using Anterior Segment Optical Coherence Tomography

PURPOSE

To report the effectiveness and clinical outcomes of corneal electrolysis for Reis-Bücklers corneal dystrophies (RBCDs) and provide in vivo histological analysis using anterior segment optical coherence tomography (AS-OCT).

METHODS

A total of 7 patients with RBCD (2 male patients, 5 female patients; mean age, 50.0 years) from 3 pedigrees were enrolled in this prospective study. All patients underwent corneal electrolysis for decreased visual acuity or blurred vision. Changes in visual acuity, refraction, and corneal thickness were evaluated 1 month after electrolysis and statistically analyzed. Changes observed in AS-OCT images before and after electrolysis were qualitatively and quantitatively assessed.

RESULTS

A total of 22 electrolysis procedures were performed on 7 patients during the median follow-up period of 10.7 years. Mean visual acuity significantly improved postoperatively, from 0.59 to 0.31 logarithm of the minimum angle of resolution (P = 0.013). Changes in refraction (from -2.42 to -2.12 D) and corneal thickness (from 570.8 to 577.6 μm) were not significant (P = 0.77 and P = 0.80, respectively). In all cases, assessment of AS-OCT images showed that the band lesion in Bowman's layer became less reflective after electrolysis. The mean thickness of the band lesion decreased from 101.5 to 88.3 μm (P = 0.002).

CONCLUSIONS

Corneal electrolysis is an excellent treatment option for corneal opacities caused by RBCD. Corneal electrolysis improves visual acuity without changing corneal thickness or refraction. Therefore, repeat corneal electrolysis over the years might be a preferred long-term treatment strategy for RBCD. Moreover, AS-OCT is suitable for evaluating the effectiveness of this treatment and might be useful during postoperative follow-up.

In vivo Imaging of Reis-Bücklers and Thiel-Behnke Corneal Dystrophies Using Anterior Segment Optical Coherence Tomography

Purpose

To investigate in vivo corneal changes of genetically confirmed Reis–Bücklers corneal dystrophy (RBCD) and Thiel–Behnke corneal dystrophy (TBCD) using anterior segment optical coherence tomography (AS-OCT).

Design

A single-center, prospective, comparative case series.

Methods

Seven patients from 3 pedigrees (3 males, 4 females) with RBCD [Arg124Leu (R124L) heterozygous missense mutation of human transforming growth factor beta-induced (TGFBI) gene] and 4 patients from 3 pedigrees (3 males, 1 female) with TBCD [Arg555Gln (R555Q) heterozygous missense mutation of TGFBI gene] were examined. Six patients with RBCD and three patients with TBCD exhibited recurrence after corneal surgery including penetrating keratoplasty, phototherapeutic keratectomy, and electrolysis. All patients were examined by slit-lamp biomicroscopy followed by AS-OCT. Selected AS-OCT images of the cornea were evaluated qualitatively for changes in shape and degree of light reflection of corneal deposits.

Results

Slit-lamp biomicroscopy showed characteristic irregular gray opacities in Bowman’s layer in each dystrophy: a geographic pattern in RBCD and a honeycomb pattern in TBCD. In each dystrophy, distinct characteristic deposits were observed by AS-OCT as a banding lesion in Bowman’s layer and its adjacent epithelium/stroma. In RBCD, the banding lesion was highly reflective and sharply margined at the stroma. In contrast, deposits in TBCD in the same layer showed a saw-tooth pattern toward the epithelium and poorly margined at the stroma.

Conclusion

AS-OCT is able to clearly identify characteristic in vivo corneal microstructural changes associated with RBCD and TBCD. As a result, in vivo differentiation of RBCD and TBCD can be achieved.

A pathogenic variant in the transforming growth factor beta I (TGFBI) in four Iranian extended families segregating granular corneal dystrophy type II: A literature review

OBJECTIVES

Granular and lattice corneal dystrophies (GCDs & LCDs) are autosomal dominant inherited disorders of the cornea. Due to genetic heterogeneity and large genes, unraveling the mutation is challenging.

MATERIALS AND METHODS

Patients underwent comprehensive clinical examination, and targeted next-generation sequencing (NGS) was used for mutation detection. Co-segregation and in silico analysis was accomplished.

RESULTS

Patients suffered from GCD. NGS disclosed a known pathogenic variant, c.371G>A (p.R124H), in exon 4 of TGFBI. The variant co-segregated with the phenotype in the family. Homozygous patients manifested with more severe phenotypes. Variable expressivity was observed among heterozygous patients.

CONCLUSION

The results, in accordance with previous studies, indicate that the c.371G>A in TGFBI is associated with GCD. Some phenotypic variations are related to factors such as modifier genes, reduced penetrance and environmental effects.

TGF-β1 enhanced myocardial differentiation through inhibition of the Wnt/β-catenin pathway with rat BMSCs

OBJECTIVES

To investigate and test the hypotheses that TGF-β1 enhanced myocardial differentiation through Wnt/β-catenin pathway with rat bone marrow mesenchymal stem cells (BMSCs).

MATERIALS AND METHODS

Lentiviral vectors carrying the TGF-β1 gene were transduced into rat BMSCs firstly. Then several kinds of experimental methods were used to elucidate the related mechanisms by which TGF-β1 adjusts myocardial differentiation in rat BMSCs.

RESULTS

Immunocytochemistry revealed that cTnI and Cx43 expressed positively in the cells that were transduced with TGF-β1. The results of Western blot (WB) test showed that the levels of intranuclear β-catenin and total β-catenin were all significantly decreased. However, the cytoplasmic β-catenin level was largely unchanged. Moreover, the levels of GSK-3β were largely unchanged in BMSCs, whereas phosphorylated GSK-3β was significantly decreased in BMSCs. When given the activator of Wnt/β-catenin pathway (lithium chloride, LiCl) to BMSCs transducted with TGF-β1, β-catenin was increased, while phosphorylated β-catenin was decreased. In addition, cyclinD1, MMP-7, and c-Myc protein in BMSCs transducted with Lenti-TGF-β1-GFP were significantly lower.

CONCLUSION

These results indicate that TGF-β1 promotes BMSCs cardiomyogenic differentiation by promoting the phosphorylation of β-catenin and inhibiting cyclinD1, MMP-7, and c-Myc expression in Wnt/β-catenin signaling pathway.

Early and late clinical landmarks of corneal dystrophies

Corneal dystrophies (CDs) represent a heterogenous group of genetic diseases (Lisch and Weiss, 2019). The International Committee of Classification of Corneal Dystrophies (IC3D) distinguishes between 22 distinct forms of corneal dystrophy (CD) which are predominantly autosomal dominant, although autosomal recessive and X-chromosomal dominant and recessive patterns do exist. A detailed corneal examination of as many affected family members as possible can show the phenotypic differences of the various generations. There are few publications which describe the different CDs with regard to the early and late phenotypes. According to early and late phenotype, three types of CD are generally classified: (1) Thirteen CDs with early and late clinical landmarks. However, it must be pointed out that the different penetrances of the gene often leads to quantitative differences in the corneal phenotype in peers in distinct generations of the same family. (2) Seven CDs with late onset and very little progression of the corneal changes. (3) Two CDs with congenital haze which can be interpreted as the final phenotype of this dystrophy. This applies to autosomal dominant and recessive inheritance.

Corneal dystrophies

Corneal dystrophies are broadly defined as inherited disorders that affect any layer of the cornea and are usually progressive, bilateral conditions that do not have systemic effects. The 2015 International Classification of Corneal Dystrophies classifies corneal dystrophies into four classes: epithelial and subepithelial dystrophies, epithelial-stromal TGFBI dystrophies, stromal dystrophies and endothelial dystrophies. Whereas some corneal dystrophies may result in few or mild symptoms and morbidity throughout a patient's lifetime, others may progress and eventually result in substantial visual and ocular disturbances that require medical or surgical intervention. Corneal transplantation, either with full-thickness or partial-thickness donor tissue, may be indicated for patients with advanced corneal dystrophies. Although corneal transplantation techniques have improved considerably over the past two decades, these surgeries are still associated with postoperative risks of disease recurrence, graft failure and other complications that may result in blindness. In addition, a global shortage of cadaveric corneal graft tissue critically limits accessibility to corneal transplantation in some parts of the world. Ongoing advances in gene therapy, regenerative therapy and cell augmentation therapy may eventually result in the development of alternative, novel treatments for corneal dystrophies, which may substantially improve the quality of life of patients with these disorders.

Investigation of TGFBI (transforming growth factor beta-induced) Gene Mutations in Families with Granular Corneal Dystrophy Type 1 in the Konya Region

Objectives:

Granular corneal dystrophies (GCD) are characterized by small, discrete, sharp-edged, grayish-white opacities in the corneal stroma. Among the genes responsible for the development of GCD, the most strongly related gene is transforming growth factor beta-induced (TGFBI), located in the 5q31.1 locus. Studies show that R124H in exon 4 and R555W in exon 12 are hot-spot mutations in the TGFBI gene that lead to GCD development. In this study, we aimed to investigate these two hot-spot mutations in exons 4 and 12 of the TGFBI gene and other possible mutations in the same regions, which code important functional regions of the protein, in Turkish families with GCD1 and to determine the relationship between the mutations and disease and related phenotypes.

Materials and Methods:

The study included, 16 individuals diagnosed with GCD type 1 (GCD1), 11 of these patients’ healthy relatives, and 28 unrelated healthy individuals. DNA was obtained from peripheral blood samples taken from each individual and polymerase chain reaction was used to amplify target gene regions. Genotyping studies were done by sequence analysis.

Results:

The R124S mutation in exon 4 of TGFBI was not detected in the patients or healthy individuals in our study. However, all individuals diagnosed as having GCD1 were found to be heterozygous carriers of the R555W mutation in exon 12 of TGFBI. This mutation was not detected in healthy family members or control individuals unrelated to these families. In addition, we detected the silent mutation F540F in exon 12 and c.32924 G>A substitution in an intronic region of the gene in a few patients and healthy individuals.

Conclusion:

Our study strongly supports the association of GCD1 with R555W mutation in exon 12 region of the TGFBI gene, as reported in the literature.

Multiple phototherapeutic keratectomy treatments in a Chinese pedigree with corneal dystrophy and an R124L mutation: a 20-year observational study

Background

To investigate the efficacy and safety of repeated phototherapeutic keratectomies (PTKs) during long-term treatment for corneal dystrophy (CD) in a Chinese pedigree carrying the R124L mutation in TGFBI.

Methods

This was a retrospective review of 20-year medical and genetic records involving five CD patients (10 eyes) from one pedigree. During this period, PTK was conducted for an eye when best-corrected distance visual acuity (BCDVA) reached > 1.0 (LogMAR), due to either primary or recurrent opacities in the cornea. All PTKs were performed by 193-nm excimer laser with or without creation of epithelial flaps. For each eye, routine measurements were conducted for the number of PTKs during follow-up, mean time to recurrence, and BCDVA pre- and post- every PTK (measurements within 3 months from each PTK). Corneal thicknesses measured after the last PTK and at the last visit were analyzed, and subjective satisfaction was assessed.

Results

Gene testing revealed an R124L mutation in TGFBI. During 19.60 ± 1.78 years of follow-up, PTKs were conducted twice for three eyes, three times for six eyes, and four times for one eye. After each PTK, effective visual acuity was maintained for 3.60 ± 1.12 years before significant recurrence. BCDVA improved significantly postoperatively than preoperatively for the first PTK for each eye (p < 0.001), as well as the second (p < 0.001) and third one (p < 0.001). After the last PTK and at the final visit, the thinnest corneal thickness was 371.50 ± 56.47 μm and 358.40 ± 101.11 μm, respectively. The average subjective satisfaction score was 8.60 ± 0.89.

Conclusions

Multiple repeated PTKs were effective and safe in a long-term study of CD patients with an R124L mutation in TGFBI.

Phototherapeutic keratectomy

Phototherapeutic keratectomy is an excimer laser-based surgical procedure widely performed by corneal surgeons for treating anterior corneal stromal pathologies. Phototherapeutic keratectomy helps by ablating the corneal stroma, thereby improving corneal clarity and smoothening the surface. Transient discomfort and induced hyperopia from corneal flattening are the immediate postoperative concerns. The long-term course is often marked by the recurrence of original corneal pathology and corneal haze formation. Phototherapeutic keratectomy, however, allows for repeat stromal ablation for managing recurrences, as the corneal thickness permits, without affecting the outcome of future keratoplasty. Adjunctive methods such as topical mitomycin-C may be additionally used to reduce recurrence rates. Also, various masking agents such as carboxymethyl cellulose, sodium hyaluronate, and dextran are used in eyes with irregular corneal surface to allow for uniform stromal ablation. Overall, phototherapeutic keratectomy has provided corneal surgeons an additional surgical tool, particularly those residing in developing nations where the availability of donor corneal tissue is an important limiting factor.

Clinical and genetic update of corneal dystrophies

The International Committee for Classification of Corneal Dystrophies (IC3D) distinguishes between 22 distinct forms of corneal dystrophy which are predominantly autosomal dominant, although autosomal recessive and X-chromosomal dominant patterns do exist. Before any genetic examination, there should be documentation of a detailed corneal exam of as many affected and unaffected family members as possible, because detailed phenotypic description is essential for accurate diagnosis. Corneal documentation should be performed in direct and indirect illumination at the slit lamp with the pharmacologically dilated pupil. For the majority of the corneal dystrophies, a phenotype-genotype correlation has not been demonstrated. However, for the dystrophies associated with mutations in the transforming growth factor, ß-induced gene (TGFBI) a general phenotype-genotype correlation is evident. The discovery of collagen, type XVII, alpha 1 mutation (COL17A1), causative in the called epithelial recurrent erosion dystrophy (ERED) was a very important step in the accurate diagnosis of corneal dystrophies. This led to the subsequent discovery that the entity previously called 10q Thiel-Behnke corneal dystrophy, was in reality actually COL17A1 ERED, and not Thiel-Behnke corneal dystrophy. In addition to the phenotypic landmarks, we describe the current genotype of the individual corneal dystrophies. Differential diagnosis can be aided by information on histopathology, optical coherence tomography (OCT), and confocal microscopy.

Clinical outcomes and time to recurrence of phototherapeutic keratectomy in Japan

To assess the indications, outcomes and time to recurrence of phototherapeutic keratectomy (PTK) for anterior corneal pathology.This study involved 714 eyes of 477 consecutive patients (mean age: 66.0 ± 15.2 years; range: 6-101 years) who underwent PTK as the initial surgical intervention for an anterior corneal pathology. In case of each patient, the cornea treated by PTK, followed up by slit-lamp examination and corrected distance visual acuity (CDVA) testing. Main outcome measures included Slit-lamp findings (1), CDVA (2), patients' complaints (3).The mean follow-up period was 44.0 ± 38.8 months (range: 1-156 months).We treated 376 granular corneal dystrophy (GCD) eyes, 238 band keratopathy (BK) eyes, 23 epithelium attachment disorder eyes, 16 gelatinous drop-like corneal dystrophy (GDLD) eyes, 13 lattice corneal dystrophy (LCD) eyes, and 48 eyes with other corneal diseases. The CDVA significantly improved from LogMAR 0.65 ± 0.61 pre PTK to LogMAR 0.26 ± 0.39 post PTK. A 2 or more lines increase of CDVA was observed in GCD eyes (67.8%), BK eyes (49.2%), epithelium attachment disorder eyes (57.1%), GDLD eyes (87.5%), LCD eyes (76.9%), and other corneal disease eyes (60.4%). The recurrence of BK was rare. GCD recurred slowly. Epithelium attachment disorder eyes remitted simultaneously, and recurred comparatively faster.PTK was proved to be a successful therapy for all 6 corneal disease categories. Disease recurrence after PTK differed among the diseases, and surgeons should recognize the different rates of disease recurrence after PTK surgery.

Transforming growth factor beta-induced p.(L558P) variant is associated with autosomal dominant lattice corneal dystrophy type IV in a large cohort of Spanish patients

IMPORTANCE

Rare transforming growth factor beta-induced (TGFBI) gene variants are involved in autosomal dominant corneal dystrophies (CDs) with heterogeneous clinical features.

BACKGROUND

The purpose of this study was to analyse TGFBI gene variants and genotype-phenotype correlations in a cohort affected by atypical stromal CD.

DESIGN

Retrospective cohort study (from May 2014 to September 2017).

PARTICIPANTS

Thirty-five individuals from 10 unrelated South European families presenting atypical lattice CD (LCD) were included.

METHODS

Corneal phenotypes were assessed by slit-lamp examination and optical coherence tomography (OCT). Contrast sensitivity was measured under mesopic conditions. Genomic DNA was obtained from blood samples, and all 17 TGFBI exons were screened for variants by Sanger sequencing.

MAIN OUTCOME MEASURES

p.(L558P) variant of TGFBI gene.

RESULTS

The p.(L558P) variant was identified in 22 members of the 10 families diagnosed with atypical LCD, characterized by late-onset and absence of recurrent erosion syndrome. OCT revealed punctiform deposits in the deep-mid stroma and normal anterior stroma. This variant was demonstrated to be transmitted with the disease according to autosomal dominant inheritance in most families.

CONCLUSIONS AND RELEVANCE

To the best of our knowledge, we describe a detailed clinical characterization of the largest CD cohort carrying the TGFBI p.(L558P) variant. We propose that the atypical phenotype of this recently reported alteration can be classified as a form of LCD type IV. The results show that OCT and anterior-posterior analysis of the stromal location of the opacities, along with a genetic analysis of TGFBI, are required to ensure accurate diagnosis and management of CDs.

Mutation update: TGFBI pathogenic and likely pathogenic variants in corneal dystrophies

Human transforming growth factor β-induced (TGFBI), is a gene responsible for various corneal dystrophies. TGFBI produces a protein called TGFBI, which is involved in cell adhesion and serves as a recognition sequence for integrins. An alteration in cell surface interactions could be the underlying cause for the progressive accumulation of extracellular deposits in different layers of the cornea with the resulting changes of refractive index and transparency. To this date, 69 different pathogenic or likely pathogenic variants in TGFBI have been identified in a heterozygous or homozygous state in various corneal dystrophies, including a novel variant reported here. All disease-associated variants were inherited as autosomal-dominant traits but one; this latter was inherited as an autosomal recessive trait. Most corneal dystrophy-associated variants are located at amino acids Arg124 and Arg555. To keep the list of corneal dystrophy-associated variant current, we generated a locus-specific database for TGFBI (http://databases.lovd.nl/shared/variants/TGFBI) containing all pathogenic and likely pathogenic variants reported so far. Non-disease-associated variants are described in specific databases, like gnomAD and ExAC but are not listed here. This article presents the most recent up-to-date list of disease-associated variants.

Cornea guttata associated with special phenotypic variants of granular corneal dystrophy type 2 in a Chinese family

PURPOSE

The aim of this study was to analyze the relevant gene mutations in a Chinese family with special phenotypic variants of granular corneal dystrophy type 2 with cornea guttata.

METHODS

A total of 11 individuals from the affected family underwent complete ophthalmic examination. Genomic DNA was extracted from peripheral leukocytes of affected and unaffected family members. High-throughput sequencing was performed to screen for mutations in 290 genes associated with inherited ophthalmic diseases. Results were validated by bidirectional Sanger sequencing.

RESULTS

An Arg124His (R124H) mutation of the transforming growth factor beta-induced gene was identified in three members of the affected family: the proband (II-1), his mother (I-2), and his son (III-1). The eyes of the proband and his mother had bilateral superficial whitish ring patches with clear centers occupying their central corneas and appeared to be discoid or ring shaped. In addition, specular microscopic examination showed the presence of dark, round bodies. In vivo confocal microscopy showed some hyporeflective round images (cornea guttata), containing occasionally central highlight, in the proband, his mother, and one of his elder sisters.

CONCLUSION

We report, for the first time, atypical granular corneal dystrophy type 2 with cornea guttata associated with a single R124H mutation in a Chinese family. Our findings emphasize that genotyping is essential for the accurate diagnosis and classification of granular corneal dystrophy type 2.

Generation of TGFBI knockout ABCG2+/ABCB5+ double-positive limbal epithelial stem cells by CRISPR/Cas9-mediated genome editing

Corneal dystrophy is an autosomal dominant disorder caused by mutations of the transforming growth factor β-induced (TGFBI) gene on chromosome 5q31.8. This disease is therefore ideally suited for gene therapy using genome-editing technology. Here, we isolated human limbal epithelial stem cells (ABCG2+/ABCB5+ double-positive LESCs) and established a TGFBI knockout using RNA-guided clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 genome editing. An LESC clone generated with a single-guide RNA (sgRNA) targeting exon 4 of the TGFBI gene was sequenced in order to identify potential genomic insertions and deletions near the Cas9/sgRNA-target sites. A detailed analysis of the differences between wild type LESCs and the single LESC clone modified by the TGFBI-targeting sgRNA revealed two distinct mutations, an 8 bp deletion and a 14 bp deletion flanked by a single point mutation. These mutations each lead to a frameshift missense mutation and generate premature stop codons downstream in exon 4. To validate the TGFBI knockout LESC clone, we used single cell culture to isolate four individual sub-clones, each of which was found to possess both mutations present in the parent clone, indicating that the population is homogenous. Furthermore, we confirmed that TGFBI protein expression is abolished in the TGFBI knockout LESC clone using western blot analysis. Collectively, our results suggest that genome editing of TGFBI in LESCs by CRISPR/Cas9 may be useful strategy to treat corneal dystrophy.