Gelatinous Drop-like Corneal Dystrophy Research Articles

TACSTD2 in gelatinous drop-like corneal dystrophy: variant functional analysis and expression in the cornea after limbal stem cell transplantation

Gelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive eye disease. GDLD is characterized by the loss of barrier function in corneal epithelial cells (CECs) and amyloid deposition due to pathogenic variants in the TACSTD2 gene. Limbal stem cell transplantation (LSCT) has been suggested as an effective therapeutic alternative for patients with GDLD. However, despite LSCT, amyloid deposition recurs in some patients. The pathogenesis of recurrence is poorly studied. We present the case of a patient with GDLD. Genetic analysis revealed a homozygous deletion, NM_002353.3:c.653del, in the TACSTD2 gene. Functional analysis in a cell model system revealed the loss of the transmembrane domain and subcellular protein mislocalization. The patient with GDLD underwent direct allogeneic LSCT with epithelial debridement followed by deep anterior lamellar keratoplasty 10 months later due to amyloid deposition and deterioration of vision. Taken together, the results of transcriptome analysis and immunofluorescence staining of post-LSCT corneal sample with amyloid deposits obtained during keratoplasty demonstrated complete restoration of wild-type TACSTD2 expression, indicating that donor CECs replaced host CECs. Our study provides experimental evidence that amyloid deposition can recur after LSCT despite complete restoration of wild-type TACSTD2 expression.

The Occurrences of Gelatinous Drop-Like Corneal Dystrophy within an Acehnese Family

The Occurrences of Gelatinous Drop-Like Corneal Dystrophy within an Acehnese Family

Rescue of secretion of rare-disease-associated misfolded mutant glycoproteins in UGGT1 knock-out mammalian cells.

Endoplasmic reticulum (ER) retention of misfolded glycoproteins is mediated by the ER-localized eukaryotic glycoprotein secretion checkpoint, UDP-glucose glycoprotein glucosyl-transferase (UGGT). The enzyme recognizes a misfolded glycoprotein and flags it for ER retention by re-glucosylating one of its N-linked glycans. In the background of a congenital mutation in a secreted glycoprotein gene, UGGT-mediated ER retention can cause rare disease, even if the mutant glycoprotein retains activity ("responsive mutant"). Using confocal laser scanning microscopy, we investigated here the subcellular localization of the human Trop-2-Q118E, E227K and L186P mutants, which cause gelatinous drop-like corneal dystrophy (GDLD). Compared with the wild-type Trop-2, which is correctly localized at the plasma membrane, these Trop-2 mutants are retained in the ER. We studied fluorescent chimeras of the Trop-2 Q118E, E227K and L186P mutants in mammalian cells harboring CRISPR/Cas9-mediated inhibition of the UGGT1 and/or UGGT2 genes. The membrane localization of the Trop-2 Q118E, E227K and L186P mutants was successfully rescued in UGGT1-/- cells. UGGT1 also efficiently reglucosylated Trop-2-Q118E-EYFP in cellula. The study supports the hypothesis that UGGT1 modulation would constitute a novel therapeutic strategy for the treatment of pathological conditions associated to misfolded membrane glycoproteins (whenever the mutation impairs but does not abrogate function), and it encourages the testing of modulators of ER glycoprotein folding quality control as broad-spectrum rescue-of-secretion drugs in rare diseases caused by responsive secreted glycoprotein mutants.

Trop2: Jack of All Trades, Master of None.

Simple SummaryMetastatic progression represents a major clinical challenge and remains the leading cause of death in cancer patients. Identification of suitable therapeutic targets, followed by a rational design of effective drug agents and their long-term, extensive pre-clinical and clinical testing is one of the key goals in cancer research. Trophoblast cell surface antigen 2 (Trop2) was first described as a protein highly expressed on the surface of trophoblast cells in 1981. Just recently, nearly 40 years after this discovery, sacituzumab govitecan, a Trop2-targeting antibody drug conjugate, has been granted an accelerated approval for therapy of metastatic triple-negative breast cancer, opening a new chapter of such successful story. The aim of this review is to summarize the current knowledge about Trop2 function in healthy tissue and pathology, with a special focus on its still controversial role in plasticity and heterogeneity during cancer progression. We further discuss the development and potential of Trop2-targeted therapy.Trophoblast cell surface antigen 2 (Trop2) is a widely expressed glycoprotein and an epithelial cell adhesion molecule (EpCAM) family member. Although initially identified as a transmembrane protein, other subcellular localizations and processed forms were described. Its congenital mutations cause a gelatinous drop-like corneal dystrophy, a disease characterized by loss of barrier function in corneal epithelial cells. Trop2 is considered a stem cell marker and its expression associates with regenerative capacity in various tissues. Trop2 overexpression was described in tumors of different origins; however, functional studies revealed both oncogenic and tumor suppressor roles. Nevertheless, therapeutic potential of Trop2 was recognized and clinical studies with drug–antibody conjugates have been initiated in various cancer types. One of these agents, sacituzumab govitecan, has been recently granted an accelerated approval for therapy of metastatic triple-negative breast cancer. In this article, we review the current knowledge about the yet controversial function of Trop2 in homeostasis and pathology.

Corneal Opacity Induced by Light in a Mouse Model of Gelatinous Drop-Like Corneal Dystrophy

Gelatinous drop-like corneal dystrophy (GDLD) is a severe inherited corneal dystrophy characterized by subepithelial corneal amyloid deposition. We had previously succeeded in identifying the responsible gene, TACSTD2, and subsequently found that the epithelial barrier function is significantly decreased. As with GDLD patients, the knockout mice showed severe loss of tight junction, progressive opacity, and neovascularization in the cornea. We devised an easy method to confirm the loss of the corneal barrier function even before corneal opacity is observed. Furthermore, by using knockout mice, we were able to verify clinical findings, such as the wound healing delay and light-induced acceleration of the disease. This mouse model should prove to be a highly useful tool for investigating the pathology of GDLD and for developing new therapies.

Clinical and Ultrastructural Studies of Gelatinous Drop-Like Corneal Dystrophy (GDLD) of a Patient with TACSTD2 Gene Mutation.

Purpose To describe clinical, molecular genetics, histopathologic and ultrastructural findings of gelatinous drop-like corneal dystrophy (GDLD) (OMIM #204870) in a Sudanese patient. Method An ocular examination revealed the onset of GDLD in a Sudanese patient (50 years old) at King Khalid Specialist Hospital, Riyadh. The 333 sequence variants in 13 GDLD genes of a DNA sample were screened by Asper Ophthalmics Ltd. It was further confirmed by sequencing. The patient had undergone a penetrating keratoplasty in the right eye. The corneal tissue was processed for histopathology and ultrastructural studies. Results Slit-lamp observation showed grayish-white multiple superficial corneal nodules of various sizes in the left and right eye. Both corneas became clear after the surgery. The GDLD deposits in the subepithelial region and in the anterior stroma were confirmed by PAS staining and their apple-green birefringence under polarized light. Ultrastructurally, the amyloid fibrils were very thin and grouped in whorl-like structures, which caused splits between and within the stromal lamellae. Collagen fibrils (CFs) and keratocytes had degenerated. A homozygous c.355T > A mutation in exon 1 of the TACSTD2 (M1S1) gene was detected, and alteration of the amino acid (p.Cysl19Ser in NCBI entry NP_002344.2) was observed. Conclusion In our patient with GDLD, a “c.355T > A” mutation in exon 1 of TACSTD2 was detected and believed to be responsible for the alteration of the amino acid leading to the formation of the amyloid deposits. The deposits caused the ultrastructural degeneration of epithelium, Bowman's layer, stroma, and keratocytes of the GDLD cornea.

A novel mutation in gelatinous drop-like corneal dystrophy and functional analysis

We identified a novel mutation of the tumor-associated calcium signal transducer 2 (TACSTD2) gene in a Japanese patient with gelatinous drop-like corneal dystrophy (GDLD). Genetic analysis revealed a novel homozygous mutation (c.798delG, which may result in frameshift mutation p.Lys267SerfsTer4) in the TACSTD2 gene. This mutated gene was devoid of its original function in helping the claudin (CLDN) 1 and 7 proteins transfer from the cytoplasm to the plasma membrane.

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.

Efficacy of therapeutic soft contact lens in the management of gelatinous drop-like corneal dystrophy

Background/AimsTo investigate the efficacy of therapeutic soft contact lenses (SCLs) in gelatinous drop-like corneal dystrophy (GDLD) management.MethodsThis was a retrospective, consecutive, observational case series, including 20 patients (40 eyes) with...

Epithelial Dystrophies of the Cornea

In 2015, the first revision of the international classification of corneal dystrophies (IC3D) has been published. According to this latest version of the IC3D the dystrophies of the cornea are divided into · epithelial and subepithelial dystrophies,. · epithelial-stromal TGFBI dystrophies,. · stromal dystrophies, and. · Descemet-membrane and endothelial dystrophies.. This article summarizes the epithelial and subepithelial dystrophies of the cornea, which, according to IC3D are the following: · epithelial basement membrane dystrophy (EBMD),. · epithelial recurrent erosion dystrophy (ERED),. · subepithelial mucinous corneal dystrophy (SMCD),. · Meesmann corneal dystrophy (MECD),. · Lisch epithelial corneal dystrophy (LECD),. · gelatinous drop-like corneal dystrophy (GDLD).. The main problem concerning almost all dystrophies of the corneal epithelium are epithelial defects (erosion) associated with pain, epiphora and red eyes. In addition, all dystrophies of the epithelium tend to relapse.While therapy is usually initiated with topical therapeutics, in the course of the disease invasive procedures like phototherapeutic keratectomy (PTK) (possibly with the administration of mitomycin C) or in severe cases even keratoplasty (preferably as deep anterior lamellar keratoplasty; DALK) have to be used. Due to the origin of the disease in the epithelial stem cells at the limbus, the replacement of these cells can also be discussed.

A New in Vitro Model of GDLD by Knocking Out TACSTD2 and Its Paralogous Gene EpCAM in Human Corneal Epithelial Cells.

PurposeGelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive corneal dystrophy that causes severe vision loss. Because of its poor prognosis, there is a demand for novel treatments for GDLD. Here, we establish a new in vitro disease model of GDLD based on immortalized human corneal epithelial (HCE-T) cells.MethodsBy using transcription activator-like effector nuclease plasmids, tumor-associated calcium signal transducer 2 (TACSTD2) and its paralogous gene, epithelial cell adhesion molecule (EpCAM), were knocked out in HCE-T cells. Fluorescence-activated cell sorting was performed to obtain cells in which both TACSTD2 and EpCAM were knocked out (DKO cells). In DKO cells, the expression levels and subcellular localizations of claudin (CLDN) 1, 4, and 7, and ZO-1 were investigated, along with epithelial barrier function. By using DKO cells, the feasibility of gene therapy for GDLD was also investigated.ResultsDKO cells exhibited decreased expression and aberrant subcellular localization of CLDN1 and CLDN7 proteins, as well as decreased epithelial barrier function. Transduction of the TACSTD2 gene into DKO cells nearly normalized expression levels and subcellular localization of CLDN1 and CLDN7 proteins, while significantly increasing epithelial barrier function.ConclusionsWe established an in vitro disease model of GDLD by knocking out TACSTD2 and its paralogous gene, EpCAM, in HCE-T cells. This cell line accurately reflected pathological aspects of GDLD.Translational RelevanceWe expect that the cell line will be useful to elucidate the pathogenesis of GDLD and develop novel treatments for GDLD.

Road to a Genetic Model of Gelatinous Drop-Like Corneal Dystrophy.

Gelatinous drop-like corneal dystrophy (GDLD; OMIM: 204870) is an autosomal recessive Mendelian-inherited disease. Subepithelial amyloid deposition results in severe visual impairment. Its pathogenesis remains unknown. Identification of the responsible gene is a useful approach to investigating the pathogenesis of genetic diseases. Such an identification is also necessary for the creation of genetic models. For this purpose, our group performed positional cloning using homozygosity mapping. The results revealed that GDLD maps to the short arm of chromosome 1. Subsequent mutation analyses identified tumor-associated calcium signal transducer 2 (TACSTD2; former name, M1S1) as the gene responsible for GDLD. After identification of the gene, we examined the phylogenetical distribution of TACSTD2 in the genomes of vertebrates.

Novel Mutations in TACSTD2 Gene in Families with Gelatinous Drop-like Corneal Dystrophy (GDLD).

In the current study, we conducted a mutation screening of tumor-associated calcium signal transducer 2 (TACSTD2) gene in six consanguineous Iranian families with gelatinous drop-like corneal dystrophy (GDLD), in order to find the causative mutations. Detailed eye examination was performed by ophthalmologist to confirm GDLD in patients. To detect the possible mutations, direct Sanger sequencing was performed for the only exon of TACSTD2 gene, and its boundary regions in all patients. In the patients with GDLD, the corneal surface showed lesions with different shapes from mild to severe forms depending on the progress of the disease. The patients showed grayish corneal deposits as a typical mulberry form, corneal dystrophy along with corneal lipid deposition, and vascularization. Targeted Sanger sequencing in TACSTD2 gene revealed the causative mutations in this gene in all studied families. Our study expanded the mutational spectrum of TACSTD2 which along with the related symptoms could help with the diagnosis, and management of the disease.

Familial Gelatinous Drop-Like Corneal Dystrophy Caused by a Novel Nonsense TACSTD2 Mutation

To describe the clinical findings and results of molecular analysis in a Mexican family diagnosed with gelatinous drop-like corneal dystrophy (GDLD). Ophthalmological examination was performed in 1 unaffected and 4 affected relatives. Molecular analysis included polymerase chain reaction amplification and direct nucleotide sequencing of the entire TACSTD2 gene-coding region in genomic DNA. The corneal phenotype in adult patients was characterized by white-yellow nodular lesions on the corneal surface and stromal neovascularization. Lesions were incipient in an affected relative aged 14 years. Nucleotide sequencing of the TACSTD2 gene demonstrated a homozygous c.331G>T transversion, which predicts a novel p.(E111*) nonsense mutation, in DNA of all 4 GDLD relatives. Our results expand the mutational spectrum of TACSTD2 in patients with GDLD. To the best of our knowledge, this is the first clinical and molecular description of patients with GDLD from Latin America.

Boston Type 1 Keratoprosthesis for Gelatinous Drop-Like Corneal Dystrophy.

To report the outcomes of Boston type 1 keratoprosthesis in the management of advanced gelatinous drop-like corneal dystrophy (GDLD). A retrospective, noncomparative, interventional case series was conducted at Ramathibodi Hospital, Bangkok, Thailand. Four eyes of three siblings with molecularly and histologically confirmed GDLD from a Thai family underwent an uneventful Boston type 1 keratoprosthesis implantation for visual rehabilitation. Clinical data were obtained from a review of the medical records. Visual acuity, device retention, and postoperative complications were the main outcome measures. The follow-up ranged from 8 to 96 months. One eye received keratoprosthesis surgery as a primary penetrating procedure. The other three eyes had the surgery as a secondary procedure after graft failure. Best-corrected visual acuity was favorably improved from counting fingers to 20/25 in two eyes, from hand movement to 20/20 in one eye, and from hand movement to counting fingers at 2 feet in one eye caused by severe amblyopia. The improved vision was maintained for 8 months to 6.2 years after surgery. Postoperative complications included disease recurrence in the donor graft (N = 3), manageable retroprosthetic membrane (N = 3), intraocular pressure elevation responded to antiglaucoma drugs (N = 2), and Pseudomonas keratitis with severe corneal melting requiring device removal (N = 1). All of our patients failed to have a comfortably well-fitting contact lens after surgery. Boston type 1 keratoprosthesis could be considered as a reasonable option in the management of advanced GDLD. However, patients remain at risk for sight-threatening postoperative complications as long as the keratoprosthesis is retained. The use of Boston keratoprosthesis implantation needed to be individualized on a case-by-case basis.

Novel TACSTD2 mutation in gelatinous drop-like corneal dystrophy.

We identified a novel mutation in the tumor-associated calcium signal transducer 2 (TACSTD2) gene in a consanguineous Thai family with gelatinous drop-like corneal dystrophy (GDLD). All affected family members presented with an intense amyloid substance deposited on the cornea, which required surgical management. Genetic analysis of these individuals revealed a homozygous mutation c.79delC, in the TACSTD2 gene. Both parents of these individuals were unaffected and showed heterozygous mutations in the TACSTD2 gene. The mutation produced a truncated protein sequence that might be the cause of GDLD.

Combined Excimer Laser Photoablation and Amniotic Membrane Overlay for Relief of Symptomatic Discomfort in Gelatinous Drop-like Corneal Dystrophy

To describe the efficacy of combined excimer laser photoablation and amniotic overlay membrane in the relief of symptomatic discomfort in a 17-year-old patient who had gelatinous drop-like corneal dystrophy. The best-corrected visual acuity (BCVA) was measured with Snellen letters. Slit-lamp examination of the ocular surface and anterior chamber was performed at baseline. Results were photodocumented. Excimer laser photoablation was performed and subsequently 2 amniotic membranes were transconjunctivally fixated with 10.0 nylon sutures. Investigations and documentation were performed at baseline, every 2 months in the first year, and then every 6 months. The duration of follow-up was 22 months. At baseline, the BCVA was 20/70 in the right eye and 20/200 in the left eye. The patient reported distinct photophobia. Slit-lamp examination was difficult because of blepharospasm. Although gelatinous drops developed again and the BCVA decreased to 2/200, the patient reported significant relief after both microsurgical treatments and remained comfortable at 20 and 22 months. Excimer laser photocoagulation combined with amniotic membrane overlay does not stop the development of gelatinous drop-like corneal dystrophy but may improve subjective comfort. Such treatment does not hinder subsequent lamellar or penetrating grafts and is helpful in providing the necessary time for preparation of matched keratoplasties.

Structural and dielectric properties of doped ferrite nanomaterials suitable for microwave and biomedical applications

The sol–gel auto-combustion method was adopted to synthesize nanomaterials of single-phase X-type hexagonal ferrites with the composition of Sr2−xGdxNi2Fe28−yCdyO46 (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5). The structural properties were carried out by XRD analysis and the lattice parameters show variation with the doping of Gd–Cd. The average particle size measured by TEM was in the range of 8–10nm which is beneficial in obtaining suitable signal-to-noise ratio in recording media and biomedical applications. The room temperature resistivity enhanced with the increase of the dopant concentration. The increase in resistivity indicates that the synthesized materials can be considered good for the formation of the multilayer chip inductors (MLCIs) as well as for the reduction of eddy current losses. The dielectric constant decreased with the increase in the frequency which is the general reported trend of the hexagonal ferrites and can be explained on the basis of Koop׳s theory and Maxwell–Wagner polarization-model. The abnormal dielectric behavior indicates the formation of small polarons in the material. The maximum value of tangent loss at low frequencies reflects the application of these materials in medium frequency devices (MF).

Temperature dependent magnetic and microwave absorption properties of doubly substituted nanosized material

The sol gel method has been adopted to synthesize a series of X-type hexagonal ferrites with concentration Sr2−x Gdx Ni2 Fe28−yCdyO46 (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5). The XRD analysis reveals the single phase of the prepared material and the lattice constants a (Å) and c (Å) varies with additives. The crystallite size of the present investigated ferrite is found in the range of 20–30nm measured from TEM image. The enhancement in the magnetic properties (saturation magnetization, remanance magnetization and coercivity) can be observed with the increase of dopping concentration and the coercivity lies in the range of (484.22–887.47) G. The saturation and remanance magnetization decreases monotonically with the temperature which is the characteristic of the hexagonal ferrites. The Gd–Cd substituted sample possesses low values of complex relative permittivity and permeability than the pure samples. The material exhibits maximum microwave absorption −23dB at 11.87GHz and attenuation peak is in good agreement with the reflection loss value. The microwave absorption properties reflect the applications of this material in super high frequency devices (SHF).

Trop2: from development to disease.

Trop2 was first discovered as a biomarker of invasive trophoblast cells. Since then most research has focused on its role in tumourigenesis because it is highly expressed in the vast majority of human tumours and animal models of cancer. It is also highly expressed in stem cells and in many organs during development. We review the multifaceted role of Trop2 during development and tumourigenesis, including its role in regulating cell proliferation and migration, self-renewal, and maintenance of basement membrane integrity. We discuss the evolution of Trop2 and its related protein Epcam (Trop1), including their distinct roles. Mutation of Trop2 leads to gelatinous drop-like corneal dystrophy, whereas over-expression of Trop2 in human tumours promotes tumour aggressiveness and increases mortality. Although Trop2 expression is sufficient to promote tumour growth, the surprising discovery that Trop2-null mice have an increased risk of tumour development has highlighted the complexity of Trop2 signaling. Recently, studies have begun to identify the mechanisms underlying TROP2’s functions, including regulated intramembrane proteolysis or specific interactions with integrin b1 and claudin proteins. Understanding the mechanisms underlying TROP2 signaling will clarify its role during development, aid in the development of better cancer treatments and unlock a promising new direction in regenerative medicine.