Myocilin Research Articles

METTL23 Variants and Patients With Normal-Tension Glaucoma

This research confirms and further establishes that pathogenic variants in a fourth gene, METTL23, are associated with autosomal dominant normal-tension glaucoma (NTG). To determine the frequency of glaucoma-causing pathogenic variants in the METTL23 gene in a cohort of patients with NTG from Iowa. This case-control study took place at a single tertiary care center in Iowa from January 1997 to January 2024, with analysis occurring between January 2023 and January 2024. Two groups of participants were enrolled from the University of Iowa clinics: 331 patients with NTG and 362 control individuals without glaucoma. Patients with a history of trauma; steroid use; stigmata of pigment dispersion syndrome; exfoliation syndrome; or pathogenic variants in MYOC, TBK1, or OPTN were also excluded. Detection of an enrichment of METTL23 pathogenic variants in individuals with NTG compared with control individuals without glaucoma. The study included 331 patients with NTG (mean [SD] age, 68.0 [11.7] years; 228 [68.9%] female and 103 [31.1%] male) and 362 control individuals without glaucoma (mean [SD] age, 64.5 [12.6] years; 207 [57.2%] female and 155 [42.8%] male). There were 5 detected instances of 4 unique METTL23 pathogenic variants in patients with NTG. Three METTL23 variants-p.Ala7Val, p.Pro22Arg, and p.Arg63Trp-were judged to be likely pathogenic and were detected in 3 patients (0.91%) with NTG. However, when all detected variants were evaluated with either mutation burden analysis or logistic regression, their frequency was not statistically higher in individuals with NTG than in control individuals without glaucoma (1.5% vs 2.5%; P = .27). This investigation provides evidence that pathogenic variants in METTL23 are associated with NTG. Within an NTG cohort at a tertiary care center, pathogenic variants were associated with approximately 1% of NTG cases, a frequency similar to that of other known normal-tension glaucoma genes, including optineurin (OPTN), TANK-binding kinase 1 (TBK1), and myocilin (MYOC). The findings suggest that METTL23 pathogenic variants are likely involved in a biologic pathway that is associated with glaucoma that occurs at lower intraocular pressures.

In vitro comparison of human and murine trabecular meshwork cells: implications for glaucoma research

The trabecular meshwork (TM) is crucial for regulating intraocular pressure (IOP), and its dysfunction significantly contributes to glaucoma, a leading cause of vision loss and blindness worldwide. Although rodents are commonly used as animal models in glaucoma research, the applicability of these findings to humans is limited due to the insufficient understanding of murine TM. This study aimed to compare primary human TM (hTM) and murine TM (mTM) cells in vitro to enhance the robustness and translatability of murine glaucoma models. In this in vitro study, we compared primary hTM and mTM cells under simulated physiological and pathological conditions by exposing both cell types to the glucocorticoid dexamethasone (DEX) and Transforming Growth Factor β (TGFB2), both of which are critical in the pathogenesis of several ophthalmological diseases, including glaucoma. Phagocytic properties were assessed using microbeads. Cells were analyzed through immunocytochemistry (ICC) and Western blot (WB) to evaluate the expression of extracellular matrix (ECM) components, such as Fibronectin 1 (FN1) and Collagen IV (COL IV). Filamentous-Actin (F-Act) staining was used to analyze cross-linked actin network (CLAN) formation. Additionally, we evaluated cytoskeletal components, including Vimentin (VIM), Myocilin (MYOC), and Actin-alpha-2 (ACTA2). Our results demonstrated significant similarities between human and murine TM cells in basic morphology, phagocytic properties, and ECM and cytoskeletal component expression under both homeostatic and pathological conditions in vitro. Both human and murine TM cells exhibited epithelial-to-mesenchymal transition (EMT) after exposure to DEX or TGFB2, with comparable CLAN formation observed in both species. However, there were significant differences in FN1 and MYOC induction between human and murine TM cells. Additionally, MYOC expression in hTM cells depended on fibronectin coating. Our study suggests that murine glaucoma models are potentially translatable to human TM. The observed similarities in ECM and cytoskeletal component expression and the comparable EMT response and CLAN formation support the utility of murine models in glaucoma research. The differences in FN1 and MYOC expression between hTM and mTM warrant further investigation due to their potential impact on TM properties. Overall, this study provides valuable insights into the species-specific characteristics of TM and highlights opportunities to refine murine models for better relevance to human glaucoma.

In Vivo Models of Steroid-Induced Intraocular Hypertension

Corticosteroids are widely utilized for their anti-inflammatory and immunosuppressive properties but often lead to ocular complications, including ocular hypertension. If untreated, ocular hypertension can progress to optic nerve atrophy and eventually result in steroid-induced glaucoma, which poses a risk of irreversible visual damage. Approximately 40% of individuals experience increased intraocular pressure after steroid use, and around 6% develop glaucoma. Although steroid-induced glaucoma is usually temporary and reversible if the treatment duration is under a year, prolonged exposure can cause permanent vision impairment. The pathogenesis of steroid-induced glaucoma is suggested to arise from increased outflow resistance of aqueous humor, primarily due to decreased expression of matrix metalloproteinases. This deficiency promotes the deposition of extracellular matrix and the dysfunction of trabecular meshwork cells. Additionally, modifications in the actin cytoskeleton increase the stiffness and alter the morphology of trabecular meshwork, further impeding aqueous humor outflow. Molecular changes, such as elevated expression of the MYOC gene, have also been implicated in restricting aqueous outflow. Various animal models, including rats, mice, primates, rabbits, cattle, sheep, cats, and dogs, have been developed to study steroid-induced glaucoma. These models exhibit pathological, pathophysiological, and molecular similarities to human disease, making them valuable for research. This review aims to summarize common animal models of steroid-induced ocular hypertension, discussing their advantages and limitations. The goal is to help researchers select appropriate models for future studies, thereby advancing the understanding of disease mechanisms and developing preventive strategies.

Mutations of CYP1B1 and FOXC1 genes for childhood glaucoma in Japanese individuals.

To explore the frequency and positions of genetic mutations in CYP1B1 and FOXC1 in a Japanese population. Molecular genetic analysis. Genomic DNA was extracted from 31 Japanese patients with childhood glaucoma (CG) from 29 families. We examined the CYP1B, FOXC1, and MYOC genes using Sanger sequencing and whole-exome sequencing (WES). For CYP1B1, we identified 9 families that harbored novel mutations, p.A202T, p.D274E, p.Q340*, and p.V420G; the remaining mutations had been previously reported. When mapped to the CYP1B1 protein structure, all mutations appeared to influence the enzymatic activity of CYP1B1 by provoking structural deformity. Five patients were homozygotes or compound heterozygotes, supporting the recessive inheritance of the CYP1B1 mutations in CG. In contrast, four patients were heterozygous for the CYP1B1 mutation, suggesting the presence of regulatory region mutations or strong modifiers. For the FOXC1 gene, we identified 3 novel mutations, p.Q23fs, p.Q70R, and p.E163*, all of which were identified in a heterozygous state. No mutation was found in the MYOC gene in these CG patients. All individuals with CYP1B1 and FOXC1 mutations were severely affected by early-onset CG. In the CYP1B1-, FOXC1-, and MYOC-negative families, we also searched for variants in the other candidate genes reported for CG through WES, but could not find any mutations in these genes. Our analyses of 29 CG families revealed 9 families with point mutations in the CYP1B1 gene, and four of those patients appeared to be heterozygotes, suggesting the presence of complex pathogenic mechanisms. FOXC1 appears to be another major causal gene of CG, indicating that panel sequencing of CYP1B1 and FOXC1 will be useful for diagnosis of CG in Japanese individuals.

Exploring the Genetic Landscape of Childhood Glaucoma.

Childhood glaucoma, a significant cause of global blindness, represents a heterogeneous group of disorders categorized into primary or secondary forms. Primary childhood glaucoma stands as the most prevalent subtype, comprising primary congenital glaucoma (PCG) and juvenile open-angle glaucoma (JOAG). Presently, multiple genes are implicated in inherited forms of primary childhood glaucoma. This comprehensive review delves into genetic investigations into primary childhood glaucoma, with a focus on identifying causative genes, understanding their inheritance patterns, exploring essential biological pathways in disease pathogenesis, and utilizing animal models to study these mechanisms. Specifically, attention is directed towards genes such as CYP1B1 (cytochrome P450 family 1 subfamily B member 1), LTBP2 (latent transforming growth factor beta binding protein 2), TEK (TEK receptor tyrosine kinase), ANGPT1 (angiopoietin 1), and FOXC1 (forkhead box C1), all associated with PCG; and MYOC (myocilin), associated with JOAG. Through exploring these genetic factors, this review aims to deepen our understanding of the intricate pathogenesis of primary childhood glaucoma, thereby facilitating the development of enhanced diagnostic and therapeutic strategies.

Lentiviral mediated delivery of CRISPR/Cas9 reduces intraocular pressure in a mouse model of myocilin glaucoma

Mutations in myocilin (MYOC) are the leading known genetic cause of primary open-angle glaucoma, responsible for about 4% of all cases. Mutations in MYOC cause a gain-of-function phenotype in which mutant myocilin accumulates in the endoplasmic reticulum (ER) leading to ER stress and trabecular meshwork (TM) cell death. Therefore, knocking out myocilin at the genome level is an ideal strategy to permanently cure the disease. We have previously utilized CRISPR/Cas9 genome editing successfully to target MYOC using adenovirus 5 (Ad5). However, Ad5 is not a suitable vector for clinical use. Here, we sought to determine the efficacy of adeno-associated viruses (AAVs) and lentiviruses (LVs) to target the TM. First, we examined the TM tropism of single-stranded (ss) and self-complimentary (sc) AAV serotypes as well as LV expressing GFP via intravitreal (IVT) and intracameral (IC) injections. We observed that LV_GFP expression was more specific to the TM injected via the IVT route. IC injections of Trp-mutant scAAV2 showed a prominent expression of GFP in the TM. However, robust GFP expression was also observed in the ciliary body and retina. We next constructed lentiviral particles expressing Cas9 and guide RNA (gRNA) targeting MYOC (crMYOC) and transduction of TM cells stably expressing mutant myocilin with LV_crMYOC significantly reduced myocilin accumulation and its associated chronic ER stress. A single IVT injection of LV_crMYOC in Tg-MYOCY437H mice decreased myocilin accumulation in TM and reduced elevated IOP significantly. Together, our data indicates, LV_crMYOC targets MYOC gene editing in TM and rescues a mouse model of myocilin-associated glaucoma.

Molecular genetics of inherited normal tension glaucoma.

Normal tension glaucoma (NTG) is a complex optic neuropathy characterized by progressive retinal ganglion cell death and glaucomatous visual field loss, despite normal intraocular pressure (IOP). This condition poses a unique clinical challenge due to the absence of elevated IOP, a major risk factor in typical glaucoma. Recent research indicates that up to 21% of NTG patients have a family history of glaucoma, suggesting a genetic predisposition. In this comprehensive review using PubMed studies from January 1990 to December 2023, our focus delves into the genetic basis of autosomal dominant NTG, the only known form of inheritance for glaucoma. Specifically exploring optineurin ( OPTN ), TANK binding kinase 1 ( TBK1 ), methyltransferase-like 23 ( METTL23 ), and myocilin ( MYOC ) mutations, we summarize their clinical manifestations, mutant protein behaviors, relevant animal models, and potential therapeutic pathways. This exploration aims to illuminate the intricate pathogenesis of NTG, unraveling the contribution of these genetic components to its complex development.

Somatic Mutations within Myocilin due to Aging May Be a Potential Risk Factor for Glaucoma.

Glaucoma is a chronic optic neuropathy that leads to irreversible vision loss. Aging and family history are the two most important risk factors of glaucoma. One of the most studied genes involved in the onset of open-angle glaucoma is myocilin (MYOC). About 105 germline mutations within MYOC are known to be associated with glaucoma and result in endoplasmic reticulum (ER) stress, which leads to trabecular meshwork (TM) cell death and subsequent intraocular pressure (IOP) elevation. However, only about 4% of the population carry these mutations. An analysis of MYOC somatic cancer-associated mutations revealed a notable overlap with pathogenic glaucoma variants. Because TM cells have the potential to accumulate somatic mutations at a rapid rate due to ultraviolet (UV) light exposure, we propose that an accumulation of somatic mutations within MYOC is an important contributor to the onset of glaucoma.

Importance of genetic studies in the diagnosis of glaucoma

Glaucoma is the world's leading cause of irreversible blindness being a known family grouping disease with a strong hereditary component. Based on the age of onset and other clinical characteristics, glaucoma has been classified into primary congenital glaucoma (PCG), juvenile glaucoma (JG), and primary open‐angle glaucoma (POAG), the latter occurring in adulthood. Early‐onset forms of glaucoma such as, PCG and JG, are typically monogenic diseases inherited as Mendelian autosomal dominant or recessive traits, whereas adult glaucoma is a complex trait, with multifactorial inheritance.Genetic variants causing early‐onset glaucoma are highly penetrant. Some examples include dominant negative pathogenic variants in the MYOC gene accounting for 10% of JG cases or biallelic pathogenic variants in CYP1B1 gene mainly associated with PCG. In our cohort of 32 patients with a diagnosis of PCG or JG, we have identified two JOAG patients with two different pathogenic variants in the olfactomedin/like domain of MYOC gene and one PGC patient with two heterozygote pathogenic variants in CYP1B1 gene. Familiar segregation studies of these genetic variants in the three families confirm their pathogenicity. On the one hand, segregation studies of both variants identified in MYOC gene revealed its presence in those relatives with a clinical diagnosis of glaucoma and its absence in healthy individuals. On the other hand, parental screening of both variants identified in CYP1B1 showed that each parent is an asymptomatic carrier of one of the variants confirming that our patient present both variants in CYP1B1 gene in compound heterozygosis. Furthermore, heterozygote pathogenic variants in FOXC1 and COL2A1 genes associated with Axenfeld‐Rieger syndrome type 3 and Stickler syndrome type 1, respectively, have been identified in two different patients with PGC. In these cases, glaucoma is a phenotypic trait of both syndromes inherited in an autosomal dominant manner.Family grouping is a known risk factor for glaucoma in the adult, with a risk 7–10 times greater than the observed in general population. The genetic study of adult glaucoma is complex since its transmission mechanisms are sometimes unclear and have variable penetrance and late onset. In our cohort of 65 patients diagnosed with adult glaucoma, we have identified rare genetic variants with uncertain clinic significance in CYP1B1, SIX6, CARD10, MFN1, OPTC, OPTN, and WDR36 glaucoma‐related genes. Some of these variants are classified as hypomorphic alleles that reduce but do not eliminate gene's functionality and they can contribute to late‐onset disorders.Glaucoma is a treatable disease if detected in early stages and treatment can stop visual loss, however if damage has already occurred it cannot be reverted. Therefore, to identify a genetic cause associated with glaucoma is not only beneficial for the patient but also to detect asymptomatic carriers of the disease in the family‐relatives, which will be susceptible for early treatment. Therefore, proper genetic analysis may provide more accurate information on the prognosis and the adequacy of the therapeutic approach to personalize the treatment of glaucoma.

Abstract 15726: Large-Scale Plasma Proteomics and Mendelian Randomization of Cardiovascular Performance and Peak Arterio-Venous Oxygen Difference Identify Novel Biology Related to VO 2 max

Introduction: VO 2 max is the product of maximal cardiac output (Q) (maximal stroke volume (SVmax) x heart rate) and peak arterio-venous oxygen content difference (a-vO 2 diff). SVmax and peak a-vO 2 diff have important implications across the spectrum of human health and performance. However, the molecular mechanisms underlying SVmax and peak a-vO 2 diff remain largely unknown. We characterize SVmax and peak a-vO 2 diff using large-scale plasma proteomics and genotyping to identify circulating proteins and putative mediators of these traits. Methods: 763 physically inactive adults without overt cardiovascular disease underwent cardiopulmonary exercise testing with rigorous measurements of Q. High-throughput plasma proteomic profiling was performed to identify proteins associated with SVmax, a-vO 2 diff, and VO 2 max. cis-Mendelian Randomization (MR) analysis was conducted to assess causal relationships between protein markers and cardiovascular performance traits. Results: Proteomic profiling revealed associations between SVmax and several adiposity-related proteins, as well as secretory muscle factors (cathepsin B, α-actinin 2, and troponin I) (Figure). Proteins associated with peak a-vO2diff reflected oxygen-carrying capacity, muscle biology, and glucose metabolism (erythropoietin, myoglobin, fructose-1,6-bisphosphatase). Significant overlap was observed between proteins associated with SVmax, a-vO 2 diff, and VO 2 max. Cis-MR identified myocilin (MYOC) and caspase recruitment domain family member 9 (CARD9) as potential mediators of cardiovascular performance and VO 2 max. Conclusions: This study provides novel insights into the molecular influences of cardiovascular performance and VO 2 max. The identified protein markers associated with SVmax and a-vO 2 diff, along with the possible mediators MYOC and CARD9, merit further investigation into their role in endurance exercise capacity and cardiometabolic health.

Identification of OPTN p.(Asn51Thr): A novel pathogenic variant in primary open-angle glaucoma

PurposePathogenic variants in TBK1, MYOC, and OPTN are associated with primary open-angle glaucoma (POAG) with severe visual field defects. This study aims to understand further POAG-related pathogenic variant(s) based on a cohort of East Asian populations that have not been well-characterized. MethodsWe conducted a comprehensive screening of TBK1, MYOC, and OPTN variants in 174 POAG Japanese patients, followed by 8380 population-specific genome sequencing data references, segregation analysis, and functional protein assays to determine pathogenic variants. ResultsDespite the small sample size, 4 variants were novel, 2 of which p.(Cys5Trp) and p.(Thr293Met) were in the MYOC gene, and 2 p.(Asn51Thr), and p.(Gln142His) were in the OPTN. Notably, the OPTN p.(Asn51Thr) missense variant adjacent to the p.(Glu50Lys) variant, a well-known POAG pathogenic variant, was segregated from all proband’s family members with POAG. Moreover, in silico and in vitro analyses revealed that the OPTN p.(Asn51Thr) protein increased binding instability, interactions of the OPTN-TBK1 complex, and enhanced protein insolubility, likewise the p.(Glu50Lys) protein. ConclusionOur findings may provide further genetic insights into rare variants of POAG and support the clear conclusion that OPTN p.(Asn51Thr) is a novel likely pathogenic variant.

CYP1B1 and MYOC Gene Analysis of Patients with Primary Congenital Glaucoma in the Cukurova Region of Türkiye.

The aim of this study was to investigate the CYP1B1 and MYOC genes in patients with primary congenital glaucoma (PCG) from the Cukurova region (located in the south of Türkiye) and reveal the relationship between gene mutations and clinical severity of the disease. Molecular genetic and clinical study was conducted in 42 eyes of 26 patients who were followed for a diagnosis of PCG. The clinical diagnosis was concluded by ophthalmological examination under general anesthesia or slit-lamp biomicroscopy, gonioscopy, and measurement of the intraocular pressure. A CYP1B1 gene mutation was detected in 12 patients (46.2%). Two of these patients had a combination of CYP1B1 and MYOC mutations. The most common pathogenic variant, c.1405C > T (p.R469W) ( n = 5), was present in patients with mutations, and the prognosis was poor compared with other modifications ( p = 0.014). The second most common variant was c.3987G > A (p.G61E) ( n = 3), which was associated with a good prognosis. The incidence of buphthalmos and the mean horizontal corneal diameter were higher in patients with mutations in the CYP1B1 and MYOC genes. All parents were found to be carriers of the mutation gene. This is the report on molecular genetic analysis of PCG in the southern region of Türkiye. Some specific genetic variants may have an effect on the prognosis of the disease. However, patients without mutations in these case groups may have mutations in genes yet to be identified.

Familial normal tension glaucoma genetics.

Glaucoma is defined by characteristic optic nerve damage and corresponding visual field defects and is the leading cause of irreversible blindness in the world. Elevated intraocular pressure (IOP) is a strong risk factor for developing glaucoma. However, glaucoma can occur at any IOP. Normal tension glaucoma (NTG) arises with IOPs that are within what has been defined as a normal range, i.e., 21mm Hg or less, which may present challenges in its diagnosis and management. Identifying inheritance patterns and genetic mutations in families with NTG has helped elucidate mechanisms of NTG, however the pathophysiology is complex and not fully understood. Approximately 2% of NTG cases are caused primarily by mutations in single genes, optineurin (OPTN), TANK binding kinase 1 (TKB1), or myocilin (MYOC). Herein, we review pedigree studies of NTG and autosomal dominant NTG caused by OPTN, TBK1, and MYOC mutations. We review identified mutations and resulting clinical features of OPTN-associated and TBK1-associated NTG, including long-term follow up of these patients with NTG. In addition, we report a new four-generation pedigree of NTG caused by a Glu50Lys OPTN mutation, including six family members with a mean follow up of 17 years. Common features of OPTN -associated NTG due to Glu50Lys mutation included early onset of disease with an IOP <21mm Hg, marked optic disc cupping, and progressive visual field loss which appeared to stabilize once an IOP of less than 10mm Hg was achieved. Lastly, we review risk factor genes which have been identified to contribute to the complex inheritance of NTG.

Predictive value of serum proteomic biomarkers for noise-induced hearing loss.

Early detection of noise-induced hearing loss (NIHL) in patients with long-term noise exposure is vital for improving public health and reducing social burden. However, at present, the diagnosis of NIHL mainly depends on audiometric testing, and the primary test is pure-tone audiometry. Moreover, testing requires professional operators and complex equipment; thus, NIHL is often diagnosed at a later disease stage. Using a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic approach, we identified 9 differentially expressed proteins (DEPs), namely, 6 upregulated serum proteins and 3 downregulated serum proteins, in samples from 50 ground crew personnel working at an air force station. Then, according to the results, we predicted that caldesmon (CALD1), myocilin (MYOC), zyxin (ZYX), creatine kinase M-type (CKM), insulin-like growth factor-binding protein 2 (IGFBP2), complement factor H-related protein 4 (CFHR4), prenylcysteine oxidase 1 (PCYOX1), heat shock cognate 71 kDa protein (HSPA8), and immunoglobulin lambda variable 3-21 (IGLV3-21) were associated with NIHL. We selected these DEPs as variables to perform logistic regression. Finally, a logistic regression model was constructed based on IGFBP2, ZYX, CKM, and CFHR4. The area under the curve was 0.894 (95% CI = 0.812 to 0.977). These findings suggested that IGFBP2, ZYX, CKM, and CFHR4 in serum are differentially expressed in NIHL patients and have the potential to be biomarkers for predicting the risk for NIHL. Further experiments in mice showed that ZYX and IGFBP2 in the cochlear were increased after noise exposure. ZYX and IGFBP2 may be involved in the occurrence and development of NIHL.

Myocilin Mutation N480K Leads to Early Onset Juvenile and Adult-onset Primary Open Angle Glaucoma in a Six Generation Family.

A pathogenic autosomal dominant MYOC mutation N480K detected in 6 generations of an Indian family is primarily responsible for juvenile open angle glaucoma (JOAG) and adult-onset primary open angle glaucoma (POAG), emphasizing the importance of screening this mutation at a younger age. To screen myocilin mutations in a large South Indian family with early-onset JOAG and adult-onset POAG. In a large South Indian family with 20 members, 8 members diagnosed as JOAG, 7 members as POAG, 4 members as JOAG suspect, and 1 member as POAG suspect were screened for myocilin ( MYOC) mutations using Sanger sequencing. Whole exome sequencing was performed on clinically suspected JOAG/POAG individuals. Myocilin gene mutation N480K (c.1440C>G) was detected in 20 family members, including proband, of whom 8 were JOAG and 7 were POAG patients, 3 were JOAG suspects, and 2 were unaffected. Among the unaffected carriers, 1 was less than 5 years old, and another was 25 years old. The earliest to develop the disease was a 10-year-old child. The penetrance of the mutation was 95% over 10 years of age. This family had JOAG/POAG suspects with no N480K MYOC mutation, and they were further screened for other mutations using whole-exome sequencing. Polymorphisms CYP1B1 L432V and MYOC R76K were detected in 3 JOAG/POAG suspects, and among these 3, one had another CYP1B1 polymorphic variant R368H. The presence of the CYP1B1 polymorphism along with an MYOC polymorphic variant among the JOAG/POAG suspects needs additional studies to explore their combined role in the onset of glaucoma. This study reveals that MYOC mutation is primarily responsible for JOAG and adult-onset POAG in a family, emphasizing the importance of screening for this mutation at a younger age for early treatment.

A rare optineurin mutation in an Indian family with coexistence of JOAG and PCG.

This study focused on the genetic screening of Myocilin (MYOC), Cytochrome P450 family 1 subfamily B member 1 (CYP1B1), Optineurin (OPTN), and SIX homeobox 6 (SIX6) genes in a family with coexistence of primary congenital glaucoma (PCG) and juvenile open-angle glaucoma (JOAG). Sanger sequencing was used to examine the coding region of all four genes. Six different online available algorithms were used for the pathogenicity prediction of missense variant. Structural analysis was done using Garnier-Osguthorpe-Robson (GOR), PyMol, ChimeraX, and Molecular Dynamic (MD) Simulations (using Graphics Processing Unit (GPU)-enabled Desmond module of Schrödinger). There were a total of three sequence variants within the family. All seven algorithms determined that a single mutation, G538E, in the OPTN gene is pathogenic. The loops connecting the strands became more flexible, as predicted structurally and functionally by pathogenic mutations. Mutations create perturbations and conformational rearrangements in proteins, hence impairing their functioning. In this study, we describe a North Indian family in which members were having JOAG and PCG due to a rare homozygous/heterozygous mutation in OPTN. The coexistence of two types of glaucoma within a single pedigree suggests that certain OPTN mutations may be responsible for the onset of different glaucoma phenotypes.

Dexamethasone Modulates the Dynamics of Wnt Signaling in Human Trabecular Meshwork Cells.

Trabecular meshwork (TM) tissue is highly specialized, and its structural integrity is crucial for maintaining homeostatic intraocular pressure (IOP). The administration of glucocorticoids, such as dexamethasone (DEX), can perturb the TM structure and significantly increase IOP in susceptible individuals, resulting in ocular diseases such as steroid-induced glaucoma, a form of open-angle glaucoma. Although the exact mechanism involved in steroid-induced glaucoma remains elusive, increasing evidence suggests that DEX may act through various signaling cascades in TM cells. Despite uncertainty surrounding the specific process by which steroid-induced glaucoma occurs, there is growing evidence to indicate that DEX can impact multiple signaling pathways within TM cells. In this study, we examined the impact of DEX treatment on the Wnt signaling pathway in TM cells, given that Wnt signaling has been reported to play a crucial role in regulating extracellular matrix (ECM) levels in the TM. To further elucidate the role of Wnt signaling in the glaucomatous phenotype, we examined mRNA expression patterns between Wnt signaling markers AXIN2 and sFRP1 and DEX-mediated induction of myocilin (MYOC) mRNA and protein levels over 10 days in DEX-treated primary TM cells. We observed a sequential pattern of peak expression between AXIN2, sFRP1, and MYOC. Based on the study, we propose that sFRP1 upregulation could be a result of a negative feedback mechanism generated by stressed TM cells to suppress abnormal Wnt signaling activities.

Analysis of glaucoma genes in Finnish patients with juvenile open-angle glaucoma.

To identify germline variants in myocilin (MYOC) and other known monogenic glaucoma genes in Finnish patients with juvenile open-angle glaucoma (JOAG). Finnish patients with JOAG treated between 2010 and 2018 at the Department of Ophthalmology, Helsinki University Hospital, Finland, were enrolled. We sequenced all exonic regions and flanking splice sites of MYOC for five patients and one healthy relative using Sanger sequencing. In 48 patients, we performed exome sequencing to identify variants also in 28 other glaucoma-related genes. Fifty-three individuals with JOAG from 50 pedigrees, and one healthy relative, participated. The mean age at diagnosis was 30.8 years [SD 7.6; range 11 to 39]. Five probands had probably pathogenic variants in MYOC: c.1102C>T p.(Gln368Ter), c.1109C>T p.(Pro370Leu), c.1130C>T p.(Thr377Met), c.1132G>A p.(Asp378Asn) and c.1456C>T p.(Leu486Phe). Four of these patients had a family history of dominantly inherited JOAG. The frequency of MYOC variants was 10% (5 of 50 families). One patient and his mother with JOAG had a novel loss-of-function variant in the FOXC1 gene, c.366G>A p.(Trp122Ter). A patient with sporadic JOAG had a homozygous likely pathogenic variant in the LTBP2 gene, c.3938G>A p.(Cys1313Tyr). The genetic variants explained 14% (7 out of 50 families; 95% CI, 6%-23%) of JOAG in our cohort. The frequency of pathogenic variants in previously known glaucoma-associated genes is low in Finnish patients with JOAG. Because of the distinct genetic background of Finns, it might be possible to identify novel glaucoma genes through our JOAG series in the future.

COBL, MKX and MYOC Are Potential Regulators of Brown Adipose Tissue Development Associated with Obesity-Related Metabolic Dysfunction in Children

Obesity is already accompanied by adipose tissue (AT) dysfunction and metabolic disease in children and increases the risk of premature death. Due to its energy-dissipating function, brown AT (BAT) has been discussed as being protective against obesity and related metabolic dysfunction. To analyze the molecular processes associated with BAT development, we investigated genome-wide expression profiles in brown and white subcutaneous and perirenal AT samples of children. We identified 39 upregulated and 26 downregulated genes in uncoupling protein 1 (UCP1)-positive compared to UCP1-negative AT samples. We prioritized for genes that had not been characterized regarding a role in BAT biology before and selected cordon-bleu WH2 repeat protein (COBL), mohawk homeobox (MKX) and myocilin (MYOC) for further functional characterization. The siRNA-mediated knockdown of Cobl and Mkx during brown adipocyte differentiation in vitro resulted in decreased Ucp1 expression, while the inhibition of Myoc led to increased Ucp1 expression. Furthermore, COBL, MKX and MYOC expression in the subcutaneous AT of children is related to obesity and parameters of AT dysfunction and metabolic disease, such as adipocyte size, leptin levels and HOMA-IR. In conclusion, we identify COBL, MKX and MYOC as potential regulators of BAT development and show an association of these genes with early metabolic dysfunction in children.

Quantitative differentiation of benign and misfolded glaucoma-causing myocilin variants on the basis of protein thermal stability.

Accurate predictions of the pathogenicity of mutations associated with genetic diseases are key to the success of precision medicine. Inherited missense mutations in the myocilin (MYOC) gene, within its olfactomedin (OLF) domain, constitute the strongest genetic link to primary open-angle glaucoma via a toxic gain of function, and thus MYOC is an attractive precision-medicine target. However, not all mutations in MYOC cause glaucoma, and common variants are expected to be neutral polymorphisms. The Genome Aggregation Database (gnomAD) lists ∼100 missense variants documented within OLF, all of which are relatively rare (allele frequency <0.001%) and nearly all are of unknown pathogenicity. To distinguish disease-causing OLF variants from benign OLF variants, we first characterized the most prevalent population-based variants using a suite of cellular and biophysical assays, and identified two variants with features of aggregation-prone familial disease variants. Next, we considered all available biochemical and clinical data to demonstrate that pathogenic and benign variants can be differentiated statistically based on a single metric: the thermal stability of OLF. Our results motivate genotyping MYOC in patients for clinical monitoring of this widespread, painless and irreversible ocular disease.