Variants in the ASB10 Gene Are Associated with Primary Open Angle Glaucoma

Evaluating Practical Approaches for Including MYOC Variants Alongside Common Variants for Genetics-Based Risk Stratification for Glaucoma

OBJECTIVE

Rare variants in the MYOC gene are associated with glaucoma risk, with p.Gln368Ter the most common pathogenic variant in Europeans. Genetics-based risk stratification may aid with early diagnosis for glaucoma but it is unclear how best to combine the p.Gln368Ter status with polygenic risk scores (PRS). Our study aimed to examine approaches for identifying p. Gln368Ter carriers using genotyping array data and the utility of integrating p.Gln368Ter status into glaucoma PRS.

DESIGN

Retrospective cohort study.

METHODS

We identified p.Gln368Ter carriers using directly genotyped and imputed data. Results were confirmed in a subset with sequencing data. We evaluated the combined effects of p.Gln368Ter status and PRS in stratified analyses by considering them as two separate factors and as an aggregate score.

PARTICIPANTS

A total of 58,452 participants from the Genetics of Glaucoma, the QSkin Sun and Health Study (QSKIN), and CARTaGENE projects, including 6015 with sequencing data.

MAIN OUTCOMES AND MEASURES

The concordance of direct genotyping, compared with imputation and sequencing for p.Gln368Ter identification.

RESULTS

Without appropriate quality control, substantial mis-calling may occur. Nevertheless, the p.Gln368Ter variant could be accurately genotyped in most cases by filtering individuals for call rate and heterozygosity. In 6015 individuals with sequencing data, direct genotyping exhibited perfect concordance with sequencing results. Filtered direct genotyping results showed high agreement with imputed results, with only 16 discrepancies among 57,468 individuals. When quality control is not possible (eg, heterozygosity filtering for an individual), we recommend comparing genotyped and imputed results to ensure accuracy. Incorporating p.Gln368Ter into PRS had additional effects on stratifying high-risk individuals, but did not improve risk prediction for the general population given the variant's rarity. The MYOC-enhanced PRS increased the proportion of p.Gln368Ter carriers classified as high risk from 32.31% to 75.38% in QSKIN and from 38.24% to 79.41% in CARTaGENE.

CONCLUSIONS

The p.Gln368Ter variant can be genotyped with high accuracy using array data, provided careful quality control measures are implemented. Incorporating p.Gln368Ter into glaucoma PRS improved risk stratification for carriers.

Asb10 accelerates pathological cardiac remodeling by stabilizing HSP70

Cardiac hypertrophy is a pivotal risk factor for heart failure. Hypertension-induced pressure overload triggers left ventricular hypertrophy and leads to heart failure. Although the precise mechanisms remain incompletely elucidated, recent studies highlighted the role of ubiquitin-proteasome system in this process. As a heart tissue-enriched E3 ligase, the function of Asb10 in cardiac hypertrophy remains unknown. Here, we aimed to dissect the role of Asb10 in the pathogenesis of cardiac hypertrophy and heart failure. Through integrated bioinformatic screening of GEO datasets and experimental verifications, we identified Asb10 as the downregulated gene in cardiac hypertrophy. Adenoviral overexpression of Asb10 exacerbated hypertrophic growth in NRVMs treated with phenylephrine or endothelin-1. Mechanistically, immunoprecipitation-mass spectrometry and co-immunoprecipitation assays revealed that Asb10 binds HSP70 and competitively blocks STUB1-mediated ubiquitination and degradation of HSP70, thereby stabilizing HSP70. Pharmacological or small interfering RNA-induced inhibition of HSP70 partially reversed Asb10 overexpression-induced hypertrophic growth in NRVMs. In vivo, mice administrated with AAV9-Asb10 exhibited worse cardiac function and more severe interstitial fibrosis following TAC surgery, while mice injected with AAV9-shAsb10 showed improved outcomes. Furthermore, we observed that the effects of Asb10 on cardiac hypertrophy were attributed to the elevation of HSP70, cardiac inflammation, and activation of pHDAC2S394. Collectively, these findings demonstrate that Asb10 stabilizes HSP70 via competitively inhibiting STUB1-mediated ubiquitin-dependent degradation, thereby exacerbating cardiac hypertrophy, highlighting the role of Asb10 in hemodynamic stress-induced cardiac hypertrophy and heart failure.

Identification of regulatory genes associated with POAG by integrating expression and sequencing data

BACKGROUND

Primary open-angle glaucoma (POAG) is a subtype of glaucoma that accounts for 60%~70% of all cases. Its pathogenic mechanism is intricate and its pathogenic process is concealed. Numerous significant biological processes associated with POAG continue to be elucidated.

METHODS

In this study, by exploring the expression data of POAG tissues and normal tissues, we mined the regulatory lncRNAs and mRNAs closely associated with the pathogenesis and progression of POAG by exploring a regulatory network of competing endogenous RNA (ceRNA), established by integrating gene expression data with the known lncRNA-miRNA and miRNA-mRNA-regulatory interactions. The key regulatory pathways and regulatory elements of POAG were identified by topological analysis. Simultaneously, the exome data of 28 cases with POAG and healthy controls were analyzed to identify high-frequency mutations and genes.

RESULTS

A total of 2712 differentially expressed genes were identified, including 1828 mRNAs and 884 lncRNAs. Network analysis suggested that lncRNAs such as HAGLR, HOTAIR and MIR29B2CHG, and mRNAs such as PPP6R3, BMPR2 and CFL2, may be involved in the onset and progression of POAG. In addition, 55 mutations with potential pathogenicity were identified.

CONCLUSION

These genes and mutations provide novel potential genetic heterogeneity and genetic susceptibility of POAG, as well as fresh suggestions for elucidating the molecular mechanism underlying the pathogenesis of POAG.

Ubiquitin proteasome system and glaucoma: A survey of genetics and molecular biology studies supporting a link with pathogenic and therapeutic relevance

Glaucoma represents a group of progressive neurodegenerative diseases characterized by the loss of retinal ganglion cells (RGCs) and their axons with subsequent visual field impairment. The disease develops through largely uncharacterized molecular mechanisms, that are likely to occur in different localized cell types, either in the anterior (e.g., trabecular meshwork cells) or posterior (e.g., Muller glia, retinal ganglion cells) segments of the eye. Genomic and preclinical studies suggest that glaucoma pathogenesis may develop through altered ubiquitin (Ub) signaling. Ubiquitin conjugation, referred to as ubiquitylation, is a major post-synthetic modification catalyzed by E1-E2-E3 enzymes, that profoundly regulates the turnover, trafficking and biological activity of the targeted protein. The development of new technologies, including proteomics workflows, allows the biology of ubiquitin signaling to be described in health and disease. This post-translational modification is emerging as a key role player in neurodegeneration, gaining relevance for novel therapeutic options, such as in the case of Proteolysis Targeting Chimeras technology. Although scientific evidence supports a link between Ub and glaucoma, their relationship is still not well-understood. Therefore, this review provides a detailed research-oriented discussion on current evidence of Ub signaling in glaucoma. A review of genomic and genetic data is provided followed by an in-depth discussion of experimental data on ASB10, parkin and optineurin, which are proteins that play a key role in Ub signaling and have been associated with glaucoma.

Molecular genetics of primary open-angle glaucoma

Glaucoma is a series of linked optic diseases resulting in progressive vision loss and total blindness due to the acquired loss of retinal ganglion cells. This harm to the optic nerve results in visual impairment and, ultimately, total blindness if left untreated. Primary open-angle glaucoma (POAG) is the most frequent variety within the large family of glaucoma. It is a multifaceted and heterogeneous condition with several environmental and genetic variables aiding in its etiology. By 2040, there will be 111.8 million glaucoma patients globally, with Asia and Africa accounting for the vast majority. The goal of this review is to elaborate on the role of genes (nuclear and mitochondrial) as well as their variants in the pathogenesis of POAG. PubMed and Google Scholar databases were searched online for papers until September 2022. Prevalence and inheritance patterns vary significantly across different ethnic and geographic populations. Numerous causative genetic loci may exist; however, only a few have been recognized and characterized. Further investigation into the genetic etiology of POAG is expected to uncover novel and intriguing causal genes, allowing for a more precise pathogenesis pattern of the disease.

Lack of Correlation between ASB10 and Normal-tension Glaucoma in a Population from the Republic of Korea

Purpose: Ankyrin repeats and suppressor of cytokine signaling box-containing protein 10 (ASB10) was identified as a novel gene for glaucoma. Since then, there have been reports on the association of ASB10 with glaucoma in various ethnic populations. In these studies, patients with different glaucoma types were included. Thus, we investigated the relationship between ASB10 and NTG in a Korean cohort.Methods: Whole-exome sequencing was performed to identify the ASB10 variants in one patient with a strong NTG family history. A total of 263 participants, comprising 157 NTG patients and 106 control subjects, were analyzed for ASB10 gene single nucleotide polymorphisms (SNPs).Results: Nine variants of the ASB10 gene were identified using whole-exome sequencing analysis, including four exonic SNPs. Of the exonic variants, three were known polymorphisms (rs3800791, rs2253592, and rs77615410), and one was newly reported (rs552803353). A nonsynonymous variant, rs552803353 was predicted as functionally damaging using PolyPhen-2. The exonic SNPs were compared against gene sequences of the control group in the NTG cohort. However, the minor allele frequency (MAF) of rs552803353 was found to be 0.029 and 0.038 in NTG cases and control subjects, respectively. The MAF of rs3800791 was found to be 0.096 and 0.118 in NTG cases and control subjects, respectively, and the MAF of rs77615410 was found to be 0.220 and 0.245 in NTG cases and control subjects, respectively, which were higher than those reported by previous studies. Genetic association analysis of four ASB10 SNPs revealed no significant difference in genotype distribution between NTG cases and control subjects in allelic, dominant, or recessive models (all, P > .05).Conclusions: The present study indicated that the MAFs of ASB10 gene polymorphisms showed a large difference among various ethnic groups, and that ASB10 gene polymorphisms may not be associated with genetic susceptibility to NTG in a Korean cohort.

Genetic testing for Mendelian glaucoma

We studied the scientific literature and disease guidelines in order to summarize the clinical utility of genetic testing for Mendelian glaucomas, a large heterogeneous group of inherited disorders, classified according to age of onset as congenital glaucoma, juvenile glaucoma and age-related glaucoma. Variations in the TEK, MYOC, ASB10, NTF4, OPA1, WDR36 and OPTN genes are inherited in an autosomal dominant manner and variations in the CYP1B1 and LTBP2 genes have autosomal recessive inheritance. The prevalence of congenital glaucoma is estimated at 1-9 per 100 000, that of juvenile glaucoma at 1 per 50 000, while there is insufficient data to establish the prevalence of age-related glaucoma. Clinical diagnosis is based on clinical findings, age of onset, family history, ophthalmological examination, intraocular pressure, gonioscopy and fundoscopy. The genetic test is useful for confirming diagnosis, and for differential diagnosis, couple risk assessment and access to clinical trials.

Identifying key genes in glaucoma based on a benchmarked dataset and the gene regulatory network

The current study aimed to identify key genes in glaucoma based on a benchmarked dataset and gene regulatory network (GRN). Local and global noise was added to the gene expression dataset to produce a benchmarked dataset. Differentially-expressed genes (DEGs) between patients with glaucoma and normal controls were identified utilizing the Linear Models for Microarray Data (Limma) package based on benchmarked dataset. A total of 5 GRN inference methods, including Zscore, GeneNet, context likelihood of relatedness (CLR) algorithm, Partial Correlation coefficient with Information Theory (PCIT) and GEne Network Inference with Ensemble of Trees (Genie3) were evaluated using receiver operating characteristic (ROC) and precision and recall (PR) curves. The interference method with the best performance was selected to construct the GRN. Subsequently, topological centrality (degree, closeness and betweenness) was conducted to identify key genes in the GRN of glaucoma. Finally, the key genes were validated by performing reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A total of 176 DEGs were detected from the benchmarked dataset. The ROC and PR curves of the 5 methods were analyzed and it was determined that Genie3 had a clear advantage over the other methods; thus, Genie3 was used to construct the GRN. Following topological centrality analysis, 14 key genes for glaucoma were identified, including IL6, EPHA2 and GSTT1 and 5 of these 14 key genes were validated by RT-qPCR. Therefore, the current study identified 14 key genes in glaucoma, which may be potential biomarkers to use in the diagnosis of glaucoma and aid in identifying the molecular mechanism of this disease.

Major review: Molecular genetics of primary open-angle glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. Primary open-angle glaucoma (POAG), the most common type, is a complex inherited disorder that is characterized by progressive retinal ganglion cell death, optic nerve head excavation, and visual field loss. The discovery of a large, and growing, number of genetic and chromosomal loci has been shown to contribute to POAG risk, which carry implications for disease pathogenesis. Differential gene expression analyses in glaucoma-affected tissues as well as animal models of POAG are enhancing our mechanistic understanding in this common, blinding disorder. In this review we summarize recent developments in POAG genetics and molecular genetics research.

Working your SOCS off: The role of ASB10 and protein degradation pathways in glaucoma

Evidence is accumulating to suggest that mutations in the Ankyrin and SOCS Box-containing protein-10 (ASB10) gene are associated with glaucoma. Since its identification in a large Oregon family with primary open-angle glaucoma (POAG), ASB10 variants have been associated with disease in US, German and Pakistani cohorts. ASB10 is a member of the ASB family of proteins, which have a common structure including a unique N-terminus, a variable number of central ankyrin (ANK) repeat domains and a suppressor of cytokine signaling (SOCS) box at the C-terminus. Mutations in ASB10 are distributed throughout the entire length of the gene including the two alternatively spliced variants of exon 1. A homozygous mutation in a Pakistani individual with POAG, which lies in the center of the SOCS box, is associated with a particularly severe form of the disease. Like other SOCS box-containing proteins, ASB10 functions in ubiquitin-mediated degradation pathways. The ANK repeats bind to proteins destined for degradation. The SOCS box recruits ubiquitin ligase proteins to form a complex to transfer ubiquitin to a substrate bound to the ANK repeats. The ubiquitin-tagged protein then enters either the proteasomal degradation pathway or the autophagic-lysosomal pathway. The choice of pathway appears to be dependent on which lysine residues are used to build polyubiquitin chains. However, these reciprocal pathways work in tandem to degrade proteins because inhibition of one pathway increases degradation via the other pathway. In this publication, we will review the literature that supports identification of ASB10 as a glaucoma-associated gene and the current knowledge of the function of the ASB10 protein. In addition, we present new data that indicates ASB10 expression is up-regulated by the inflammatory cytokines tumor necrosis factor-α and interleukin-1α. Finally, we will describe the emerging role of other SOCS box-containing proteins in protein degradation pathways in ocular cells.