Evaluation of Shared Genetic Susceptibility to High and Low Myopia and Hyperopia

Axial Elongation Trajectories in Chinese Children and Adults With High Myopia

Importance

Understanding the long-term axial elongation trajectory in high myopia is important to prevent blindness.

Objective

To evaluate axial elongation trajectories and related visual outcomes in children and adults with high myopia.

Design, Setting, and Participants

In this cohort study, participants in the Zhongshan Ophthalmic Centre-Brien Holden Vision Institute high myopia cohort were followed up every other year for 8 years. Participants with axial length measurements at baseline (2011 or 2012) and at least 1 follow-up visit were included. Participants were grouped according to baseline age as children and adolescents (7 to <18 years), young adults (18 to <40 years), and older adults (≥40 to 70 years). Data were analyzed from November 1, 2022, to June 1, 2023.

Exposure

High myopia (spherical power ≤-6.00 diopters).

Main Outcomes and Measures

Longitudinal axial elongation trajectories were identified by cluster analysis. Axial elongation rates were calculated by linear mixed-effects models. A 2-sided P < .05 was defined as statistically significant.

Results

A total of 793 participants (median [range] age, 17.8 [6.8-69.7] years; 418 females [52.7%]) and 1586 eyes were included in the analyses. Mean axial elongation rates were 0.46 mm/y (95% CI, 0.44-0.48 mm/y) for children and adolescents, 0.07 mm/y (95% CI, 0.06-0.09 mm/y) for young adults, and 0.13 mm/y (95% CI, 0.07-0.19 mm/y) for older adults. Cluster analysis identified 3 axial elongation trajectories, with the stable, moderate, and rapid progression trajectories having mean axial elongation rates of 0.02 mm/y (95% CI, 0.01-0.02 mm/y), 0.12 mm/y (95% CI, 0.11-0.13 mm/y), and 0.38 mm/y (95% CI, 0.35-0.42 mm/y), respectively. At 8 years of follow-up, compared with the stable progression trajectory, the rapid progression trajectory was associated with a 6.92 times higher risk of developing pathological myopic macular degeneration (defined as diffuse or patchy chorioretinal atrophy or macular atrophy; odds ratio, 6.92 [95% CI, 1.07-44.60]; P = .04), and it was associated with a 0.032 logMAR decrease in best-corrected visual acuity (β = 0.032 [95% CI, 0.001-0.063]; P = .04).

Conclusions and Relevance

The findings of this 8-year follow-up study suggest that axial length in high myopia continues to increase from childhood to late adulthood following 3 distinct trajectories. At 8 years of follow-up, the rapid progression trajectory was associated with a higher risk of developing pathological myopic macular degeneration and poorer best-corrected visual acuity compared with the stable progression trajectory. These distinct axial elongation trajectories could prove valuable for early identification and intervention for high-risk individuals.

Association of hyperopia with incident clinically significant depression: epidemiological and genetic evidence in the middle-aged and older population

AIMS

To investigate the association between hyperopia and clinically significant depression (CSD) in middle-aged and older individuals. The effect of genetic determinants of hyperopia on incident CSD was also explored.

METHODS

We included participants who had available data on mean spherical equivalent (MSE) and were free of depression at baseline from the UK Biobank. For the phenotypic association, hyperopia was defined as MSE of+2.00 dioptres (D) or greater, and was divided into mild, moderate and high groups. Diagnosis of CSD across follow-up was determined based on electronic hospital inpatients records. For the genetic association analysis, the association between hyperopia Polygenic Risk Score and incident CSD was assessed. Mendelian randomisation was assessed for causality association.

RESULTS

Over a median follow-up of 11.11 years (IQR: 10.92-11.38), hyperopia was significantly associated with incident CSD independent of genetic risk (HR 1.29, 95% CI 1.05 to 1.59) compared with emmetropia participants, especially in those hyperopic patients without optical correction (HR 1.38, 95% CI 1.07 to 1.76). In addition, participants in the high degree of hyperopia were more likely to have incident CSD than participants in the mild degree of hyperopia (P for trend=0.009). Genetic analyses did not show any significant associations between hyperopia and incident CSD (p≥0.1).

CONCLUSIONS

Hyperopia was significantly associated with an increased risk of incident CSD. This was independent of genetic predisposition to hyperopia, emphasising the importance of regular vision screening and correction of hyperopia to reduce the risk of CSD regardless of genetic risk.

Genetic and clinical landscape of ARR3-associated MYP26: the most common cause of Mendelian early-onset high myopia with a unique inheritance

AIMS

To elucidate genetic background of early-onset high myopia (eoHM) and characteristics of ARR3-associated MYP26.

METHODS

Variants in 14 genes reported to contribute to eoHM, including ARR3, were selected from exome sequencing data set and classified into different categories following American College of Medical Genetics and Genomics guidelines based on in silico prediction, associated phenotypes, confirmation and cosegregation analysis. The available clinical data of individuals were summarised.

RESULTS

Pathogenic and likely pathogenic variants in three of 14 genes were identified in 52 of 928 families with eoHM, including 29 in ARR3, 22 in OPN1LW and 1 in LRPAP1. For ARR3, 24 pathogenic variants (16 truncation and 8 missense) were identified in 66 women and 12 men, in whom 64 women and 4 men had eoHM by X-linked female-limited inheritance. Refraction ranged from -5.00 to -28.75 diopter (-12.58±4.83). Mild-to-moderately reduced cone responses were recorded in 76.9% (10/13) of patients with electroretinogram recordings. Most patients (75.9%, 41/54) had mild myopic fundus changes (C0 to C1). Genotype-phenotype analysis suggested that the myopic retinopathy degree was correlated with age and the variant's nature. Peripheral retinal degeneration was observed in 38.5% (5/13) patients using wide-field examinations.

CONCLUSION

This study reveals ARR3 as the most frequently implicated gene for Mendelian eoHM. Truncations and highly scored missense variants in ARR3 are pathogenic. Myopia due to ARR3 mutations is transmitted in X-linked female-limited inheritance, manifests with mild cone impairment and slowly progresses to pathologic myopia. Identification of the most common cause for Mendelian eoHM provides a valuable starting point into the molecular mechanism of myopia.

Ocular and neural genes jointly regulate the visuospatial working memory in ADHD children

OBJECTIVE

Working memory (WM) deficits have frequently been linked to attention deficit hyperactivity disorder (ADHD). Despite previous studies suggested its high heritability, its genetic basis, especially in ADHD, remains unclear. The current study aimed to comprehensively explore the genetic basis of visual-spatial working memory (VSWM) in ADHD using wide-ranging genetic analyses.

METHODS

The current study recruited a cohort consisted of 802 ADHD individuals, all met DSM-IV ADHD diagnostic criteria. VSWM was assessed by Rey-Osterrieth complex figure test (RCFT), which is a widely used psychological test include four memory indexes: detail delayed (DD), structure delayed (SD), structure immediate (SI), detail immediate (DI). Genetic analyses were conducted at the single nucleotide polymorphism (SNP), gene, pathway, polygenic and protein network levels. Polygenic Risk Scores (PRS) were based on summary statistics of various psychiatric disorders, including ADHD, autism spectrum disorder (ASD), major depressive disorder (MDD), schizophrenia (SCZ), obsessive compulsive disorders (OCD), and substance use disorder (SUD).

RESULTS

Analyses at the single-marker level did not yield significant results (5E-08). However, the potential signals with P values less than E-05 and their mapped genes suggested the regulation of VSWM involved both ocular and neural system related genes, moreover, ADHD-related genes were also involved. The gene-based analysis found RAB11FIP1, whose encoded protein modulates several neurodevelopment processes and visual system, as significantly associated with DD scores (P = 1.96E-06, Padj = 0.036). Candidate pathway enrichment analyses (N = 53) found that forebrain neuron fate commitment significantly enriched in DD (P = 4.78E-04, Padj = 0.025), and dopamine transport enriched in SD (P = 5.90E-04, Padj = 0.031). We also observed a significant negative relationship between DD scores and ADHD PRS scores (P = 0.0025, Empirical P = 0.048).

CONCLUSIONS

Our results emphasized the joint contribution of ocular and neural genes in regulating VSWM. The study reveals a shared genetic basis between ADHD and VSWM, with GWAS indicating the involvement of ADHD-related genes in VSWM. Additionally, the PRS analysis identifies a significant relationship between ADHD-PRS and DD scores. Overall, our findings shed light on the genetic basis of VSWM deficits in ADHD, and may have important implications for future research and clinical practice.

Myopia: Histology, clinical features, and potential implications for the etiology of axial elongation

Myopic axial elongation is associated with various non-pathological changes. These include a decrease in photoreceptor cell and retinal pigment epithelium (RPE) cell density and retinal layer thickness, mainly in the retro-equatorial to equatorial regions; choroidal and scleral thinning pronounced at the posterior pole and least marked at the ora serrata; and a shift in Bruch's membrane opening (BMO) occurring in moderately myopic eyes and typically in the temporal/inferior direction. The BMO shift leads to an overhang of Bruch's membrane (BM) into the nasal intrapapillary compartment and BM absence in the temporal region (i.e., parapapillary gamma zone), optic disc ovalization due to shortening of the ophthalmoscopically visible horizontal disc diameter, fovea-optic disc distance elongation, reduction in angle kappa, and straightening/stretching of the papillomacular retinal blood vessels and retinal nerve fibers. Highly myopic eyes additionally show an enlargement of all layers of the optic nerve canal, elongation and thinning of the lamina cribrosa, peripapillary scleral flange (i.e., parapapillary delta zone) and peripapillary choroidal border tissue, and development of circular parapapillary beta, gamma, and delta zone. Pathological features of high myopia include development of macular linear RPE defects (lacquer cracks), which widen to round RPE defects (patchy atrophies) with central BM defects, macular neovascularization, myopic macular retinoschisis, and glaucomatous/glaucoma-like and non-glaucomatous optic neuropathy. BM thickness is unrelated to axial length. Including the change in eye shape from a sphere in emmetropia to a prolate (rotational) ellipsoid in myopia, the features may be explained by a primary BM enlargement in the retro-equatorial/equatorial region leading to axial elongation.

The Genetic Determinants of Axial Length: From Microphthalmia to High Myopia in Childhood

The axial length of the eye is critical for normal visual function by enabling light to precisely focus on the retina. The mean axial length of the adult human eye is 23.5 mm, but the molecular mechanisms regulating ocular axial length remain poorly understood. Underdevelopment can lead to microphthalmia (defined as a small eye with an axial length of less than 19 mm at 1 year of age or less than 21 mm in adulthood) within the first trimester of pregnancy. However, continued overgrowth can lead to axial high myopia (an enlarged eye with an axial length of 26.5 mm or more) at any age. Both conditions show high genetic and phenotypic heterogeneity associated with significant visual morbidity worldwide. More than 90 genes can contribute to microphthalmia, and several hundred genes are associated with myopia, yet diagnostic yields are low. Crucially, the genetic pathways underpinning the specification of eye size are only now being discovered, with evidence suggesting that shared molecular pathways regulate under- or overgrowth of the eye. Improving our mechanistic understanding of axial length determination will help better inform us of genotype-phenotype correlations in both microphthalmia and myopia, dissect gene-environment interactions in myopia, and develop postnatal therapies that may influence overall eye growth.

Epitranscriptomic investigation of myopia-associated RNA editing in the retina

Myopia is one of the most common causes of vision loss globally and is significantly affected by epigenetics. Adenosine-to-inosine (A-to-I RNA) editing is an epigenetic process involved in neurological disorders, yet its role in myopia remains undetermined. We performed a transcriptome-wide analysis of A-to-I RNA editing in the retina of form-deprivation myopia mice. Our study identified 91 A-to-I RNA editing sites in 84 genes associated with myopia. Notably, at least 27 (32.1%) of these genes with myopia-associated RNA editing showed existing evidence to be associated with myopia or related ocular phenotypes in humans or animal models, such as very low-density lipoprotein receptor (Vldlr) in retinal neovascularization and hypoxia-induced factor 1 alpha (Hif1a). Moreover, functional enrichment showed that RNA editing enriched in FDM was primarily involved in response to fungicides, a potentially druggable process for myopia prevention, and epigenetic regulation. In contrast, RNA editing enriched in controls was mostly involved in post-embryonic eye morphogenesis. Our results demonstrate altered A-to-I RNA editing associated with myopia in an experimental mouse model and warrant further study on its role in myopia development.

Sequencing of 19,219 exomes identifies a low-frequency variant in FKBP5 promoter predisposing to high myopia in a Han Chinese population

High myopia (HM) is one of the leading causes of visual impairment and blindness worldwide. Here, we report a whole-exome sequencing (WES) study in 9,613 HM cases and 9,606 controls of Han Chinese ancestry to pinpoint HM-associated risk variants. Single-variant association analysis identified three newly identified -genetic loci associated with HM, including an East Asian ancestry-specific low-frequency variant (rs533280354) in FKBP5. Multi-ancestry meta-analysis with WES data of 2,696 HM cases and 7,186 controls of European ancestry from the UK Biobank discerned a newly identified European ancestry-specific rare variant in FOLH1. Functional experiments revealed a mechanism whereby a single G-to-A transition at rs533280354 disrupted the binding of transcription activator KLF15 to the promoter of FKBP5, resulting in decreased transcription of FKBP5. Furthermore, burden tests showed a significant excess of rare protein-truncating variants among HM cases involved in retinal blood vessel morphogenesis and neurotransmitter transport.

A new polygenic score for refractive error improves detection of children at risk of high myopia but not the prediction of those at risk of myopic macular degeneration

BACKGROUND

High myopia (HM), defined as a spherical equivalent refractive error (SER) ≤ -6.00 diopters (D), is a leading cause of sight impairment, through myopic macular degeneration (MMD). We aimed to derive an improved polygenic score (PGS) for predicting children at risk of HM and to test if a PGS is predictive of MMD after accounting for SER.

METHODS

The PGS was derived from genome-wide association studies in participants of UK Biobank, CREAM Consortium, and Genetic Epidemiology Research on Adult Health and Aging. MMD severity was quantified by a deep learning algorithm. Prediction of HM was quantified as the area under the receiver operating curve (AUROC). Prediction of severe MMD was assessed by logistic regression.

FINDINGS

In independent samples of European, African, South Asian and East Asian ancestry, the PGS explained 19% (95% confidence interval 17-21%), 2% (1-3%), 8% (7-10%) and 6% (3-9%) of the variation in SER, respectively. The AUROC for HM in these samples was 0.78 (0.75-0.81), 0.58 (0.53-0.64), 0.71 (0.69-0.74) and 0.67 (0.62-0.72), respectively. The PGS was not associated with the risk of MMD after accounting for SER: OR = 1.07 (0.92-1.24).

INTERPRETATION

Performance of the PGS approached the level required for clinical utility in Europeans but not in other ancestries. A PGS for refractive error was not predictive of MMD risk once SER was accounted for.

FUNDING

Supported by the Welsh Government and Fight for Sight (24WG201).

Emmetropization and nonmyopic eye growth

Most eyes start with a hypermetropic refractive error at birth, but the growth rates of the ocular components, guided by visual cues, will slow in such a way that this refractive error decreases during the first 2 years of life. Once reaching its target, the eye enters a period of stable refractive error as it continues to grow by balancing the loss in corneal and lens power with the axial elongation. Although these basic ideas were first proposed over a century ago by Straub, the exact details on the controlling mechanism and the growth process remained elusive. Thanks to the observations collected in the last 40 years in both animals and humans, we are now beginning to get an understanding how environmental and behavioral factors stabilize or disrupt ocular growth. We survey these efforts to present what is currently known regarding the regulation of ocular growth rates.

Differential methylation of microRNA encoding genes may contribute to high myopia

Introduction: High myopia (HM), an eye disorder with a refractive error ≤-6.0 diopters, has multifactorial etiology with environmental and genetic factors involved. Recent studies confirm the impact of alterations in DNA methylation and microRNAs (miRNAs) on myopia. Here, we studied the combined aspects evaluating to the role of methylation of miRNA encoding genes in HM. Materials and Methods: From the genome-wide DNA methylation data of 18 Polish children with HM and 18 matched controls, we retrieved differentially methylated CG dinucleotides localized in miRNA encoding genes. Putative target genes of the highest-ranked miRNAs were obtained from the miRDB and included in overrepresentation analyses in the ConsensusPathDB. Expression of target genes was assessed using the RNA sequencing data of retinal ARPE-19 cell line. Results: We identified differential methylation of CG dinucleotides in promoter regions of MIR3621, MIR34C, MIR423 (increased methylation level), and MIR1178, MIRLET7A2, MIR885, MIR548I3, MIR6854, MIR675, MIRLET7C, MIR99A (decreased methylation level) genes. Several targets of these miRNAs, e.g. GNAS, TRAM1, CTNNB1, EIF4B, TENM3 and RUNX were previously associated with myopia/HM/refractive error in Europeans in genome-wide association studies. Overrepresentation analyses of miRNAs' targets revealed enrichment in pathways/processes related to eye structure/function, such as axon guidance, transcription, focal adhesion, and signaling pathways of TGF-β, insulin, MAPK and EGF-EGFR. Conclusion: Differential methylation of indicated miRNA encoding genes might influence their expression and contribute to HM pathogenesis via disrupted regulation of transcription of miRNAs' target genes. Methylation of genes encoding miRNAs may be a new direction in research on both the mechanisms determining HM and non-invasive indicators in diagnostics.

Analysis of SNHG14: A Long Non-Coding RNA Hosting SNORD116, Whose Loss Contributes to Prader-Willi Syndrome Etiology

The Small Nucleolar Host Gene 14 (SNHG14) is a host gene for small non-coding RNAs, including the SNORD116 small nucleolar C/D box RNA encoding locus. Large deletions of the SNHG14 locus, as well as microdeletions of the SNORD116 locus, lead to the neurodevelopmental genetic disorder Prader-Willi syndrome. This review will focus on the SNHG14 gene, its expression patterns, its role in human cancer, and the possibility that single nucleotide variants within the locus contribute to human phenotypes in the general population. This review will also include new in silico data analyses of the SNHG14 locus and new in situ RNA expression patterns of the Snhg14 RNA in mouse midbrain and hindbrain regions.

Prevalence of refractive error among Chinese preschool children: The Changsha children eye study

Purpose

We aimed to investigate the refractive status and prevalence of refractive error, as well as its characteristics in Chinese preschool children aged 1-6 years old.

Methods

A population-based cross-sectional study-Changsha Children Eye Study (CCES) was conducted. The prevalence of refractive errors among children aged 1-6 years old from 18 community health service centers was surveyed. A handheld child vision screener, Suowei, was used for examination.

Results

A total of 43,105 preschool children were included. The mean spherical equivalent (SE) was 0.42 ± 1.05 D for the right eyes. The mean astigmatism (diopter of cylinder, DC) was -0.83 ± 1.02 D for the right eyes. The magnitude of refractive error was lower in older children, indicating the ongoing of the emmetropization during the 1-6-year-old children. The prevalence of myopia (SE ≤ -1.00 D), hyperopia (SE ≥ +2.00 D) and astigmatism (DC ≥1.50 D) was 2.94, 13.8 and 17.6%, respectively. The prevalence of myopia decreased with the increase of age between the six age groups (P < 0.001). The prevalence of hyperopia was lower in 5-6 years old, whereas, the prevalence of myopia was slightly higher at this period of time. With-the-rule (WTR) astigmatism (+ cylinder axis 90° ± 15°) was the most prevalent type of astigmatism than against-the-rule (ATR) astigmatism (+ cylinder axis 180° ± 15°) and oblique (OBL) astigmatism (X ² = 209.5, P < 0.001). The binary logistic regression model showed that older age and suffering astigmatism were independently associated with the development of myopia. In addition, there was no significant gender difference in the prevalence of myopia, emmetropia, and hyperopia.

Conclusions

Our population-based cross-sectional study investigated the prevalence of myopia, hyperopia, and astigmatism in preschool children aged 1-6 years old. The distribution of the refractive error was disperse in the younger group and gradually turned more centralized in older group. Similar to hyperopia, with age increased, the prevalence of myopia was lower in preschool children younger than 5 years old and then slightly increased at 5-6 years, which may indicate an early sign of myopia in school-age children. Therefore, we emphasize that more attention should be given to the children at this age.

Decreased Levels of DNA Methylation in the PCDHA Gene Cluster as a Risk Factor for Early-Onset High Myopia in Young Children

Purpose

High myopia (HM), an eye disorder with at least –6.0 diopters refractive error, has a complex etiology with environmental, genetic, and likely epigenetic factors involved. To complement the DNA methylation assessment in children with HM, we analyzed genes that had significantly lower DNA methylation levels.

Methods

The DNA methylation pattern was studied based on the genome-wide methylation data of 18 Polish children with HM paired with 18 controls. Genes overlapping CG dinucleotides with decreased methylation level in HM cases were assessed by enrichment analyses. From those, genes with CG dinucleotides in promoter regions were further evaluated based on exome sequencing (ES) data of 16 patients with HM from unrelated Polish families, Sanger sequencing data of the studied children, and the RNA sequencing data of human retinal ARPE-19 cells.

Results

The CG dinucleotide with the most decreased methylation level in cases was identified in a promoter region of PCDHA10 that overlaps intronic regions of PCDHA1–9 of the PCDHA gene cluster in myopia 5q31 locus. Also, two single nucleotide variants, rs200661444, detected in our ES, and rs246073, previously found as associated with a refractive error in a genome-wide association study, were revealed within this gene cluster. Additionally, genes previously linked to ocular phenotypes, myopia-related traits, or loci, including ADAM20, ZFAND6, ETS1, ABHD13, SBSPON, SORBS2, LMOD3, ATXN1, and FARP2, were found to have decreased methylation.

Conclusions

Alterations in the methylation pattern of specific CG dinucleotides may be associated with early-onset HM, so this could be used to develop noninvasive biomarkers of HM in children and adolescents.

Single-cell multiome of the human retina and deep learning nominate causal variants in complex eye diseases

Genome-wide association studies (GWASs) of eye disorders have identified hundreds of genetic variants associated with ocular disease. However, the vast majority of these variants are noncoding, making it challenging to interpret their function. Here we present a joint single-cell atlas of gene expression and chromatin accessibility of the adult human retina with more than 50,000 cells, which we used to analyze single-nucleotide polymorphisms (SNPs) implicated by GWASs of age-related macular degeneration, glaucoma, diabetic retinopathy, myopia, and type 2 macular telangiectasia. We integrate this atlas with a HiChIP enhancer connectome, expression quantitative trait loci (eQTL) data, and base-resolution deep learning models to predict noncoding SNPs with causal roles in eye disease, assess SNP impact on transcription factor binding, and define their known and novel target genes. Our efforts nominate pathogenic SNP-target gene interactions for multiple vision disorders and provide a potentially powerful resource for interpreting noncoding variation in the eye.

Whole exome sequence analysis in 51 624 participants identifies novel genes and variants associated with refractive error and myopia

Refractive errors are associated with a range of pathological conditions, such as myopic maculopathy and glaucoma, and are highly heritable. Studies of missense and putative loss of function (pLOF) variants identified via whole exome sequencing (WES) offer the prospect of directly implicating potentially causative disease genes. We performed a genome-wide association study for refractive error in 51 624 unrelated adults, of European ancestry, aged 40-69 years from the UK and genotyped using WES. After testing 29 179 pLOF and 495 263 missense variants, 1 pLOF and 18 missense variants in 14 distinct genomic regions were taken forward for fine-mapping analysis. This yielded 19 putative causal variants of which 18 had a posterior inclusion probability >0.5. Of the 19 putative causal variants, 12 were novel discoveries. Specific variants were associated with a more myopic refractive error, while others were associated with a more hyperopic refractive error. Association with age of onset of spectacle wear (AOSW) was examined in an independent validation sample (38 100 early AOSW cases and 74 243 controls). Of 11 novel variants that could be tested, 8 (73%) showed evidence of association with AOSW status. This work identified COL4A4 and ATM as novel candidate genes associated with refractive error. In addition, novel putative causal variants were identified in the genes RASGEF1, ARMS2, BMP4, SIX6, GSDMA, GNGT2, ZNF652 and CRX. Despite these successes, the study also highlighted the limitations of community-based WES studies compared with high myopia case-control WES studies.

Myopia Genetics and Heredity

Myopia is the most common eye condition leading to visual impairment and is greatly influenced by genetics. Over the last two decades, more than 400 associated gene loci have been mapped for myopia and refractive errors via family linkage analyses, candidate gene studies, genome-wide association studies (GWAS), and next-generation sequencing (NGS). Lifestyle factors, such as excessive near work and short outdoor time, are the primary external factors affecting myopia onset and progression. Notably, besides becoming a global health issue, myopia is more prevalent and severe among East Asians than among Caucasians, especially individuals of Chinese, Japanese, and Korean ancestry. Myopia, especially high myopia, can be serious in consequences. The etiology of high myopia is complex. Prediction for progression of myopia to high myopia can help with prevention and early interventions. Prediction models are thus warranted for risk stratification. There have been vigorous investigations on molecular genetics and lifestyle factors to establish polygenic risk estimations for myopia. However, genes causing myopia have to be identified in order to shed light on pathogenesis and pathway mechanisms. This report aims to examine current evidence regarding (1) the genetic architecture of myopia; (2) currently associated myopia loci identified from the OMIM database, genetic association studies, and NGS studies; (3) gene-environment interactions; and (4) the prediction of myopia via polygenic risk scores (PRSs). The report also discusses various perspectives on myopia genetics and heredity.

Genome-wide Association Study of Axial Length in Population-based Cohorts in Japan

Purpose

To elucidate the differences in ocular biometric parameters by generation and gender and to identify axial length (AL)-associated genetic variants in Japanese individuals, we analyzed Tohoku Medical Megabank Organization (ToMMo) Eye Study data.

Design

We designed the ToMMo Eye Study, examined AL variations, and conducted genome-wide association studies (GWASs).

Participants

In total, 33 483 participants aged > 18 years who were recruited into the community-based cohort (CommCohort) and the birth and three-generation cohort (BirThree Cohort) of the ToMMo Eye Study were examined.

Methods

Each participant was screened with an interview, ophthalmic examinations, and a microarray analysis. The GWASs were performed in 22 379 participants in the CommCohort (discovery stage) and 11 104 participants in the BirThree Cohort (replication stage). We evaluated the associations of single nucleotide polymorphisms (SNPs) with AL using a genome-wide significance threshold (5 × 10^-8) in each stage of the study and in the subsequent meta-analysis.

Main Outcome Measures

We identified the association of SNPs with AL and distributions of AL in right and left eyes and individuals of different sexes and ages.

Results

In the discovery stage, the mean AL of the right eye (23.99 mm) was significantly greater than that of the left eye (23.95 mm). This difference was reproducible across sexes and ages. The GWASs revealed 703 and 215 AL-associated SNPs with genome-wide significance in the discovery and validation stages, respectively, and many of the SNPs in the discovery stage were replicated in the validation stage. Validated SNPs and their associated loci were meta-analyzed for statistical significance (P < 5 × 10^-8). This study identified 1478 SNPs spread over 31 loci. Of the 31 loci, 5 are known AL loci, 15 are known refractive-error loci, 4 are known corneal-curvature loci, and 7 loci are newly identified loci that are not known to be associated with AL. Of note, some of them shared functional relationships with previously identified loci.

Conclusions

Our large-scale GWASs exploiting ToMMo Eye Study data identified 31 loci linked to variations in AL, 7 of which are newly reported in this article. The results revealed genetic heterogeneity and similarity in SNPs related to ethnic variations in AL.

Novel BMP4 Truncations Resulted in Opposite Ocular Anomalies: Pathologic Myopia Rather Than Microphthalmia

BMP4 variants have been reported to be associated with syndromic microphthalmia (MCOPS6, OMIM 607932). This study aims to describe BMP4 truncation mutations contributing to a novel phenotype in eight patients from four Chinese families. In this study, BMP4 variants were collected from a large dataset from in-house exome sequencing. Candidate variants were filtered by multiple in silico tools as well as comparison with data from multiple databases. Potential pathogenic variants were further confirmed by Sanger sequencing and cosegregation analysis. Four novel truncation variants in BMP4 were detected in four out of 7,314 unrelated probands with different eye conditions. These four mutations in the four families solely cosegregated in all eight patients with a specific form of pathologic myopia, characterized by significantly extended axial length, posterior staphyloma, macula patchy, chorioretinal atrophy, myopic optic neuropathy or glaucoma, vitreous opacity, and unique peripheral snow-grain retinopathy. The extreme rarity of the truncations in BMP4 (classified as intolerant in the gnomAD database, pLI = 0.96), the exclusive presence of these variants in the four families with pathologic myopia, variants fully co-segregated with the same specific phenotypes in eight patients from the four families, and the association of the pathogenicity of truncations with syndromic microphthalmia in previous studies, all support a novel association of BMP4 truncations with a specific form of pathologic myopia. The data presented in this study demonstrated that heterozygous BMP4 truncations contributed to a novel phenotype: pathologic myopia rather than microphthalmia. Mutations in the same gene resulting in both high myopia and microphthalmia have been observed for a few other genes like FZD5 and PAX6, suggesting bidirectional roles of these genes in early ocular development. Further studies are expected to elucidate the molecular mechanism of the bidirectional regulation.