OBJECTIVE: Mutations of G protein-coupled receptor 143 (GPR143) and FERM domain containing 7 (FRMD7) may result in congenital nystagmus (CN) in the first 6 months of life. We aimed to compare the differences in ocular oscillations between patients with these two gene mutations as well as the functional and structural changes in their retinas and visual pathways.
METHODS: Medical records were retrospectively reviewed to identify patients of congenital nystagmus with confirmed mutations in either GPR143 or FMRD7 genes from January 2018 to May 2023. The parameters of the ocular oscillations were recorded using Eyelink 1000 Plus. The retinal structure and function were evaluated using optical coherence tomography and multi-focal electroretinography (mERG). The visual pathway and optical nerve projection were evaluated using visual evoked potentials. The next-generation sequencing technique was used to identify the pathogenic variations in the disease-causing genes for CN.
RESULTS: Twenty nystagmus patients of GPR143 and 21 patients of FMRD7 who had been confirmed by molecular testing between January 2018 and May 2023 were included. Foveal hypoplasia was detected only in patients with the GPR143 pathogenic variant. mERG examination showed a flat response topography in the GPR143 group compared to the FRMD7 group. VEP showed that bilateral amplitude inconsistency was detected only in the patients with GPR143 gene mutation. The amplitude and frequency of the ocular oscillations were not found to differ between patients with two different genetic mutations.
CONCLUSIONS: Although the etiology and molecular mechanisms are completely different between CN patients, they may have similar ocular oscillations. A careful clinical examination and electrophysiological test will be helpful in making a differential diagnosis. Our novel identified variants will further expand the spectrum of the GPR143 and FRMD7 variants.

Idiopathic congenital nystagmus (ICN) manifests as involuntary and periodic eye movements. To identify the genetic defect associated with X-linked ICN, Whole Exome Sequencing (WES) was conducted in two affected families. We identified two frameshift mutations in FRMD7, c.1492dupT/p.(Y498Lfs*15) and c.1616delG/p.(R539Kfs*2). Plasmids harboring the mutated genes and qPCR analysis revealed mRNA stability, evading degradation via the NMD pathway, and corroborated truncated protein production via Western-blot analysis. Notably, both truncated proteins were degraded through the proteasomal (ubiquitination) pathway, suggesting potential therapeutic avenues targeting this pathway for similar mutations. Moreover, we conducted a comprehensive analysis, summarizing 140 mutations within the FRMD7 gene. Our findings highlight the FERM and FA structural domains as mutation-prone regions. Interestingly, exons 9 and 12 are the most mutated regions, but 90% (28/31) mutations in exon 9 are missense while 84% (21/25) mutations in exon 12 are frameshift. A predominant occurrence of shift code mutations was observed in exons 11 and 12, possibly associated with the localization of premature termination codons (PTCs), leading to the generation of deleterious truncated proteins. Additionally, our conjecture suggests that the loss of FRMD7 protein function might not solely drive pathology; rather, the emergence of aberrant protein function could be pivotal in nystagmus etiology. We propose a dependence of FRMD7 protein normal function primarily on its anterior domain. Future investigations are warranted to validate this hypothesis.

Infantile nystagmus syndrome (INS), or congenital nystagmus (CN), refers to a group of ocular motor disorders characterized by rapid to-and-fro oscillations of the eyes. GPR143 is the causative gene of ocular albinism type 1 (OA1), which is a special type of INS that manifests as reduced vision, nystagmus, and iris and fundus hypopigmentation. Here, we explored the genetic spectrum of INS and the genotype-phenotype correlation.
A total of 98 families with INS from Southeast China were recruited for this study. A sample from each participant was subjected to PCR-based DNA direct sequencing of GPR143. Varied bioinformatics analysis was subsequently used in a mutation assessment. All participants received detailed ophthalmic examinations.
Genetic analysis identified 11 GPR143 mutations in 11.2% (11/98) of the X-linked INS families. These included seven novel mutations (c.899 C>T, c.886-2 A>G, c.1A>G, c.633_643del CCTGTTCCAAA, c.162_198delCGCGGGCCCCGGGTCCCCCGCGACGTCCCCGCCGGCC, c.628C>A, and c.178_179insGGGTCCC) and four known mutations. Patients who carried a GPR143 mutation were found to present a typical or atypical phenotype of OA1. All patients with GPR143 mutations manifested foveal hypoplasia; thus, about 45.8% (11/24) of the families with total X-linked INS exhibited foveal hypoplasia.
We discovered seven novel mutations and four previously reported mutations of GPR143 in a cohort of families with X-linked INS and enlarged the Chinese genetic spectrum of INS. These findings offer new insights for developing genetic screening strategies and shed light on the importance of conducting genetic analysis in confirming the clinical diagnosis in unresolved patients and atypical phenotypes.

UNASSIGNED: 48, XXYY syndrome is a rare sex chromosome aneuploidy with severe systemic features. Ophthalmic manifestation of 48, XXYY syndrome include hypertelorism, epicanthic folds, hooded eye lids, strabismus, retinitis pigmentosa and Duane\'s syndrome.
UNASSIGNED: We present mild foveal hypoplasia in a 12-year-old boy with 48, XXYY syndrome using swept-source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). The boy was referred for assessment of strabismus and poor visual acuity. OCT revealed persistence of inner retinal layers, and thinning of the outer nuclear layer in the perifoveal region with thickening of the outer plexiform layer. OCTA revealed increased vessel density with reduced foveal avascular zone.
UNASSIGNED: We described novel OCT and OCTA features of bilateral foveal hypoplasia and reduction of FAZ in a case of 48, XXYY syndrome based on detailed clinical observation and thorough genetic testing. This case expanded the current literature of this rare sex chromosome abnormality and suggest the importance of retinal examinations in 48, XXYY syndrome.

The visual function of patients with infantile nystagmus (IN) can be significantly decreased owing to constant eye movement. While, reaching a definitive diagnosis becomes a challenge due to genetic heterozygous of this disease. To address it, we investigated whether best-corrected visual acuity (BCVA) results can facilitate the molecular diagnosis of IN patients harboring FRMD7 mutations. 200 patients with IN from 55 families and 133 sporadic cases were enrolled. Mutations were comprehensively screened by direct sequencing using gene-specific primers for FRMD7. We also retrieved related literature to verify the results based on our data. We found that the BCVA of patients with IN harboring FRMD7 mutations was between 0.5 and 0.7, which was confirmed by data retrieved from the literature. Our results showed that BCVA results facilitate the molecular diagnosis of patients with IN harboring FRMD7 mutations. In addition, we identified 31 FRMD7 mutations from the patients, including six novel mutations, namely, frameshift mutation c.1492_1493insT (p.Y498LfsTer14), splice-site mutation c.353C > G, three missense mutations [c.208C > G (p.P70A), c.234G > A (p.M78I), and c.1109G > A (p.H370R)], and nonsense mutation c.1195G > T (p.E399Ter). This study demonstrates that BCVA results may facilitate the molecular diagnosis of IN patients harboring FRMD7 mutations.

Idiopathic congenital nystagmus (CN) is a rare eye disease that can cause early blindness (EB). CN deficits are observed most frequently with oculomotor dysfunction; however, it is still unclear what neuromechanics underly CN with EB. Based on that visual experience requires the functional integration of both hemispheres, we hypothesized that CN adolescents with EB might exhibit impaired interhemispheric synchrony. Our study aimed to investigate the interhemispheric functional connectivity alterations using voxel-mirrored homotopic connectivity (VMHC) and their relationships with clinical features in CN patients.
This study included 21 patients with CN and EB, and 21 sighted controls (SC), who were matched for sex, age and educational level. The 3.0 T MRI scan and ocular examination were performed. The VMHC differences were examined between the two groups, and the relationships between mean VMHC values in altered brain regions and clinical variables in the CN group were evaluated by Pearson correlation analysis.
Compared with the SC group, the CN had increased VMHC values in the bilateral cerebellum posterior and anterior lobes/cerebellar tonsil/declive/pyramis/culmen/pons, middle frontal gyri (BA 10) and frontal eye field/superior frontal gyri (BA 6 and BA 8). No particular areas of the brain had lower VMHC values. Furthermore, no correlation with the duration of disease or blindness could be demonstrated in CN.
Our results suggest the existence of interhemispheric connectivity changes and provide further evidence for the neurological basis of CN with EB.

Mutations in the FERM domain containing 7 (FRMD7) gene have been proven to be responsible for infantile nystagmus (IN). The purpose of this study is to investigate FRMD7 gene mutations in patients with IN, and to evaluate the nystagmus intensity among patients with and without FRMD7 mutations. The affected males were subdivided into three groups according to whether or not having FRMD7 mutations and the types of mutations. Fifty-two mutations were detected in FRMD7 in 56 pedigrees and 34 sporadic patients with IN, including 28 novel and 24 previous reported mutations. The novel identified mutations further expand the spectrum of FRMD7 mutations. The parameters of nystagmus intensity and the patients\' best corrected visual acuity were not statistically different among the patients with and without identified FRMD7 mutations, and also not different among patients with different mutant types. The FERM-C domain, whose amino acids are encoded by exons 7, 8 and 9, could be the harbor region for most mutations. Loss-of-function is suggested to be the common molecular mechanism for the X-linked infantile nystagmus.

Objective: To explore the feasibility of applying machine-learning hierarchical clustering algorithm to waveform-type automatic classification and diagnosis in congenital nystagmus (CN). Methods: A retrospective case series study. A total of 90 patients (90 eyes) diagnosed with CN at Tianjin Eye Hospital from December 2018 to September 2019 were included in the study, including 67 males and 23 females, aged (12±9) years old. Eye movement waveforms were recorded with the video eye tracker in all patients. Analyses with unsupervised machine-learning hierarchical clustering algorithm were performed on the normalized eye movement waveforms. The visualized clustering results were obtained for further waveform naming. The occurrence rate of each waveform type was calculated, and the correlation between the proportion of each waveform type and the visual function of CN patients was analyzed. Independent sample t-test and Pearson correlation analysis were used for statistical analysis. Results: The 46 620 cycles of validated waveforms from the 90 CN patients were categorized into 7 types of waveforms through machine-learning hierarchical clustering algorithm, named type Ⅰ, type Ⅱ, type Ⅲ, and types Ⅳ1-4, respectively. In the 46 620 cycles of eye movement waveforms from the 90 patients with CN, there were 14 259 cycles of type Ⅰ (30.59%), 11 498 cycles of type Ⅱ (24.66%), 4 083 cycles of type Ⅲ (8.76%), 5 430 cycles of type Ⅳ1 (11.65%), 3 451 cycles of type Ⅳ2 (7.40%), 3 015 cycles of type Ⅳ3 (6.47%), 2 663 cycles of type Ⅳ4 (5.71%) and 2 221 cycles of unclassified waveforms (4.76%). The waveforms of types Ⅰ, Ⅱ and Ⅲ corresponded to the 3 basic CN eye movement waveforms (velocity-increasing jerk waveform, velocity-decreasing jerk waveform and pendular waveform) described in the textbooks, and the waveforms of types Ⅳ1-4 were complex waveforms. The proportions of patients with the 7 types of waveforms were 78.89% (71 cases), 41.11% (37 cases), 17.78% (16 cases), 20.00% (18 cases), 7.78% (7 cases), 15.56% (14 cases) and 11.11% (10 cases), respectively. According to the results of automatic classification, 38 (42.22%) CN patients presented with only one type of waveforms, and the remaining 52 (57.78%) CN patients presented with two or more types of waveforms, including 23 (25.56%) patients with 3 or more types of waveforms and 5 (5.56%) patients with 4 types of waveforms. The proportions of type Ⅰ component were significantly correlated with the patients\' best corrected visual acuities (BCVAs;logarithm of the minimum angle of resolution) (r=-0.39; P<0.01), and there was no relationship between the proportions of type Ⅱ component and the patients\' BCVAs (P>0.05). The BCVAs of the patients with type Ⅰ as the dominant component were better than those of the patients with type Ⅱ as the dominant component, with statistically significant difference (0.19±0.14 vs. 0.45±0.37;t=2.77; P<0.05). Conclusion: Machine-learning hierarchical clustering algorithm can be used for waveform-type automatic classification and discrimination in CN and provide an auxiliary method for the precise diagnosis and evaluation of the disease.
目的： 探讨机器学习层次聚类算法用于先天性眼球震颤（CN）眼动波形自动分类和波形诊断的可行性。 方法： 回顾性病例系列研究。收集2018年12月至2019年9月就诊于天津市眼科医院的90例（90只眼）CN患者资料，其中男性67例，女性23例，年龄（12±9）岁。所有患者采用高速视频眼动仪记录眼动波形。对标准化后的眼动波形进行无监督机器学习层次聚类分析，获得可视化分类结果并予以波形命名，统计每种波形的发生比例，分析波形成分与CN患者视功能的相关性。统计学方法为独立样本t检验和Pearson相关性分析。 结果： 在90例（90只眼）CN患者的46 620个有效眼动波形中，通过机器学习层次聚类算法自动分出7种波形，分别命名为波形Ⅰ（14 259个，30.59%）、波形Ⅱ（11 498个，24.66%）、波形Ⅲ（4 083个，8.76%）、波形Ⅳ1（5 430个，11.65%）、波形Ⅳ2（3 451个，7.40%）、波形Ⅳ3（3 015个，6.47%）及波形Ⅳ4（2 663个，5.71%）；有2 221个（4.76%）波形未分类。波形Ⅰ、Ⅱ、Ⅲ分别与3种CN基本眼动波形即速度递增型冲动型、速度递减型冲动型及钟摆型波形相符，波形Ⅳ1~4为复杂波形。波形Ⅰ、Ⅱ、Ⅲ及Ⅳ1~4在90例患者中的发生比例依次为78.89%（71例）、41.11%（37例）、17.78%（16例）、20.00%（18例）、7.78%（7例）、15.56%（14例）和11.11%（10例）。38例（42.22%）患者仅表现为1种眼动波形，其余52例（57.78%）同时存在2种或2种以上眼动波形，其中23例（25.56%）存在3种或3种以上眼动波形，5例（5.56%）存在4种眼动波形。患者眼动波形中波形Ⅰ所占比例与最佳矫正视力（最小分辨角对数视力）有显著相关性（r=-0.39；P<0.01），波形Ⅱ所占比例与最佳矫正视力无相关性（P>0.05）。以波形Ⅰ为主导的CN患者的最佳矫正视力（0.19±0.14）优于以波形Ⅱ为主导的CN患者（0.45±0.37），差异有统计学意义（t=2.77；P<0.05）。 结论： 机器学习层次聚类算法可实现CN眼动波形的自动分类和波形诊断，为CN的精准诊断与评估提供辅助依据。.

In recent years, exome sequencing (ES) has shown great utility in the diagnoses of Mendelian disorders. However, after rigorous filtering, a typical ES analysis still involves the interpretation of hundreds of variants, which greatly hinders the rapid identification of causative genes. Since the interpretations of ES data require comprehensive clinical analyses, taking clinical expertise into consideration can speed the molecular diagnoses of Mendelian disorders. To leverage clinical expertise to prioritize candidate genes, we developed PhenoApt, a phenotype-driven gene prioritization tool that allows users to assign a customized weight to each phenotype, via a machine-learning algorithm. Using the ability to rank causative genes in top-10 lists as an evaluation metric, baseline analysis demonstrated that PhenoApt outperformed previous phenotype-driven gene prioritization tools by a relative increase of 22.7%-140.0% in three independent, real-world, multi-center cohorts (cohort 1, n = 185; cohort 2, n = 784; and cohort 3, n = 208). Additional trials showed that, by adding weights to clinical indications, which should be explained by the causative gene, PhenoApt performance was improved by a relative increase of 37.3% in cohort 2 (n = 471) and 21.4% in cohort 3 (n = 208). Moreover, PhenoApt could assign an intrinsic weight to each phenotype based on the likelihood of its being a Mendelian trait using term frequency-inverse document frequency techniques. When clinical indications were assigned with intrinsic weights, PhenoApt performance was improved by a relative increase of 23.7% in cohort 2 and 15.5% in cohort 3. For the integration of PhenoApt into clinical practice, we developed a user-friendly website and a command-line tool.

Foveal hypoplasia (FVH) is defined as the lack of fovea with a relatively preserved neuroretina, occurring either as an isolated FVH (IFVH) condition or associated with other diseases. This study aimed to systemically molecularly characterize IFVH.
Genetic defects in 33 families with IFVH were analyzed by exome sequencing. Variants in three genes (PAX6, SLC38A8, and AHR) were selected and evaluated with multistep bioinformatic tools.
Mutations in the three genes were identified in 69.7% (23/33) of families with IFVH and infantile nystagmus, including 18 families with PAX6 mutations, 5 with SLC38A8 mutations, but none with AHR mutations. Clinical data from 32 patients in the 23 families showed FVH, infantile nystagmus, and full iris. Careful follow-up visits revealed subtle changes in iris in 9 of 14 patients with PAX6 variants. The PAX6 variants of the 18 families (15 missense and one stop-loss) were mostly located in the C-terminal region of the paired box domain. Variants in AHR, SLC38A8, and PAX6 contributed to IFVH in one (2%), 25 (45%), and 30 (53%) families with identified genetic defects (23 families in this study and 33 reported previously), respectively.
PAX6 and SLC38A8 mutations are the main cause of IFVH based on our data and a systematic review. IFVH-associated PAX6 variants are mostly missense with a specific location, indicating a specific correlation of these variants with IFVH but not with typical aniridia. Full iris with subtle structural abnormalities is more common in patients with PAX6-associated IFVH, suggesting a potential diagnostic indicator.