De Novo Mutations Contributes Approximately 7% of Pathogenicity in Inherited Eye Diseases

Genomic landscape of medulloblastoma subtypes in an Asian cohort

Background

Medulloblastoma (MB) is a highly malignant childhood brain tumor. Previous research on the genetic underpinnings of MB subtypes has predominantly focused on European and American cohorts. Given the notable genetic differences between Asian and other populations, a subtype-specific study on an Asian cohort is essential to provide comprehensive insights into MB within this demographic. The aim of this study is to investigate the genomic landscape of MB subtypes in an Asian cohort to better understand the genetic variations and potential implications for clinical practice.

Methods

We conducted a study on an Asian cohort comprising 113 MB patients. Genomic sequencing was performed using MGISEQ-2000 platform. We analyzed the participants' characteristics and compared them with previous studies. All germline variants of the ten susceptibility genes of interest (APC, BRCA2, PTCH1, PTCH2, ELP1, SUFU, CTNNB1, SMARCA4, GPR161, and TP53) were annotated and validated.

Results

Our study identified 14 valid germline variants that met our criteria, with these variants being detected in the genes APC, BRCA2, PTCH1, PTCH2, ELP1, and SUFU. Of these, six variants were classified as pathogenic in ClinVar: two in PTCH2 (c.C1573T), one in ELP1 (c.C583T), and three in PTCH1 (c.G1370T, c.C2066T, c.C529T). The remaining eight variants were of uncertain significance, including those in SUFU (c.T833C), ELP1 (c.T2A), BRCA2 (c.G7488C), and APC (c.C3247A, c.A1G, c.A8042G, c.A3056G, c.G822C). Our findings highlight a subtype-based germline variant landscape specific to the Asian cohort and reinforce the connection between SUFU, PTCH1, and the SHH subtype of MB. Additionally, the identification of ELP1-related cases supports the newest findings in this area and provides typical copy number variation (CNV) results for future investigation.

Conclusions

This study provides valuable insights into the genetic landscape of MB in an Asian cohort, emphasizing the importance of population-specific research. The subtype-specific germline variant landscape identified in this study contributes to the understanding of MB and its genetic underpinnings in Asian populations, potentially guiding future research and therapeutic strategies.

Genotype Associated With Visual Prognosis in Patients With Congenital Ectopia Lentis Following Lens Surgery: A Prospective Cohort Study

PURPOSE

To investigate the relationship between visual prognosis and genotype in patients undergoing lens surgery for congenital ectopia lentis (EL).

DESIGN

Prospective clinical cohort study.

METHODS

Patients with congenital EL who underwent lens removal and intraocular lens implantation received panel-based next-generation sequencing. Patients were grouped into children and adolescents/adults based on the age at surgery. The visual prognosis, including best-corrected visual acuity (BCVA) and amblyopia, was stratified into short-term and medium to long-term.

RESULTS

This study included 329 probands with congenital EL, with a median age at lens surgery of 7.00 years (interquartile range [IQR] = 5.00, 12.50 years). Children with the non-FBN1 mutation exhibited inferior medium to long-term postoperative BCVA (0.26 [IQR: 0.14, 0.33] vs 0.15 [IQR: 0.10, 0.22], P = .034) and a higher prevalence of amblyopia (44.4% vs 16.8%, P = .012) compared to those with FBN1 mutation. Multivariable analysis showed that genotype (FBN1 vs non-FBN1 mutation) was significantly associated with medium to long-term postoperative BCVA (b = -0.128, 95% CI -0.214 to -0.042, P = .004) and amblyopia (OR = 0.20, 95% CI 0.05-0.78, P = .020) in children. Further classification of FBN1 genotype did not yield significant correlations with visual prognosis. However, no significant correlation was observed between genotype and short-term visual prognosis in the children. Children with less severe EL (OR = 0.13, 95% CI 0.02-0.85, P = .033) had lower risks of amblyopia in the short-term follow-up. For adolescent and adult patients with congenital EL, those with poor preoperative BCVA and long axial length should be informed of suboptimal visual prognosis.

CONCLUSIONS

Genotype significantly influences the medium to long-term visual prognosis in children with congenital EL. Genotype, along with preoperative BCVA, may assist in establishing reasonable expectations for patients regarding their visual outcomes after the lens surgery.

Atypic Retinitis Pigmentosa Clinical Features Associated with a Peculiar CRX Gene Mutation in Italian Patients

Purpose: To describe an atypical phenotypic pattern of late-onset retinitis pigmentosa (RP) due to the same specific c.425A>G (p.Tyr142Cys) heterozygous mutation in the cone-rod homeobox gene (CRX gene) in two unrelated Italian patients. Case 1: A 67-year-old woman (P.P.) was incidentally diagnosed with sector RP at the age of 50. The patient was initially asymptomatic and did not have any family history of retinal dystrophy. Fundus examination showed the presence of typical retinal pigmentary deposits with a peculiar pericentral/sector distribution. Genomic sequencing disclosed the missense mutation c.425A>G (p.Tyr142Cys) in the CRX gene. During the follow-up period of 7 years, the patient maintained good visual acuity and complained only of mild symptoms. Case 2: A 76-year-old man (P.E.) presented with nyctalopia and visual field constriction since the age of 50. Fundus examination showed the presence of retinal pigment deposits with a concentric pericentral and perimacular pattern. A full-field electroretinogram (ffERG) showed extinguished scotopic responses and reduced abnormal photopic and flicker cone responses. Genomic sequencing identified the same missense mutation, c.425A>G (p.Tyr142Cys), in the CRX gene. Similarly to the first case, during the whole follow-up of 7 years, the visual acuity remained stable, as did the visual field and the patient's symptoms. Conclusions: We report the first cases of late-onset retinitis pigmentosa related to a specific heterozygous CRX gene mutation in exon 4. We also report two atypical phenotypic RP patterns related to mutations in the CRX gene.

Cell-cell interaction in the pathogenesis of inherited retinal diseases

The retina is part of the central nervous system specialized for vision. Inherited retinal diseases (IRD) are a group of clinically and genetically heterogenous disorders that lead to progressive vision impairment or blindness. Although each disorder is rare, IRD accumulatively cause blindness in up to 5.5 million individuals worldwide. Currently, the pathophysiological mechanisms of IRD are not fully understood and there are limited treatment options available. Most IRD are caused by degeneration of light-sensitive photoreceptors. Genetic mutations that abrogate the structure and/or function of photoreceptors lead to visual impairment followed by blindness caused by loss of photoreceptors. In healthy retina, photoreceptors structurally and functionally interact with retinal pigment epithelium (RPE) and Müller glia (MG) to maintain retinal homeostasis. Multiple IRD with photoreceptor degeneration as a major phenotype are caused by mutations of RPE- and/or MG-associated genes. Recent studies also reveal compromised MG and RPE caused by mutations in ubiquitously expressed ciliary genes. Therefore, photoreceptor degeneration could be a direct consequence of gene mutations and/or could be secondary to the dysfunction of their interaction partners in the retina. This review summarizes the mechanisms of photoreceptor-RPE/MG interaction in supporting retinal functions and discusses how the disruption of these processes could lead to photoreceptor degeneration, with an aim to provide a unique perspective of IRD pathogenesis and treatment paradigm. We will first describe the biology of retina and IRD and then discuss the interaction between photoreceptors and MG/RPE as well as their implications in disease pathogenesis. Finally, we will summarize the recent advances in IRD therapeutics targeting MG and/or RPE.

Genetics in ophthalmology: molecular blueprints of retinoblastoma

This review presents current knowledge on the molecular biology of retinoblastoma (RB). Retinoblastoma is an intraocular tumor with hereditary and sporadic forms. 8,000 new cases of this ocular malignancy of the developing retina are diagnosed each year worldwide. The major gene responsible for retinoblastoma is RB1, and it harbors a large spectrum of pathogenic variants. Tumorigenesis begins with mutations that cause RB1 biallelic inactivation preventing the production of functional pRB proteins. Depending on the type of mutation the penetrance of RB is different. However, in small percent of tumors additional genes may be required, such as MYCN, BCOR and CREBBP. Additionally, epigenetic changes contribute to the progression of retinoblastoma as well. Besides its role in the cell cycle, pRB plays many additional roles, it regulates the nucleosome structure, participates in apoptosis, DNA replication, cellular senescence, differentiation, DNA repair and angiogenesis. Notably, pRB has an important role as a modulator of chromatin remodeling. In recent years high-throughput techniques are becoming essential for credible biomarker identification and patient management improvement. In spite of remarkable advances in retinoblastoma therapy, primarily in high-income countries, our understanding of retinoblastoma and its specific genetics still needs further clarification in order to predict the course of this disease and improve therapy. One such approach is the tumor free DNA that can be obtained from the anterior segment of the eye and be useful in diagnostics and prognostics.