Mutational screening of AGRN, SLC39A5, SCO2, P4HA2, BSG, ZNF644, and CPSF1 in a Chinese cohort of 103 patients with nonsyndromic high myopia.

Purpose: High myopia (HM) is one of the leading causes of irreversible vision loss in the world. Many myopia loci have been uncovered with linkage analysis, genome-wide association studies, and sequencing analysis. Numerous pathogenic genes within these loci have been detected in a portion of HM cases. In the present study, we aimed to investigate the genetic basis of 103 patients with nonsyndromic HM, focusing on the reported causal genes. Methods: A total of 103 affected individuals with nonsyndromic HM were recruited, including 101 patients with unrelated sporadic HM and a mother and son pair. All participants underwent comprehensive ophthalmic examinations, and genomic DNA samples were extracted from the peripheral blood. Whole exome sequencing was performed on the mother and son pair as well as on the unaffected father. Sanger sequencing was used to identify mutations in the remaining 101 patients. Bioinformatics analysis was subsequently applied to verify the mutations. Results: An extremely rare mutation in AGRN (c.2627A>T, p.K876M) was identified in the mother and son pair but not in the unaffected father. Another two mutations in AGRN (c.4787C>T, p.P1596L/c.5056G>A, p.G1686S) were identified in two unrelated patients. A total of eight heterozygous variants potentially affecting the protein function were detected in eight of the remaining 99 patients, including c.1350delC, p.V451Cfs*76 and c.1023_1024insA, p.P342Tfs*41 in SLC39A5; c.244_246delAAG, p.K82del in SCO2; c.545A>G, p.Y182C in P4HA2; c.415C>T, p.P139S in BSG; c.3266A>G, p.Y1089C in ZNF644; and c.2252C>T, p.S751L and c.1708C>T, p.R570C in CPSF1. Multiple bioinformatics analyses were conducted, and a comparison to a group with geographically matched controls was performed, which supported the potential pathogenicity of these variants. Conclusions: We provide further evidence for the potential role of AGRN in HM inheritance and enlarged the current genetic spectrum of nonsyndromic HM by comprehensively screening the reported causal genes.

Expanding the Phenotypic and Genotypic Landscape of Nonsyndromic High Myopia: A Cross-Sectional Study in 731 Chinese Patients.

Purpose: High myopia (HM) is defined as a refractive error worse than -6.00 diopter (D). This study aims to update the phenotypic and genotypic landscape of nonsyndromic HM and to establish a biological link between the phenotypic traits and genetic deficiencies. Methods: A cross-sectional study involving 731 participants varying in refractive error, axial length (AL), age, myopic retinopathy, and visual impairment. The phenotypic traits were analyzed by four ophthalmologists while mutational screening was performed in eight autosomal causative genes. Finally, we assessed the clinical relevance of identified mutations under the guidance of the American College of Medical Genetics and Genomics. Results: The relationship between refractive error and AL varied in four different age groups ranging from 3- to 85-years old. In adult groups older than 21 years, 1-mm increase in AL conferred 10.84% higher risk of pathologic retinopathy (Category ≥2) as well as 7.35% higher risk of low vision (best-corrected visual acuities <0.3) with P values < 0.001. The prevalence rates of pathologic retinopathy and low vision both showed a nonlinear positive correlation with age. Forty-five patients were confirmed to harbor pathogenic mutations, including 20 novel mutations. These mutations enriched the mutational pool of nonsyndromic HM to 1.5 times its previous size and enabled a statistically significant analysis of the genotype-phenotype correlation. Finally, SLC39A5, CCDC111, BSG, and P4HA2 were more relevant to eye elongation, while ZNF644, SCO2, and LEPREL1 appeared more relevant to refracting media. Conclusions: Our findings shed light on how multiple HM-related phenotypes are associated with each other and their link with gene variants.

Slc7a14 Is Indispensable in Zebrafish Retinas.

Previous study has identified SLC7A14 as a new causative gene of retinitis pigmentosa (RP). However, the role of SLC7A14 has not been fully characterized. The goal of this study was to investigate the biological features of slc7a14 in zebrafish. To determine the expression of slc7a14 in developing zebrafish, we performed in situ hybridization (ISH) and quantitative real-time PCR. Morpholino knockdown and overexpression experiments were performed to study the role of slc7a14 in zebrafish retinas. Immunostaining was carried out to observe structural changes. Visual motor responses (VMR) and optokinetic responses (OKR) were analyzed to assess visual behaviors. Terminal deoxynucleotidyl transferase (dUTP) nick-end labeling (TUNEL) staining was performed to survey apoptotic retinal cells. We found that slc7a14 was highly expressed in neuronal tissues, including the brain, spinal cord and retina, and that the expression levels increased during early embryogenesis. Consistently, ISH showed a similar expression pattern. Knockdown of slc7a14 led to dose-dependent microphthalmia that was reversed by overexpression. The immunostaining results revealed that the rod-specific protein zpr-3 and the retinal pigment epithelium-specific protein zpr-2 (decreased to 44.48%) were significantly suppressed in the slc7a14-silenced morphants. Notably, visual behaviors (the VMR and the OKR) were severely impaired in the slc7a14-deficient morphant, especially the VMR OFF response. In addition, apoptotic cells were observed in the retina at 3 days post fertilization (dpf) and 5 dpf by TUNEL assay. Our results demonstrated that slc7a14 is essential for visually mediated behaviors in zebrafish. Temporary silencing of slc7a14 in larvae led to severe visual impairments, consistent with the manifestations observed in RP patients. Our findings provide further insights into the genetic mechanisms of RP predisposition caused by SLC7A14 mutations.