Genetic investigation of 211 Chinese families expands the mutational and phenotypical spectra of hereditary retinopathy genes through targeted sequencing technology

Nuclear Receptor Subfamily 2 Group E Member 3 (NR2E3): Role in Retinal Development and Disease

NR2E3 is a nuclear hormone receptor gene required for the correct development of the retinal rod photoreceptors. Expression of NR2E3 protein in rod cell precursors suppresses cone-specific gene expression and, in concert with other transcription factors including NRL, activates the expression of rod-specific genes. Pathogenic variants involving NR2E3 cause a spectrum of retinopathies, including enhanced S-cone syndrome, Goldmann-Favre syndrome, retinitis pigmentosa, and clumped pigmentary retinal degeneration, with limited evidence of genotype-phenotype correlations. A common feature of NR2E3-related disease is an abnormally high number of cone photoreceptors that are sensitive to short wavelength light, the S-cones. This characteristic has been supported by mouse studies, which have also revealed that loss of Nr2e3 function causes photoreceptors to develop as cells that are intermediate between rods and cones. While there is currently no available cure for NR2E3-related retinopathies, there are a number of emerging therapeutic strategies under investigation, including the use of viral gene therapy and gene editing, that have shown promise for the future treatment of patients with NR2E3 variants and other inherited retinal diseases. This review provides a detailed overview of the current understanding of the role of NR2E3 in normal development and disease, and the associated clinical phenotypes, animal models, and therapeutic studies.

Case Report: The First Reported Concurrence of Wilson Disease and Bilateral Retinitis Pigmentosa

Background

Wilson disease (WD) and retinitis pigmentosa (RP) are common genetic disorders in clinical practice, however, the concurrence of WD and RP has never been reported before. WD occurs due to mutations that cause copper metabolic abnormalities; in turn, change in copper metabolism has been suggested to be related with RP. Here, we report the first case of concurrent WD and bilateral RP, and investigate possible pathogenesis to illuminate whether the two genetic disorders are causality or coincidence.

Case Presentation

The patient was a 43-year-old Chinese female diagnosed with WD 12 years ago. She had suffered from night blindness since childhood and faced diminution of bilateral vision within 10 years, for which she was referred to our Eye Center during hospitalization for routine copper excretion treatment. The ceruloplasmin, skull magnetic resonance imaging (MRI), and abdominal ultrasound results accorded with hepatolenticular degeneration. Ocular examinations revealed corneal Kayser-Fleischer (K-F) ring, sunflower-like cataract, retinal osteocyte-like pigmentation, bilateral atrophy of outer retina, cystoid macular edema (CME), and tubular vision in both eyes. Phacoemulsification combined with intraocular lens implantation was performed in the right and left eye, but there was limited improvement in her visual acuity. Whole exome sequencing (WES) detected a deleterious homozygous mutation in the ATP7B gene related to WD, and a homozygous mutation in the CNGA1 gene very likely to cause RP.

Conclusions

We reported the first case of concurrent WD and RP. WES detected two pathogenic gene mutations, ATP7B and CNGA1. Though we cannot completely rule out a causal effect of WD-related abnormal copper metabolism with RP, we speculate that the two gene mutations lead to the coincidence of the two genetic disorders, respectively.