Novel deletion of the RPGR gene in a Chinese family with X-linked retinitis pigmentosa

Clinical characteristics of high myopia in female carriers of pathogenic RPGR mutations: a case series and review of the literature

BACKGROUND

RPGR mutations are the most common cause of X-linked retinitis pigmentosa (XLRP). High myopia has been described as a very frequent feature among affected female carriers of XLRP. However, the clinical phenotype of female patients presenting with X-linked RPGR-related high myopia has not been well described.

MATERIALS AND METHODS

Retrospective case series of four female patients with RPGR mutations and a diagnosis of high myopia, who presented to two academic eye centers. Clinical data, including age, family history, visual acuity, refractive error, dilated fundus exam, fundus photography, optical coherence tomography, electroretinography, and results of genetic testing, were collected.

RESULTS

Three RPGR variants identified in the present study have not been previously associated with myopia in female carriers. One variant (c.2405_2406delAG, p.Glu802Glyfs *32) has been previously associated with a myopic phenotype in a female patient. Patients became symptomatic between the first and sixth decades of life. Myopia-associated tilted optic discs and posterior staphyloma were present in all patients. Two patients presented with intraretinal migration of the retinal pigment epithelium.

CONCLUSION

RPGR-related high myopia has been associated with mutations in exons 1-14 and ORF15 in heterozygous females. There is a wide range of visual function among carriers. Although the exact mechanism of RPGR-related high myopia is still unclear, continued molecular diagnosis and description of phenotypes remain a crucial step in understanding the impact of RPGR mutations on visual function in female XLRP carriers.

Genotype-Phenotype Analysis of RPGR Variations: Reporting of 62 Chinese Families and a Literature Review

Purpose

RPGR is the most common cause of X-linked retinitis pigmentosa (RP), of which female carriers are also frequently affected. The aim of the current study was to explore the RPGR variation spectrum and associated phenotype based on the data from our lab and previous studies.

Methods

Variants in RPGR were selected from exome sequencing data of 7,092 probands with different eye conditions. The probands and their available family members underwent comprehensive ocular examinations. Similar data were collected from previous reports through searches in PubMed, Web of Science, and Google Scholar. Systematic analyses of genotypes, phenotypes and their correlations were performed.

Results

A total of 46 likely pathogenic variants, including nine missense and one in-frame variants in RCC1-like domain and 36 truncation variants, in RPGR were detected in 62 unrelated families in our in-house cohort. In addition, a total of 585 variants, including 491 (83.9%) truncation variants, were identified from the literature. Systematic analysis of variants from our in-house dataset, literature, and gnomAD suggested that most of the pathogenic variants of RPGR were truncation variants while pathogenic missense and in-frame variants were enriched in the RCC1-like domain. Phenotypic variations were present between males and female carriers, including more severe refractive error but better best corrected visual acuity (BCVA) in female carriers than those in males. The male patients showed a significant reduction of BCVA with increase of age and males with exon1-14 variants presented a better BCVA than those with ORF15 variants. For female carriers, the BCVA also showed significant reduction with increase of age, but BCVA in females with exon1-14 variants was not significant difference compared with those with ORF15 variants.

Conclusion

Most pathogenic variants of RPGR are truncations. Missense and in-frame variants located outside of the RCC1-like domain might be benign and the pathogenicity criteria for these variants should be considered with greater caution. The BCVA and refractive error are different between males and female carriers. Increase of age and location of variants in ORF15 contribute to the reduction of BCVA in males. These results are valuable for understanding genotypes and phenotypes of RPGR.

Identification of novel X-linked gain-of-function RPGR-ORF15 mutation in Italian family with retinitis pigmentosa and pathologic myopia

The aim of this study was to describe a new pathogenic variant in the mutational hot spot exon ORF15 of retinitis pigmentosa GTPase regulator (RPGR) gene within an Italian family with X-linked retinitis pigmentosa (RP), detailing its distinctive genotype-phenotype correlation with pathologic myopia (PM). All members of this RP-PM family underwent a complete ophthalmic examination. The entire open reading frames of RPGR and retinitis pigmentosa 2 genes were analyzed by Sanger sequencing. A novel frame-shift mutation in exon ORF15 of RPGR gene (c.2091_2092insA; p.A697fs) was identified as hemizygous variant in the male proband with RP, and as heterozygous variant in the females of this pedigree who invariably exhibited symmetrical PM in both eyes. The c.2091_2092insA mutation coherently co-segregated with the observed phenotypes. These findings expand the spectrum of X-linked RP variants. Interestingly, focusing on Caucasian ethnicity, just three RPGR mutations are hitherto reported in RP-PM families: one of these is located in exon ORF15, but none appears to be characterized by a high penetrance of PM trait as observed in the present, relatively small, pedigree. The geno-phenotypic attributes of this heterozygosity suggest that gain-of-function mechanism could give rise to PM via a degenerative cell-cell remodeling of the retinal structures.

Genetic analysis of Chinese families reveals a novel truncation allele of the retinitis pigmentosa GTPase regulator gene

AIM

To make comprehensive molecular diagnosis for retinitis pigmentosa (RP) patients in a consanguineous Han Chinese family using next generation sequencing based Capture-NGS screen technology.

METHODS

A five-generation Han Chinese family diagnosed as non-syndromic X-linked recessive RP (XLRP) was recruited, including four affected males, four obligate female carriers and eleven unaffected family members. Capture-NGS was performed using a custom designed capture panel covers 163 known retinal disease genes including 47 RP genes, followed by the validation of detected mutation using Sanger sequencing in all recruited family members.

RESULTS

Capture-NGS in one affected 47-year-old male reveals a novel mutation, c.2417_2418insG:p.E806fs, in exon ORF15 of RP GTPase regulator (RPGR) gene results in a frameshift change that results in a premature stop codon and a truncated protein product. The mutation was further validated in three of four affected males and two of four female carriers but not in the other unaffected family members.

CONCLUSION

We have identified a novel mutation, c.2417_2418insG:p.E806fs, in a Han Chinese family with XLRP. Our findings expand the mutation spectrum of RPGR and the phenotypic spectrum of XLRP in Han Chinese families, and confirms Capture-NGS could be an effective and economic approach for the comprehensive molecular diagnosis of RP.

Novel deletion in the pre-mRNA splicing gene PRPF31 causes autosomal dominant retinitis pigmentosa in a large Chinese family

We report the identification of a novel 12 bp deletion of the pre-mRNA splicing gene PRPF31 in a large Chinese family with autosomal dominant retinitis pigmentosa (adRP). This mutation results in the deletion of four amino acids (DeltaH(111)K(112)F(113)I(114)) including H(111), an amino acid residue that is highly conserved throughout evolution. The 12 bp deletion co-segregates with the disease phenotype in 19 RP patients in the family, but is not present in unaffected relatives or 100 normal individuals. Our data indicate that the novel 12 bp deletion in PRPF31 causes retinitis pigementosa in this Chinese adRP family. In contrast to the incomplete penetrance observed in most adRP families linked to chromosome band 19q13.4 (RP11), the 12 bp PRPF31 deletion identified in this study appears to show high penetrance. These data expand the spectrum of PRPF31 mutations causing adRP, and confirm the role of PRPF31 in the pathogenesis of RP.