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Published online: 2024-08-22

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Review

DOI: 10.5603/oj.99259

Retinitis pigmentosa caused by mutations in the RPGR gene — review of the literature

Katarzyna BaltaziakKatarzyna NowomiejskaRobert Rejdak
Chair and Department of General and Pediatric Ophthalmology, Medical University of Lublin, Lublin, Poland

Corresponding author:

Katarzyna Baltaziak, Chair and Department of General and Pediatric Ophthalmology, Medical University of Lublin, 20–059 Lublin, Poland; e-mail: k.baltaziak@gmail.com

This article is available in open access under Creative Common Attribution-Non-Commercial-No Derivatives 4.0 International (CC BY-NC-ND 4.0) license, allowing to download articles and share them with others as long as they credit the authors and the publisher, but without permission to change them in any way or use them commercially

ABSTRACT
Retinitis pigmentosa (RP) is a varied collection of inherited disorders marked by numerous genes, mutations, and clinical manifestations. Progress in the treatment hinges on identifying causative genes and mutations, involving gene discovery and mutation screening for potential gene therapy. Significant advances have been made in detecting RP genes and mutations, with 30–80% detection rates using techniques like next-generation sequencing (NGS), revealing several novel RP genes and clarifying many unresolved cases. However, discrepancies between molecular findings and clinical symptoms often require genetic reevaluation. This review provides a concise overview of the current strategies and challenges in gene discovery and mutation detection in RP. It suggests that these considerations may also be relevant to other inherited retinal diseases. This review examines the RPGR gene’s pivotal role in X-linked RP (XLRP) and associated retinal dystrophies, focusing on its isoforms’ impact on ciliary function and protein trafficking. We discuss the genetic and clinical implications of RPGR mutations, particularly novel pathogenic variants, and their genotype-phenotype correlations. Ultimately, this synthesis aims to enhance understanding of RPGR’s role in retinal dystrophies, informing future research and potential treatments.
Key words: next-generation sequencing; inherited retinal diseases; genetic screening; RPGR, retinitis pigmentosa; genotype-phenotype correlation; RPGR-related retinal dystrophies
Ophthalmol J 2024; Vol. 9, 114–120

Introduction

Retinitis pigmentosa (RP) encompasses a varied group of hereditary degenerative disorders marked by the gradual decline in function of rod and cone photoreceptors in the retina. This primarily affects photoreceptor and pigment epithelial functions and leads to retinal degeneration. RP is the most common inherited retinal dystrophy globally, affecting 1 in 4,000 individuals [1].

RP can be inherited in various patterns, including autosomal recessive (50–60% of cases), autosomal dominant (30–40% of cases), and X-linked (5–15% of cases). X-linked RP (XLRP) is one of the most severe forms of RP, and a family history of the condition is present in about 70% of patients [1, 2].

The RP GTPase regulator (RPGR) gene, situated on the X chromosome, has emerged as a significant focus in understanding the molecular genetics behind RP and related retinal dystrophies. This gene’s mutations are predominantly associated with X-linked forms of retinitis pigmentosa (XLRP) and, to a lesser extent, with cone dystrophy (COD) and cone-rod dystrophy (CORD) [3].

The intricate nature of RPGR, characterized by its extensive alternative splicing resulting in multiple isoforms, underscores the complexity of its role in the retina and the diversity of phenotypic expressions observed in affected individuals. Recent studies have provided substantial insights into the structural and functional facets of RPGR, particularly highlighting the significance of its major isoforms, RPGRex1–19, RPGR ORF15, and RPGRskip14/15, in ciliary genesis, maintenance, and protein trafficking within the retina [4].

The loss of RPGR function leads to disrupted protein transport, affecting photoreceptor viability and causing various forms of retinal dystrophies. The pathogenic variants in RPGR have been linked to a range of clinical manifestations, with the type and severity of the disorder often determined by the variant’s specific location within the gene [5].

So far, there has been no dedicated screening for disease-causing variants of the RPGR gene in the Polish RP patient population. Literature on pathogenic variants within the Polish group of individuals with inherited retinal dystrophies (IRDs) is limited [6–8].

This review aims to consolidate the current understanding of RPGR-related RP, delving into the genetic and clinical spectrum associated with its mutations. By examining recent advancements from cohort studies and case reports, including the identification of novel pathogenic variants and the exploration of genotype-phenotype correlations, we endeavor to provide a comprehensive overview of the role of RPGR in retinal dystrophies.

Heterogeneity of pathology, clinical manifestations, and genetics of RP

During the early stage, the primary symptom is night blindness (nyctalopia), which may manifest at various ages, from early childhood to the second decade of life or later. Patients might experience defects in peripheral visual fields under dim light at this stage, but their vision remains normal in daylight conditions. Diagnosing RP in the early stage is challenging, particularly when there is no familial history. Clinical examinations might show normal fundus, optic disc, and color vision, while electroretinogram (ERG) tests are crucial for better understanding the condition.

In the middle stage, patients become aware of the loss of peripheral visual field in daylight conditions, missing objects, or gestures like handshaking. Night blindness becomes more evident, making it difficult to drive at night or walk in dark environments. Dyschromatopsia, or difficulty distinguishing light colors (yellow and blue hues), also appears. Patients may experience photophobia, particularly in diffuse lights, leading to reading problems due to lower visual acuity and a narrow window between too bright and insufficient light. Clinical examination at this stage reveals retinal atrophy, bone-spicule-shaped pigments in the midperiphery, a fairly pale optic disc, and narrowing of retinal vessels [9].

During the end stage, peripheral vision loss severely impacts patients’ mobility, making it impossible for them to move from one place to another without assistance. Reading becomes increasingly difficult and ultimately impossible as the central visual field deteriorates. Photophobia intensifies, and clinical examination shows widespread pigment deposits in the macular area, an achromatic optic disc, and thin blood vessels. ERG becomes unrecordable at this stage [10].

RP typically begins with night blindness, followed by a gradual loss of peripheral vision, ultimately leading to central vision loss. However, there is significant variability in age of onset, progression rate, rod versus cone involvement, and the participation of other retinal cells, such as the retinal pigment epithelium (RPE). RP can manifest as non-syndromic, lacking other clinical symptoms, or as syndromic/systemic RP, which may include additional neurosensory disorders, developmental anomalies, or complex clinical phenotypes. Examples of syndromic RP include Usher syndrome, marked by RP and congenital or early-onset deafness, and Bardet-Biedl syndrome (BBS), characterized by RP along with kidney disease, obesity, polydactyly, and developmental delay.

The heterogeneity of RP encompasses genetic, allelic, phenotypic, and clinical dimensions. This extensive diversity can be perplexing for both patients and clinicians, posing challenges in diagnosis. Enhancing the understanding of RP necessitates a more systematic collection of mutation phenotype-genotype data for inherited retinal diseases, similar to the initiatives undertaken by the Leiden Open Variation Database [11].

Ocular findings

Classic fundoscopic manifestations of RP are often characterized by a trio of symptoms: thinning of the retinal vessels, pallid optic nerve head, and intraretinal pigmentation following a bone-spicule pattern. A study found that 94% of the 384 eyes examined exhibited retinal vascular thinning, and 52% showed optic disc pallor [11].

Retinal pigmentary changes arise as melanin from disintegrating retinal pigment epithelial cells relocates to the superficial retina in response to photoreceptor loss [12]. Initially, pigmentary alterations present as a subtle scattering from the mid to outer peripheral retina. Subsequently, “bone spicules” develop across the mid and outer retinal periphery, forming clusters around the retinal vessels [13]. In advanced stages of RP, choriocapillaris atrophy may reveal underlying larger choroidal vessels.

As the condition progresses to moderate or advanced phases, the macula or central retina becomes compromised, leading to retinal atrophy and diminishing visual acuity due to ongoing photoreceptor degeneration [12]. Some individuals may exhibit a central atrophic or bulls-eye lesion.

RP patients might also experience cellophane maculopathy (or “surface wrinkling retinopathy”) and foveal cysts, with or without accompanying edema, further diminishing visual acuity beyond that caused by photoreceptor loss. Notably, about half of RP patients develop cataracts, especially posterior subcapsular types [11], with a higher incidence in the autosomal dominant variant [14].

Additional observations in RP include the presence of dust-like pigment granules in the vitreous humor [15] and functional anomalies in refractive error, visual acuity and fields, contrast sensitivity, and color perception.

Genetics

RP can present with various inheritance patterns, such as autosomal dominant, autosomal recessive, X-linked, or mitochondrial, and may manifest as either syndromic or non-syndromic [16]. Numerous genes implicated in phototransduction, cellular trafficking, and rhodopsin recycling pathways have been identified [17].

While the impact of these mutations on the functioning of photoreceptors is understood, the exact processes causing their deterioration are still undefined. It’s vital to determine and understand the shared pathways of cell death in the varied landscape of RP to create therapies effective across all gene variations causing the disease. This review synthesizes recent studies to identify the cell death routes implicated in RP and how specific mutations trigger these pathways [19].

Different symptoms may arise in various individuals with the same genetic mutation, and distinct mutations can cause the same syndrome [20].

In the last 20 years, significant progress has been made in pinpointing genes linked to inherited retinal diseases like RP, leading to a more complex understanding of the relationship between genes, mutations, and clinical symptoms. This understanding not only deepens our knowledge of vision but also sheds light on retinal disease mechanisms. From a clinical perspective, two crucial questions emerge: the status of mutation identification in patients and the implications for clinical practice. While focused on RP, this discussion is relevant to other inherited eye conditions. RP is characterized by diverse inheritance patterns and genetic causes. A single mutation can manifest differently in individuals (phenotypic pleiotropy), and different mutations can cause the same condition (allelic heterogeneity). The RetNet website provides a comprehensive list of RP-related genes [21].

Determining the exact genetic defect causing RP offers multiple advantages, including verifying RP diagnosis in uncertain situations, predicting the outlook for patients and the risk for relatives, identifying specific RP variants to qualify for clinical trials as targeted therapies emerge, and isolating the root of the disease to deepen knowledge of retinal biology and disease processes. In the United States, non-syndromic RP, which typically presents symptoms confined to the eye, constitutes approximately 65% of all RP cases [20]. The inheritance patterns for these cases are distributed as follows: approximately 30% autosomal dominant, 20% autosomal recessive, 15% X-linked, and 5% recessive early-onset [Leber congenital amaurosis (LCA)]. The remaining 30% are sporadic.

In autosomal dominant RP, there’s a 50% chance that an affected individual’s children will inherit the condition. For autosomal recessive RP, when both parents are carriers, each child has a 25% chance of being affected. Usually, males are the ones who manifest X-linked RP. However, female carriers of the X-linked RP gene can also show signs of visual impairment [22]. Affected males won’t transmit the defective gene to their sons, but all their daughters will inherit the carrier status. If there’s no known RP in the family and the abnormal gene remains undetected, the chance of children having RP drops below 5%, except in instances of blood relation (consanguinity) within the family [23].

Beyond standard RP types, syndromic variants affect multiple organs. The most common, Usher syndrome, involves early hearing loss and subsequent RP. Bardet-Biedl syndrome, another prevalent form, includes extra fingers or toes, obesity, kidney issues, and intellectual delays. Nephronophthisis (NPHP) gene mutations lead to early kidney failure and RP. Through family studies, many genetic regions linked to RP have been discovered, with the first identified mutation in the rhodopsin gene (RHO) on chromosome 3q21.3 in 1989 [24].

In 1990, researchers discovered that a proline-to-histidine change at the 23rd amino acid of rhodopsin, a light-sensitive pigment in rod cell membranes, accounts for 10% of autosomal dominant RP cases among the White population in the United States. The identification of RP-related mutations has accelerated significantly, with over 3000 mutations across approximately 70 genes now recognized [25].

Non-syndromic RP is linked to 71 genes, while syndromic RP involves 66 genes, and LCA is associated with 14 genes. The proteins these genes encode are engaged in various functions, including phototransduction processes, vitamin A metabolism, cytoskeletal components, communication and signaling, RNA splicing, protein transport, and phagocytosis. As of 2007, the three most common genes related to RP, making up about 30% of all cases, are RHO (over 26% of autosomal dominant RP cases), USH2A (Usherin) (10% of autosomal recessive RP cases and also implicated in both non-syndromic RP and Usher syndrome), and RPGR; approximately 75% of X-linked RP [26].

In 2008, another gene, EYS — a homolog of Drosophila eyes shut was identified as the gene responsible for autosomal recessive RP at the RP25 locus [27].

This gene is implicated in a substantial number of autosomal recessive RP cases across various global ancestries. EYS, the largest eye gene spanning more than 2 million base pairs, is believed to contribute to a protein essential for the structural integrity of the eye’s outer segment. Mutations linked to the disease are identified in over 50% of autosomal dominant RP cases, 30% of recessive RP cases, 70% of recessive LCA cases, and nearly 90% of X-linked RP cases [28].

Molecular genetics of the RPGR gene

The RPGR gene is situated in the Xp11.4 chromosomal region, covering 172 kb and comprising up to 22 exons, depending on the splicing process [29, 30].

The RPGR protein is detected in a range of human tissues, including the lungs, kidneys, testes, brain, and particularly the retina [31]. It is located in the transitional area of primary and motile cilia, as well as in centrosomes and centrioles of cells undergoing division [32]. While its precise function in the retina has yet to be fully understood, the RPGR gene is believed to play a vital role in the formation, maintenance, and functionality of cilia, including protein trafficking and organization [17]. The role of RPGR as a guanine nucleotide exchange factor (GEF) for small guanine triphosphatases (GTPases) may be essential for transporting substances to the outer segments of photoreceptors [33].

Research indicates that mouse photoreceptor cells can form properly, conduct light signals, and stay alive for the first few months without the RPGR protein. However, over time, the lack of RPGR disrupts the movement of proteins to the photoreceptors’ outer segments, and the partial displacement of opsins seems to diminish the survival of these cells [34]. Therefore, RPGR’s role in ciliary operations doesn’t seem to be essential but rather supportive, playing a crucial part in the prolonged preservation of photoreceptors [35].

Due to alternative splicing, over 20 distinct RPGR isoforms have been identified [36, 37].

In the retina, three main RPGR isoforms are prevalent: RPGRex1–19, RPGR ORF15, and RPGRskip14/15. RPGRex1–19 is derived from exons 1–19, RPGR ORF15 from exons 1–14 (shared with RPGRex1–19) and the additional ORF15 exon, which includes exon 15 and part of intron 15 at the 3’ end [38], and RPGRskip14/15 is generated through an alternative splicing process [39].

Although the RPGR ORF15 isoform has fewer exons than RPGRex1–19, its ORF15 exon exceeds the total length of exons 16–19. This exon features a large 1.5 kb sequence of purine-rich repeats and encodes a 560 amino acid protein domain, ending with a sequence of basic amino acids known as the RPGR-C2 domain (1071–1152 amino acids). The Glu-Gly region of RPGR is similar to the polyglutamated sections of alpha-tubulin [40]. The glutamylation process in RPGR ORF15 is regulated by the tubulin-tyrosine ligase-like 5 (TTLL5) enzyme, which is linked to various retinal dystrophies [41].

Retinal dystrophies associated with the RPGR gene

Mutations in the RPGR gene can lead to various retinal conditions, such as RP in 70–90% of cases, cone dystrophy (COD) in about 7%, and cone-rod dystrophy (CORD) in approximately 6–23% [42, 43]. Studies suggest that the specific disorder may depend on the mutation’s location: mutations in exons 1–14 and the initial segment of the ORF15 exon are typically associated with RP. In contrast, mutations in the latter part of the ORF15 exon are linked to COD/CORD [44, 45]. The ORF15 exon, which encodes a highly repetitive domain, is considered a mutational hot spot, as most disease-associated variations are truncating [46]. De Silva et al. identified a critical zone of approximately 100 amino acids between these regions where variations can lead to either phenotype [47].

X-linked inheritance is rare in COD/CORD (only 1%) [48], but the RPGR gene is responsible for 73% of COD/CORD cases [49]. Primary symptoms include reduced VA, abnormal color vision, central scotoma, and photophobia. These symptoms are associated with variations in all isoforms, though conflicting reports exist regarding the association between the location of the variation within the RPGR gene and disease severity. Signs of rod dysfunction may develop as the disease progresses, and patients may also experience night blindness and peripheral VF loss [50].

Unlike RP, symptom onset in COD/CORD occurs later (in the fourth decade) but can progress to blindness relatively quickly by 40–50 years of age [51, 52]. In a study by Nassisi et al., the rate of best-corrected visual acuity (BCVA) decline was assessed at about 7% per year, with most patients reaching a BCVA ≥ 1 logMAR during the fifth decade of life [3].

Conclusions

This review emphasizes the significance of the RPGR gene in the pathogenesis of RP and related retinal dystrophies. The genetic and phenotypic diversity of RP, especially due to various RPGR mutations, presents diagnostic and therapeutic challenges. Understanding the gene’s role in ciliary function and photoreceptor maintenance is key to advancing targeted therapies. The severity and progression of RPGR-related disorders are mutation-specific, necessitating precise genetic identification for prognosis and treatment planning. Ongoing research and comprehensive genetic screening are essential to improving management and outcomes for individuals with these complex retinal conditions.

Author contributions

Conceptualization: K.B., K.N., R.R.; data curation: K.B., K.N., R.R.; formal analysis: K.B., K.N., R.R.; investigation: K.B., K.N., R.R.; methodology: K.B., K.N., R.R.; supervision: K.B., K.N., R.R.; writing — original draft preparation: K.B., K.N., R.R.; writing — review & editing: K.B., K.N., R.R. All authors have equally contributed to each stage of the manuscript preparation.

Conflict of interest

The authors report no competing interests.

Acknowledgements and Funding

This research was funded by the Medical University of Lublin, Poland, grant number 178.

References

  1. Hartong DT, Berson EL, Dryja TP. Retinitis pigmentosa. Lancet. 2006; 368(9549): 1795–1809, doi: 10.1016/S0140-6736(06)69740-7, indexed in Pubmed: 17113430.
  2. von Krusenstiern L, Liu J, Liao E, et al. XIRIUS Part 1 Study GroupXOLARIS Study Group. Changes in Retinal Sensitivity Associated With Cotoretigene Toliparvovec in X-Linked Retinitis Pigmentosa With RPGR Gene Variations. JAMA Ophthalmol. 2023; 141(3): 275–283, doi: 10.1001/jamaophthalmol.2022.6254, indexed in Pubmed: 36757689.
  3. Nassisi M, De Bartolo G, Mohand-Said S, et al. Retrospective Natural History Study of -Related Cone- and Cone-Rod Dystrophies While Expanding the Mutation Spectrum of the Disease. Int J Mol Sci. 2022; 23(13), doi: 10.3390/ijms23137189, indexed in Pubmed: 35806195.
  4. Hadalin V, Buscarino M, Sajovic J, et al. Genetic Characteristics and Long-Term Follow-Up of Slovenian Patients with RPGR Retinal Dystrophy. Int J Mol Sci. 2023; 24(4), doi: 10.3390/ijms24043840, indexed in Pubmed: 36835250.
  5. Wang Y, Liu S, Zhai Y, et al. Identification of a novel RPGR mutation associated with X-linked cone-rod dystrophy in a Chinese family. BMC Ophthalmol. 2021; 21(1): 401, doi: 10.1186/s12886-021-02166-0, indexed in Pubmed: 34800980.
  6. Nowomiejska K, Baltaziak K, Całka P, et al. Identification of the RPGR Gene Pathogenic Variants in a Cohort of Polish Male Patients with Retinitis Pigmentosa Phenotype. Genes (Basel). 2023; 14(10), doi: 10.3390/genes14101950, indexed in Pubmed: 37895299.
  7. Tracewska AM, Kocyła-Karczmarewicz B, Rafalska A, et al. Non-syndromic inherited retinal diseases in Poland: Genes, mutations, and phenotypes. Mol Vis. 2021; 27: 457–465, indexed in Pubmed: 34321860.
  8. Skorczyk-Werner A, Chiang WC, Wawrocka A, et al. Autosomal recessive cone-rod dystrophy can be caused by mutations in the ATF6 gene. Eur J Hum Genet. 2017; 25(11): 1210–1216, doi: 10.1038/ejhg.2017.131, indexed in Pubmed: 28812650.
  9. Waseem NH, Vaclavik V, Webster A, et al. Mutations in the gene coding for the pre-mRNA splicing factor, PRPF31, in patients with autosomal dominant retinitis pigmentosa. Invest Ophthalmol Vis Sci. 2007; 48(3): 1330–1334, doi: 10.1167/iovs.06-0963, indexed in Pubmed: 17325180.
  10. Vithana EN, Abu-Safieh L, Pelosini L, et al. Expression of PRPF31 mRNA in patients with autosomal dominant retinitis pigmentosa: a molecular clue for incomplete penetrance? Invest Ophthalmol Vis Sci. 2003; 44(10): 4204–4209, doi: 10.1167/iovs.03-0253, indexed in Pubmed: 14507862.
  11. Bowne SJ, Humphries MM, Sullivan LS, et al. A dominant mutation in RPE65 identified by whole-exome sequencing causes retinitis pigmentosa with choroidal involvement. Eur J Hum Genet. 2011; 19(10): 1074–1081, doi: 10.1038/ejhg.2011.86, indexed in Pubmed: 21654732.
  12. Merin S, Auerbach E. Retinitis pigmentosa. Surv Ophthalmol. 1976; 20(5): 303–346, doi: 10.1016/s0039-6257(96)90001-6, indexed in Pubmed: 817406.
  13. Novack RL, Foos RY. Drusen of the optic disk in retinitis pigmentosa. Am J Ophthalmol. 1987; 103(1): 44–47, doi: 10.1016/s0002-9394(14)74167-4, indexed in Pubmed: 3799789.
  14. Heckenlively J, Daiger S. Hereditary retinal and choroidal degenerations. In: Daiger S. ed. Emery and Rimoin’s Princials and Practice of Medical Genetics. 5th edn. Elsevier, Philadelphia 2007: 3197–227.
  15. Li ZY, Possin DE, Milam AH. Histopathology of bone spicule pigmentation in retinitis pigmentosa. Ophthalmology. 1995; 102(5): 805–816, doi: 10.1016/s0161-6420(95)30953-0, indexed in Pubmed: 7777280.
  16. Sahel JA, Marazova K, Audo I. Clinical characteristics and current therapies for inherited retinal degenerations. Cold Spring Harb Perspect Med. 2014; 5(2): a017111, doi: 10.1101/cshperspect.a017111, indexed in Pubmed: 25324231.
  17. Megaw RD, Soares DC, Wright AF. RPGR: Its role in photoreceptor physiology, human disease, and future therapies. Exp Eye Res. 2015; 138: 32–41, doi: 10.1016/j.exer.2015.06.007, indexed in Pubmed: 26093275.
  18. McLaughlin ME, Sandberg MA, Berson EL, et al. Recessive mutations in the gene encoding the beta-subunit of rod phosphodiesterase in patients with retinitis pigmentosa. Nat Genet. 1993; 4(2): 130–134, doi: 10.1038/ng0693-130, indexed in Pubmed: 8394174.
  19. Hollingsworth TJ, Gross AK. Defective trafficking of rhodopsin and its role in retinal degenerations. Int Rev Cell Mol Biol. 2012; 293: 1–44, doi: 10.1016/B978-0-12-394304-0.00006-3, indexed in Pubmed: 22251557.
  20. Daiger SP, Bowne SJ, Sullivan LS. Perspective on genes and mutations causing retinitis pigmentosa. Arch Ophthalmol. 2007; 125(2): 151–158, doi: 10.1001/archopht.125.2.151, indexed in Pubmed: 17296890.
  21. RetNet — Retinal Information Network [Internet]. https://web.sph.uth.edu/RetNet/ (8 May 2023).
  22. Comander J, Weigel-DiFranco C, Sandberg MA, et al. Visual Function in Carriers of X-Linked Retinitis Pigmentosa. Ophthalmology. 2015; 122(9): 1899–1906, doi: 10.1016/j.ophtha.2015.05.039, indexed in Pubmed: 26143542.
  23. Weleber RG, Gregory-Evans K. Retinitis Pigmentosa and Allied Disorders. In: Volume 1 [Internet]. Elsevier Inc.; 2005, p. 395–498. http://www.scopus.com/inward/record.url?scp=84917055945&partnerID=8YFLogxK (8 May 2023).
  24. McWilliam P, Farrar GJ, Kenna P, et al. Autosomal dominant retinitis pigmentosa (ADRP): localization of an ADRP gene to the long arm of chromosome 3. Genomics. 1989; 5(3): 619–622, doi: 10.1016/0888-7543(89)90031-1, indexed in Pubmed: 2613244.
  25. Dias MF, Joo K, Kemp JA, et al. Molecular genetics and emerging therapies for retinitis pigmentosa: Basic research and clinical perspectives. Prog Retin Eye Res. 2018; 63: 107–131, doi: 10.1016/j.preteyeres.2017.10.004, indexed in Pubmed: 29097191.
  26. Gao FJ, Wang DD, Chen F, et al. Prevalence and genetic-phenotypic characteristics of patients with mutations in a large cohort of Chinese patients with inherited retinal disease. Br J Ophthalmol. 2021; 105(1): 87–92, doi: 10.1136/bjophthalmol-2020-315878, indexed in Pubmed: 32188678.
  27. Abd El-Aziz MM, Barragan I, O’Driscoll CA, et al. EYS, encoding an ortholog of Drosophila spacemaker, is mutated in autosomal recessive retinitis pigmentosa. Nat Genet. 2008; 40(11): 1285–1287, doi: 10.1038/ng.241, indexed in Pubmed: 18836446.
  28. Cook B, Zelhof AC. Photoreceptors in evolution and disease. Nat Genet. 2008; 40(11): 1275–1276, doi: 10.1038/ng1108-1275, indexed in Pubmed: 18957984.
  29. Shu X, Fry AM, Tulloch B, et al. RPGR ORF15 isoform co-localizes with RPGRIP1 at centrioles and basal bodies and interacts with nucleophosmin. Hum Mol Genet. 2005; 14(9): 1183–1197, doi: 10.1093/hmg/ddi129, indexed in Pubmed: 15772089.
  30. Gakovic M, Shu X, Kasioulis I, et al. The role of RPGR in cilia formation and actin stability. Hum Mol Genet. 2011; 20(24): 4840–4850, doi: 10.1093/hmg/ddr423, indexed in Pubmed: 21933838.
  31. Khanna H. More Than Meets the Eye: Current Understanding of RPGR Function. Adv Exp Med Biol. 2018; 1074: 521–538, doi: 10.1007/978-3-319-75402-4_64, indexed in Pubmed: 29721984.
  32. Gakovic M, Shu X, Kasioulis I, et al. The role of RPGR in cilia formation and actin stability. Hum Mol Genet. 2011; 20(24): 4840–4850, doi: 10.1093/hmg/ddr423, indexed in Pubmed: 21933838.
  33. Rao KN, Li L, Anand M, et al. Ablation of retinal ciliopathy protein RPGR results in altered photoreceptor ciliary composition. Sci Rep. 2015; 5: 11137, doi: 10.1038/srep11137, indexed in Pubmed: 26068394.
  34. Vössing C, Atigbire P, Eilers J, et al. The Major Ciliary Isoforms of RPGR Build Different Interaction Complexes with INPP5E and RPGRIP1L. Int J Mol Sci. 2021; 22(7), doi: 10.3390/ijms22073583, indexed in Pubmed: 33808286.
  35. Hong DH, Pawlyk BS, Shang J, et al. A retinitis pigmentosa GTPase regulator (RPGR)-deficient mouse model for X-linked retinitis pigmentosa (RP3). Proc Natl Acad Sci U S A. 2000; 97(7): 3649–3654, doi: 10.1073/pnas.97.7.3649, indexed in Pubmed: 10725384.
  36. He S, Parapuram SK, Hurd TW, et al. Retinitis Pigmentosa GTPase Regulator (RPGR) protein isoforms in mammalian retina: insights into X-linked Retinitis Pigmentosa and associated ciliopathies. Vision Res. 2008; 48(3): 366–376, doi: 10.1016/j.visres.2007.08.005, indexed in Pubmed: 17904189.
  37. Hong DH, Li T. Complex expression pattern of RPGR reveals a role for purine-rich exonic splicing enhancers. Invest Ophthalmol Vis Sci. 2002; 43(11): 3373–3382, indexed in Pubmed: 12407146.
  38. Hosch J, Lorenz B, Stieger K. RPGR: role in the photoreceptor cilium, human retinal disease, and gene therapy. Ophthalmic Genet. 2011; 32(1): 1–11, doi: 10.3109/13816810.2010.535889, indexed in Pubmed: 21174525.
  39. Schmid F, Glaus E, Cremers FPM, et al. Mutation- and tissue-specific alterations of RPGR transcripts. Invest Ophthalmol Vis Sci. 2010; 51(3): 1628–1635, doi: 10.1167/iovs.09-4031, indexed in Pubmed: 19834030.
  40. Rao KN, Li L, Zhang W, et al. Loss of human disease protein retinitis pigmentosa GTPase regulator (RPGR) differentially affects rod or cone-enriched retina. Hum Mol Genet. 2016; 25(7): 1345–1356, doi: 10.1093/hmg/ddw017, indexed in Pubmed: 26908598.
  41. Sun X, Park JH, Gumerson J, et al. Loss of RPGR glutamylation underlies the pathogenic mechanism of retinal dystrophy caused by TTLL5 mutations. Proc Natl Acad Sci U S A. 2016; 113(21): E2925–E2934, doi: 10.1073/pnas.1523201113, indexed in Pubmed: 27162334.
  42. Sharon D, Sandberg MA, Rabe VW, et al. RP2 and RPGR mutations and clinical correlations in patients with X-linked retinitis pigmentosa. Am J Hum Genet. 2003; 73(5): 1131–1146, doi: 10.1086/379379, indexed in Pubmed: 14564670.
  43. Talib M, van Schooneveld MJ, Thiadens AA, et al. Clinical and Genetic Characteristics of Male Patients with RPGR-Associated Retinal Dystrophies: A Long-Term Follow-up Study. Retina. 2019; 39(6): 1186–1199, doi: 10.1097/IAE.0000000000002125, indexed in Pubmed: 29528978.
  44. Tee JJL, Smith AJ, Hardcastle AJ, et al. RPGR-associated retinopathy: clinical features, molecular genetics, animal models and therapeutic options. Br J Ophthalmol. 2016; 100(8): 1022–1027, doi: 10.1136/bjophthalmol-2015-307698, indexed in Pubmed: 26843488.
  45. De Silva SR, Arno G, Robson AG, et al. The X-linked retinopathies: Physiological insights, pathogenic mechanisms, phenotypic features and novel therapies. Prog Retin Eye Res. 2021; 82: 100898, doi: 10.1016/j.preteyeres.2020.100898, indexed in Pubmed: 32860923.
  46. Vervoort R, Lennon A, Bird AC, et al. Mutational hot spot within a new RPGR exon in X-linked retinitis pigmentosa. Nat Genet. 2000; 25(4): 462–466, doi: 10.1038/78182, indexed in Pubmed: 10932196.
  47. Koller S, Beltraminelli T, Maggi J, et al. Functional Analysis of a Novel, Non-Canonical Splice Variant Causing X-Linked Retinitis Pigmentosa. Genes (Basel). 2023; 14(4), doi: 10.3390/genes14040934, indexed in Pubmed: 37107692.
  48. Birtel J, Gliem M, Mangold E, et al. Next-generation sequencing identifies unexpected genotype-phenotype correlations in patients with retinitis pigmentosa. PLoS One. 2018; 13(12): e0207958, doi: 10.1371/journal.pone.0207958, indexed in Pubmed: 30543658.
  49. Gill JS, Georgiou M, Kalitzeos A, et al. Progressive cone and cone-rod dystrophies: clinical features, molecular genetics and prospects for therapy. Br J Ophthalmol. 2019 [Epub ahead of print]; 103(5): 711–720, doi: 10.1136/bjophthalmol-2018-313278, indexed in Pubmed: 30679166.
  50. Ebenezer ND, Michaelides M, Jenkins SA, et al. Identification of novel RPGR ORF15 mutations in X-linked progressive cone-rod dystrophy (XLCORD) families. Invest Ophthalmol Vis Sci. 2005; 46(6): 1891–1898, doi: 10.1167/iovs.04-1482, indexed in Pubmed: 15914600.
  51. Talib M, van Schooneveld MJ, Thiadens AA, et al. Clinical and genetic characteristics of male patients with RPGR-associated retinal dystrophies. Retina. 2019; 39(6): 1186–1199, doi: 10.1097/IAE.0000000000002125, indexed in Pubmed: 29528978.
  52. Thiadens AA, Soerjoesing GG, Florijn RJ, et al. Clinical course of cone dystrophy caused by mutations in the RPGR gene. Graefes Arch Clin Exp Ophthalmol. 2011; 249(10): 1527–1535, doi: 10.1007/s00417-011-1789-3, indexed in Pubmed: 21866333.

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