Identification of Novel Genomic-Variant Patterns of OR56A5, OR52L1, and CTSD in Retinitis Pigmentosa Patients by Whole-Exome Sequencing.

Inherited retinal dystrophies (IRDs) are rare but highly heterogeneous genetic disorders that affect individuals and families worldwide. However, given its wide variability, its analysis of the driver genes for over 50% of the cases remains unexplored. The present study aims to identify novel driver genes, disease-causing variants, and retinitis pigmentosa (RP)-associated pathways. Using family-based whole-exome sequencing (WES) to identify putative RP-causing rare variants, we identified a total of five potentially pathogenic variants located in genes OR56A5, OR52L1, CTSD, PRF1, KBTBD13, and ATP2B4. Of the variants present in all affected individuals, genes OR56A5, OR52L1, CTSD, KBTBD13, and ATP2B4 present as missense mutations, while PRF1 and CTSD present as frameshift variants. Sanger sequencing confirmed the presence of the novel pathogenic variant PRF1 (c.124_128del) that has not been reported previously. More causal-effect or evidence-based studies will be required to elucidate the precise roles of these SNPs in the RP pathogenesis. Taken together, our findings may allow us to explore the risk variants based on the sequencing data and upgrade the existing variant annotation database in Taiwan. It may help detect specific eye diseases such as retinitis pigmentosa in East Asia.

The spermatogenesis-associated protein-7 (SPATA7) gene - an overview.

BACKGROUND: The spermatogenesis-associated protein-7 (SPATA7) gene encodes a ciliary protein that is expressed in the photoreceptors and in spermatocytes. Mutations in the SPATA7 gene are associated with congenital and early-onset forms of retinal dystrophy. METHODS: Papers and review articles on SPATA7 were retrieved from the PubMed database using the search terms "SPATA7" and "spermatogenesis-associated protein 7". Those that were relevant to retinal disease or to the function of the SPATA7 gene were selected for review. RESULTS: The SPATA7 locus was mapped as LCA3 to chromosome 14, and the gene identified by screening of all genes in the refined genomic interval. Mutations in SPATA7 are associated with Leber congenital amaurosis (LCA) and early-onset retinitis pigmentosa. There are no clear-cut correlations between the genotypes and phenotypes in SPATA7-associated disease, and phenotypic heterogeneity occurs among patients with the same mutation. The SPATA7 protein is expressed in the photoreceptor connecting cilia. Murine models of Spata7 knockout have been useful in understanding the role of this gene in the retina at the cellular and molecular levels. CONCLUSION: Most of the mutations in the SPATA7 are nonsense or frameshifts and are predicted to lead to loss of function. Clinical heterogeneity is often seen in patients with SPATA7 mutations. Animal models of SPATA7 knockout indicate that the protein has a key role in organizing the ciliary protein complexes.

Genetic spectrum of retinal dystrophies in Tunisia.

We report the molecular basis of the largest Tunisian cohort with inherited retinal dystrophies (IRD) reported to date, identify disease-causing pathogenic variants and describe genotype-phenotype correlations. A subset of 26 families from a cohort of 73 families with clinical diagnosis of autosomal recessive IRD (AR-IRD) excluding Usher syndrome was analyzed by whole exome sequencing and autozygosity mapping. Causative pathogenic variants were identified in 50 families (68.4%), 42% of which were novel. The most prevalent pathogenic variants were observed in ABCA4 (14%) and RPE65, CRB1 and CERKL (8% each). 26 variants (8 novel and 18 known) in 19 genes were identified in 26 families (14 missense substitutions, 5 deletions, 4 nonsense pathogenic variants and 3 splice site variants), with further allelic heterogeneity arising from different pathogenic variants in the same gene. The most common phenotype in our cohort is retinitis pigmentosa (23%) and cone rod dystrophy (23%) followed by Leber congenital amaurosis (19.2%). We report the association of new disease phenotypes. This research was carried out in Tunisian patients with IRD in order to delineate the genetic population architecture.

Differences in Intraretinal Pigment Migration Across Inherited Retinal Dystrophies.

PURPOSE: To determine whether there are differences in the prevalence of intraretinal pigment migration (IPM) across ages and genetic causes of inherited retinal dystrophies (IRDs). DESIGN: Retrospective cohort study. METHODS: Patients were evaluated at a single tertiary referral center. All patients with a clinical diagnosis of IRD and confirmatory genetic testing were included in these analyses. A total of 392 patients fit inclusion criteria, and 151 patients were excluded based on inconclusive genetic testing. Patients were placed into 3 groups, ciliary and ciliary-related photoreceptor, nonciliary photoreceptor, and retinal pigment epithelium (RPE), based on the cellular expression of the gene and the primary affected cell type. The presence of IPM was evaluated by using slit lamp biomicroscopy, indirect ophthalmoscopy, and wide-field color fundus photography. RESULTS: IPM was seen in 257 of 339 patients (75.8%) with mutations in photoreceptor-specific genes and in 18 of 53 patients (34.0%) with mutations in RPE-specific genes (P < .0001). Pairwise analysis following stratification by age and gene category suggested significant differences at all age groups between patients with mutations in photoreceptor-specific genes and patients with mutations in RPE-specific genes (P < .05). A fitted multivariate logistic regression model was produced and demonstrated that the incidence of IPM increases as a function of both age and gene category. CONCLUSIONS: IPM is a finding more commonly observed in IRDs caused by mutations in photoreceptor-specific genes than RPE-specific genes. The absence of IPM does not always rule out IRD and should raise suspicion for disease mutations in RPE-specific genes.

Comparative Analysis of Functional and Structural Decline in Retinitis Pigmentosas.

Retinitis pigmentosa (RP) is a category of inherited retinal dystrophies that is best prognosticated using electroretinography (ERG). In this retrospective cohort study of 25 patients with RP, we evaluated the correlation between 30 Hz flicker ERG and structural parameters in the retina. Internationally standardized 30 Hz flicker ERG recordings, short-wavelength autofluorescence (SW-AF), and spectral domain-optical coherence tomography (SD-OCT) were acquired at two visits at least one year apart. Vertical and horizontal hyperautofluorescent ring diameter measurements with SW-AF, as well as ellipsoid zone (EZ) line width measurements with SD-OCT, were used as structural parameters of disease progression. The 30 Hz flicker ERG amplitude decreased by 2.2 ± 0.8 µV/year (p = 0.011), while implicit times remained unchanged. For SD-OCT, the EZ line decreased by 204.1 ± 34.7 µm/year (p < 0.001). Horizontal and vertical hyperautofluorescent ring diameters decreased by 161.9 ± 25.6 µm/year and 146.9 ± 34.6 µm/year, respectively (p = 0.001), with SW-AF. A correlation was found between the progression rates of the 30 Hz flicker amplitude recorded with Burian-Allen electrodes and both the horizontal ring diameter (p = 0.020) and EZ line (p = 0.044). SW-AF and SD-OCT, two readily available imaging techniques, may be used to prognosticate disease progression because of the reliability of their measurements and correlation with functional outcome.

RPE65 and retinal dystrophy: Report of new and recurrent mutations.

BACHGROUND: Leber congenital amaurosis (LCA) is a severe and congenital or early onset form of inherited retinitis pigmentosa (RP). To date, approximately 25 genes have been introduced in relation to LCA. In this regard, retinal pigment epithelium-specific 65 kDa (RPE65) is a well-known gene mutation that plays a role in the pathogenesis of 5-10% of LCA cases. METHOS: Two individuals fromseparate families were subjected to ehole exome sequencing (WES). Causativevariants were searched further assessed using Sanger sequencing. RESULTS: Here, two families with mutations in the RPE65 gene show severe and early onset LCA, as expected. In addition to the characterization of the phenotype, by reporting a new mutation (c.1451-1G>A), we further expand the mutation spectrum of RPE65. Likewise, as an interesting aspect of our study, we report on a previously reported RP-linked mutation associated with severe early onset LCA (c.T200G:p.L67R). CONCLUSIONS: Considering this variant in different populations, it is likely that it represents a hotspot and affects the function of the coded protein. The variable expressivity of the phenotype can be assumed by the presence of the modifier allele(s) as a result of a different genetic background or the effect of different environments on phenotype expression.

Novel CERKL variant in consanguineous Jordanian pedigrees with inherited retinal dystrophies.

OBJECTIVE: To identify the disease-causing variants in 2 families with autosomal recessive inherited retinal dystrophies (IRDs) and to characterize phenotypic variability across the affected family members. DESIGN: Exome sequencing and ophthalmic clinical examination study. PARTICIPANTS: Six members from 2 consanguineous Jordanian families with IRD. METHODS: Ophthalmic examinations and whole-exome sequencing (WES) were performed to identify IRD-causing variants in affected individuals from each family, followed by segregation analysis of candidate variants in affected and unaffected family members by Sanger sequencing. RESULTS: We identified 2 different homozygous deletion variants in CERKL in each family: a novel pathogenic variant, c.450_451delAT, and a known variant, c.1187_1188delTG. Both variants co-segregated with the disease in all affected family members. The resulting phenotypes further supported that CERKL is associated with cone-rod dystrophy (CRD) rather than retinitis pigmentosa (RP), as originally established. CONCLUSION: Our study expands the genotypic spectra of CERKL variants, providing insights into the relevant pathogenesis of RP/CRD. We also confirm that the WES approach is a valuable tool for the molecular diagnosis of retinopathies.

Unravelling the genetics of inherited retinal dystrophies: Past, present and future.

The identification of the genes underlying monogenic diseases has been of interest to clinicians and scientists for many years. Using inherited retinal dystrophies as an example of monogenic disease we describe the history of molecular genetic techniques that have been pivotal in the discovery of disease causing genes. The methods that were developed in the 1970's and 80's are still in use today but have been refined and improved. These techniques enabled the concept of the Human Genome Project to be envisaged and ultimately realised. When the successful conclusion of the project was announced in 2003 many new tools and, as importantly, many collaborations had been developed that facilitated a rapid identification of disease genes. In the post-human genome project era advances in computing power and the clever use of the properties of DNA replication has allowed the development of next-generation sequencing technologies. These methods have revolutionised the identification of disease genes because for the first time there is no need to define the position of the gene in the genome. The use of next generation sequencing in a diagnostic setting has allowed many more patients with an inherited retinal dystrophy to obtain a molecular diagnosis for their disease. The identification of novel genes that have a role in the development or maintenance of retinal function is opening up avenues of research which will lead to the development of new pharmacological and gene therapy approaches. Neither of which can be used unless the defective gene and protein is known. The continued development of sequencing technologies also holds great promise for the advent of truly personalised medicine.

Illness Perceptions, Psychiatric Manifestations, and Quality of Life in Patients with Inherited Retinal Dystrophies.

PURPOSE: We aimed to assess psychiatric manifestations, health-related quality of life (HRQoL), and associated illness perceptions in patients with inherited retinal dystrophies (IRD). METHODS: In 48 IRD patients, we assessed a wide range of psychological distress symptoms (Symptom Distress Checklist-90-R), depressive symptom severity (PHQ-9), generic HRQoL (WHOQOL-BREF), and Illness Perceptions (B-IPQ). Ninety-six alleged healthy participants matched for age, sex, and education served as healthy controls and 331 patients with rheumatological disorders served as disease controls. RESULTS: IRD patients exhibited elevated symptoms of phobic anxiety (p=0.049) and paranoid ideation (p=0.028) compared to healthy and disease controls and were less satisfied with their general health (p<0.001) compared to disease controls. They shared, however, similar levels on all other aspects of psychiatric manifestations and HRQoL. The majority of patients acknowledged the hereditary and chronic nature of the illness. They also attributed more symptoms to their disease (illness identity) compared to people with rheumatological disorders (p<0.001), and this attribution was associated with paranoid ideation (p<0.05) and phobic anxiety (p<0.001). CONCLUSIONS: Broadening our view of the psychological variables which should be assessed in IRD patients may help to better identify those psychological parameters which impair the patients' well-being and yet may be amenable to treatment. The design of psycho-educational therapies targeting illness representations may have a beneficial effect upon the IRD patients' psychological distress and HRQoL.