Genetic testing and gene therapy in retinal diseases: Knowledge and perceptions of optometrists in Australia and New Zealand

With advances in gene-based therapies for heritable retinal diseases, primary eye care clinicians should be informed on ocular genetics topics. This cross-sectional survey evaluated knowledge, attitudes, and concerns regarding genetic testing and gene therapy for retinal diseases among optometrists in Australia and New Zealand. Survey data included practitioner background, attitudes and practices towards genetic testing for monogenic inherited retinal disease (IRDs) and age-related macular degeneration, and knowledge of ocular genetics and gene therapy. Responses were received from 516 optometrists between 1 April and 31 December 2022. Key perceived barriers to accessing genetic testing were lack of clarity on referral pathways (81%), cost (65%), and lack of treatment options if a genetic cause is identified (50%). Almost all respondents (98%) believed that ophthalmologists should initiate genetic testing for IRDs and fewer understood the role of genetic counsellors and clinical geneticists. This study found that optometrists in Australia and New Zealand have a high level of interest in ocular genetics topics. However, knowledge gaps include referral pathways and awareness of genetic testing and gene therapy outcomes. Addressing perceived barriers to access and promoting sharing of knowledge between interdisciplinary networks can set the foundation for genetic education agendas in primary eye care.     

Genetic testing for inherited retinal degenerations: Triumphs and tribulations

Inherited retinal degenerations (IRDs) are a genotypically and phenotypically diverse group of conditions. Great strides have been made toward identifying the genetic basis for these conditions over the last 30 years—more than 270 different genes involved in syndromic and nonsyndromic forms of retinal dystrophies have now been identified. The identification of these genes and the improvement of clinical laboratory techniques have led to the identification of the genetic basis of disease in 56–76% of patients with IRDs through next generation sequencing and copy number variant analysis. Genetic testing is an essential part of clinical care for patients affected with IRDs and is required to confirm the diagnosis, understand the inheritance of the condition, and determine eligibility for gene‐specific treatments or clinical trials. Despite the success achieved in determining the genetic cause of these conditions, several challenges remain, which must be considered when providing genetic testing and genetic counseling to patients. For this reason, an integrated team of ophthalmic and genetic clinicians who are familiar with these challenges is necessary to provide optimal comprehensive care to these patients.     

Implementation of a registry and open access genetic testing program for inherited retinal diseases within a non‐profit foundation

The Foundation Fighting Blindness is a 50‐year old 501c(3) non‐profit organization dedicated to supporting the development of treatments and cures for people affected by the inherited retinal diseases (IRD), a group of clinical diagnoses that include orphan diseases such as retinitis pigmentosa, Usher syndrome, and Stargardt disease, among others. Over $760 M has been raised and invested in preclinical and clinical research and resources. Key resources include a multi‐national clinical consortium, an international patient registry with over 15,700 members that is expanding rapidly, and an open access genetic testing program that provides no cost comprehensive genetic testing to people clinically diagnosed with an IRD living in the United States. These programs are described with particular focus on the challenges and outcomes of establishing the registry and genetic testing program.     

Current understanding of genetics and genetic testing and information needs and preferences of adults with inherited retinal disease

Advances in sequencing technology and the movement of genetic testing into all areas of medicine will increase opportunities for molecular confirmation of a clinical diagnosis. For health-care professionals without formal genetics training, there is a need to know what patients understand about genetics and genetic testing and their information needs and preferences for the disclosure of genetic testing results. These topics were explored during face-to-face interviews with 50 adults with inherited retinal disease, selected in order to provide a diversity of opinions. Participants had variable understanding of genetics and genetic testing, including basic concepts such as inheritance patterns and the risk to dependents, and many did not understand the term ‘genetic counselling''. Most were keen for extra information on the risk to others, the process for genetic testing and how to share the information with other family members. Participants were divided as to whether genetic testing should be offered at the time of the initial diagnosis or later. Many would prefer the results to be given by face-to-face consultation, supplemented by further information in a format accessible to those with visual impairment. Health-care professionals and either leaflets or websites of trusted agencies were the preferred sources of information. Permission should be sought for disclosure of genetic information to other family members. The information needs of many patients with inherited retinal disease appear to be unmet. An understanding of their information needs and preferences is required to help health-care professionals provide optimal services that meet patient expectations.     

Clinical diagnostic exome sequencing in dystonia: Genetic testing challenges for complex conditions

Patients with dystonia are particularly appropriate for diagnostic exome sequencing (DES), due to the complex, diverse features and genetic heterogeneity. Personal and family history data were collected from test requisition forms and medical records from 189 patients with reported dystonia and available family members received for clinical DES. Of them, 20.2% patients had a positive genetic finding associated with dystonia. Detection rates for cases with isolated and combined dystonia were 22.4% and 25.0%, respectively. 71.4% of the cohort had co-occurring non-movement-related findings and a detection rate of 24.4%. Patients with childhood-onset dystonia trended toward higher detection rates (31.8%) compared to infancy (23.6%), adolescence (12.5%), and early-adulthood onset (16%). Uncharacterized gene findings were found in 6.7% (8/119) of cases that underwent analysis for genes without an established disease relationship. Patients with intellectual disability/developmental delay, seizures/epilepsy and/or multifocal dystonia were more likely to have positive findings (P = .0093, .0397, .0006). Four (2.1%) patients had findings in two genes, and seven (3.7%) had reclassification after the original report due to new literature, new clinical information or reanalysis request. Pediatric patients were more likely to have positive findings (P = .0180). Our observations show utility of family-based DES in patients with dystonia and illustrate the complexity of testing.     

A genetic and clinical study of individuals with nonsyndromic retinopathy consequent upon sequence variants in HGSNAT,the gene associated with Sanfilippo C mucopolysaccharidosis

Pathogenic variants in the gene HGSNAT (heparan‐α‐glucosaminide N‐acetyltransferase) have been reported to underlie two distinct recessive conditions, depending on the specific genotype, mucopolysaccharidosis type IIIC (MPSIIIC)—a severe childhood‐onset lysosomal storage disorder, and adult‐onset nonsyndromic retinitis pigmentosa (RP). Here we describe the largest cohort to‐date of HGSNAT‐associated nonsyndromic RP patients, and describe their retinal phenotype, leukocyte enzymatic activity, and likely pathogenic genotypes. We identified biallelic HGSNAT variants in 17 individuals (15 families) as the likely cause of their RP. None showed any other symptoms of MPSIIIC. All had a mild but significant reduction of HGSNAT enzyme activity in leukocytes. The retinal condition was generally of late‐onset, showing progressive degeneration of a concentric area of paramacular retina, with preservation but reduced electroretinogram responses. Symptoms, electrophysiology, and imaging suggest the rod photoreceptor to be the cell initially compromised. HGSNAT enzymatic testing was useful in resolving diagnostic dilemmas in compatible patients. We identified seven novel sequence variants [p.(Arg239Cys); p.(Ser296Leu); p.(Phe428Cys); p.(Gly248Ala); p.(Gly418Arg), c.1543‐2A>C; c.1708delA], three of which were considered to be retina‐disease‐specific alleles. The most prevalent retina‐disease‐specific allele p.(Ala615Thr) was observed heterozygously or homozygously in 8 and 5 individuals respectively (7 and 4 families). Two siblings in one family, while identical for the HGSNAT locus, but discordant for retinal disease, suggest the influence of trans‐acting genetic or environmental modifying factors.     

A nationwide genetic analysis of inherited retinal diseases in Israel as assessed by the Israeli inherited retinal disease consortium (IIRDC)

Inherited retinal diseases (IRDs) cause visual loss due to dysfunction or progressive degeneration of photoreceptors. These diseases show marked phenotypic and genetic heterogeneity. The Israeli IRD consortium (IIRDC) was established in 2013 with the goal of performing clinical and genetic mapping of the majority of Israeli IRD patients. To date, we recruited 2,420 families including 3,413 individuals with IRDs. On the basis of our estimation, these patients represent approximately 40% of Israeli IRD patients. To the best of our knowledge, this is, by far, the largest reported IRD cohort, and one of the first studies addressing the genetic analysis of IRD patients on a nationwide scale. The most common inheritance pattern in our cohort is autosomal recessive (60% of families). The most common retinal phenotype is retinitis pigmentosa (43%), followed by Stargardt disease and cone/cone–rod dystrophy. We identified the cause of disease in 56% of the families. Overall, 605 distinct mutations were identified, of which 12% represent prevalent founder mutations. The most frequently mutated genes were ABCA4, USH2A, FAM161A, CNGA3, and EYS. The results of this study have important implications for molecular diagnosis, genetic screening, and counseling, as well as for the development of new therapeutic strategies for retinal diseases.     

Molecular diagnostic challenges for non‐retinal developmental eye disorders in the United Kingdom

Overall, approximately one‐quarter of patients with genetic eye diseases will receive a molecular diagnosis. Patients with developmental eye disorders face a number of diagnostic challenges including phenotypic heterogeneity with significant asymmetry, coexisting ocular and systemic disease, limited understanding of human eye development and the associated genetic repertoire, and lack of access to next generation sequencing as regarded not to impact on patient outcomes/management with cost implications. Herein, we report our real world experience from a pediatric ocular genetics service over a 12 month period with 72 consecutive patients from 62 families, and that from a cohort of 322 patients undergoing whole genome sequencing (WGS) through the Genomics England 100,000 Genomes Project; encompassing microphthalmia, anophthalmia, ocular coloboma (MAC), anterior segment dysgenesis anomalies (ASDA), primary congenital glaucoma, congenital cataract, infantile nystagmus, and albinism. Overall molecular diagnostic rates reached 24.9% for those recruited to the 100,000 Genomes Project (73/293 families were solved), but up to 33.9% in the clinic setting (20/59 families). WGS was able to improve genetic diagnosis for MAC patients (15.7%), but not for ASDA (15.0%) and congenital cataracts (44.7%). Increased sample sizes and accurate human phenotype ontology (HPO) terms are required to improve diagnostic accuracy. The significant mixed complex ocular phenotypes distort these rates and lead to missed variants if the correct gene panel is not applied. Increased molecular diagnoses will help to explain the genotype–phenotype relationships of these developmental eye disorders. In turn, this will lead to improved integrated care pathways, understanding of disease, and future therapeutic development.     

Genetic testing for RAD51C mutations: in the clinic and community

Much of the observed familial clustering of breast and ovarian cancer cannot be explained by mutations in BRCA1 and BRCA2. Several other cancer susceptibility genes have been identified, but their value in routine clinical genetic testing is still unclear. Germline mutations in RAD51C have been identified in about 1% of hereditary breast and ovarian cancer families. RAD51C mutations are predominantly found in families with a history of ovarian cancer and are rare in families with a history of breast cancer alone. RAD51C is primarily an ovarian cancer susceptibility gene. A mutation is present in approximately 1% of unselected ovarian cancers. Among mutation carriers, the lifetime risk of ovarian cancer is approximately 9%. The average age at onset is approximately 60 years; this suggests that preventive oophorectomy can be delayed until after natural menopause. Under current guidelines, genetic testing for RAD51C is expected to have a limited impact on ovarian cancer incidence at a population level. This is because the penetrance is 9% to age 80; the great majority of families with mutations would be represented by a single case of ovarian cancer, these are potentially preventable through population screening but not through screening of established ovarian cancer families.     

On attitudes and appreciation 6 months after predictive DNA testing for huntington disease in the Dutch program

We have studied the 6-month follow-up attitudes of 63 individuals, after predictive testing for Huntington disease (HD). Reducing uncertainty (81%) and family planning (60%) were the major reasons for taking the test. Twenty-four individuals were diagnosed as having an increased risk (± 98%), and 39 a decreased risk (± 2%). Among those with an increased risk, denial or minimization of the ultimate impact of the increased risk result was observed. Most of them (84%) rated their current life situation, at the very least, as being good. Twenty-one percent of individuals with an increased risk who originally planned to have a family, decided to refrain from having children. Sixty percent of those with increased risk who still wished to have children, would choose to have prenatal testing. In most individuals with increased risk, the test result did not increase the previously expected control over their own future. Half of the partners of persons with increased risk acknowledged the burden of the future disease. Half had no one in whom they could confide. They showed loyalty to the denial and avoidance reactions of their spouses. Half of the individuals with decreased risk denied the impact of the result, as reflected by absence of relief, and emotional numbness. A third of persons with decreased risk experienced involvement with problems of affected relatives. We found that 20% of all participants were discontented with the support given by their general practitioner, who is normally regarded as being the most significant professional for aftercare. Our findings suggest that the perpetuation of psychological defenses, which may temporarily be adequate, may ultimately prevent an individual from taking advantage of being informed. These questions should be further addressed in long-term follow-up studies. © 1993 Wiley-Liss, Inc.     

Children and young people's understanding of inherited conditions and their attitudes towards genetic testing: A systematic review

Children and young people are increasingly likely to receive information regarding inherited health risks relevant to their genetic relatives and themselves. We reviewed the literature to determine what children and young people (21 years and younger) understand about inherited conditions and their attitudes towards genetic testing. We screened 1815 abstracts to identify 20 studies representing the perspectives of 1811 children and young people between the ages of 6 and 21 years (1498 children or young people at general population-level risk from 9 studies, 313 affected/at risk from 15 studies). Children and young people at general population-level risk demonstrated a basic understanding that disease predisposition can be inherited within families. Those affected by or at risk of genetic conditions inferred their genetic status from observable, relational characteristics within their family and the results of personal genetic testing if it had occurred, but some misunderstandings of important genetic concepts were evident. Children and young people expressed interest in and a willingness to undertake personal genetic testing, but also articulated concerns about the limitations and risks of testing. Paediatric patients require developmentally-sensitive genetic counselling and support in navigating the unique landscape of their condition.     

The genetic landscape of inherited eye disorders in 74 consecutive families from the United Arab Emirates

Genetic eye diseases are phenotypically and genetically heterogeneous, affecting 1 in 1,000 people worldwide. This prevalence can increase in populations where endogamy is a social preference, such as in Arab populations. A retrospective consecutive cohort of 91 patients from 74 unrelated families affected with non‐syndromic and syndromic inherited eye disease presenting to the ocular genetics service at Moorfields Eye Hospitals United Arab Emirates (UAE) between 2017 and 2019, underwent clinically accredited genetic testing using targeted gene panels. The mean ± SD age of probands was 27.4 ± 16.2 years, and 45% were female (41/91). The UAE has a diverse and dynamic population, and the main ethnicity of families in this cohort was 74% Arab (n = 55), 8% Indian (n = 6) and 7% Pakistani (n = 5). Fifty‐six families (90.3%) were genetically solved, with 69 disease‐causing variants in 40 genes. Fourteen novel variants were detected with large deletions in CDHR1 and TTLL5, a multiexon (1–8) duplication in TEAD1 and 11 single nucleotides variants in 9 further genes. ABCA4‐retinopathy was the most frequent cause accounting for 21% of cases, with the confirmed UAE founder mutation c.5882G>A p.(Gly1961Glu)/c.2570T>C p.(Leu857Pro) in 25%. High diagnostic yield for UAE patients can guide prognosis, family decision‐making, access to clinical trials and approved treatments.     

Genetic testing for heart disease susceptibility: potential impact on motivation to quit smoking

As genetic tests for common gene variants and multifactorial, lifestyle-related conditions become available, it will be increasingly important to determine the psychological and behavioral impact of this emerging class of genetic tests. Our aim was to examine the potential impact of genetic testing for heart disease susceptibility on psychological predictors of smoking cessation. Two hundred and sixty-one smokers were asked to imagine that they had undergone a test for heart disease risk. They were randomly assigned to a genetic test scenario (low- or high-risk result) or an oxidative test scenario (high-risk result). Smokers in the genetic test-high risk group reported greater intention to quit smoking than smokers in the oxidative test-high risk group (p = 0.009); 30% of this was mediated by their holding stronger beliefs that quitting would reduce their heart disease risk (outcome expectations) (p = 0.011). The effect of genetic test-high risk feedback on outcome expectations was greatest amongst smokers with no heart disease family history (p = 0.038). The results suggest that genetic testing for heart disease risk may enhance interventions designed to improve health via increasing smoking cessation rates. Whether the findings hold true in studies that use real rather than hypothetical genetic tests remains to be seen.     

Genetic architecture of inherited retinal degeneration in Germany: A large cohort study from a single diagnostic center over a 9‐year period

We aimed to unravel the molecular genetic basis of inherited retinal degeneration (IRD) in a comprehensive cohort of patients diagnosed in the largest center for IRD in Germany. A cohort of 2,158 affected patients from 1,785 families diagnosed with IRD was analyzed by targeted next‐generation sequencing (NGS). Patients with single‐gene disorders (i.e., choroideremia and retinoschisis) were analyzed by Sanger sequencing and multiplex ligation‐dependent probe amplification. Our study cohort accounts for ～7% of the estimated 30,000 patients with IRD in Germany, thereby providing representative data for both the prevalence of IRDs and the mutation spectrum of IRD genes for the population in Germany. We achieved a molecular diagnostic rate of 35–95%, depending on the clinical entities, with a high detection rate for achromatopsia, retinoschisis, and choroideremia, and a low detection rate for central areolar choroidal dystrophy and macular dystrophy. A total of 1,161 distinct variants were identified, including 501 novel variants, reaffirming the known vast genetic heterogeneity of IRD in a mainly outbred European population. This study demonstrates the clinical utility of panel‐based NGS in a large and highly heterogeneous cohort from an outbred population and for the first time gives a comprehensive representation of the genetic landscape of IRDs in Germany. The data are valuable and crucial for the scientific community and healthcare providers, but also for the pharmaceutical industry in the progressing field of personalized medicine and gene therapy.     

Preimplantation genetic testing for Huntington disease and certain other dominantly inherited disorders

Preimplantation genetic testing (PGT) on embryos from couples at risk for Huntington disease can achieve disease prevention in offspring without disclosure of parental genotype. This strategy may also be applicable to other extremely deleterious dominant traits.     

Next-generation sequencing through multigene panel testing for the diagnosis of hereditary epidermolysis bullosa in Chinese population

Epidermolysis bullosa (EB) is a heritable blistering disorder. We performed a next-generation sequencing-based multigene panel test and successfully predicted 100% of the EB types, including, 36 EB simplex (EBS), 13 junctional EB (JEB), 86 dystrophic EB (DEB), and 3 Kindler EB. Chinese JEB and recessive DEB (RDEB) patients have relatively mild phenotypes; for severe type separately accounts for 45.5% and 23.8%, respectively. We identified 96 novel and 49 recurrent pathogenic variants in 11 genes, although we failed to detect the second mutation in one JEB and five RDEB patients. We identified one novel p.E475K mosaic mutation in the clinically normal mother of one out of 13 EBS patients with KRT5 mutations, one recurrent p.G2034R mosaic mutation, and one novel p.G2043R mosaic mutation in the clinically normal relatives of two out of 19 dominant DEB patients. This study shows that next-generation technology could be an effective tool in diagnosing EB.     

Documentation of inherited disorders and mutation frequencies in the different religious communities in Israel in the Israeli National Genetic Database

The National and Ethnic Mutation Databases (NEMDBs) are continuously updated mutation depositories that contain extensive information on the described genetic heterogeneity of an ethnic group or population. Here, we report the construction of the Israeli National Genetic database (Available at: www.goldenhelix.org/israeli; Last accessed: 20 April 2007) to document the sheer genetic heterogeneity found in the Jewish and non-Jewish populations in Israel. The database is built and maintained online using a newly developed customized version of the ETHNOS platform. The Israeli NEMDB is the richest in information among individual NEMDB, containing summaries of 347 genetic disorders studied for the Israeli populations with numerous relevant references and links to the respective Online Mendelian Inheritance in Man (OMIM) entries. Summaries can be selected from an alphabetical summary index or queried using a keyword-based search functionality. An easy-to-use query interface provides access to the over 600 entries on allelic and carrier frequencies of the different mutations responsible for certain inherited disorders in the Jewish and non-Jewish populations, although such documentation is not as extensive as in the other ETHNOS-based NEMDBs. Also, the Israeli NEMDB provides a comprehensive listing of all laboratories providing molecular genetic testing services in Israel with a separate query interface for the user to select which genetic service is provided to a certain laboratory. The Israeli NEMDB is a useful user-friendly and extendable online resource for genetic services in Israel, while the modified version of the ETHNOS software can be particularly useful for similar projects in other populations.