Shedding light on myopia by studying complete congenital stationary night blindness

Myopia is the most common eye disorder, caused by heterogeneous genetic and environmental factors. Rare progressive and stationary inherited retinal disorders are often associated with high myopia. Genes implicated in myopia encode proteins involved in a variety of biological processes including eye morphogenesis, extracellular matrix organization, visual perception, circadian rhythms, and retinal signaling. Differentially expressed genes (DEGs) identified in animal models mimicking myopia are helpful in suggesting candidate genes implicated in human myopia. Complete congenital stationary night blindness (cCSNB) in humans and animal models represents an ON-bipolar cell signal transmission defect and is also associated with high myopia. Thus, it represents also an interesting model to identify myopia-related genes, as well as disease mechanisms. While the origin of night blindness is molecularly well established, further research is needed to elucidate the mechanisms of myopia development in subjects with cCSNB. Using whole transcriptome analysis on three different mouse models of cCSNB (in Gpr179^-/-, Lrit3^-/- and Grm6^-/-), we identified novel actors of the retinal signaling cascade, which are also novel candidate genes for myopia. Meta-analysis of our transcriptomic data with published transcriptomic databases and genome-wide association studies from myopia cases led us to propose new biological/cellular processes/mechanisms potentially at the origin of myopia in cCSNB subjects. The results provide a foundation to guide the development of pharmacological myopia therapies.

The validation of inherited retinal disease-specific patient-reported outcome measures in adolescent patients

PURPOSE

To determine the validity of the validate the adult patient-reported outcome measure tools, the Michigan Retinal Degeneration Questionnaire (MRDQ) and Michigan Vision-Related Anxiety Questionnaire (MVAQ), in adolescent patients with inherited retinal diseases (IRDs).

METHODS

Ninety-one adolescent patients diagnosed with IRDs were recruited at the Hospital for Sick Children (University of Toronto) and the Kellogg Eye Center (University of Michigan). The patients were administered the MRDQ, MVAQ, and Patient Health Questionnaire-4 (PHQ-4). Test-retest variability was assessed in eighteen patients within 14 days of the initial administration. Adolescent responses were analyzed for validity and reliability. As a further validation step, comparisons were made to adult data from the original MRDQ and MVAQ studies to ensure consistency in response ranges.

RESULTS

The existing MRDQ and MVAQ content and format could accurately detect the impact of IRD on activities of daily living in adolescents with IRDs. No floor/ceiling effects were identified, test-retest reliability was established (r = 0.73-0.86), and no items were excluded after differential item functioning analysis. Domain and trait associations with visual acuity and IRD phenotypes were similar between adolescents and adults.

CONCLUSIONS

The MRDQ and MVAQ are psychometrically validated questionnaires for which we have shown validity for use in adolescent patients with IRDs.

Gene therapy: perspectives from young adults with Leber's congenital amaurosis

AIMS/PURPOSE

To investigate Leber congenital amaurosis (LCA) patients' expectations, decision-making processes and gene therapy-related concerns.

METHODS

Using a qualitative approach, we explored perceptions of gene therapy and clinical trials among individuals with LCA. Young adults with a clinical diagnosis of LCA were recruited through the Ocular Genetics Programme at the Hospital for Sick Children. Semi-structured interviews were conducted with ten patients and analysed following the principles of qualitative description.

RESULTS

Study participants were aware of ongoing gene therapy research trials and actively sought information regarding advances in ophthalmology and vision restoration. The majority of participants would enrol or were enrolled in a gene-replacement therapy trial, while a minority was ambivalent or would not enrol if provided an opportunity. Participants attributed different values to clinical trials, which influenced their willingness to participate. Intrinsic factors related to coping, adaptation to vision loss and resilience also influenced decision-making.

DISCUSSION

This study highlights the complex factors involved in gene-therapy-related decision-making and acts as a proponent for adopting patient-centred care strategies when counselling individuals considering gene therapy or clinical trial participation.

Novel OPN1LW/OPN1MW Exon 3 Haplotype-Associated Splicing Defect in Patients with X-Linked Cone Dysfunction

Certain combinations of common variants in exon 3 of OPN1LW and OPN1MW, the genes encoding the apo-protein of the long- and middle-wavelength sensitive cone photoreceptor visual pigments in humans, induce splicing defects and have been associated with dyschromatopsia and cone dysfunction syndromes. Here we report the identification of a novel exon 3 haplotype, G-C-G-A-T-T-G-G (referring to nucleotide variants at cDNA positions c.453, c.457, c.465, c.511, c.513, c.521, c.532, and c.538) deduced to encode a pigment with the amino acid residues L-I-V-V-A at positions p.153, p.171, p.174, p.178, and p.180, in OPN1LW or OPN1MW or both in a series of seven patients from four families with cone dysfunction. Applying minigene assays for all observed exon 3 haplotypes in the patients, we demonstrated that the novel exon 3 haplotype L-I-V-V-A induces a strong but incomplete splicing defect with 3-5% of residual correctly spliced transcripts. Minigene splicing outcomes were similar in HEK293 cells and the human retinoblastoma cell line WERI-Rb1, the latter retaining a cone photoreceptor expression profile including endogenous OPN1LW and OPN1MW gene expression. Patients carrying the novel L-I-V-V-A haplotype presented with a mild form of Blue Cone Monochromacy or Bornholm Eye Disease-like phenotype with reduced visual acuity, reduced cone electroretinography responses, red-green color vision defects, and frequently with severe myopia.

The State of Patient-Reported Outcome Measures for Pediatric Patients with Inherited Retinal Disease

Patient-reported outcome measures (PROMs) are questionnaires that assess health outcomes meaningful to the patient. PROMs have multiple applications, such as supporting clinicians’ decision-making for patient care, understanding the impact of disease on patient functioning, and evaluating the efficacy of therapeutics. Though PROMs were developed for various eye conditions, no PROM was tailored to pediatric patients with inherited retinal disease (IRD). Hence, a literature search was conducted using MEDLINE and Embase to identify PROMs potentially relevant to this patient population. This review evaluated selected pediatric PROMs against the US Food and Drug Administration (FDA) guidelines and found restricted use in the context of IRD. As there is a need for PROMs tailored to pediatric patients with IRD, we provide a perspective on applying the International Society for Pharmacoeconomics and Outcomes Research and FDA standards on the development of PROMs specific to IRD.

Inherited retinal diseases refer to a group of genetic conditions that affect the eye’s light-sensing cells and lead to vision loss. When a patient undergoes an eye assessment, the measures used are technical (e.g., visual acuity, visual field) and do not routinely address the patient’s experience. It is increasingly evident that the technical tools used do not really reflect how patients’ vision affects their daily lives. Questionnaires designed to assess how a condition impacts a daily activity are referred to as patient-reported outcome measures. The perspective of the impact of a condition on daily activities differs between adults and children. These tools are being created to evaluate health outcomes important to the patient on the basis of their condition and age. This is especially important when determining the value of therapies from the patient perspective. To date, no such questionnaire has been designed for pediatric patients with inherited retinal disease, an important cause of blindness. We explored the literature to evaluate existing pediatric vision tools and found that those could not be used to fill this gap. Given that we found a need to develop questionnaires tailored to pediatric patients with IRD, we also provide insight into how such a tool can be created for this population.

ABCA4 c.859-25A>G, a Frequent Palestinian Founder Mutation Affecting the Intron 7 Branchpoint, Is Associated With Early-Onset Stargardt Disease

Purpose

The effect of noncoding variants is often unknown in the absence of functional assays. Here, we characterized an ABCA4 intron 7 variant, c.859-25A>G, identified in Palestinian probands with Stargardt disease (STGD) or cone-rod dystrophy (CRD). We investigated the effect of this variant on the ABCA4 mRNA and retinal phenotype, and its prevalence in Palestine.

Methods

The ABCA4 gene was sequenced completely or partially in 1998 cases with STGD or CRD. The effect of c.859-25A>G on splicing was investigated in silico using SpliceAI and in vitro using splice assays. Homozygosity mapping was performed for 16 affected individuals homozygous for c.859-25A>G. The clinical phenotype was assessed using functional and structural analyses including visual acuity, full-field electroretinography, and multimodal imaging.

Results

The smMIPs-based ABCA4 sequencing revealed c.859-25A>G in 10 Palestinian probands from Hebron and Jerusalem. SpliceAI predicted a significant effect of this putative branchpoint-inactivating variant on the nearby intron 7 splice acceptor site. Splice assays revealed exon 8 skipping and two partial inclusions of intron 7, each having a deleterious effect. Additional genotyping revealed another 46 affected homozygous or compound heterozygous individuals carrying variant c.859-25A>G. Homozygotes shared a genomic segment of 59.6 to 87.9 kb and showed severe retinal defects on ophthalmoscopic evaluation.

Conclusions

The ABCA4 variant c.859-25A>G disrupts a predicted branchpoint, resulting in protein truncation because of different splice defects, and is associated with early-onset STGD1 when present in homozygosity. This variant was found in 25/525 Palestinian inherited retinal dystrophy probands, representing one of the most frequent inherited retinal disease-causing variants in West-Bank Palestine.

KCNV2-Associated Retinopathy: Detailed Retinal Phenotype and Structural Endpoints-KCNV2 Study Group Report 2

PURPOSE

To describe the detailed retinal phenotype of KCNV2-associated retinopathy.

STUDY DESIGN

Multicenter international retrospective case series.

METHODS

Review of retinal imaging including fundus autofluorescence (FAF) and optical coherence tomography (OCT), including qualitative and quantitative analyses.

RESULTS

Three distinct macular FAF features were identified: (1) centrally increased signal (n = 35, 41.7%), (2) decreased autofluorescence (n = 27, 31.1%), and (3) ring of increased signal (n = 37, 44.0%). Five distinct FAF groups were identified based on combinations of those features, with 23.5% of patients changing the FAF group over a mean (range) follow-up of 5.9 years (1.9-13.1 years). Qualitative assessment was performed by grading OCT into 5 grades: (1) continuous ellipsoid zone (EZ) (20.5%); (2) EZ disruption (26.1%); (3) EZ absence, without optical gap and with preserved retinal pigment epithelium complex (21.6%); (4) loss of EZ and a hyporeflective zone at the foveola (6.8%); and (5) outer retina and retinal pigment epithelium complex loss (25.0%). Eighty-six patients had scans available from both eyes, with 83 (96.5%) having the same grade in both eyes, and 36.1% changed OCT grade over a mean follow-up of 5.5 years. The annual rate of outer nuclear layer thickness change was similar for right and left eyes.

CONCLUSIONS

KCNV2-associated retinopathy is a slowly progressive disease with early retinal changes, which are predominantly symmetric between eyes. The identification of a single OCT or FAF measurement as an endpoint to determine progression that applies to all patients may be challenging, although outer nuclear layer thickness is a potential biomarker. Findings suggest a potential window for intervention until 40 years of age.

KCNV2-Associated Retinopathy: Genetics, Electrophysiology, and Clinical Course-KCNV2 Study Group Report 1

PURPOSE

To investigate genetics, electrophysiology, and clinical course of KCNV2-associated retinopathy in a cohort of children and adults.

STUDY DESIGN

This was a multicenter international clinical cohort study.

METHODS

Review of clinical notes and molecular genetic testing. Full-field electroretinography (ERG) recordings, incorporating the international standards, were reviewed and quantified and compared with age and recordings from control subjects.

RESULTS

In total, 230 disease-associated alleles were identified from 117 patients, corresponding to 75 different KCNV2 variants, with 28 being novel. The mean age of onset was 3.9 years old. All patients were symptomatic before 12 years of age (range, 0-11 years). Decreased visual acuity was present in all patients, and 4 other symptoms were common: reduced color vision (78.6%), photophobia (53.5%), nyctalopia (43.6%), and nystagmus (38.6%). After a mean follow-up of 8.4 years, the mean best-corrected visual acuity (BCVA ± SD) decreased from 0.81 ± 0.27 to 0.90 ± 0.31 logarithm of minimal angle of resolution. Full-field ERGs showed pathognomonic waveform features. Quantitative assessment revealed a wide range of ERG amplitudes and peak times, with a mean rate of age-associated reduction indistinguishable from the control group. Mean amplitude reductions for the dark-adapted 0.01 ERG, dark-adapted 10 ERG a-wave, and LA 3.0 30 Hz and LA3 ERG b-waves were 55%, 21%, 48%, and 74%, respectively compared with control values. Peak times showed stability across 6 decades.

CONCLUSION

In KCNV2-associated retinopathy, full-field ERGs are diagnostic and consistent with largely stable peripheral retinal dysfunction. Report 1 highlights the severity of the clinical phenotype and established a large cohort of patients, emphasizing the unmet need for trials of novel therapeutics.

Phenotype Driven Analysis of Whole Genome Sequencing Identifies Deep Intronic Variants that Cause Retinal Dystrophies by Aberrant Exonization

Purpose

To demonstrate the effectiveness of combining retinal phenotyping and focused variant filtering from genome sequencing (GS) in identifying deep intronic disease causing variants in inherited retinal dystrophies.

Methods

Affected members from three pedigrees with classical enhanced S-cone syndrome (ESCS; Pedigree 1), congenital stationary night blindness (CSNB; Pedigree 2), and achromatopsia (ACHM; Pedigree 3), respectively, underwent detailed ophthalmologic evaluation, optical coherence tomography, and electroretinography. The probands underwent panel-based genetic testing followed by GS analysis. Minigene constructs (NR2E3, GPR179 and CNGB3) and patient-derived cDNA experiments (NR2E3 and GPR179) were performed to assess the functional effect of the deep intronic variants.

Results

The electrophysiological findings confirmed the clinical diagnosis of ESCS, CSNB, and ACHM in the respective pedigrees. Panel-based testing revealed heterozygous pathogenic variants in NR2E3 (NM_014249.3; c.119-2A>C; Pedigree 1) and CNGB3 (NM_019098.4; c.1148delC/p.Thr383Ilefs*13; Pedigree 3). The GS revealed heterozygous deep intronic variants in Pedigrees 1 (NR2E3; c.1100+1124G>A) and 3 (CNGB3; c.852+4751A>T), and a homozygous GPR179 variant in Pedigree 2 (NM_001004334.3; c.903+343G>A). The identified variants segregated with the phenotype in all pedigrees. All deep intronic variants were predicted to generate a splice acceptor gain causing aberrant exonization in NR2E3 [89 base pairs (bp)], GPR179 (197 bp), and CNGB3 (73 bp); splicing defects were validated through patient-derived cDNA experiments and/or minigene constructs and rescued by antisense oligonucleotide treatment.

Conclusions

Deep intronic mutations contribute to missing heritability in retinal dystrophies. Combining results from phenotype-directed gene panel testing, GS, and in silico splice prediction tools can help identify these difficult-to-detect pathogenic deep intronic variants.

Progress in treating inherited retinal diseases: Early subretinal gene therapy clinical trials and candidates for future initiatives

Due to improved phenotyping and genetic characterization, the field of 'incurable' and 'blinding' inherited retinal diseases (IRDs) has moved substantially forward. Decades of ascertainment of IRD patient data from Philadelphia and Toronto centers illustrate the progress from Mendelian genetic types to molecular diagnoses. Molecular genetics have been used not only to clarify diagnoses and to direct counseling but also to enable the first clinical trials of gene-based treatment in these diseases. An overview of the recent reports of gene augmentation clinical trials by subretinal injections is used to reflect on the reasons why there has been limited success in this early venture into therapy. These first-in human experiences have taught that there is a need for advancing the techniques of delivery of the gene products - not only for refining further subretinal trials, but also for evaluating intravitreal delivery. Candidate IRDs for intravitreal gene delivery are then suggested to illustrate some of the disorders that may be amenable to improvement of remaining central vision with the least photoreceptor trauma. A more detailed understanding of the human IRDs to be considered for therapy and the calculated potential for efficacy should be among the routine prerequisites for initiating a clinical trial.

Deregulation of Neuro-Developmental Genes and Primary Cilium Cytoskeleton Anomalies in iPSC Retinal Sheets from Human Syndromic Ciliopathies

Ciliopathies are heterogeneous genetic diseases affecting primary cilium structure and function. Meckel-Gruber (MKS) and Bardet-Biedl (BBS) syndromes are severe ciliopathies characterized by skeletal and neurodevelopment anomalies, including polydactyly, cognitive impairment, and retinal degeneration. We describe the generation and molecular characterization of human induced pluripotent stem cell (iPSC)-derived retinal sheets (RSs) from controls, and MKS (TMEM67) and BBS (BBS10) cases. MKS and BBS RSs displayed significant common alterations in the expression of hundreds of developmental genes and members of the WNT and BMP pathways. Induction of crystallin molecular chaperones was prominent in MKS and BBS RSs suggesting a stress response to misfolded proteins. Unique to MKS photoreceptors was the presence of supernumerary centrioles and cilia, and aggregation of ciliary proteins. Unique to BBS photoreceptors was the accumulation of DNA damage and activation of the mitotic spindle checkpoint. This study reveals how combining cell reprogramming, organogenesis, and next-generation sequencing enables the elucidation of mechanisms involved in human ciliopathies.

Transient pupillary light reflex in CEP290- or NPHP5-associated Leber congenital amaurosis: Latency as a potential outcome measure of cone function

Mutations in photoreceptor cilium genes CEP290 and NPHP5 cause a form of Leber congenital amaurosis (LCA) which typically lacks rods but retains central cones. The current study evaluated the transient pupillary light reflex (TPLR) as an objective outcome measure to assess efficacy of ongoing and future therapies. Eleven eyes of six patients selected for retained cone function were tested with TPLR using full-field stimuli in the dark-adapted state. Stimuli were red or blue with 1 s duration and spanned a 6-log unit dynamic range. TPLR response amplitude was quantified at fixed times of 0.9 and 2 s after stimulus onset and TPLR latency was defined as the time to reach 0.3 mm constriction. Full-field stimulus testing (FST) and static perimetry were used to correlate subjective perception with objective TPLR parameters. TPLR and FST thresholds with both red and blue stimuli were abnormally elevated in patients to near -1.25 log phot-cd·m-2 consistent with the lack of rods. TPLR latencies were delayed on average but showed some differences among patients. Remnant extrafoveal vision was correlated with faster TPLR latencies. Our results support the use of a short TPLR protocol with full-field red stimuli of 0.7 log phot-cd·m-2 or brighter as an objective and convenient outcome measure of cone function in CEP290- and NPHP5-LCA. The latency parameter of the TPLR would be expected to show a detectable change when an intervention modifies cone sensitivity in the extrafoveal region.

Characterization of Retinal Structure in ATF6-Associated Achromatopsia

Purpose

Mutations in six genes have been associated with achromatopsia (ACHM): CNGA3, CNGB3, PDE6H, PDE6C, GNAT2, and ATF6. ATF6 is the most recent gene to be identified, though thorough phenotyping of this genetic subtype is lacking. Here, we sought to test the hypothesis that ATF6-associated ACHM is a structurally distinct form of congenital ACHM.

Methods

Seven genetically confirmed subjects from five nonconsanguineous families were recruited. Foveal hypoplasia and the integrity of the ellipsoid zone (EZ) band (a.k.a., IS/OS) were graded from optical coherence tomography (OCT) images. Images of the photoreceptor mosaic were acquired using confocal and nonconfocal split-detection adaptive optics scanning light ophthalmoscopy (AOSLO). Parafoveal cone and rod density values were calculated and compared to published normative data as well as data from two subjects harboring CNGA3 or CNGB3 mutations who were recruited for comparative purposes. Additionally, nonconfocal dark-field AOSLO images of the retinal pigment epithelium were obtained, with quantitative analysis performed in one subject with ATF6-ACHM.

Results

Foveal hypoplasia was observed in all subjects with ATF6 mutations. Absence of the EZ band within the foveal region (grade 3) or appearance of a hyporeflective zone (grade 4) was seen in all subjects with ATF6 using OCT. There was no evidence of remnant foveal cone structure using confocal AOSLO, although sporadic cone-like structures were seen in nonconfocal split-detection AOSLO. There was a lack of cone structure in the parafovea, in direct contrast to previous reports.

Conclusions

Our data demonstrate a near absence of cone structure in subjects harboring ATF6 mutations. This implicates ATF6 as having a major role in cone development and suggests that at least a subset of subjects with ATF6-ACHM have markedly fewer cellular targets for cone-directed gene therapies than do subjects with CNGA3- or CNGB3-ACHM.

Healthcare recommendations for Joubert syndrome

Joubert syndrome (JS) is a recessive neurodevelopmental disorder defined by a characteristic cerebellar and brainstem malformation recognizable on axial brain magnetic resonance imaging as the "Molar Tooth Sign". Although defined by the neurological features, JS is associated with clinical features affecting many other organ systems, particularly progressive involvement of the retina, kidney, and liver. JS is a rare condition; therefore, many affected individuals may not have easy access to subspecialty providers familiar with JS (e.g., geneticists, neurologists, developmental pediatricians, ophthalmologists, nephrologists, hepatologists, psychiatrists, therapists, and educators). Expert recommendations can enable practitioners of all types to provide quality care to individuals with JS and know when to refer for subspecialty care. This need will only increase as precision treatments targeting specific genetic causes of JS emerge. The goal of these recommendations is to provide a resource for general practitioners, subspecialists, and families to maximize the health of individuals with JS throughout the lifespan.

Retrotransposon insertion as a novel mutational event in Bardet-Biedl syndrome

Background

Bardet‐Biedl syndrome (BBS) is an autosomal recessive pleiotropic disorder of the primary cilia that leads to severe visual loss in the teenage years. Approximately 80% of BBS cases are explained by mutations in one of the 21 identified genes. Documented causative mutation types include missense, nonsense, copy number variation (CNV), frameshift deletions or insertions, and splicing variants.

Methods

Whole genome sequencing was performed on a patient affected with BBS for whom no mutations were identified using clinically approved genetic testing of the known genes. Analysis of the WGS was done using internal protocols and publicly available algorithms. The phenotype was defined by retrospective chart review.

Results

We document a female affected with BBS carrying the most common BBS1 mutation (BBS1: Met390Arg) on the maternal allele and an insertion of a ~1.7‐kb retrotransposon in exon 13 on the paternal allele. This retrotransposon insertion was not automatically annotated by the standard variant calling protocols used. This novel variant was identified by visual inspection of the alignment file followed by specific genome analysis with an available algorithm for transposable elements.

Conclusion

This report documents a novel mutation type associated with BBS and highlights the importance of systematically performing transposon detection analysis on WGS data of unsolved cases.

IFT80 mutations cause a novel complex ciliopathy phenotype with retinal degeneration

Ciliopathies, a growing pleotropic class of diseases due to mutations in genes that play an important role in primary cilia function. These highly conserved organelles are key to cell signaling. We now know, that mutations in one gene may lead to more than one ciliopathy phenotype and that one ciliopathy phenotype may be due to mutations in more than one gene. We studied the case of a female child with a novel ciliopathy phenotype and identified two novel mutations in the gene IFT80. Previously, mutations in IFT80 have been associated with a very narrow rib cage and failure of the lungs. Bone anomalies are also part of this IFT80-condition but with no vision problems documented. Our case had none of the features known to be associated with IFT80 mutations and had retinal degeneration (RD). This work broadens the IFT80-phenotype spectrum and also shows RD can be a feature of many ciliopathies.

Optical Coherence Tomography-Guided Decisions in Retinoblastoma Management

PURPOSE

Assess the role of handheld optical coherence tomography (OCT) in guiding management decisions during diagnosis, treatment, and follow-up of eyes affected by retinoblastoma.

DESIGN

Retrospective, noncomparative, single-institution case series.

PARTICIPANTS

All children newly diagnosed with retinoblastoma from January 2011 to December 2015 who had an OCT session during their active treatment at The Hospital for Sick Children (SickKids) in Toronto, Canada. The OCT sessions for fellow eyes of unilateral retinoblastoma without any suspicious lesion and those performed more than 6 months after the last treatment were excluded.

METHODS

Data collected included age at presentation, sex, family history, RB1 mutation status, 8th edition TNMH cancer staging and International Intraocular Retinoblastoma Classification (IIRC), and number of OCT sessions per eye. Details of each session were scored for indication-related details (informative or not) and assessed for guidance (directive or not), diagnosis (staging changed, new tumors found or excluded), treatment (modified, stopped, or modality shifted), or follow-up modified.

MAIN OUTCOME MEASURES

Frequency of OCT-guided management decisions, stratified by indication and type of guidance (confirmatory vs. influential).

RESULTS

Sixty-three eyes of 44 children had 339 OCT sessions over the course of clinical management (median number of OCT scans per eye, 5; range, 1-15). The age at presentation and presence of a heritable RB1 mutation significantly correlated with an increased number of OCT sessions. Indications included evaluation of post-treatment scar (55%) or fovea (16%), and posterior pole scanning for new tumors (11%). Of all sessions, 92% (312/339) were informative; 19 of 27 noninformative sessions had large, elevated lesions; of these, 14 of 19 were T2a or T2b (IIRC group C or D) eyes. In 94% (293/312) of the informative sessions, OCT directed treatment decisions (58%), diagnosis (16%), and follow-up (26%). Optical coherence tomography influenced and changed management from pre-OCT clinical plans in 15% of all OCT sessions and 17% of directive sessions.

CONCLUSIONS

Optical coherence tomography improves the accuracy of clinical evaluation in retinoblastoma management.

The combination of vestibular impairment and congenital sensorineural hearing loss predisposes patients to ocular anomalies, including Usher syndrome

The co-occurrence of hearing impairment and visual dysfunction is devastating. Most deaf-blind etiologies are genetically determined, the commonest being Usher syndrome (USH). While studies of the congenitally deaf population reveal a variable degree of visual problems, there are no effective ophthalmic screening guidelines. We hypothesized that children with congenital sensorineural hearing loss (SNHL) and vestibular impairment were at an increased risk of having USH. A retrospective chart review of 33 cochlear implants recipients for severe to profound SNHL and measured vestibular dysfunction was performed to determine the ocular phenotype. All the cases had undergone ocular examination and electroretinogram (ERG). Patients with an abnormal ERG underwent genetic testing for USH. We found an underlying ocular abnormality in 81.81% (27/33) of cases; of which 75% had refractive errors, and 50% of those patients showed visual improvement with refractive correction. A total of 14 cases (42.42%; 14/33) had generalized rod-cone dysfunction on ERG suggestive of Usher syndrome type 1, confirmed by mutational analysis. This work shows that adding vestibular impairment as a criterion for requesting an eye exam and adding the ERG to detect USH increases the chances of detecting ocular anomalies, when compared with previous literature focusing only on congenital SNHL.

Prenatal versus Postnatal Screening for Familial Retinoblastoma

PURPOSE

To compare overall outcomes of conventional postnatal screening of familial retinoblastoma and prenatal RB1 mutation identification followed by planned early-term delivery.

DESIGN

Retrospective, observational study.

PARTICIPANTS

Twenty children with familial retinoblastoma born between 1996 and 2014 and examined within 1 week of birth.

METHODS

Cohort 1 included spontaneously delivered neonates examined within 1 week of birth and confirmed postnatal to carry their family's RB1 mutant allele. Cohort 2 included infants identified by amniocentesis to carry their family's RB1 mutant allele, and therefore scheduled for early-term delivery (36-38 weeks' gestation). Treatment for retinoblastoma was performed at the Hospital for Sick Children, Toronto, Canada.

MAIN OUTCOME MEASURES

Age at first tumor in each eye, eye stage, treatments given, ocular salvage, treatment success (defined as avoidance of enucleation, external-beam irradiation, or both), visual outcome, number of anesthetics, pregnancy or delivery complications, and estimated treatment burden.

RESULTS

Vision-threatening tumors were present at birth in 4 of 8 infants in cohort 1 and in 3 of 12 infants in cohort 2. Eventually, all infants demonstrated tumors in both eyes. At the first treatment, 1 of 8 infants in cohort 1 had eyes in stage cT1a/cT1a or cT1a/cT0 (smallest and least vision-threatening tumors), compared with 8 of 12 infants in cohort 2 (P = 0.02). Null RB1 germline alleles induced earlier tumors than low-penetrance alleles (P = 0.03). Treatment success was achieved in 3 of 8 children in cohort 1 compared with 11 of 12 children in cohort 2 (P = 0.002). Acceptable vision (better than 0.2 decimal) was achieved for 8 of 16 eyes in cohort 1 compared with 21 of 24 eyes in cohort 2 (P = 0.014). Useful vision (better than 0.1, legal blindness) was achieved for 8 of 9 children in cohort 1 compared with 12 of 12 children in cohort 2. There were no complications related to early-term delivery. Median follow-up was 5.6 years, cohort 1 and 5.8 years, cohort 2.

CONCLUSIONS

When a parent had retinoblastoma, prenatal molecular diagnosis with early-term delivery increased the likelihood of infants born with no detectable tumors, better vision outcomes, and less invasive therapy. Prenatal molecular diagnosis facilitates anticipatory planning for both the child and family.

Spondyloocular Syndrome: Novel Mutations in XYLT2 Gene and Expansion of the Phenotypic Spectrum

Spondyloocular syndrome is an autosomal-recessive disorder with spinal compression fractures, osteoporosis, and cataract. Mutations in XYLT2, encoding isoform of xylosyltransferase, were recently identified as the cause of the syndrome. We report on 4 patients, 2 unrelated patients and 2 siblings, with spondyloocular syndrome and novel mutations in XYLT2. Exome sequencing revealed a homozygous nonsense mutation, NM_022167.3(XYLT2): c.2188C>T, resulting in a premature stop codon (p.Arg730*) in a female patient. The patient presents visual impairment, generalized osteoporosis, short stature with short trunk, spinal compression fractures, and increased intervertebral disc space and hearing loss. We extended our XYLT2 analysis to a cohort of 22 patients with generalized osteoporosis, mostly from consanguineous families. In this cohort, we found by Sanger sequencing 2 siblings and 1 single patient who were homozygous for missense mutations in the XYLT2 gene (p.Arg563Gly and p.Leu605Pro). The patients had osteoporosis, compression fractures, cataracts, and hearing loss. Bisphosphonate treatment in 1 patient resulted in almost complete normalization of vertebral structures by adolescence, whereas treatment response in the others was variable. This report together with a previous study shows that mutations in the XYLT2 gene result in a variable phenotype dominated by spinal osteoporosis, cataract, and hearing loss. © 2016 American Society for Bone and Mineral Research.

Biallelic Mutations in GNB3 Cause a Unique Form of Autosomal-Recessive Congenital Stationary Night Blindness

Congenital stationary night blindness (CSNB) is a heterogeneous group of non-progressive inherited retinal disorders with characteristic electroretinogram (ERG) abnormalities. Riggs and Schubert-Bornschein are subtypes of CSNB and demonstrate distinct ERG features. Riggs CSNB demonstrates selective rod photoreceptor dysfunction and occurs due to mutations in genes encoding proteins involved in rod phototransduction cascade; night blindness is the only symptom and eye examination is otherwise normal. Schubert-Bornschein CSNB is a consequence of impaired signal transmission between the photoreceptors and bipolar cells. Schubert-Bornschein CSNB is subdivided into complete CSNB with an ON bipolar signaling defect and incomplete CSNB with both ON and OFF pathway involvement. Both subtypes are associated with variable degrees of night blindness or photophobia, reduced visual acuity, high myopia, and nystagmus. Whole-exome sequencing of a family screened negative for mutations in genes associated with CSNB identified biallelic mutations in the guanine nucleotide-binding protein subunit beta-3 gene (GNB3). Two siblings were compound heterozygous for a deletion (c.170_172delAGA [p.Lys57del]) and a nonsense mutation (c.1017G>A [p.Trp339(∗)]). The maternal aunt was homozygous for the nonsense mutation (c.1017G>A [p.Trp339(∗)]). Mutational analysis of GNB3 in a cohort of 58 subjects with CSNB identified a sporadic case individual with a homozygous GNB3 mutation (c.200C>T [p.Ser67Phe]). GNB3 encodes the β subunit of G protein heterotrimer (Gαβγ) and is known to modulate ON bipolar cell signaling and cone transducin function in mice. Affected human subjects showed an unusual CSNB phenotype with variable degrees of ON bipolar dysfunction and reduced cone sensitivity. This unique retinal disorder with dual anomaly in visual processing expands our knowledge about retinal signaling.

Retinal degeneration in autoimmune polyglandular syndrome type 1: a case series

BACKGROUND

Autoimmune polyglandular syndrome type 1 (APS1) is a rare autosomal recessive disorder due to mutations in the AIRE gene.

AIM

To report the ocular features and characterise the retinal phenotype in molecularly confirmed APS1.

METHOD

This retrospective case series reviewed five molecularly confirmed cases with APS1 known to have ocular involvement (age range: 19 months-44 years; mean follow-up of 8 years). The medical history, ocular history and evaluation, visual field testing, full-field electroretinogram (ERG) and antiretinal antibody results were reviewed.

RESULTS

All but one case had decreased vision at first presentation. All cases had peripheral pigmentary retinal changes; macular atrophy was noted in 80% of cases. The most common feature on spectral-domain optical coherence tomography was a disruption of the external limiting membrane and inner segment ellipsoid band (n=3). Fundus autofluorescence imaging demonstrated a parafoveal ring of hyper-autofluorescence (n=1) or a stippled and patchy autofluorescence pattern in the macula (n=1). The visual fields were constricted in all tested patients (n=3). The rod ERG was abnormal in all cases; the relative involvement of rods and cones differed. Four patients who were tested for antiretinal antibodies were found positive by immunohistochemistry (n=3) and/or western blot (n=2).

CONCLUSIONS

Photoreceptor degeneration is part of APS1 phenotype and the presence of antiretinal antibodies strongly supports an aetiology similar to that of non-paraneoplastic autoimmune retinopathy. Periodic retinal evaluation and imaging, visual field testing and ERG would assist in monitoring the retinopathy in APS1-related disease.

North Carolina Macular Dystrophy Is Caused by Dysregulation of the Retinal Transcription Factor PRDM13

PURPOSE

To identify specific mutations causing North Carolina macular dystrophy (NCMD).

DESIGN

Whole-genome sequencing coupled with reverse transcription polymerase chain reaction (RT-PCR) analysis of gene expression in human retinal cells.

PARTICIPANTS

A total of 141 members of 12 families with NCMD and 261 unrelated control individuals.

METHODS

Genome sequencing was performed on 8 affected individuals from 3 families affected with chromosome 6-linked NCMD (MCDR1) and 2 individuals affected with chromosome 5-linked NCMD (MCDR3). Variants observed in the MCDR1 locus with frequencies <1% in published databases were confirmed using Sanger sequencing. Confirmed variants absent from all published databases were sought in 8 additional MCDR1 families and 261 controls. The RT-PCR analysis of selected genes was performed in stem cell-derived human retinal cells.

MAIN OUTCOME MEASURES

Co-segregation of rare genetic variants with disease phenotype.

RESULTS

Five sequenced individuals with MCDR1-linked NCMD shared a haplotype of 14 rare variants spanning 1 Mb of the disease-causing allele. One of these variants (V1) was absent from all published databases and all 261 controls, but was found in 5 additional NCMD kindreds. This variant lies in a DNase 1 hypersensitivity site (DHS) upstream of both the PRDM13 and CCNC genes. Sanger sequencing of 1 kb centered on V1 was performed in the remaining 4 NCMD probands, and 2 additional novel single nucleotide variants (V2 in 3 families and V3 in 1 family) were identified in the DHS within 134 bp of the location of V1. A complete duplication of the PRDM13 gene was also discovered in a single family (V4). The RT-PCR analysis of PRDM13 expression in developing retinal cells revealed marked developmental regulation. Next-generation sequencing of 2 individuals with MCDR3-linked NCMD revealed a 900-kb duplication that included the entire IRX1 gene (V5). The 5 mutations V1 to V5 segregated perfectly in the 102 affected and 39 unaffected members of the 12 NCMD families.

CONCLUSIONS

We identified 5 rare mutations, each capable of arresting human macular development. Four of these strongly implicate the involvement of PRDM13 in macular development, whereas the pathophysiologic mechanism of the fifth remains unknown but may involve the developmental dysregulation of IRX1.

Exploration of the cognitive, adaptive and behavioral functioning of patients affected with Bardet-Biedl syndrome

The aim of the study was to investigate the behavioral phenotype of patients affected with Bardet-Biedl syndrome (BBS). Twenty-four patients with molecularly confirmed diagnosis of BBS (6-38 years old) were evaluated using standardized neuropsychological tests. Results were compared with normative data. The mean intellectual functioning of participants fell 1.5 standard deviations below normal expectations; though, the majority of participants (75-80%) did not display an intellectual disability. The group's mean performance on most cognitive tasks and all scales of adaptive functioning was significantly weaker than norms. The majority (55-60%) of participants displayed broadly average verbal fluency and auditory rote learning, while 22-40% were severely impaired in the same areas. The majority of participants were severely impaired in perceptual reasoning (53%), attentional capacity (69%), and functional independence (74%). Symptoms associated with Autism were reported for 77% of participants. Behavioral issues were unrelated to intellectual ability but significantly correlated with adaptive functioning. This first neurocognitive evaluation of a molecularly confirmed cohort of BBS patients shows that the majority of patients experience significant difficulties with perceptual intellectual abilities, auditory attentional capacity, adaptive independence, and behavior. The frequency of autism-related symptoms far exceeds the incidence rate of diagnosed autism in general and warrants further investigations.

Mutations in the unfolded protein response regulator ATF6 cause the cone dysfunction disorder achromatopsia

Achromatopsia (ACHM) is an autosomal recessive disorder characterized by color blindness, photophobia, nystagmus and severely reduced visual acuity. Using homozygosity mapping and whole-exome and candidate gene sequencing, we identified ten families carrying six homozygous and two compound-heterozygous mutations in the ATF6 gene (encoding activating transcription factor 6A), a key regulator of the unfolded protein response (UPR) and cellular endoplasmic reticulum (ER) homeostasis. Patients had evidence of foveal hypoplasia and disruption of the cone photoreceptor layer. The ACHM-associated ATF6 mutations attenuate ATF6 transcriptional activity in response to ER stress. Atf6(-/-) mice have normal retinal morphology and function at a young age but develop rod and cone dysfunction with increasing age. This new ACHM-related gene suggests a crucial and unexpected role for ATF6A in human foveal development and cone function and adds to the list of genes that, despite ubiquitous expression, when mutated can result in an isolated retinal photoreceptor phenotype.

A detailed clinical and molecular survey of subjects with nonsyndromic USH2A retinopathy reveals an allelic hierarchy of disease-causing variants

Defects in USH2A cause both isolated retinal disease and Usher syndrome (ie, retinal disease and deafness). To gain insights into isolated/nonsyndromic USH2A retinopathy, we screened USH2A in 186 probands with recessive retinal disease and no hearing complaint in childhood (discovery cohort) and in 84 probands with recessive retinal disease (replication cohort). Detailed phenotyping, including retinal imaging and audiological assessment, was performed in individuals with two likely disease-causing USH2A variants. Further genetic testing, including screening for a deep-intronic disease-causing variant and large deletions/duplications, was performed in those with one likely disease-causing change. Overall, 23 of 186 probands (discovery cohort) were found to harbour two likely disease-causing variants in USH2A. Some of these variants were predominantly associated with nonsyndromic retinal degeneration (‘retinal disease-specific'); these included the common c.2276 G>T, p.(Cys759Phe) mutation and five additional variants: c.2802 T>G, p.(Cys934Trp); c.10073 G>A, p.(Cys3358Tyr); c.11156 G>A, p.(Arg3719His); c.12295-3 T>A; and c.12575 G>A, p.(Arg4192His). An allelic hierarchy was observed in the discovery cohort and confirmed in the replication cohort. In nonsyndromic USH2A disease, retinopathy was consistent with retinitis pigmentosa and the audiological phenotype was variable. USH2A retinopathy is a common cause of nonsyndromic recessive retinal degeneration and has a different mutational spectrum to that observed in Usher syndrome. The following model is proposed: the presence of at least one ‘retinal disease-specific' USH2A allele in a patient with USH2A-related disease results in the preservation of normal hearing. Careful genotype–phenotype studies such as this will become increasingly important, especially now that high-throughput sequencing is widely used in the clinical setting.

Hypersensitivity to sub-Tenon's topotecan in fibrin adhesive in patients with retinoblastoma

Sub-Tenon's space delivery of topotecan in a fibrin sealant was used as an adjunct to laser therapy for small retinoblastoma tumors in 25 children (77 injections). We report serious hypersensitivity reactions in 2 children on their third sub-Tenon's injection of topotecan in fibrin sealant. One child subsequently had topotecan in an autologous blood clot with no allergic reaction. Although allergic reaction to topotecan has been reported in the literature, fibrin glue reactions are more common and are likely due to aprotinin hypersensitivity.

OTX2 mutations cause autosomal dominant pattern dystrophy of the retinal pigment epithelium

PURPOSE

To identify the genetic cause of autosomal-dominant pattern dystrophy (PD) of the retinal pigment epithelium (RPE) in two families.

METHODS AND RESULTS

Two families with autosomal-dominant PD were identified. Eight members of family 1 (five affected) were subjected to whole-genome SNP genotyping; multipoint genome-wide linkage analysis identified 7 regions of potential linkage, and genotyping four additional individuals from family 1 resulted in a maximum logarithm of odds score of 2.09 observed across four chromosomal regions. Exome sequencing of two affected family 1 members identified 15 shared non-synonymous rare coding sequence variants within the linked regions; candidate genes were prioritised and further analysed. Sanger sequencing confirmed a novel heterozygous missense variant (E79K) in orthodenticle homeobox 2 (OTX2) that segregated with the disease phenotype. Family 2 with PD (two affected) harboured the same missense variant in OTX2. A shared haplotype of 19.68 cM encompassing OTX2 was identified between affected individuals in the two families. Within the two families, all except one affected demonstrated distinct 'patterns' at the macula. In vivo structural retinal imaging showed discrete areas of RPE-photoreceptor separation at the macula in all cases. Electroretinogram testing showed generalised photoreceptor degeneration in three cases. Mild developmental anomalies were observed, including optic nerve head dysplasia (four cases), microcornea (one case) and Rathke's cleft cyst (one case); pituitary hormone levels were normal.

CONCLUSIONS

This is the first report implicating OTX2 to underlie PD. The retinal disease resembles conditional mice models that show slow photoreceptor degeneration secondary to loss of Otx2 function in the adult RPE.

Abstract 767: Cyclosporin-modulated intensified-dosage chemotherapy for saving eyes with Group D intraocular retinoblastoma

PURPOSE: Cyclosporin (CSA) inhibits the multidrug resistance P-glycoprotein. Since 2000, we tested increased carboplatin and increased etoposide dosages in a cyclosporin-modulated carboplatin-etoposide-vincristine protocol, followed by focal laser/cryotherapy consolidation, to avoid elective radiation of newly diagnosed retinoblastoma (RB) patients, since radiation increases the secondary cancer risk in patients with heritable RB. We report the results for International Classification Groups A, B, C and D intraocular eyes (Ophthalmol Clinic North Am 2005; 18:41-53).

METHOD: When Neupogen support became available, we increased the predominantly myelotoxic carboplatin to 28 mg/kg (from 18.7 mg/kg in our previous trial) and etoposide to 12 mg/kg (from 7.7 mg/kg in our previous trial), but kept the predominantly neurotoxic vincristine unchanged at 0.05 mg/kg, modulated by the same cyclosporin schedule (33 mg/kg over 3 hours on each of the 2 days per cycle). We treated 34 eyes in 23 patients: 2 A eyes, 11 B eyes, 6 C eyes and 15 D eyes. This report focuses only on the most difficult to save Group D eyes, and compares results with a non-cyclosporin carboplatin (26 mg/kg) and etoposide (10 mg/kg), vincristine (0.05 mg/kg) regimen. Radiation or enucleation for recurrence was considered failure.

RESULTS: We report the long-term results of 15 Group D eyes in 10 patients, at mean followup of 11.1 years and median followup of 10.8 years (range 5.7-13.4 years). Eye event-free rate was 53% for Group D (8/15) eyes. Seven D eyes failed, and 6 were enucleated and 1 radiated. No child lost both eyes. Toxicity rates were acceptable with 15.7% fever-and-neutropenia, 0.7% bacterial sepsis, 9.7% blood transfusion and 27.6% platelet transfusion, and no long-term renotoxicity or ototoxicity. In comparison, at mean followup of 4.5 years (range 0.4-9.8 years), in a previously reported (Pediatr Blood Cancer 2013; 60:688-693) non-cyclosporin regimen, the non-radiation eye event-free rate was 47% for Group D (26/55) eyes, with 5 eyes enucleated, and 24 eyes radiated (19 irradiated eyes retained; 5 irradiated eyes required enucleation).

CONCLUSION: This cyclosporin-modulated intensified-dosage protocol was well-tolerated, with a non-radiation eye salvage rate of 53%, and 60% overall if the one irradiated but retained eye was included, in the most difficult to save Group D eyes. No child lost both eyes, and most avoided radiation. This same protocol is being tested in a multicenter trial.

Citation Format: Helen S.L. Chan, Elise Héon, A Linn Murphree, Paulita P. Astudillo, Helen Dimaras, Furqan Shaikh, Brenda L. Gallie. Cyclosporin-modulated intensified-dosage chemotherapy for saving eyes with Group D intraocular retinoblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 767. doi:10.1158/1538-7445.AM2014-767

Late-diagnosis retinoblastoma with germline mosaicism in an 8-year-old

We describe bilateral retinoblastoma in an 8-year-old girl presenting with macular tumor in one eye and a small peripheral tumor in the other but no detected RB1 gene mutation. Despite chemotherapy, multiple focal laser, cryotherapy, and periocular chemotherapy, tumor activity persisted and enucleation was performed. Two RB1 mutations were found in the tumor; one RB1 mutation was present in 10% of blood cells, identifying mosaicsm.

Mutational spectrum of the ZEB1 gene in corneal dystrophies supports a genotype-phenotype correlation

PURPOSE

Mutations in ZEB1 have been reported in posterior polymorphous corneal dystrophy (PPCD3; MIM #609141) and Fuchs' endothelial corneal dystrophy (FECD6; MIM #613270). Although PPCD and keratoconus are clinically and pathologically distinct, PPCD has been associated with keratoconus, suggesting a common genetic basis. The purpose of our study was to perform mutational screening of the ZEB1 gene in patients affected with keratoconus or PPCD.

METHODS

Sanger sequencing of ZEB1 was performed in 70 unrelated patients with keratoconus and 18 unrelated patients with PPCD. Real-time quantitative PCR (RT-qPCR) was performed on RNA from cultured corneal keratocytes obtained from a keratoconic patient harboring a missense ZEB1 mutation (p.Gln640His) undergoing corneal transplantation.

RESULTS

Mutational analysis of ZEB1 in PPCD identified a previously reported frameshift mutation (C.1578_1579INSG) and a novel nonsense mutation (C.2249C A) in exon 7 of ZEB1 causing the insertion of a stop codon: p.Ser750X. In the keratoconus cohort, a novel heterozygous pathogenic mutation in exon 7 (c.1920G > T; p.Gln640His) of ZEB1 was identified in a family affected with keratoconus and Fuchs' endothelial corneal dystrophy. RT-qPCR performed on cultured corneal keratocytes harboring the missense ZEB1 mutation (p.Gln640His) demonstrated that COL4A1 and COL4A2 were markedly downregulated, and COL4A3, COL4A4, and COL8A2 were moderately downregulated.

CONCLUSIONS

Our data combined with the previously reported mutational spectrum of ZEB1 support a genotypephenotype correlation: missense substitutions in the ZEB1 protein are associated with FECD6 and keratoconus, whereas protein truncating ZEB1 mutations result in PPCD3. The dysregulation of α-type IV collagens represents a common link between ZEB1 mutation and the clinical phenotypes (PPCD3, FECD, and keratoconus).

Phenotypic characteristics including in vivo cone photoreceptor mosaic in KCNV2-related "cone dystrophy with supernormal rod electroretinogram"

PURPOSE

To report phenotypic characteristics including macular cone photoreceptor morphology in KCNV2-related "cone dystrophy with supernormal rod electroretinogram" (CDSR).

METHODS

Seven patients, aged 9 to 18 years at last visit, with characteristic full-field electroretinographic (ERG) features of CDSR were screened for mutations in the KCNV2 gene. All patients underwent detailed ophthalmological evaluation, which included distance and color vision testing, contrast sensitivity measurement, fundus photography, fundus autofluorescence (FAF) imaging, and spectral domain-optical coherence tomography (SD-OCT). Follow-up visits were available in six cases. Rod photoreceptor function was assessed using a bright white flash ERG protocol (240 cd·s/m(2)). Macular cone photoreceptor morphology was assessed from 2° by 2° zonal images obtained using adaptive optics scanning laser ophthalmoscopy (AOSLO) in six cases.

RESULTS

Pathogenic mutations in KCNV2 were identified in all seven cases. Best corrected vision was 20/125 or worse in all cases at the latest visit (20/125-20/400). Vision loss was progressive in two cases. Color vision and contrast sensitivity was abnormal in all cases. Retinal exam revealed minimal pigment epithelial changes at the fovea in four cases. A peri- or parafoveal ring of hyperfluorescence was the most common FAF abnormality noted (five cases). The SD-OCT showed outer retinal abnormalities in all cases. The rod photoreceptor maximal response was reduced but rod sensitivity was normal. AOSLO showed markedly reduced cone density in all six patients tested.

CONCLUSIONS

Central vision parameters progressively worsen in CDSR. Structural retinal and lipofuscin accumulation abnormalities are commonly present. Macular cone photoreceptor mosaic is markedly disrupted early in the disease.

Molecular testing prognostic of low risk in epithelioid uveal melanoma in a child

AIMS

To characterise a histologically unusual paediatric uveal melanoma by gene expression and karyotypic profiling and assess prognosis.

METHODS

The tumour was studied by histopathology, karyotype analysis, single nucleotide polymorphism and gene expression profile analysis for correlation with clinical outcome.

RESULTS

The tumour had predominantly epithelioid histology. Karyotype analysis showed none of the poor prognosis features normally associated with uveal melanoma. single nucleotide polymorphism analysis revealed no imbalance at chromosome 3. Gene expression profiling indicated low risk disease.

CONCLUSIONS

We report a child remaining relapse-free 6 years after diagnosis of a very rare uveal melanoma, with poor prognosis epithelioid histology, but gene expression profiling that accurately predicted low risk disease.

Detection of optic nerve disease in retinoblastoma by use of spectral domain optical coherence tomography

We present the case of a child affected with retinoblastoma and evolving optic nerve pathology detected by spectral domain optical coherence tomography (SD-OCT) before magnetic resonance imaging. At 6 months of age, the patient was diagnosed with bilateral retinoblastoma, which was managed with systemic chemotherapy and focal therapy. Six months after the third and final cycle of systemic chemotherapy, the right optic disk clinically appeared progressively edematous, raising concerns of tumor infiltration of the optic nerve head. Images obtained via magnetic resonance imaging could not confirm the presence of a tumor at the optic nerve head, whereas findings on SD-OCT were suggestive of optic nerve head disease. Histopathologic findings after enucleation revealed viable tumor over the optic nerve head, supporting the OCT findings.

Mutational analysis of SDCCAG8 in Bardet-Biedl syndrome patients with renal involvement and absent polydactyly

PURPOSE

To assess for SDCCAG8 mutations in Bardet-Biedl syndrome (BBS) subjects with renal involvement and no polydactyly, and to describe phenotypic characteristics of SDCCAG8-related disease.

MATERIAL AND METHODS

Five patients (from 4 pedigrees) with clinical diagnosis of BBS, who had retinal and renal involvement and no polydactyly, were assessed. Sequence analysis of SDCCAG8 was undertaken and a detailed clinical review of an affected sibship was performed.

RESULTS

A sibship of East Indian origin who carried a putative clinical diagnosis of BBS had compound heterozygous mutations in SDCCAG8 (p.Thr482LysfsX12/p.Asp543AlafsX24). The renal involvement was early and required transplant in both cases. Both were short statured and had asthma since childhood. The younger sister also had non-alcoholic fatty liver disease. Visual acuity and central fields were preserved in the teenage years in both patients. The optical coherence tomography showed preservation of the retinal lamination at the fovea; fundus autofluorescence demonstrated a perifoveal ring of hyperfluorescence as commonly observed in other forms of retinitis pigmentosa. Full-field electroretinogram revealed rod function to be more severely affected than cone function in both cases.

CONCLUSION

Our results and prior literature suggest that SDCCAG8 could play an important role in presumed BBS patients affected with severe kidney disease and absent polydactyly. This report enhances the phenotypic description of SDCCAG8-related disease.

Autosomal recessive retinitis pigmentosa caused by mutations in the MAK gene

PURPOSE

To determine the disease expression in autosomal recessive (ar) retinitis pigmentosa (RP) caused by mutations in the MAK (male germ cell-associated kinase) gene.

METHODS

Patients with RP and MAK gene mutations (n = 24; age, 32-77 years at first visit) were studied by ocular examination, perimetry, and optical coherence tomography (OCT).

RESULTS

All but one MAK patient were homozygous for an identical truncating mutation in exon 9 and had Ashkenazi Jewish heritage. The carrier frequency of this mutation among 1207 unrelated Ashkenazi control subjects was 1 in 55, making it the most common cause of heritable retinal disease in this population and MAK-associated RP the sixth most common Mendelian disease overall in this group. Visual acuities could be normal into the eighth decade of life. Kinetic fields showed early loss in the superior-temporal quadrant. With more advanced disease, superior and midperipheral function was lost, but the nasal field remained. Only a central island was present at late stages. Pigmentary retinopathy was less prominent in the superior nasal quadrant. Rod-mediated vision was abnormal but detectable in the residual field; all patients had rod>cone dysfunction. Photoreceptor layer thickness was normal centrally but decreased with eccentricity. At the stages studied, there was no evidence of photoreceptor ciliary elongation.

CONCLUSIONS

The patterns of disease expression in the MAK form of arRP showed some resemblance to patterns described in autosomal dominant RP, especially the form caused by RP1 mutations. The similarity in phenotypes is of interest, considering that there is experimental evidence of interaction between Mak and RP1 in the photoreceptor cilium.

Mutations in a guanylate cyclase GCY-35/GCY-36 modify Bardet-Biedl syndrome-associated phenotypes in Caenorhabditis elegans

Ciliopathies are pleiotropic and genetically heterogeneous disorders caused by defective development and function of the primary cilium. Bardet-Biedl syndrome (BBS) proteins localize to the base of cilia and undergo intraflagellar transport, and the loss of their functions leads to a multisystemic ciliopathy. Here we report the identification of mutations in guanylate cyclases (GCYs) as modifiers of Caenorhabditis elegans bbs endophenotypes. The loss of GCY-35 or GCY-36 results in suppression of the small body size, developmental delay, and exploration defects exhibited by multiple bbs mutants. Moreover, an effector of cGMP signalling, a cGMP-dependent protein kinase, EGL-4, also modifies bbs mutant defects. We propose that a misregulation of cGMP signalling, which underlies developmental and some behavioural defects of C. elegans bbs mutants, may also contribute to some BBS features in other organisms.

Bardet-Biedl syndrome (BBS) is a genetically heterogeneous, multisystemic disorder. Defects to the cilium, an evolutionarily conserved organelle, cause ciliopathies, a growing class of diseases that includes BBS. BBS proteins are involved in the vesicular transport of proteins to the cilium and in the process of intraflagellar transport. Here we show that, in addition to sensory defects, Caenorhabditis elegans bbs mutants exhibit reduced body size and delayed developmental timing. The reduced body size phenotype is not fully recapitulated by IFT mutants, suggesting that BBS proteins may have additional functions beyond bridging IFT motors. We further identified that the loss of function mutations in the soluble guanylate cyclase complex, GCY-35/GCY-36, results in a suppression of these defects. Interestingly, GCY-35/GCY-36 influences the body size through a cGMP-dependent protein kinase EGL-4 in a group of body cavity neurons. BBS proteins, on the other hand, function through a non-overlapping set of ciliated sensory neurons to influence cGMP signalling in the body cavity neurons. In conclusion, this study reveals a non-cell autonomous role for sensory cilia in regulating cGMP signalling during development. We propose that aberrant cGMP signalling, essential for a number of cellular processes, may also contribute to some ciliopathy features in other systems.

BBS genotype-phenotype assessment of a multiethnic patient cohort calls for a revision of the disease definition

Bardet-Biedl syndrome (BBS) is a ciliopathy characterized by retinal degeneration, obesity, polydactyly, renal abnormalities, and cognitive impairment for which 15 causative genes have been identified. Here we present the results of a mutational analysis of our multiethnic cohort of 83 families (105 cases); 75.9% of them have their mutations identified including 26 novel changes. Comprehensive phenotyping of these patients demonstrate that the spectrum of clinical features is greater than expected and overlapped with the features of other ciliopathies; specifically Alström and McKusick-Kauffman syndromes.