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Eukaryotic cells use G protein-coupled receptors (GPCRs) to convert external stimuli into internal signals to elicit cellular responses. However, how mutations in GPCR-coding genes affect GPCR activation and downstream signaling pathways remain poorly understood. Approaches such as deep mutational scanning show promise in investigations of GPCRs, but a high-throughput method to measure rhodopsin activation has yet to be achieved. Here, we scale up a fluorescent reporter assay in budding yeast that we engineered to study rhodopsin's light-activated signal transduction. Using this approach, we measured the mutational effects of over 1200 individual human rhodopsin mutants, generated by low-frequency random mutagenesis of the GPCR rhodopsin (RHO) gene. Analysis of the data in the context of rhodopsin's three-dimensional structure reveals that transmembrane helices are generally less tolerant to mutations compared to flanking helices that face the lipid bilayer, which suggest that mutational tolerance is contingent on both the local environment surrounding specific residues and the specific position of these residues in the protein structure. Comparison of functional scores from our screen to clinically identified rhodopsin disease variants found many pathogenic mutants to be loss of function. Lastly, functional scores from our assay were consistent with a complex counterion mechanism involved in ligand-binding and rhodopsin activation. Our results demonstrate that deep mutational scanning is possible for rhodopsin activation and can be an effective method for revealing properties of mutational tolerance that may be generalizable to other transmembrane proteins. [ABSTRACT FROM AUTHOR]

Non‐syndromic retinitis pigmentosa (NSRP) is a clinically and genetically heterogeneous group of disorders characterized by progressive degeneration of the rod and cone photoreceptors, often leading to blindness. The evolving association of syndromic genes to cause NSRP and the increasing role of intronic variants in explaining missing heritability in genetic disorders present challenges in establishing conclusive clinical and genetic diagnoses. This study sought to identify and validate the causative genetic variant(s) in a 13‐year‐old male initially diagnosed with NSRP. Genome sequencing identified a pathogenic missense variant in MVK [NM_000431.3:c.803T>C (p.Ile268Thr)], in trans with a novel intronic variant predicted to create a new donor splice site (c.768+71C>A). Proband cDNA analysis confirmed the inclusion of the first 68 base pairs of intron 8 that resulted in a frameshift in MVK (r.768_769ins[768+1_768+68]) and significantly reduced the expression of reference transcript (17.6%). Patient re‐phenotyping revealed ataxia, cerebellar atrophy, elevated urinary mevalonate and LTE4, in keeping with mild mevalonic aciduria and associated syndromic retinitis pigmentosa. Leakage of reference transcript likely explains the milder phenotype observed in our patient. This is the first association of a deep intronic splice variant to cause MVK‐related disorder. This report highlights the importance of variant validation and patient re‐phenotyping in establishing accurate diagnosis in the era of genome sequencing. [ABSTRACT FROM AUTHOR]

We assessed genotype–phenotype correlations among the visual, auditory, and olfactory phenotypes of 127 participants with Usher syndrome (USH2) (n =80) or nonsyndromic autosomal recessive retinitis pigmentosa (ARRP) (n = 47) due to USH2A variants, using clinical data and molecular diagnostics from the Rate of Progression in USH2A Related Retinal Degeneration (RUSH2A) study. USH2A truncating alleles were associated with USH2 and had a dose‐dependent effect on hearing loss severity with no effect on visual loss severity within the USH2 subgroup. A group of missense alleles in an interfibronectin domain appeared to be hypomorphic in ARRP. These alleles were associated with later age of onset, larger visual field area, better sensitivity thresholds, and better electroretinographic responses. No effect of genotype on the severity of olfactory deficits was observed. This study unveils a unique, tissue‐specific USH2A allelic hierarchy with important prognostic implications for patient counseling and treatment trial endpoints. These findings may inform clinical care or research approaches in others with allelic disorders or pleiotropic phenotypes. [ABSTRACT FROM AUTHOR]

Leber congenital amaurosis (LCA), a form of autosomal recessive severe early-onset retinal degeneration, is an important cause of childhood blindness. This may be associated with systemic features or not. Here we identified COG5 compound-heterozygous variants in patients affected with a complex LCA phenotype associated with microcephaly and skeletal dysplasia. COG5 is a component of the COG complex, which facilitates retrograde Golgi trafficking; if disrupted this can result in protein misfolding. To date, variants in COG5 have been associated with a distinct congenital disorder of glycosylation (type IIi) and with a variant of Friedreich's ataxia. We show that COG5 variants can also result in fragmentation of the Golgi apparatus and upregulation of the UPR modulator, PKR-like endoplasmic reticulum kinase (PERK). In addition, upregulation of PERK induces DNA damage in cultured cells and in murine retina. This study identifies a novel role for COG5 in maintaining ER protein homeostasis and that disruption of that role results in activation of PERK and early-onset retinal degeneration, microcephaly and skeletal dysplasia. These results also highlight the importance of the UPR pathway in early-onset retinal dystrophy and as potential therapeutic targets for patients. [ABSTRACT FROM AUTHOR]

Objective: To report a unique retinal signaling defect in GNB5-related disease. Methods: A 3-year-old female child underwent detailed systemic and ophthalmological evaluation. The eye examination included fundus photography, spectral domain optical coherence tomography and an extended protocol full-field electroretinography (ERG) including the ISCEV recommended standard steps. The dark-adapted (DA) ERGs were performed to a series of white flashes (range 0.006–30.0 cd s m−2) and two red flashes. The DA ERGs to higher stimulus intensities (3.0, 10.0 and 30.0 cd s m−2) were tested using a range of inter-stimulus intervals (ISI) of up to 60 s. In addition to standard light-adapted (LA) ERGs, a short-duration (0.5 s) LA 3.0 30-Hz flicker ERG and a long-duration LA ON–OFF ERG were also performed. Genetic testing included microarray, mitochondrial genome testing and whole exome sequencing. Results: The child was diagnosed to have status epilepticus and bradycardia at 6 months of age. Subsequently, she was diagnosed to have global developmental delay and hypotonia. On ophthalmological evaluation, the child fixes and follows light. Fundus evaluation showed mild optic disk pallor; macular SD-OCT was normal. The dim flash DA ERGs (DA 0.006 and DA 0.01 cd s m−2) were non-detectable. DA red flash ERGs showed the presence of an x-wave (cone component) and no rod component. The DA 3.0, 10.0 and 30.0 ERGs showed electronegative configuration regardless of the ISI; the averaged a-wave amplitude (4 flashes) was smaller at shorter ISI but became normal at a prolonged ISI (60 s). The LA 30-Hz flicker ERG was severely reduced but detectable for the initial 0.5 s; this became non-detectable after 5 s of averaging. The LA 3.0 2-Hz ERG showed markedly reduced a- and b-wave amplitudes and a reduced b:a ratio; the LA ON–OFF ERGs were non-detectable. WES identified a homozygous null mutation in G protein subunit beta 5 (GNB5; c.1032C>A/p.Tyr344*). Conclusion: This report identifies for the first time a unique retinopathy associated with biallelic mutations in GNB5. The observed phenotype is consistent with a dual retinal signaling defect reminiscent of features of bradyopsia and rod ON-bipolar dysfunction. [ABSTRACT FROM AUTHOR]

Cataract, the loss of ocular lens transparency, accounts for ∼50% of worldwide blindness and has been associated with water and solute transport dysfunction across lens cellular barriers. We show that neutral amino acid antiporter LAT2 (Slc7a8) and uniporter TAT1 (Slc16a10) are expressed on mouse ciliary epithelium and LAT2 also in lens epithelium. Correspondingly, deletion of LAT2 induced a dramatic decrease in lens essential amino acid levels that was modulated by TAT1 defect. Interestingly, the absence of LAT2 led to increased incidence of cataract in mice, in particular in older females, and a synergistic effect was observed with simultaneous lack of TAT1. Screening SLC7A8 in patients diagnosed with congenital or age-related cataract yielded one homozygous single nucleotide deletion segregating in a family with congenital cataract. Expressed in HeLa cells, this LAT2 mutation did not support amino acid uptake. Heterozygous LAT2 variants were also found in patients with cataract some of which showed a reduced transport function when expressed in HeLa cells. Whether heterozygous LAT2 variants may contribute to the pathology of cataract needs to be further investigated. Overall, our results suggest that defects of amino acid transporter LAT2 are implicated in cataract formation, a situation that may be aggravated by TAT1 defects. [ABSTRACT FROM AUTHOR]

We report on a girl diagnosed prenatally with agenesis of the corpus callosum (ACC) on fetal ultrasound and MRI. On postnatal follow-up she was noted to have developmental delay, facial dysmorphism, autism spectrum disorder, and posterior polymorphous corneal dystrophy (PPD). Array-comparative genomic hybridization analysis (Array-CGH) showed a 2.05 Mb de novo interstitial deletion at 10p11.23p11.22. The deleted region overlaps 1 OMIM Morbid Map gene, ZEB1 (the zinc finger E-box binding homeobox transcription factor 1), previously associated with posterior polymorphous corneal dystrophy type 3 (PPCD3). To our best knowledge this is the first reported case with a deletion of the ZEB1 gene in an individual with ACC and PPD, showing that the haploinsufficiency of the ZEB1 is likely the cause of our patient's phenotype. [ABSTRACT FROM AUTHOR]

Mutations in the EYS (eyes shut homolog) gene are a common cause of autosomal recessive (ar) retinitis pigmentosa (RP). Without a mammalian model of human EYS disease, there is limited understanding of details of disease expression and rates of progression of the retinal degeneration. We studied clinically and with chromatic static perimetry, spectral-domain optical coherence tomography (OCT), and en face autofluoresence imaging, a cohort of 15 patients (ages 12-51 at first visit), some of whom had longitudinal data of function and structure. Rod sensitivity was able to be measured by chromatic perimetry in most patients at their earliest visits and some patients retained patchy rod function into the fifth decade of life. As expected from RP, cone sensitivity persisted after rod function was no longer measurable. The photoreceptor nuclear layer of the central retina was abnormal except at the fovea in most patients at first visit. Perifoveal disease measured over a period of years indicated that photoreceptor structural loss was followed by dysmorphology of the inner retina and loss of retinal pigment epithelial integrity. Although there could be variability in severity, preliminary analyses of the rates of vision loss suggested that EYS is a more rapidly progressive disease than other ciliopathies causing arRP, such as USH2A and MAK. [ABSTRACT FROM AUTHOR]

Purpose: To identify the genetic basis of posterior polymorphous corneal dystrophy (PPCD) in families mapped to the PPCD1 locus and in affected individuals without ZEB1 coding region mutations. Methods: The promoter, 5’ UTR, and coding regions of OVOL2 was screened in the PPCD family in which linkage analysis established the PPCD1 locus and in 26 PPCD probands who did not harbor a ZEB1 mutation. Copy number variation (CNV) analysis in the PPCD1 and PPCD3 intervals was performed on DNA samples from eight probands using aCGH. Luciferase reporter assays were performed in human corneal endothelial cells to determine the impact of the identified potentially pathogenic variants on OVOL2 promoter activity. Results: OVOL2 mutation analysis in the first PPCD1-linked family demonstrated segregation of the c.-307T>C variant with the affected phenotype. In the other 26 probands screened, one heterozygous coding region variant and five promoter region heterozygous variants were identified, though none are likely pathogenic based on allele frequency. Array CGH in the PPCD1 and PPCD3 loci excluded the presence of CNV involving either OVOL2 or ZEB1, respectively. The c.-307T>C variant demonstrated increased promoter activity in corneal endothelial cells when compared to the wild-type sequence as has been demonstrated previously in another cell type. Conclusions: Previously identified as the cause of PPCD1, the OVOL2 promoter variant c.-307T>C was herein identified in the original family that established the PPCD1 locus. However, the failure to identify presumed pathogenic coding or non-coding OVOL2 or ZEB1 variants, or CNV involving the PPCD1 and PPCD3 loci in 26 other PPCD probands suggests that other genetic loci may be involved in the pathogenesis of PPCD. [ABSTRACT FROM AUTHOR]

Background: The use of MRI in isolated pediatric nystagmus remains a gray area in clinical management. Many clinicians prefer to order an MRI to rule out intracranial pathology despite the lack of clinically significant findings in most cases.Objective: To assess the yield of MR imaging in isolated pediatric nystagmus and define a management algorithm to minimize avoidable MRI referrals and streamline MRI protocols.Materials and Methods: We reviewed the charts of 148 children who underwent neuro MRI for isolated nystagmus between January 2008 and September 2014. We noted nystagmus onset and clinical characteristics and compared them with the MRI features and visual electrophysiology results.Results: We included 85 boys and 63 girls (total 148, average age at MRI 4.24 ± 4.19 years). Twenty-three (15.5%) children had abnormal intracranial findings on MRI including abnormal signal lesions (4.1%; n=6), Chiari I malformations (3.4%; n=5) and optic pathway glioma (2.0%; n=3). The time of onset of nystagmus was not associated with an abnormal MRI (P=0.2). Seventy children underwent visual electrophysiology testing but this test could not predict abnormality at MRI, either (P=0.12).Conclusion: Among children with isolated nystagmus, 15.5% had abnormalities on neuroimaging. Neither clinical characteristics of nystagmus nor the visual electrophysiology results allowed prediction of intracranial pathology. We were unable to formulate a management algorithm for the optimal sequence of investigations (MRI preceding visual electrophysiology or vice versa), but we discuss the use of gadolinium contrast agent and orbital sequences in isolated pediatric nystagmus. [ABSTRACT FROM AUTHOR]

PRPS1 codes for the enzyme phosphoribosyl pyrophosphate synthetase-1 (PRS-1). The spectrum of PRPS1-related disorders associated with reduced activity includes Arts syndrome, Charcot-Marie-Tooth disease-5 (CMTX5) and X-linked non-syndromic sensorineural deafness (DFN2). We describe a novel phenotype associated with decreased PRS-1 function in two affected male siblings. Using whole exome and Sanger sequencing techniques, we identified a novel missense mutation in PRPS1. The clinical phenotype in our patients is characterized by high prenatal maternal α-fetoprotein, intrauterine growth restriction, dysmorphic facial features, severe intellectual disability and spastic quadraparesis. Additional phenotypic features include macular coloboma-like lesions with retinal dystrophy, severe short stature and diabetes insipidus. Exome sequencing of the two affected male siblings identified a shared putative pathogenic mutation c.586C>T p.(Arg196Trp) in the PRPS1 gene that was maternally inherited. Follow-up testing showed normal levels of hypoxanthine in urine samples and uric acid levels in blood serum. The PRS activity was significantly reduced in erythrocytes of the two patients. Nucleotide analysis in erythrocytes revealed abnormally low guanosine triphosphate and guanosine diphosphate. This presentation is the most severe form of PRPS1-deficiency syndrome described to date and expands the spectrum of PRPS1-related disorders. [ABSTRACT FROM AUTHOR]

Purpose Hand-held spectral domain optical coherence tomography (HHSD OCT) has greatly expanded the imaging/diagnostic capacity for clinicians managing children with intraocular retinoblastoma. We present our early experience with HHSD OCT and conventional spectral domain OCT imaging in these patients. Methods In this retrospective cross-sectional observational study, infants were imaged during examination under anaesthesia with HHSD OCT in the supine position. Older cooperative retinoblastoma patients were additionally imaged with upright conventional OCT. Clinical data were derived from patient charts and from a prospectively maintained interinstitutional retinoblastoma database. Complementary imaging techniques, including RetCam™, fluorescein angiography and B-scan ultrasound, were assessed. Results Twenty-two intraocular lesions in 16 patients were imaged. HHSD OCT was used exclusively in 19 lesions, while conventional OCT was also performed in three cases. Small lesions were imaged in five cases, all of which were localised to the middle retinal layers. Clinical uses for HHSD OCT imaging identified included: diagnosis of new lesions, monitoring response to laser therapy and the identification of edge recurrences. Conclusions Although indirect ophthalmoscopy remains the gold standard for diagnosis and treatment of retinoblastoma, HHSD OCT is a valuable tool in better understanding and managing retinoblastoma. [ABSTRACT FROM AUTHOR]

Objective: To determine the safety and efficacy of subretinal gene therapy in the RPE65 form of Leber congenital amaurosis using recombinant adeno-associated virus 2 (rAAV2) carrying the RPE65 gene. Design: Open-label, dose-escalation phase I study of 15 patients (range, 11-30 years of age) evaluated after subretinal injection of the rAAV2-RPE65 vector into the worse-functioning eye. Five cohorts represented 4 dose levels and 2 different injection strategies. Main Outcome Measures: Primary outcomes were systemic and ocular safety. Secondary outcomes assayed visual function with dark-adapted full-field sensitivity testing and visual acuity with Early Treatment Diabetic Retinopathy Study charts. Further assays included immune responses to the vector, static visual fields, pupillometry, mobility performance, and optical coherence tomography. Results: No systemic toxicity was detected; ocular adverse events were related to surgery. Visual function improved in all patients to different degrees; improvements were localized to treated areas. Cone and rod sensitivities increased significantly in the study eyes but not in the control eyes. Minor acuity improvements were recorded in many study and control eyes. Major acuity improvements occurred in study eyes with the lowest entry acuities and parafoveal fixation loci treated with subretinal injections. Other patients with better foveal structure lost retinal thickness and acuity after subfoveal injections. Conclusions: Gene therapy for Leber congenital amaurosis caused by RPE65 mutations is sufficiently safe and substantially efficacious in the extrafoveal retina. There is no benefit and some risk in treating the fovea. No evidence of age-dependent effects was found. Our results point to specific treatment strategies for subsequent phases. [ABSTRACT FROM AUTHOR]

The RPE65 gene encodes the isomerase of the retinoid cycle, the enzymatic pathway that underlies mammalian vision. Mutations in RPE65 disrupt the retinoid cycle and cause a congenital human blindness known as Leber congenital amaurosis (LCA). We used adeno-associated virus-2-based RPE65 gene replacement therapy to treat three young adults with RPE65-LCA and measured their vision before and up to 90 days after the intervention. All three patients showed a statistically significant increase in visual sensitivity at 30 days after treatment localized to retinal areas that had received the vector. There were no changes in the effect between 30 and 90 days. Both coneand rod-photoreceptor-based vision could be demonstrated in treated areas. For cones, there were increases of up to 1.7 log units (i.e., 50 fold); and for rods, there were gains of up to 4.8 log units (i.e., 63,000 fold). To assess what fraction of full vision potential was restored by gene therapy, we related the degree of light sensitivity to the level of remaining photoreceptors within the treatment area. We found that the intervention could overcome nearly all of the loss of light sensitivity resulting from the biochemical blockade. However, this reconstituted retinoid cycle was not completely normal. Resensitization kinetics of the newly treated rods were remarkably slow and required 8 h or more for the attainment of full sensitivity, compared with <1 h in normal eyes. Cone-sensitivity recovery time was rapid. These results demonstrate dramatic, albeit imperfect, recovery of rodand cone-photoreceptor-based vision after RPE65 gene therapy. [ABSTRACT FROM AUTHOR]

The visual (retinoid) cycle, the enzymatic pathway that regenerates chromophore after light absorption, is located primarily in the retinal pigment epithelium (RPE) and is essential for rod photoreceptor survival. Whether this pathway also is essential for cone photoreceptor survival is unknown, and there are no data from man or monkey to address this question. The visual cycle is naturally disrupted in humans with Leber congenital amaurosis (LCA), which is caused by mutations in RPE65, the gene that encodes the retinoid isomerase. We investigated such patients over a wide age range (3-52 years) for effects on the cone-rich human fovea. In vivo microscopy of the fovea showed that, even at the youngest ages, patients with RPE65-LCA exhibited cone photoreceptor loss. This loss was incomplete, however, and residual cone photoreceptor structure and function persisted for decades. Basic questions about localization of RPE65 and isomerase activity in the primate eye were addressed by examining normal macaque. RPE65 was definitively localized by immunocytochemistry to the central RPE and, by immunoblotting, appeared to concentrate in the central retina. The central retinal RPE layer also showed a 4-fold higher retinoid isomerase activity than more peripheral RPE. Early cone photoreceptor losses in RPE65-LCA suggest that robust RPE65-based visual chromophore production is important for cones; the residual retained cone structure and function support the speculation that alternative pathways are critical for cone photoreceptor survival. [ABSTRACT FROM AUTHOR]

Mutations in RPE65, a gene essential to normal operation of the visual (retinoid) cycle, cause the childhood blindness known as Leber congenital amaurosis (LCA). Retinal gene therapy restores vision to blind canine and murine models of LCA. Gene therapy in blind humans with LCA from RPE65 mutations may also have potential for success but only if the retinal photoreceptor layer is intact, as in the early-disease stage-treated animals. Here, we use high-resolution in vivo microscopy to quantify photoreceptor layer thickness in the human disease to define the relationship of retinal structure to vision and determine the potential for gene therapy success. The normally cone photoreceptor-rich central retina and rod-rich regions were studied. Despite severely reduced cone vision, many RPE65-mutant retinas had near-normal central micro-structure Absent rod vision was associated with a detectable but thinned photoreceptor layer. We asked whether abnormally thinned RPE65-mutant retina with photoreceptor loss would respond to treatment. Gene therapy in Rpe65-/- mice at advanced-disease stages, a more faithful mimic of the humans we studied, showed success but only in animals with better-preserved photo-receptor structure. The results indicate that identifying and then targeting retinal locations with retained photoreceptors will be a prerequisite for successful gene therapy in humans with RPE65 mutations and in other retinal degenerative disorders now moving from proof-of-concept studies toward clinical trials. [ABSTRACT FROM AUTHOR]

Ocular albinism type I (OA1) is an X-linked disorder. mainly characterized by a severe reduction in visual acuity, foxeal hypoplasia, nystagmus, hypopigmentation of the retina, the presence of macromelanosomes in the skin and eyes, and the misrouting of optic pathways, resulting in the loss of stereoscopic vision. We screened the OA1 gene for mutations in three unrelated Canadian and French families and in two isolated patients with OA1. We found three different missense mutations and two different nonsense mutations, three of which were novel. To date, 41 mutations (including missense mutations. insertions, and deletions) have been reported in the OA1 gene. Mutation and polymorphism data for this gene are available from the international albinism center albinism database website: http://www.cbc.umn.edu/tad/oa1map.htm. [ABSTRACT FROM AUTHOR]

Background: Focal subtenon carboplatin injections have recently been used as a presumably toxicity-free adjunct to systemic chemotherapy for intraocular retinoblastoma. Objective: To report our clinical experience with abnormal ocular motility in patients treated with subtenon carboplatin chemotherapy. Methods: We noted abnormal ocular motility in 10 consecutive patients with retinoblastoma who had received subtenon carboplatin. During ocular manipulation under general anesthesia, we assessed their eyes by forced duction testing, comparing ocular motility after tumor control with ocular motility at diagnosis. Eyes subsequently enucleated because of treatment failure (n = 4) were examined histologically. Results: Limitation of ocular motility was detected in all 12 eyes of 10 patients treated for intraocular retinoblastoma with 1 to 6 injections of subtenon carboplatin as part of multimodality therapy. Histopathological examination revealed many lipophages in the periorbital fat surrounding the optic nerve in 1 eye, indicative of phagocytosis of previously existing fat cells and suggesting prior fat necrosis. The enucleations were technically difficult and hazardous for globe rupture because of extensive orbital soft tissue adhesions. Conclusions: Subtenon carboplatin chemotherapy is associated with significant fibrosis of orbital soft tissues, leading to mechanical restriction of eye movements and making subsequent enucleation difficult. Subtenon carboplatin is not free of toxicity, and its use is best restricted to specific indications. [ABSTRACT FROM AUTHOR]

Objective We examined sleep, daytime sleepiness and the ability to stay awake during the day in patients affected with retinitis pigmentosa (RP), to further delineate the role of photoreceptors in the circadian cycle. Methods Twelve individuals diagnosed with RP (40 ± 8 years) And 12 normally sighted healthy individuals (39 ± 7 years) matched for age, body mass index (BMI) and sex were selected for the study. Participants had their sleep recorded on two consecutive nights and were monitored on the two following days. On the first day, their ability to stay awake and on the second, their sleep propensity were assessed using the Maintenance of Wakefulness Test (MWT) and the Multiple Sleep Latency Test (MSLT), respectively. Self-report measures were obtained using the Pittsburgh Sleep Quality Index (PSQI), the Epworth Sleepiness Scale (ESS), and the Toronto Hospital Alertness Test (THAT). Results Subjective daytime sleepiness (ESS: 9 ± 5 vs. 6 ± 4, P=0.053) and objectively measured sleep propensity (MSLT: 10 ± 5 vs. 17 ± 3 min, P < 0.000) were significantly higher in RP patients than controls, whilst their alertness (THAT: 29 ± 9 vs. 38 ± 7, P=0.016) and ability to stay awake (MWT: 21 ± 9 vs. 29 ± 2 min, P=0.006) were significantly reduced. Retinitis pigmentosa participants had more disturbed nighttime sleep, with significantly more awakenings (arousal index: 14 ± 8 vs. 8 ± 6 h, P=0.039), and tended to have less rapid eye movement (REM) sleep (19 ± 5 vs. 22 ± 3%, P=0.094). Conclusion Patients with RP have increased daytime sleepiness, reduced alertness and more disturbed nighttime sleep of poorer quality than their normally sighted counterparts, suggesting an influence of photoreceptor degeneration on the circadian cycle. [ABSTRACT FROM AUTHOR]

Bardet–Biedl syndrome (BBS) is a genetically heterogeneous autosomal recessive disorder with the primary clinical features of obesity, pigmented retinopathy, polydactyly, hypogenitalism, mental retardation and renal anomalies. Associated features of the disorder include diabetes mellitus, hypertension and congenital heart disease. There are six known BBS loci, mapping to chromosomes 2, 3, 11, 15, 16 and 20. The BBS2 locus was initially mapped to an 18 cM interval on chromosome 16q21 with a large inbred Bedouin kindred. Further analysis of the Bedouin population allowed for the fine mapping of this locus to a 2 cM region distal to marker D16S408. Physical mapping and sequence analysis of this region resulted in the identification of a number of known genes and expressed sequence tag clusters. Mutation screening of a novel gene (BBS2) with a wide pattern of tissue expression revealed homozygous mutations in two inbred pedigrees, including the large Bedouin kindred used to initially identify the BBS2 locus. In addition, mutations were found in three of 18 unrelated BBS probands from small nuclear families. [ABSTRACT FROM PUBLISHER]

Studies the positional cloning of a novel gene on chromosome 16q causing Bardet-Biedl syndrome. Description of Bardet-Biedl syndrome; Clinical features of obesity, pigmented retinopathy and others; Homozygous mutations in two inbred pedigrees.

Hemizygous pathogenic variants in CACNA1F lead to defective signal transmission from retinal photoreceptors to bipolar cells and cause incomplete congenital stationary night blindness in humans. Although the primary defect is at the terminal end of first-order neurons (photoreceptors), there is limited knowledge of higher-order neuronal changes (inner retinal) in this disorder. This study aimed to investigate inner retinal changes in CACNA1F-retinopathy by analyzing macular ganglion cell layer-inner plexiform layer (GCL-IPL) thickness and optic disc pallor in 22 subjects with molecularly confirmed CACNA1F-retinopathy. Detailed ocular phenotypic data including distance and color vision, refraction and electroretinogram (ERG) were collected. Distance vision was universally reduced (mean: 0.42 LogMAR), six had abnormal color vision and myopia was common (n = 15; mean: −6.32 diopters). Mean GCL-IPL thickness was significantly lower in patients (55.00 µm) compared to age-matched controls (n = 87; 84.57 µm; p << 0.001). The GCL-IPL thickness correlated with scotopic standard (p = 0.04) and bright-flash (p = 0.014) ERG b/a ratios and photopic b-wave amplitudes (p = 0.05). Twenty-one patients had some degree of disc pallor (bilateral in 19). Fifteen putative disease-causing, including five novel variants were identified. This study establishes macular inner retinal thinning and optic atrophy as characteristic features of CACNA1F-retinopathy, which are independent of myopia and could impact potential future treatment strategies. [ABSTRACT FROM AUTHOR]

Leber congenital amaurosis (LCA) is an autosomal recessive retinal dystrophy that manifests with genetic heterogeneity. We sequenced the exome of an individual with LCA and identified nonsense (c.507G>A, p.Trp169*) and missense (c.769G>A, p.Glu257Lys) mutations in NMNAT1, which encodes an enzyme in the nicotinamide adenine dinucleotide (NAD) biosynthesis pathway implicated in protection against axonal degeneration. We also found NMNAT1 mutations in ten other individuals with LCA, all of whom carry the p.Glu257Lys variant. [ABSTRACT FROM AUTHOR]

Innovation is important for the improvement of health care. A small grant innovation funding program was implemented by the Hospital for Sick Children(SickKids) for the Perioperative Services group, awarding relatively small funds (approximately $10 000) in order to stimulate innovation. Of 48 applications,26 (54.2%) different innovation projects were funded for a total allocation of $227 870. This program demonstrated the ability of small grants to stimulate many applications with novel ideas, a wide range of innovations and reasonable academic productivity. [ABSTRACT FROM AUTHOR]

Responds to a letter to the editor about periocular chemotherapy for retinoblatoma.

Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder with locus heterogeneity. None of the ‘responsible’ genes have previously been identified. Some BBS cases (approximately 10%) remain unassigned to the five previously mapped loci. McKusick-Kaufma syndrome (MKS) includes hydrometrocolpos, postaxial polydactyly and congenital heart disease, and is also inherited in an autosomal recessive manner. We ascertained 34 unrelated probands with classic features of BBS including retinitis pigmentosa (RP), obesity and polydactyly. The probands were from families unsuitable for linkage because of family size. We found MKKS mutations in four typical BBS probands (Table 1). The first is a 13-year-old Hispanic girl with severe RP, PAP, mental retardation and obesity (BMI >40). She was a compound heterozygote for a missense (1042G→A, G52D) and a nonsense (1679T→A, Y264stop) mutation in exon 3. Cloning and sequencing of the separate alleles confirmed that the mutations were present in trans. A second BBS proband (from Newfoundland), born to consanguineous parents, was homozygous for two deletions (1316delC and 1324-1326delGTA) in exon 3, predicting a frameshift. An affected brother was also homozygous for the deletions, whereas an unaffected sibling had two normal copies of MKKS. Both the proband and her affected brother had RP, PAP, mild mental retardation, morbid obesity (BMI >50 and 37, respectively), lobulated kidneys with prominent calyces and diabetes mellitus (diagnosed at ages 33 and 30, respectively). A deceased sister (DNA unavailable) had similar phenotypic features (RP with blindness by age 13, BMI >45, abnormal glucose tolerance test and IQ=64, vaginal atresia and syndactyly of both feet). Both parents and the maternal grandfather were heterozygous for the deletions. Genotyping with markers from the MKKS region confirmed homozygosity at 20p12 in both affected individuals. [ABSTRACT FROM AUTHOR]