Multisystem involvement, defective lysosomes and impaired autophagy in a novel rat model of nephropathic cystinosis.

Recessive mutations in the CTNS gene encoding the lysosomal transporter cystinosin cause cystinosis, a lysosomal storage disease leading to kidney failure and multisystem manifestations. A Ctns knockout mouse model recapitulates features of cystinosis, but the delayed onset of kidney manifestations, phenotype variability and strain effects limit its use for mechanistic and drug development studies. To provide a better model for cystinosis, we generated a Ctns knockout rat model using CRISPR/Cas9 technology. The Ctns-/- rats display progressive cystine accumulation and crystal formation in multiple tissues including kidney, liver and thyroid. They show an early onset and progressive loss of urinary solutes, indicating generalized proximal tubule dysfunction, with development of typical swan-neck lesions, tubulointerstitial fibrosis and kidney failure, and decreased survival. The Ctns-/- rats also present crystals in the cornea, and bone and liver defects, as observed in patients. Mechanistically, the loss of cystinosin induces a phenotype switch associating abnormal proliferation and dedifferentiation, loss of apical receptors and transporters, and defective lysosomal activity and autophagy in the cells. Primary cultures of proximal tubule cells derived from the Ctns-/- rat kidneys confirmed the key changes caused by cystine overload, including reduced endocytic uptake, increased proliferation and defective lysosomal dynamics and autophagy. The novel Ctns-/- rat model and derived proximal tubule cell system provide invaluable tools to investigate the pathogenesis of cystinosis and to accelerate drug discovery.

Limited Added Diagnostic Value of Whole Genome Sequencing in Genetic Testing of Inherited Retinal Diseases in a Swiss Patient Cohort.

The purpose of this study was to assess the added diagnostic value of whole genome sequencing (WGS) for patients with inherited retinal diseases (IRDs) who remained undiagnosed after whole exome sequencing (WES). WGS was performed for index patients in 66 families. The datasets were analyzed according to GATK's guidelines. Additionally, DeepVariant was complemented by GATK's workflow, and a novel structural variant pipeline was developed. Overall, a molecular diagnosis was established in 19/66 (28.8%) index patients. Pathogenic deletions and one deep-intronic variant contributed to the diagnostic yield in 4/19 and 1/19 index patients, respectively. The remaining diagnoses (14/19) were attributed to exonic variants that were missed during WES analysis due to bioinformatic limitations, newly described loci, or unclear pathogenicity. The added diagnostic value of WGS equals 5/66 (9.6%) for our cohort, which is comparable to previous studies. This figure would decrease further to 1/66 (1.5%) with a standardized and reliable copy number variant workflow during WES analysis. Given the higher costs and limited added value, the implementation of WGS as a first-tier assay for inherited eye disorders in a diagnostic laboratory remains untimely. Instead, progress in bioinformatic tools and communication between diagnostic and clinical teams have the potential to ameliorate diagnostic yields.

Nanopore Deep Sequencing as a Tool to Characterize and Quantify Aberrant Splicing Caused by Variants in Inherited Retinal Dystrophy Genes.

The contribution of splicing variants to molecular diagnostics of inherited diseases is reported to be less than 10%. This figure is likely an underestimation due to several factors including difficulty in predicting the effect of such variants, the need for functional assays, and the inability to detect them (depending on their locations and the sequencing technology used). The aim of this study was to assess the utility of Nanopore sequencing in characterizing and quantifying aberrant splicing events. For this purpose, we selected 19 candidate splicing variants that were identified in patients affected by inherited retinal dystrophies. Several in silico tools were deployed to predict the nature and estimate the magnitude of variant-induced aberrant splicing events. Minigene assay or whole blood-derived cDNA was used to functionally characterize the variants. PCR amplification of minigene-specific cDNA or the target gene in blood cDNA, combined with Nanopore sequencing, was used to identify the resulting transcripts. Thirteen out of nineteen variants caused aberrant splicing events, including cryptic splice site activation, exon skipping, pseudoexon inclusion, or a combination of these. Nanopore sequencing allowed for the identification of full-length transcripts and their precise quantification, which were often in accord with in silico predictions. The method detected reliably low-abundant transcripts, which would not be detected by conventional strategies, such as RT-PCR followed by Sanger sequencing.

Novel CRYGC Mutation in Conserved Ultraviolet-Protective Tryptophan (p.Trp131Arg) Is Linked to Autosomal Dominant Congenital Cataract.

Congenital cataract (CC), the most prevalent cause of childhood blindness and amblyopia, necessitates prompt and precise genetic diagnosis. The objective of this study is to identify the underlying genetic cause in a Swiss patient with isolated CC. Whole exome sequencing (WES) and copy number variation (CNV) analysis were conducted for variant identification in a patient born with a total binocular CC without a family history of CC. Sanger Sequencing was used to confirm the variant and segregation analysis was used to screen the non-affected parents. The first de novo missense mutation at c.391T>C was identified in exon 3 of CRYGC on chromosome 2 causing the substitution of a highly conserved Tryptophan to an Arginine located at p.Trp131Arg. Previous studies exhibit significant changes in the tertiary structure of the crystallin family in the following variant locus, making CRYGC prone to aggregation aggravated by photodamage resulting in cataract. The variant can be classified as pathogenic according to the American College of Medical Genetics and Genomics (ACMG) criteria (PP3 + PM1 + PM2 + PS2; scoring 10 points). The identification of this novel variant expands the existing knowledge on the range of variants found in the CRYGC gene and contributes to a better comprehension of cataract heterogeneity.

Atonal homolog 7 (ATOH7) loss-of-function mutations in predominant bilateral optic nerve hypoplasia.

Optic nerve hypoplasia (ONH) is a congenital optic nerve abnormality caused by underdevelopment of retinal ganglion cells (RGCs). Despite being a rare disease, ONH is the most common optic disk anomaly in ophthalmological practice. So far, mutations in several genes have been identified as causative; however, many cases of ONH remain without a molecular explanation. The early transcription factor atonal basic-helix-loop-helix (bHLH) transcription factor 7 (ATOH7) is expressed in retinal progenitor cells and has a crucial role in RGC development. Previous studies have identified several mutations in the ATOH7 locus in cases of eye developmental diseases such as non-syndromic congenital retinal non-attachment and persistent hyperplasia of the primary vitreous. Here we present two siblings with a phenotype predominated by bilateral ONH, with additional features of foveal hypoplasia and distinct vascular abnormalities, where whole-exome sequencing identified two compound heterozygous missense mutations affecting a conserved amino acid residue within the bHLH domain of ATOH7 (NM_145178.3:c.175G>A; p.(Ala59Thr) and c.176C>T; p.(Ala59Val)). ATOH7 expression constructs with patient single nucleotide variants were cloned for functional characterization. Protein analyses revealed decreased protein amounts and significantly enhanced degradation in the presence of E47, a putative bHLH dimerization partner. Protein interaction assays revealed decreased heterodimerization and DNA-binding of ATOH7 variants, resulting in total loss of transcriptional activation of luciferase reporter gene expression. These findings strongly support pathogenicity of the two ATOH7 mutations, one of which is novel. Additionally, this report highlights the possible impact of altered ATOH7 dimerization on protein stability and function.

Flicker electroretinogram in newborn infants.

PURPOSE: To develop and validate a flicker electroretinogram (ERG) protocol in term-born neonates as a potential tool for assessing preterm infants at risk of developing retinopathy of prematurity. METHODS: A custom flicker ERG protocol was developed for use with the hand-held RETeval® electrophysiology device. Feasibility of measuring flicker ERG through closed eyelids and without mydriasis was established in a pilot study enabling optimisation of the test protocol. Following this, healthy term-born neonates (gestational age 37-42 weeks) were recruited at the Neonatology clinic of the University Hospital Zurich. Flicker ERG recordings were performed using proprietary disposable skin electrodes during the first four days of life when the infants were sleeping. Flicker stimuli were presented at 28.3 Hz for a stimulus series at 3, 6, 12, 30, and 50 cd·s/m2, with two measurements at each stimulus level. Results were analysed offline. Flicker ERG peak times and amplitudes were derived from the averaged measurements per stimulus level for each subject. RESULTS: 28 term-born neonates were included in the analysis. All infants tolerated the testing procedure well. Flicker ERG recording was achieved in all subjects with reproducible flicker ERG waveforms for 30 and 50 cd·s/m2 stimuli. Reproducible ERGs were recorded in the majority of infants for the weaker stimuli (with detectable ERGs in 20/28, 25/28, and 27/28 at 3, 6, and 12 cd·s/m2, respectively). Flicker ERG amplitudes increased with increasing stimulus strength, with peak times concurrently decreasing slightly. CONCLUSION: Flicker ERG recording is feasible and reliably recorded in sleeping neonates through closed eyelids using skin electrodes and without mydriasis. Flicker ERG amplitude decreases for lower luminance flicker but remains detectable for 3 cd·s/m2 flicker in the majority of healthy term-born neonates. These data provide a basis to study retinal function in premature infants using this protocol.

A three-year longitudinal study of retinal function and structure in patients with multiple sclerosis.

BACKGROUND: Researchers have in recent years begun to investigate ophthalmological manifestations of multiple sclerosis (MS) other than optic neuritis (ON), and it is now clear that changes to retinal function (measured using the electroretinogram, ERG) and structure (measured using optical coherence tomography, OCT) are found in MS patients irrespective of prior ON episodes. ERG results are consistent with dysfunctional bipolar cells, as in other autoimmune diseases. To date, studies have presented only cross-sectional data regarding ERG and OCT. We, therefore, studied the longitudinal course of ERG and OCT in patients with MS, as well as the effect of disability changes and non-ON clinical relapses on these functional and structural measures. METHODS: MS patients (n = 23) participating in an ongoing longitudinal observational study were invited to take part in a 3-year ophthalmological substudy. ERG and OCT were performed, and measures of MS-related disability and relapse history were obtained. Study visits were repeated annually. ERG peak times, rod b-wave amplitude, mixed rod/cone and cone b-/a-wave amplitude ratios, thickness of the peripapillary retinal nerve fibre layer, and volumes of the segmented retinal layers/complexes were analysed. Using generalised estimating equation models adjusted for age, ON, and MS treatment status, we assessed changes to ERG and OCT over the study duration, the effect of changes in disability and recent non-ON MS relapses on ERG and OCT, and the effect of selected OCT parameters on corresponding ERG parameters. RESULTS: At the group level, small fluctuations of several ERG peak times were recorded, with OCT values remaining stable. Increased disability between visits was associated with significant prolongation of mixed rod-cone ERG b-wave peak times. No evidence of associations between OCT and ERG parameters was observed. CONCLUSIONS: Retinal bipolar cell function may be affected by changes in disability in patients with MS; however, recent non-ON MS clinical relapses appear not to affect ERG or OCT results. As ERG changes in MS patients over 3 years are likely to be small and of uncertain clinical relevance, longitudinal studies of retinal function in MS should be planned over an extended period.

The "Eyelet Sign" as an MRI Clue for Inflammatory Brown Syndrome.

BACKGROUND: Brown syndrome is characterized by a restrictive elevation deficit of the affected eye in adduction. Besides the well-known congenital form, different acquired etiologies including inflammation, trauma, and surgery may prevent the superior oblique (SO) tendon from gliding freely through the trochlea on attempted upgaze. We present MRI findings in pediatric and adult patients with inflammatory acquired Brown syndrome. METHODS: Retrospective review of clinical and MRI findings of 6 patients (4 children: median age 8.4 years [range 6.1-8.7]; 2 adults: age 46.4 and 51.1 years). Median follow-up was 23 months (range 1-52). RESULTS: In all 6 patients, orbital MRI demonstrated inflammatory changes of the SO tendon-trochlea complex. A striking feature was circumferential contrast enhancement of the trochlea with central sparing where the tendon passes, reminiscent of an eyelet. In all cases, the motility restriction improved either spontaneously or with systemic anti-inflammatory treatment. Although both adult patients had a history of known seronegative spondyloarthritis, there was no associated systemic condition in the children in our series. CONCLUSIONS: Both in children and in adults, MRI can provide evidence of inflammatory changes located at the trochlea-tendon complex in acquired Brown syndrome here referred to as the "eyelet sign," which may be helpful in confirming the clinical diagnosis and guide appropriate treatment.

Homozygosity for a Novel DOCK7 Variant Due to Segmental Uniparental Isodisomy of Chromosome 1 Associated with Early Infantile Epileptic Encephalopathy (EIEE) and Cortical Visual Impairment.

Early infantile epileptic encephalopathy (EIEE) is a severe neurologic and neurodevelopmental disease that manifests in the first year of life. It shows a high degree of genetic heterogeneity, but the genetic origin is only identified in half of the cases. We report the case of a female child initially diagnosed with Leber congenital amaurosis (LCA), an early-onset retinal dystrophy due to photoreceptor cell degeneration in the retina. The first examination at 9 months of age revealed no reaction to light or objects and showed wandering eye movements. Ophthalmological examination did not show any ocular abnormalities. The patient displayed mildly dysmorphic features and a global developmental delay. Brain MRI demonstrated pontine hypo-/dysplasia. The patient developed myoclonic epileptic seizures and epileptic spasms with focal and generalized epileptiform discharges on electroencephalogram (EEG) at the age of 16 months. Genetic screening for a potentially pathogenic DNA sequence variant by whole-exome sequencing (WES) revealed a novel, conserved, homozygous frameshift variant (c.5391delA, p.(Ala1798LeufsTer59)) in exon 42 of the DOCK7 gene (NM_001271999.1). Further analysis by SNP array (Karyomapping) showed loss of heterozygosity (LOH) in four segments of chromosome 1. WES data of the parents and the index patient (trio analysis) demonstrated that chromosome 1 was exclusively inherited from the mother. Four LOH segments of chromosome 1 alternately showed isodisomy (UPiD) and heterodisomy (UPhD). In WES data, the father was a noncarrier, and the mother was heterozygous for this DOCK7 variant. The DOCK7 gene is located in 1p31.3, a region situated in one of the four isodisomic segments of chromosome 1, explaining the homozygosity seen in the affected child. Finally, Sanger sequencing confirmed maternal UPiD for the DOCK7 variant. Homozygous or compound heterozygous pathogenic variants in the DOCK7 (dedicator of cytokinesis 7) gene are associated with autosomal recessive, early infantile epileptic encephalopathy 23 (EIEE23; OMIM #615,859), a rare and heterogeneous group of neurodevelopmental disorders diagnosed during early childhood. To our knowledge, this is the first report of segmental uniparental iso- and heterodisomy of chromosome 1, leading to homozygosity of the DOCK7 frameshift variant in the affected patient.

[Non-Organic Visual Loss in Children and Teenagers]. / Nicht organische Sehstörungen bei Kindern und Jugendlichen.

BACKGROUND: Functional visual disorders in children and adolescents are an important but challenging differential diagnosis. What is characteristic is the discrepancy between the symptomatology and the objective findings. The aim of our work was to analyse the data of those patients who were cared for at our clinic with the diagnosis "functional visual disorders". PATIENTS AND METHODS: A retrospective data analysis was performed: age < 18 years, with diagnosis "functional visual disorder" 2011 to 2020. Historical and clinical data were extracted from the patient's file. In addition, parents or patients were contacted using a questionnaire about current symptoms. The study was approved by the cantonal ethics committee of Zürich (KEK Nr. 2020-01268). RESULTS: A total of 92 patients were identified, and analysis could be performed in 53% (49/92; 32 female, 17 male) with available consent. The age ranged from 3 to 18 years (median 10.5 years) with a follow-up of 1 to 58 months (median 7 months). The most common symptoms were bilateral visual loss (55%) and/or blurred vision (18%) with headache (35%), motility pain (14%), photophobia (4%), dizziness (4%), and malaise (2%). A reduction in distant (22/49 bilateral, 9/49 unilateral) and near (24/49 bilateral, 3/49 unilateral) visual acuity was documented. Subjective visual acuity reduction was no longer detectable in 20% of patients at testing. Psychological distress was documented in 13/49 patients. Moisturising eye drops (18/49), eyeglass prescription (15/49), or no therapy (20/49) was recommended. Subjective and/or objective improvement was documented at follow-up in 49% (24/49). The questionnaire was answered in 86%: no complete remission of visual symptoms (10/42), remission within 1 week (14/41), 1 month (3/41), 2 - 6 months (8/41), 1 year (6/41). There was no correlation between duration of visual symptoms and age at onset or gender. The consultation at our clinic was reported as "supportive and helpful" in 31/42 patients. CONCLUSION: Despite a low incidence during the history, the psychosocial and psychological component should not be neglected.

Confirmation of Ogden syndrome as an X-linked recessive fatal disorder due to a recurrent NAA10 variant and review of the literature.

Ogden syndrome is a rare lethal X-linked recessive disorder caused by a recurrent missense variant (Ser37Pro) in the NAA10 gene, encoding the catalytic subunit of the N-terminal acetyltransferase A complex (NatA). So far eight boys of two different families have been described in the literature, all presenting the distinctive and recognizable phenotype, which includes mostly postnatal growth retardation, global severe developmental delay, characteristic craniofacial features, and structural cardiac anomalies and/or arrhythmias. Here, we report the ninth case of Ogden syndrome with an independent recurrence of the Ser37Pro variant. We were able to follow the clinical course of the affected boy and delineate the evolving phenotype from his birth until his unfortunate death at 7 months. We could confirm the associated phenotype as well as the natural history of this severe disease. By describing new presenting features, we are further expanding the clinical spectrum associated with Ogden syndrome and review other phenotypes associated with NAA10 variants.

Long-Range PCR-Based NGS Applications to Diagnose Mendelian Retinal Diseases.

The purpose of this study was to develop a flexible, cost-efficient, next-generation sequencing (NGS) protocol for genetic testing. Long-range polymerase chain reaction (PCR) amplicons of up to 20 kb in size were designed to amplify entire genomic regions for a panel (n = 35) of inherited retinal disease (IRD)-associated loci. Amplicons were pooled and sequenced by NGS. The analysis was applied to 227 probands diagnosed with IRD: (A) 108 previously molecularly diagnosed, (B) 94 without previous genetic testing, and (C) 25 undiagnosed after whole-exome sequencing (WES). The method was validated with 100% sensitivity on cohort A. Long-range PCR-based sequencing revealed likely causative variant(s) in 51% and 24% of proband from cohorts B and C, respectively. Breakpoints of 3 copy number variants (CNVs) could be characterized. Long-range PCR libraries spike-in extended coverage of WES. Read phasing confirmed compound heterozygosity in 5 probands. The proposed sequencing protocol provided deep coverage of the entire gene, including intronic and promoter regions. Our method can be used (i) as a first-tier assay to reduce genetic testing costs, (ii) to elucidate missing heritability cases, (iii) to characterize breakpoints of CNVs at nucleotide resolution, (iv) to extend WES data to non-coding regions by spiking-in long-range PCR libraries, and (v) to help with phasing of candidate variants.

[Acute Acquired Comitant Esotropia Type 2 - A Retrospective Analysis]. / Akut erworbene konkomitante Esotropie Typ 2 ­ eine retrospektive Analyse.

BACKGROUND: Acute acquired comitant esotropia (AACE) is an uncommon form of strabismus. The main characteristics of AACE Type 2 in childhood are: acute onset of strabismus around 3 years of age, large and comitant angle of strabismus, absence of accommodative component, hyperopia of not more than 3 dpt, and measurable stereopsis. Strabismus surgery is urgently indicated in AACE Type 2 in order to avoid maldevelopment or loss of stereopsis. Therefore, in order to better describe the characteristics of AACE Type 2, we performed a retrospective analysis of patients previously seen in our clinic. PATIENTS AND METHODS: Retrospective analysis of data from patients who underwent strabismus surgery between October 2011 and September 2019 due to suspected AACE Type 2 could be confirmed during postoperative visits by evaluating ocular alignment and stereopsis at our hospital. Analysed data included: age and symptoms at first visit, visual acuity, refractive status, correction by glasses, age at surgery, period of time between first symptoms and surgery, surgical procedure, stereopsis and angle of strabismus (before surgery and 1 day, 3 months, and 12 months after surgery). Ethical approval was obtained from the Cantonal Ethics Committee of Zurich. RESULTS: 18 patients (12 male, 6 female) with mean hyperopia of 1.4 ± 0.6 dpt were identified as meeting the inclusion criteria during the defined time period. Amblyopia was present at first assessment in two patients. Strabismus surgery was performed at 2.0 to 11.1 years of age and between 0.4 and 24.6 months after onset of symptoms. Surgery was performed within 6 months after onset of symptoms in 12/18 children. Before surgery, angle of strabismus at near was measured as 38 ± 10 prism diopters (PD) and was reduced after surgery to 3 ± 3 PD at 3 months and 2 ± 2 PD at 12 months. Stereopsis was confirmed in 5/18 patients one day after surgery and in 18/18 patients 12 months after surgery. CONCLUSION: Our analysis showed that our patients with diagnosis of AACE Type 2 had mild hyperopia and large comitant non-accommodative esotropia; prognosis for recovery of stereopsis is excellent. Preoperative amblyopia does not exclude the diagnosis of AACE Type 2. Therapeutic intervention is advisable within a short period of time after first symptoms and the diagnosis of AACE Type 2.

Higher incidence of retinopathy of prematurity in extremely preterm infants associated with improved survival rates.

AIM: This study assessed possible reasons for the increasing incidence of retinopathy of prematurity (ROP) since mid-2015 at our institution. METHODS: Retrospective analysis of all preterm infants born July 2013 to June 2017 with a gestational age (GA) <29 completed weeks admitted to the neonatal intensive care unit at the University Hospital Zurich during the first 28 days of life. The primary outcome measures were severest ROP stage. Statistical analysis was performed using generalised additive models in R. RESULTS: During the study period, survival increased in extremely preterm infants. Significant predictors for severest ROP stage were GA, days of mechanical ventilation and multiple gestation (P = .0322). A composite of severe comorbidities had no significant effect on severest ROP stage. GA was identified as the only significant risk factor the for severest ROP stage (P = .0045). CONCLUSION: Increased survival rate of extremely preterm infants was associated with an increased incidence of ROP at our institution. Despite the increase, the incidence is still very low compared with other countries. No other additive factors were identified.

[Ocular Phenotype and Complications in Patients with Tuberous Sclerosis Complex (TSC)]. / Tuberöse-Sklerose-Komplex: Analyse des okulären Phänotyps und assoziierter Komplikationen.

BACKGROUND: Evaluation and comparison of the ocular phenotype in patients diagnosed with tuberous sclerosis complex (TSC). Analysis of ocular complications during follow-up. PATIENTS AND METHODS: A retrospective chart review was performed of patients with TSC who had received an ocular examination at the eye clinic of the University Hospital Zurich. Data were analysed on visual acuity (VA) assessment, refraction, anterior and posterior eye examination including the distinction of different types of hamartomas and, when available, visual fields. The study was approved by the Cantonal Ethics Committee of Zurich. RESULTS: A total of 30 patients who were diagnosed with TSC (19 female, 11 male) were included in the analysis. The age at first examination varied from 7 months to 44 years (mean 13.3 years, standard deviation 11.31). 17/30 patients received a follow-up examination between 4 months and 19 years (mean 4.3 years, standard deviation 5.24). Data of VA were available in 26/30 patients, of whom 22 had normal vision in both eyes. The causes of reduced VA in the 4 patients were: complications of a subependymal giant cell astrocytoma followed by a bilateral optic nerve atrophy; vigabatrin-associated optic atrophy; anterior segment dysgenesis; unilateral amblyopia. Adequate VA testing was not possible in 4 patients because of intellectual disabilities. Retinal hamartomas were described in 15/30 patients: 8 unilateral, 7 bilateral. The flat hamartoma type was described in 10/15 patients, the multinodular type in 6/15 patients. CONCLUSIONS: The ocular phenotype in our patient cohort shows similar TSC involvement to that described in the literature. Patients diagnosed with TSC require regular ophthalmic examinations to diagnose secondary ocular complications, such as papilloedema, severe vision loss or visual field constriction.

A secreted WNT-ligand-binding domain of FZD5 generated by a frameshift mutation causes autosomal dominant coloboma.

Ocular coloboma is a common eye malformation resulting from incomplete fusion of the optic fissure during development. Coloboma is often associated with microphthalmia and/or contralateral anophthalmia. Coloboma shows extensive locus heterogeneity associated with causative mutations identified in genes encoding developmental transcription factors or components of signaling pathways. We report an ultra-rare, heterozygous frameshift mutation in FZD5 (p.Ala219Glufs*49) that was identified independently in two branches of a large family with autosomal dominant non-syndromic coloboma. FZD5 has a single-coding exon and consequently a transcript with this frameshift variant is not a canonical substrate for nonsense-mediated decay. FZD5 encodes a transmembrane receptor with a conserved extracellular cysteine rich domain for ligand binding. The frameshift mutation results in the production of a truncated protein, which retains the Wingless-type MMTV integration site family member-ligand-binding domain, but lacks the transmembrane domain. The truncated protein was secreted from cells, and behaved as a dominant-negative FZD5 receptor, antagonizing both canonical and non-canonical WNT signaling. Expression of the resultant mutant protein caused coloboma and microphthalmia in zebrafish, and disruption of the apical junction of the retinal neural epithelium in mouse, mimicking the phenotype of Fz5/Fz8 compound conditional knockout mutants. Our studies have revealed a conserved role of Wnt-Frizzled (FZD) signaling in ocular development and directly implicate WNT-FZD signaling both in normal closure of the human optic fissure and pathogenesis of coloboma.

Prediction of ROP Treatment and Evaluation of Screening Criteria in VLBW Infants-a Population Based Analysis.

BACKGROUND: The incidence of retinopathy of prematurity (ROP) and ROP screening criteria differ between countries. We assessed whether ROP screening could be reduced based on the local ROP incidence. METHODS: Observational cohort study of infants born in Switzerland between 2006 and 2015 <32 0/7 weeks. Chronological and postmenstrual ages at ROP treatment were analyzed. A model to identify ROP treatment on patients born between 2006 and 2012 (training set) was developed and tested on patients born between 2013 and 2015 (validation set). RESULTS: Of 7817 live-born infants, 1098 died within the first 5 weeks of life. The remaining 6719 infants were included into analysis. All patients requiring ROP treatment would have been identified if screening had been performed before reaching 60 days of life or 37 3/7 weeks postmenstrual age, whichever came first. The training and validation sets included 4522 and 2197 preterm infants encompassing 56 and 20 patients receiving ROP treatment, respectively. All patients would have required screening to reach 100% sensitivity. To reach a sensitivity of 95.0% and a specificity of 87.6%, we predicted a reduction in 13.2% of patients requiring screening (c-statistic = 0.916). CONCLUSIONS: A substantial reduction of infants requiring screening seems possible, but necessitates prospective testing of new screening criteria.

Retinal Ganglion Cell Topography in Patients With Visual Pathway Pathology.

BACKGROUND: To investigate and quantify the impact of intracranial lesions at different locations within the visual pathway on the ganglion cell layer-inner plexiform layer (GCL-IPL) complex and the retinal nerve fiber layer (RNFL). METHODS: Patients with intracranial lesions affecting the optic chiasm (Group I) or the optic tract and/or lateral geniculate nucleus (Group II) were included. All patients received kinetic visual field assessment and underwent spectral domain optical coherence tomography. Peripapillary and papillomacular bundle (PMB) RNFL and macular GCL-IPL thickness in 4 perifoveal areas were measured and compared with normal values derived from 52 age-matched healthy control subjects. Z-scores for each parameter of every patient were calculated and compared with the normative data. Z-scores less than -2.0 (e.g., -2.5) were considered as being statistically significant. RESULTS: Twenty-two patients (Group I and II: 13 and 9, respectively) were included. Ten of 13 patients in Group I showed significant binasal GCL-IPL thinning, with associated temporal sector thinning in 8 patients. In Group II, all 9 patients showed significant reduction of the GCL-IPL corresponding to the homonymous visual field defect, but only 4 demonstrated RNFL thinning. Contralateral RNFL thinning within the PMB clinically similar to bow-tie atrophy was evident in all patients in Group II. GCL-IPL and RNFL thinning varied in severity from mild (isolated PMB RNFL thickness reduction) to severe (bilateral asymmetrical reduction of PMB RNFL associated with asymmetric, predominantly nasal reduction of GCL-IPL) in Group I. CONCLUSION: Clinical abnormalities in patients with visual pathway lesions are more likely to demonstrate abnormalities of GCL-IPL than global peripapillary RNFL thickness. However, PMB thickness measurement appears to be a valuable tool to detect abnormalities of the anterior visual pathways. If peripapillary RNFL measurements are performed in such patients, PMB thickness should be considered the most useful quantitative parameter.