Autosomal Recessive Bestrophinopathy: Clinical Features, Natural History, and Genetic Findings in Preparation for Clinical Trials.

PURPOSE: To investigate the clinical course, genetic findings, and phenotypic spectrum of autosomal recessive bestrophinopathy (ARB) in a large cohort of children and adults. DESIGN: Retrospective case series. PARTICIPANTS: Patients with a detailed clinical phenotype consistent with ARB, biallelic likely disease-causing sequence variants in the BEST1 gene, or both identified at a single tertiary referral center. METHODS: Review of case notes, retinal imaging (color fundus photography, fundus autofluorescence, OCT), electrophysiologic assessment, and molecular genetic testing. MAIN OUTCOME MEASURES: Visual acuity (VA), retinal imaging, and electrophysiologic changes over time. RESULTS: Fifty-six eyes of 28 unrelated patients were included. Compound heterozygous variants were detected in most patients (19/27), with 6 alleles recurring in apparently unrelated individuals, the most common of which was c.422G→A, p.(Arg141His; n = 4 patients). Mean presenting VA was 0.52 ± 0.36 logarithm of the minimum angle of resolution (logMAR), and final VA was 0.81 ± 0.75 logMAR (P = 0.06). The mean rate of change in VA was 0.05 ± 0.13 logMAR/year. A significant change in VA was detected in patients with a follow-up of 5 years or more (n = 18) compared with patients with a follow-up of 5 years or less (n = 10; P = 0.001). Presence of subretinal fluid and vitelliform material were early findings in most patients, and this did not change substantially over time. A reduction in central retinal thickness was detected in most eyes (80.4%) over the course of follow-up. Many patients (10/26) showed evidence of generalized rod and cone system dysfunction. These patients were older (P < 0.001) and had worse VA (P = 0.02) than those with normal full-field electroretinography results. CONCLUSIONS: Although patients with ARB are presumed to have no functioning bestrophin channels, significant phenotypic heterogeneity is evident. The clinical course is characterized by a progressive loss of vision with a slow rate of decline, providing a wide therapeutic window for anticipated future treatment strategies.

Genetic Basis of Inherited Retinal Disease in a Molecularly Characterized Cohort of More Than 3000 Families from the United Kingdom.

PURPOSE: In a large cohort of molecularly characterized inherited retinal disease (IRD) families, we investigated proportions with disease attributable to causative variants in each gene. DESIGN: Retrospective study of electronic patient records. PARTICIPANTS: Patients and relatives managed in the Genetics Service of Moorfields Eye Hospital in whom a molecular diagnosis had been identified. METHODS: Genetic screening used a combination of single-gene testing, gene panel testing, whole exome sequencing, and more recently, whole genome sequencing. For this study, genes listed in the Retinal Information Network online resource (https://sph.uth.edu/retnet/) were included. Transcript length was extracted for each gene (Ensembl, release 94). MAIN OUTCOME MEASURES: We calculated proportions of families with IRD attributable to variants in each gene in the entire cohort, a cohort younger than 18 years, and a current cohort (at least 1 patient encounter between January 1, 2017, and August 2, 2019). Additionally, we explored correlation between numbers of families and gene transcript length. RESULTS: We identified 3195 families with a molecular diagnosis (variants in 135 genes), including 4236 affected individuals. The pediatric cohort comprised 452 individuals from 411 families (66 genes). The current cohort comprised 2614 families (131 genes; 3130 affected individuals). The 20 most frequently implicated genes overall (with prevalence rates per families) were as follows: ABCA4 (20.8%), USH2A (9.1%), RPGR (5.1%), PRPH2 (4.6%), BEST1 (3.9%), RS1 (3.5%), RP1 (3.3%), RHO (3.3%), CHM (2.7%), CRB1 (2.1%), PRPF31 (1.8%), MY07A (1.7%), OPA1 (1.6%), CNGB3 (1.4%), RPE65 (1.2%), EYS (1.2%), GUCY2D (1.2%), PROM1 (1.2%), CNGA3 (1.1%), and RDH12 (1.1%). These accounted for 71.8% of all molecularly diagnosed families. Spearman coefficients for correlation between numbers of families and transcript length were 0.20 (P = 0.025) overall and 0.27 (P = 0.017), -0.17 (P = 0.46), and 0.71 (P = 0.047) for genes in which variants exclusively cause recessive, dominant, or X-linked disease, respectively. CONCLUSIONS: Our findings help to quantify the burden of IRD attributable to each gene. More than 70% of families showed pathogenic variants in 1 of 20 genes. Transcript length (relevant to gene delivery strategies) correlated significantly with numbers of affected families (but not for dominant disease).

Missense variants in the X-linked gene PRPS1 cause retinal degeneration in females.

Retinal dystrophies are a heterogeneous group of disorders of visual function leading to partial or complete blindness. We report the genetic basis of an unusual retinal dystrophy in five families with affected females and no affected males. Heterozygous missense variants were identified in the X-linked phosphoribosyl pyrophosphate synthetase 1 (PRPS1) gene: c.47C > T, p.(Ser16Phe); c.586C > T, p.(Arg196Trp); c.641G > C, p.(Arg214Pro); and c.640C > T, p.(Arg214Trp). Missense variants in PRPS1 are usually associated with disease in male patients, including Arts syndrome, Charcot-Marie-Tooth, and nonsyndromic sensorineural deafness. In our study families, affected females manifested a retinal dystrophy with interocular asymmetry. Three unrelated females from these families had hearing loss leading to a diagnosis of Usher syndrome. Other neurological manifestations were also observed in three individuals. Our data highlight the unexpected X-linked inheritance of retinal degeneration in females caused by variants in PRPS1 and suggest that tissue-specific skewed X-inactivation or variable levels of pyrophosphate synthetase-1 deficiency are the underlying mechanism(s). We speculate that the absence of affected males in the study families suggests that some variants may be male embryonic lethal when inherited in the hemizygous state. The unbiased nature of next-generation sequencing enables all possible modes of inheritance to be considered for association of gene variants with novel phenotypic presentation.

Clinician and parent views on urine collection in precontinent children in the UK: a qualitative interview study.

OBJECTIVE: To explore the experiences of healthcare professionals (HCPs) and parents of urine collection methods, to identify barriers to successful sampling and what could improve the process. DESIGN: Qualitative research, using individual semistructured interviews with HCPs and parents. The interviews were audiorecorded, transcribed and thematically analysed. SETTING: UK-based HCPs from primary and secondary care settings and parents with experience with urine collection in primary and/or secondary care settings. PARTICIPANTS: HCPs who were involved in aiding, supervising or ordering urine samples. Parents who had experience with urine collection in at least one precontinent child. RESULTS: 13 HCPs and 16 parents were interviewed. 2 participating HCPs were general practitioners (GPs), 11 worked in paediatric secondary care settings (8 were nurses and 3 were doctors). Two parents had children with underlying conditions where frequent urine collection was required to rule out infections.HCPs and parents reported that there were no straightforward methods of urine collection for precontinent children. Each method-'clean catch', urine bag and urine pad-had limitations and problems with usage. 'Clean catch', regarded as the gold standard by HCPs with a lower risk of contamination, often proved difficult for parents to achieve. Other methods had elevated risk of contamination but were more acceptable to parents because they were less challenging. Many of the parents expressed the need for more information about urine collection. CONCLUSIONS: Current methods of urine collection are challenging to use and may be prone to contamination. A new device is required to assist with urine collection in precontinent children, to simplify and reduce the stress of the situation for those involved. Parents are key partners in the process of urine collection with young children. Meeting their expressed need for more information could be an important way to achieve better-quality samples while awaiting a new device.

The effect of Functional Electrical Stimulation-assisted posture-shifting in bone mineral density: case series-pilot study.

STUDY DESIGN: A training intervention study using standing dynamic load-shifting Functional Electrical Stimulation (FES) in a group of individuals with complete spinal cord injury (SCI) T2 to T10. OBJECTIVES: Investigate the effect of FES-assisted dynamic load-shifting exercises on bone mineral density (BMD). SETTING: University Lab within the Biomedical Engineering METHODS: Twelve participants with ASIA A SCI were recruited for this study. Three participants completed side-to-side load-shifting FES-assisted exercises for 29 ± 5 weeks, 2× per week for 1 h, and FES knee extension exercises on alternate days 3× per week for 1 h. Volumetric Bone Mineral density (vBMD) at the distal femur and tibia were assessed using peripheral quantitative computed tomography (pQCT) before and after the intervention study. RESULTS: Participants with acute and subacute SCI showed an absolute increase of f trabecular vBMD (vBMDTRAB) in the proximal (mean of 26.9%) and distal tibia (mean of 22.35%). Loss of vBMDTRAB in the distal femur was observed. CONCLUSION: Improvements in vBMDTRAB in the distal tibia were found in acute and subacute SCI participants, and in the proximal tibia of acute participants, when subjected to anti-gravity FES-assisted load-bearing exercises for 29 ± 5 weeks. No vBMD improvement in distal femur or tibial shaft were observed in any of the participants as was expected. However, improvements of vBMD in the proximal and distal tibia were observed in two participants. This study provides evidence of an improvement of vBMDTRAB, when combining high-intensity exercises with lower intensity exercises 5× per week for 1 h.

Novel instrumented frame for standing exercising of users with complete spinal cord injuries.

This paper describes a Functional Electrical Stimulation (FES) standing system for rehabilitation of bone mineral density (BMD) in people with Spinal Cord Injury (SCI). BMD recovery offers an increased quality of life for people with SCI by reducing their risk of fractures. The standing system developed comprises an instrumented frame equipped with force plates and load cells, a motion capture system, and a purpose built 16-channel FES unit. This system can simultaneously record and process a wide range of biomechanical data to produce muscle stimulation which enables users with SCI to safely stand and exercise. An exergame provides visual feedback to the user to assist with upper-body posture control during exercising. To validate the system an alternate weight-shift exercise was used; 3 participants with complete SCI exercised in the system for 1 hour twice-weekly for 6 months. We observed ground reaction forces over 70% of the full body-weight distributed to the supporting leg at each exercising cycle. Exercise performance improved for each participant by an increase of 13.88 percentage points of body-weight in the loading of the supporting leg during the six-month period. Importantly, the observed ground reaction forces are of higher magnitude than other studies which reported positive effects on BMD. This novel instrumentation aims to investigate weight bearing standing therapies aimed at determining the biomechanics of lower limb joint force actions and postural kinematics.

A clinical and molecular characterisation of CRB1-associated maculopathy.

To date, over 150 disease-associated variants in CRB1 have been described, resulting in a range of retinal disease phenotypes including Leber congenital amaurosis and retinitis pigmentosa. Despite this, no genotype-phenotype correlations are currently recognised. We performed a retrospective review of electronic patient records to identify patients with macular dystrophy due to bi-allelic variants in CRB1. In total, seven unrelated individuals were identified. The median age at presentation was 21 years, with a median acuity of 0.55 decimalised Snellen units (IQR = 0.43). The follow-up period ranged from 0 to 19 years (median = 2.0 years), with a median final decimalised Snellen acuity of 0.65 (IQR = 0.70). Fundoscopy revealed only a subtly altered foveal reflex, which evolved into a bull's-eye pattern of outer retinal atrophy. Optical coherence tomography identified structural changes-intraretinal cysts in the early stages of disease, and later outer retinal atrophy. Genetic testing revealed that one rare allele (c.498_506del, p.(Ile167_Gly169del)) was present in all patients, with one patient being homozygous for the variant and six being heterozygous. In trans with this, one variant recurred twice (p.(Cys896Ter)), while the four remaining alleles were each observed once (p.(Pro1381Thr), p.(Ser478ProfsTer24), p.(Cys195Phe) and p.(Arg764Cys)). These findings show that the rare CRB1 variant, c.498_506del, is strongly associated with localised retinal dysfunction. The clinical findings are much milder than those observed with bi-allelic, loss-of-function variants in CRB1, suggesting this in-frame deletion acts as a hypomorphic allele. This is the most prevalent disease-causing CRB1 variant identified in the non-Asian population to date.

A Design Method for FES Bone Health Therapy in SCI.

FES assisted activities such as standing, walking, cycling and rowing induce forces within the leg bones and have been proposed to reduce osteoporosis in spinal cord injury (SCI). However, details of the applied mechanical stimulus for osteogenesis is often not reported. Typically, comparisons of bone density results are made after costly and time consuming clinical trials. These studies have produced inconsistent results and are subject to sample size variations. Here we propose a design process that may be used to predict the clinical outcome based on biomechanical simulation and mechano-biology. This method may allow candidate therapies to be optimized and quantitatively compared. To illustrate the approach we have used data obtained from a rower with complete paraplegia using the RowStim (III) system.

Inhomogeneous Response of Articular Cartilage: A Three-Dimensional Multiphasic Heterogeneous Study.

Articular cartilage exhibits complex mechano-electrochemical behaviour due to its anisotropy, inhomogeneity and material non-linearity. In this work, the thickness and radial dependence of cartilage properties are incorporated into a 3D mechano-electrochemical model to explore the relevance of heterogeneity in the behaviour of the tissue. The model considers four essential phenomena: (i) osmotic pressure, (ii) convective and diffusive processes, (iii) chemical expansion and (iv) three-dimensional through-the-thickness heterogeneity of the tissue. The need to consider heterogeneity in computational simulations of cartilage behaviour and in manufacturing biomaterials mimicking this tissue is discussed. To this end, healthy tibial plateaus from pigs were mechanically and biochemically tested in-vitro. Heterogeneous properties were included in the mechano-electrochemical computational model to simulate tissue swelling. The simulation results demonstrated that swelling of the heterogeneous samples was significantly lower than swelling under homogeneous and isotropic conditions. Furthermore, there was a significant reduction in the flux of water and ions in the former samples. In conclusion, the computational model presented here can be considered as a valuable tool for predicting how the variation of cartilage properties affects its behaviour, opening up possibilities for exploring the requirements of cartilage-mimicking biomaterials for tissue engineering. Besides, the model also allows the establishment of behavioural patterns of swelling and of water and ion fluxes in articular cartilage.