Spectrum of Cav1.4 dysfunction in congenital stationary night blindness type 2.

Defective retinal synaptic transmission in patients affected with congenital stationary night blindness type 2 (CSNB2) can result from different dysfunction phenotypes in Cav1.4 L-type calcium channels. Here we investigated two prototypical Cav1.4 variants from either end of the functional spectrum. Using whole-cell and single-channel patch-clamp techniques, we provide analysis of the biophysical characteristics of the point mutation L860P and the C-terminal truncating mutation R1827X. L860P showed a typical loss-of-function phenotype attributed to a reduced number of functional channels expressed at the plasma membrane as implied by gating current and non-stationary noise analyses. This phenotype can be rationalized, because the inserted proline is predicted to break an amphipatic helix close to the transmembrane segment IIIS1 and thus to reduce channel stability and promote misfolding. In fact, L860P was subject to an increased turnover. In contrast, R1827X displayed an apparent gain-of-function phenotype, i.e., due to a hyperpolarizing shift of the IV-curve and increased single-channel activity. However, truncation also resulted in the loss of functional C-terminal modulation and thus unmasked calcium-dependent inactivation. Thus R1827X failed to support continuous calcium influx. Current inactivation curtails the dynamic range of photoreceptors (e.g., when adapting to variation in illumination). Taken together, the analysis of two representative mutations that occur in CSNB2 patients revealed fundamental differences in the underlying defect. These may explain subtle variations in the clinical manifestation and must be taken into account, if channel function is to be restored by pharmacochaperones or related approaches.

Quality of life, functioning and participation of children and adolescents with visual impairment: A scoping review.

BACKGROUND: Vision has a key role in children's neuromotor, cognitive and social development. Children with visual impairment attain developmental milestones at later stages and are at higher risk of developing psychological disorders and social withdrawn. AIMS: We performed a scoping review to summarize the mostly used instruments assessing the impact of visual impairment on quality of life, functioning and participation of children and adolescents. In addition, the main findings of the included studies are discussed. METHODS AND PROCEDURES: We searched for papers assessing quality of life, functioning and participation of children and adolescents with visual impairment from 0 to 18 years old conducted between 2000 and 2023. OUTCOMES AND RESULTS: In total, 69 studies met the inclusion criteria and were included in the review. Child self-report, caregivers-proxy and self-report questionnaires as well as interviews were used. The results showed that quality of life, functioning and participation are significantly reduced in children and adolescents with visual impairment, and that the impact depends on different factors (e.g., severity of the impairment, age). CONCLUSIONS AND IMPLICATIONS: Considering the significant impact of visual impairment on quality of life, functioning and participation on this population, it is fundamental to develop integrated and multi-dimensional assessment programs that evaluate the impact of visual impairment on those dimensions considering different contexts of life (e.g., family, school, leisure time). WHAT THIS PAPER ADDS?: The present review aims to give an overview of what is known about the impact of visual impairment on quality of life, functioning and participation of children and adolescents. We assumed a biopsychosocial perspective which, in line with the definition of health by the International Classification of Functioning, Disability and Health (WHO, 2001), considered how body functions and structures, functioning, participation and environmental factors dynamically interact to define the health, or the disease, status of a person at a certain moment of life. We reported the most used instruments for the assessment of quality of life, participation, and functioning, with a specific interest on Patient-Reported Outcome Measures and self-report measures. By reporting the different instruments used, we gave a broad overview about the available tools that can be used in clinical as well as in research field to assess quality of life, functioning and participation in this population. Additionally, the review of the existing literature allowed us to demonstrate that those dimensions are negatively impacted by visual impairment and thus they should be considered in the assessment programs. Specifically, there is the need to provide more integrated assessment programs that investigate the impact of visual impairment on children and adolescents' social and emotional wellbeing, everyday functioning and social relationship, considering their subjective experience together with the one of caregivers, teachers, health care professionals, and other relevant adults involved in their life. Additionally, it is essential to plan and implement multidimensional assessment programs that consider how all areas of life are differently impacted by visual impairment.

Characterising the refractive error in paediatric patients with congenital stationary night blindness: a multicentre study.

BACKGROUND/AAIMS: Congenital stationary night blindness (CSNB) is an inherited retinal disease that is often associated with high myopia and can be caused by pathological variants in multiple genes, most commonly CACNA1F, NYX and TRPM1. High myopia is associated with retinal degeneration and increased risk for retinal detachment. Slowing the progression of myopia in patients with CSNB would likely be beneficial in reducing risk, but before interventions can be considered, it is important to understand the natural history of myopic progression. METHODS: This multicentre, retrospective study explored CSNB caused by variants in CACNA1F, NYX or TRPM1 in patients who had at least 6 measurements of their spherical equivalent of refraction (SER) before the age of 18. A mixed-effect model was used to predict progression of SER overtime and differences between genotypes were evaluated. RESULTS: 78 individuals were included in this study. All genotypes showed a significant myopic predicted SER at birth (-3.076D, -5.511D and -5.386D) for CACNA1F, NYX and TRPM1 respectively. Additionally, significant progression of myopia per year (-0.254D, -0.257D and -0.326D) was observed for all three genotypes CACNA1F, NYX and TRPM1, respectively. CONCLUSIONS: Patients with CSNB tend to be myopic from an early age and progress to become more myopic with age. Patients may benefit from long-term myopia slowing treatment in the future and further studies are indicated. Additionally, CSNB should be considered in the differential diagnosis for early-onset myopia.

CRB1-associated retinal dystrophies in a Belgian cohort: genetic characteristics and long-term clinical follow-up.

AIM: To investigate the natural history in a Belgian cohort of CRB1-associated retinal dystrophies. METHODS: An in-depth retrospective study focusing on visual function and retinal structure. RESULTS: Forty patients from 35 families were included (ages: 2.5-80.1 years). In patients with a follow-up of >1 year (63%), the mean follow-up time was 12.0 years (range: 2.3-29.2 years). Based on the patient history, symptoms and/or electroretinography, 22 patients (55%) were diagnosed with retinitis pigmentosa (RP), 15 (38%) with Leber congenital amaurosis (LCA) and 3 (8%) with macular dystrophy (MD), the latter being associated with the p.(Ile167_Gly169del) mutation (in compound heterozygosity). MD later developed into a rod-cone dystrophy in one patient. Blindness at initial presentation was seen in the first decade of life in LCA, and in the fifth decade of life in RP. Eventually, 28 patients (70%) reached visual acuity-based blindness (<0.05). Visual field-based blindness (<10°) was documented in 17/25 patients (68%). Five patients (13%) developed Coats-like exudative vasculopathy. Intermediate/posterior uveitis was found in three patients (8%). Cystoid maculopathy was common in RP (9/21; 43%) and MD (3/3; 100%). Macular involvement, varying from retinal pigment epithelium alterations to complete outer retinal atrophy, was observed in all patients. CONCLUSION: Bi-allelic CRB1 mutations result in a range of progressive retinal disorders, most of which are generalised, with characteristically early macular involvement. Visual function and retinal structure analysis indicates a window for potential intervention with gene therapy before the fourth decade of life in RP and the first decade in LCA.