Identification of the p. R116H mutation in a Chinese Family with Novel Variable Cataract Phenotype: Evidence for a Mutational Hot Spot in αA-Crystallin Gene

Purpose: To report the recurrent p.R116H mutation in the αA-crystallin gene (CRYAA) which causes a novel variable cataract phenotype, and to determine whether this mutation represents a mutational hot spot.

Methods: Family history and clinical data were recorded. The genomic DNA was extracted from peripheral blood leukocytes. Microsatellite markers at loci considered to be associated with autosomal dominant cataracts were selected and genotyped for two-point linkage analysis. Direct sequencing was performed to identify the disease-causing mutation. Haplotype analysis was constructed to compare the affected haplotype in this family and in another Chinese family previously reported by us.

Results: Clinical features of cataract in this family were asymmetric in two eyes of some affected subjects. Evidence of linkage was obtained with marker D21S1411 (logarithm of odds [LOD] score [Z]?=?2.42, recombination fraction [θ]?=?0.0). Sequencing of the candidate CRYAA gene revealed a single base alteration c.347 G > A in exon 3, which resulted in the substitution of highly conserved arginine by histidine at codon 116 (p.R116H). This mutation co-segregated with all affected individuals and was not observed in unaffected family members or 100 normal unrelated individuals. The comparative haplotype analysis showed that the affected haplotypes in the two families were different.

Conclusions: This study identified a novel cataract-microcornea phenotype caused by the recurrent mutation p.R116H in CRYAA, and suggested that this mutation site is not likely the consequence of a founder effect, but probably a result of a mutational hot spot.     

Expression of PRPF31 mRNA in patients with autosomal dominant retinitis pigmentosa: a molecular clue for incomplete penetrance?

PURPOSE. To investigate whether the incomplete penetrance phenotype characteristic of adRP families linked to chromosome 19q13.4 (RP11) with mutations in the PRPF31 gene is due to differentially expressed wild-type alleles in symptomatic and asymptomatic individuals. METHODS. Real-time quantitative RT-PCR was performed on RNA from lymphoblastoid cell lines derived from a large adRP family (RP856/AD5) that segregates an 11bp deletion in exon 11 of PRPF31. The mRNA levels from only the wild-type allele of PRPF31 were assayed using a probe designed across the deletion. The Mann-Whitney U test was used to compare the median mRNA copy numbers of the symptomatic with the asymptomatic carriers of the mutant PRPF31 allele. The PRPF31 protein levels from symptomatic and asymptomatic individuals were also assayed by Western blot analysis using an antibody specific to the wild-type PRPF31 protein. RESULTS. The use of cell lines was validated by the observation that cell transformation did not alter PRPF31 expression in the cell lines compared with nucleated blood cells and donor retinas. A significant difference in wild-type PRPF31 mRNA levels was observed between symptomatic and asymptomatic individuals (P < 0.001) and was supported by Western blot analysis of the PRPF31 protein. CONCLUSIONS. Partial penetrance in RP11 could be due to the coinheritance of a PRPF31 gene defect and a low-expressed wild-type allele. This study revealed a potential avenue for future therapy in that it appears the moderate overexpression of wild-type PRPF31 may prevent clinical manifestation of the disease.     

Calcium-independent release of neurotransmitter in the retina: a “Copernican” viewpoint change

The release of synaptic transmitter in chemical synapses is brought about by Ca²⁺ influx through voltage-dependent Ca²⁺ channels opened by depolarisation of presynaptic terminals. However, in some preparations transmitter release persists or increases in low-Ca²⁺ media, and it has therefore been proposed that transmitter release could also occur through a Ca²⁺-independent, carrier mediated process. In particular it has been suggested that this may be the case for synaptic transmission between photoreceptors and second order neurones of the vertebrate retina. From our recent experiments on synaptic transmission from photoreceptors to horizontal cells of turtle and salamander retinas, it appears that lowering extracellular Ca²⁺ can actually promote Ca²⁺ influx through voltage-activated Ca²⁺ channels via a modification of surface potential of plasma membranes. On the basis of this apparently paradoxical effect of low Ca²⁺ media, it is possible to reaccommodate the so-called Ca²⁺-independent release within the framework of Ca²⁺-dependent synaptic transmission without invoking unconventional mechanisms.     

No evidence for a genetic blueprint: The case of the “complex” mammalian photoreceptor

Despite the intensity of the search for genes causing inherited retinal degenerations over the past 3 decades, of the approximately 200 disease genes identified to date, all appear to be ordinary housekeeping genes specifying proteins playing basic structural and functional roles in the mature photoreceptor cells. No genes or genetic elements have been identified which can be construed as having a specific morphogenic role, directing the development of the cytoarchitecture of any particular retinal cell. The evidence suggests that the cytoarchitecture of the retinal photoreceptors, although enormously complex, arises from the self-organization of the cells constituents without any regulation or direction from an external genetic blueprint.     

Magnetic nanoparticles conjugated with “RPE cell -MCP-1 antibody -VEGF antibody” compounds for the targeted therapy of age-related macular degeneration: a hypothesis

Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly throughout the world. Treatment of AMD utilizing retinal pigment epithelium (RPE) transplantation represents a promising therapy. However, simplex RPE transplantation can only replace the diseased RPE cells, but has no abilities to stop the development of AMD. It has been indicated that oxidization triggers the development of AMD by inducing the dysfunction and degeneration of RPE cells, which results in the upregulation of local monocyte chemotactic protein-1 (MCP-1) expression. MCP-1 induces macrophage recruiment which triggers local inflammation. As a result, the expression of vascular endothelial growth factor (VEGF) is upregulated by MCP-1 mediated inflammation and results in the formation of choroidal neovascularization (CNV). We accordingly propose a targeted therapy of AMD by subretinal transplanting the compound of RPE cell, MCP-1 antibody, and VEGF antibody and using a magnetic system to guide RPE cell compounds conjugated with superparamagnetic iron oxide nanoparticles (SPIONs). Furthermore, SPION-labelled RPE cells can be tracked and detected in vivo by non-invasive magnetic resonance imaging (MRI). This novel RPE cell transplantation methodology seems very promising to provide a new therapeutic approach for the treatment of AMD.     

Reply to the comments on “Macular buckle technique in myopic traction maculopathy: a 16-year review of the literature and a comparison with vitreous surgery”

Graefe's Archive for Clinical and Experimental Ophthalmology -     

Impact of COVID-19 on outpatient visits and intravitreal treatments in a referral retina unit: let’s be ready for a plausible “rebound effect”

Graefe's Archive for Clinical and Experimental Ophthalmology - To quantify the shrinking in outpatient and intravitreal injections’ volumes in a tertiary referral retina unit secondary to...     

Early Vitrectomy for Severe Proliferative Diabetic Retinopathy in Eyes with Useful Vision: Results of a Randomized Trial—Diabetic Retinopathy Vitrectomy Study Report 3

Three hundred seventy eyes with advanced, active, proliferative diabetic retinopathy (PDR) and visual acuity of 10/200 or better were randomly assigned to either early vitrectomy or conventional management. After 4 years of follow-up, the percentage of eyes with a visual acuity of 10/20 or better was 44% in the early vitrectomy group and 28% in the conventional management group. The proportion with very poor visual outcome was similar in the two groups. The advantage of early vitrectomy tended to increase with increasing severity of new vessels. In the group with the least severe new vessels, no advantage of early vitrectomy was apparent.     

Letter of response to “Comment re: Comparison of the horizontal diameter to a modeled area of traction in eyes with vitreomacular traction: is the diameter close enough to the truth?”

Graefe's Archive for Clinical and Experimental Ophthalmology -     

“Balancing risk in ophthalmic prescribing: assessing the safety of anti-VEGF therapies and the risks associated with unlicensed medicines”

Vascular endothelial growth factor (VEGF) inhibitor medications such as ranibizumab, pegaptanib and bevacizumab are in use for the treatment of neovascular age-related macular degeneration (AMD) and other retinal conditions, although only ranibizumab and pegaptanib are approved for these conditions. In contrast, bevacizumab was developed for the intravenous systemic treatment of colorectal cancer and is not formulated for intravitreal use, but is commonly used off-label in ophthalmology. European Union legislation permits the use of drugs outside the terms of their licence (‘off-label’) only under certain circumstances, such as during clinical trials, compassionate/named patient use in the absence of a licensed alternative, emergency scenarios (e.g., pandemics) or at the discretion of a treating physician. In such cases, patients should be fully informed regarding their treatment and any potential risks involved. Off-label drug use can be an important tool to provide patients with treatment in cases of unmet medical need. However, the use of an unlicensed medicinal product, when a suitable licensed alternative is available, puts prescribing physicians at risk of liability if safety issues arise. Emerging clinical evidence suggests safety differences exist between ranibizumab and bevacizumab.