Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Novel insights into the molecular pathogenesis of CYP4V2-associated Bietti's retinal dystrophy

Contains fulltext : 153526.pdf (publisher's version ) (Open Access)Bietti's crystalline dystrophy (BCD) is a rare, autosomal recessive retinal degenerative disease associated with mutations in CYP4V2. In this study, we describe the genetic and clinical findings in 19 unrelated BCD patients recruited from five international retinal dystrophy clinics. Patients underwent ophthalmic examinations and were screened for CYP4V2 mutations by Sanger sequencing and quantitative polymerase chain reaction (qPCR) copy number variation screening. Eight CYP4V2 mutations were found in 10/19 patients, including three patients in whom only monoallelic mutations were detected. Four novel mutations were identified: c.604G>A; p.(Glu202Lys), c.242C>G; p.(Thr81Arg), c.604+4A>G; p.(?), and c.1249dup; p.(Thr417Asnfs*2). In addition, we identified a heterozygous paternally inherited genomic deletion of at least 3.8 Mb, encompassing the complete CYP4V2 gene and several other genes, which is novel. Clinically, patients demonstrated phenotypic variability, predominantly showing choroidal sclerosis, attenuated vessels, and crystalline deposits of varying degrees of severity. To our knowledge, our study reports the first heterozygous CYP4V2 deletion and hence a novel mutational mechanism underlying BCD. Our results emphasize the importance of copy number screening in BCD. Finally, the identification of CYP4V2-negative patients with indistinguishable phenotypes from CYP4V2-positive patients might suggest the presence of mutations outside the coding regions of CYP4V2, or locus heterogeneity, which is unreported so far

Novel compound heterozygous NMNAT1 variants associated with Leber congenital amaurosis

Contains fulltext : 136408.pdf (publisher's version ) (Open Access)PURPOSE: The gene encoding nicotinamide nucleotide adenylyltransferase 1 (NMNAT1) was recently found to be mutated in a subset of patients with Leber congenital amaurosis (LCA) with macular atrophy. The aim of this study was to determine the occurrence and frequency of NMNAT1 mutations and associated phenotypes in different types of inherited retinal dystrophies. METHODS: DNA samples of 161 patients with LCA without genetic diagnosis were analyzed for variants in NMNAT1 using Sanger sequencing. Variants in exon 5 of NMNAT1, which harbors the majority of the previously identified mutations, were screened in 532 additional patients with retinal dystrophies. This cohort encompassed 108 persons with isolated or autosomal recessive cone-rod dystrophy (CRD), 271 with isolated or autosomal recessive retinitis pigmentosa (RP), and 49 with autosomal dominant RP, as well as 104 persons with LCA in whom the causative mutation was previously identified. RESULTS: Compound heterozygous alterations were found in six patients with LCA and in one person with early-onset RP. All except one carried the common p.E257K variant on one allele. Macular atrophy was absent in one patient, who carried this variant in combination with a truncating mutation on the other allele. The p.E257K alteration was also found in a heterozygous state in five individuals with LCA and one with RP while no mutation was detected on the other allele. Two individuals with LCA carried other NMNAT1 variants in a heterozygous state, whereas no NMNAT1 variants in exon 5 were identified in individuals with CRD. The p.E257K variant was found to be enriched in a heterozygous state in individuals with LCA (0.94%) compared to Caucasian controls (0.18%), although the difference was statistically insignificant (p=0.12). CONCLUSIONS: Although macular atrophy can occur in LCA and CRD, no NMNAT1 mutations were found in the latter cohort. NMNAT1 variants were also not found in a large group of patients with sporadic or autosomal recessive RP. The enrichment of p.E257K in a heterozygous state in patients with LCA versus controls suggests that this allele could act as a modifier in other genetic subtypes of LCA

Molecular and clinical analysis of 27 German patients with Leber congenital amaurosis

Contains fulltext : 200254.pdf (publisher's version ) (Open Access

CEP290 Mutation Spectrum and Delineation of the Associated Phenotype in a Large German Cohort: A Monocentric Study

Contains fulltext : 218255.pdf (Publisher’s version ) (Closed access)PURPOSE: Gene therapy for Leber congenital amaurosis (LCA) is becoming available, and therefore it is crucial to identify eligible candidates. We report the spectrum and associated phenotype of CEP290 mutations in the largest German cohort observed by a single clinical site. DESIGN: Prospective cohort study. METHODS: Twenty-three patients with mutations in CEP290 were included. Genomic DNA was analyzed by Sanger sequencing or high-throughput sequencing for all retinitis pigmentosa-associated genes in patients, and segregation analysis was done in family members. Patients underwent functional and morphologic examinations, including fundus autofluorescence and spectral-domain optical coherence tomography. RESULTS: The most frequent mutation was c.2991+1655A>G, found in 87% of patients (20/23). Thirty percent of patients (7/23) carried the mutation in an apparent homozygous state and 57% (13/23) in a likely compound heterozygous state. The most common clinical diagnosis was LCA and/or early onset severe retinal dystrophy in 82% (19/23), followed by retinitis pigmentosa in 14% (3/23) and cone-rod dystrophy (4%, 1/23). Best-corrected visual acuity was severely reduced to residual light perception and hand motion vision, with the exception of 3 patients with best-corrected visual acuity of 0.8 (Snellen). The visual field was severely decreased and electroretinogram was undetectable in most cases; however, retinal layers at the fovea appeared to be relatively well preserved. Systemic disorders were not noticed. CONCLUSIONS: c.2991+1655A>G is by far the most important CEP290 mutation, contributing to 87% of patients with the CEP290 mutation in Germany. In our cohort, a homozygous c.2991+1655A>G genotype presented with a more severe phenotype. National studies and further detailed phenotype analysis seem to be important to assess the need for and promise of specific gene therapies

Visual cortex organisation in a macaque monkey with macular degeneration.

The visual field is retinotopically represented in early visual areas. It has been suggested that when adult primary visual cortex (V1) is deprived of normal retinal input it is capable of large-scale reorganisation, with neurons inside the lesion projection zone (LPZ) being visually driven by inputs from intact retinal regions. Early functional magnetic resonance imaging (fMRI) studies in humans with macular degeneration (MD) report > 1 cm spread of activity inside the LPZ border, whereas recent results report no shift of the LPZ border. Here, we used fMRI population receptive field measurements to study, for the first time, the visual cortex organisation of one macaque monkey with MD and to compare it with normal controls. Our results showed that the border of the V1 LPZ remained stable, suggesting that the deafferented area V1 zone of the MD animal has limited capacity for reorganisation. Interestingly, the pRF size of non-deafferented V1 voxels increased slightly (~20% on average), although this effect appears weaker than that in previous single-unit recording reports. Area V2 also showed limited reorganisation. Remarkably, area V5/MT of the MD animal showed extensive activation compared to controls stimulated over the part of the visual field that was spared in the MD animal. Furthermore, population receptive field size distributions differed markedly in area V5/MT of the MD animal. Taken together, these results suggest that V5/MT has a higher potential for reorganisation after MD than earlier visual cortex