Biomedical subjects

Dror Sharon

Publications and source records attributed to Dror Sharon.

9 recordsLinked to original sources

PubMed2025

Founder Homozygous Nonsense CREB3 Variant and Variable-Onset Retinal Degeneration.

IMPORTANCE: Uncovering the genetic basis of inherited retinal diseases (IRDs) can enhance both diagnostic accuracy and the development of targeted treatment strategies. OBJECTIVE: To evaluate the association between a homozygous nonsense variant in CREB3 with IRDs. DESIGN, SETTING, AND PARTICIPANTS: Thirteen patients with a clinical diagnosis of retinitis pigmentosa or cone-rod degeneration were analyzed by whole-genome sequencing (WGS) and whole-exome sequencing (WES). Clinically, patients presented with 2 main phenotypes, rod-cone and cone-rod dystrophies, demonstrating variable electrophysiological and fundoscopic findings. Expression analysis was performed on patient-derived skin fibroblasts using the reverse transcription-polymerase chain reaction and Western blot analysis, and by interrogating previously published retinal single-cell RNA sequence data. Immunohistochemistry staining was performed on wild-type mouse retinal sections using an anti-CREB3 antibody. Patients with variable phenotypes of IRDs were recruited from 3 medical centers in Israel and Italy. Ophthalmologists clinically diagnosed patients at the relevant medical centers and referred them for genetic screening. WES and WGS were performed at different national and international centers, and the findings of the previously unreported gene were shared between investigators. EXPOSURES: CREB3 and IRDs. MAIN OUTCOMES AND MEASURES: The main outcome was evidence supporting an association between CREB3 and IRD. Measures included WES, WGS, and immunohistochemistry staining. RESULTS: A founder homozygous nonsense variant in CREB3 (c.881G>A, p.Trp294*) was identified in 13 patients from 4 unrelated families; 12 descendent from North-African Jewish origins and 1 from Italian origins. All patients manifested retinal degeneration with varying ages at onset. In patient-derived fibroblasts, the variant mRNA transcript generated a truncated CREB3 protein. Expression analysis and immunohistochemistry staining revealed CREB3 RNA and protein expression in various retinal cell types, indicating its vital role in photoreceptor function. CONCLUSIONS AND RELEVANCE: This study found an association between CREB3 and IRDs. CREB3 was previously shown to be upregulated following ultraviolet radiation. This might contribute to the extensive clinical variability observed in this relatively large cohort of homozygous patients with the same truncated variant.

Humans↗

PubMed2025

Non-coding single-nucleotide and structural variants affecting the EYS putative promoter cause autosomal recessive retinitis pigmentosa.

PURPOSE: Variants in untranslated genomic regions are difficult to identify as pathogenic but are capable of causing disease by interfering with gene expression. This study aimed to characterize the effect of variants identified in the 5'-untranslated region of EYS in patients with autosomal recessive retinitis pigmentosa (RP). METHODS: Variant screening included gene panels, Sanger, exome, and genome sequencing. Functional validation included an electrophoretic mobility shift assay and various luciferase assays. RESULTS: Patients with RP from 6 EYS biallelic Arab-Muslim families harbored a 5' noncoding EYS variant, c.-453G>T, and 4 harbored a structural variant affecting the 5' noncoding exons. Electrophoretic mobility shift assay analysis revealed an effect on binding of transcription factors for c.-453G>T and a neighboring variant c.-454G>T. Dual luciferase assays using overexpression of various transcription factors showed distinct effects on expression. c.-453G>T was associated with higher luciferase expression with CRX overexpression and c.-454G>C with OTX2 overexpression. In addition, the 2 variants were found to influence translation by affecting upstream initiation codons. Interestingly, visual function of EYS RP patients who harbor c.-453G>T are better than those with biallelic null EYS variants. CONCLUSION: Our analysis revealed both single-nucleotide and structural variants in the EYS promoter as the cause of autosomal recessive RP. These variants may affect EYS expression via a dual mechanism by altering transcription factor binding affinity at the EYS promoter and by affecting upstream open reading frames.

Humans↗

PubMed2025

Biallelic null variants in C19orf44 cause a unique late-onset retinal dystrophy phenotype characterized by patchy perifoveal chorioretinal atrophy.

PURPOSE: To identify the genetic cause for disease in individuals affected with inherited retinal disease and to characterize their retinal phenotype and the properties of the underlying gene. METHODS: Participants underwent a comprehensive ophthalmological evaluation, including best-corrected visual acuity, visual field testing, fundus autofluorescence, optical coherence tomography, and electroretinography. Genetic analyses included exome, genome, and Sanger sequencing. Gene expression pattern was analyzed by reverse transcription-polymerase chain reaction. Localization of the encoded protein in cells and in the human retina was examined by immunofluorescence staining. RESULTS: Four different pathogenic variants in C19orf44 were identified in 15 biallelic individuals from 11 unrelated families. The most common variant was c.549_550del p.(Ser185ProfsTer2). Most individuals were affected with a unique clinical phenotype characterized by late-onset patchy perifoveal chorioretinal atrophy and electroretinographic features of rod-cone degeneration. C19orf44 is expressed in various human tissues, including the retina, where it was found in the outer nuclear layer and in the outer plexiform layer. In cultured cells (hTERT RPE-1 and HeLa) and in human primary fibroblasts, C19orf44 is found in the nucleus, and it is downregulated during mitosis. CONCLUSION: Based on our results, C19orf44 is crucial for normal human retinal function, and pathogenic variants in this gene are associated with autosomal recessive inherited retinal disease.

Humans↗

PubMed2004

Novel mutations in the cellular retinaldehyde-binding protein gene (RLBP1) associated with retinitis punctata albescens: evidence of interfamilial genetic heterogeneity and fundus changes in heterozygotes.

OBJECTIVE: To evaluate the molecular genetic defects associated with retinitis punctata albescens (RPA) in 5 patients from 3 families with this disease. METHODS: We examined 3 probands and 2 clinically affected relatives with RPA. Clinical examinations included best-corrected visual acuity, visual field testing, electroretinography, dilated fundus examination, and fundus photography. Leukocyte DNA was analyzed for mutations in the exons of the genes encoding cellular retinaldehyde-binding protein 1 (RLBP1), 11-cis-retinol dehydrogenase (RDH5), interphotoreceptor retinoid-binding protein (RBP3), and photoreceptor all-trans-retinol dehydrogenase (RDH8). Not all patients were evaluated for mutations in each gene. The exons were individually amplified and screened for mutations by single-stranded conformational polymorphism analysis or direct genomic sequencing. RESULTS: The 3 probands had similar clinical findings, including a history of poor night vision, the presence of punctate white deposits in the retina, and substantially reduced or absent rod responses on electroretinogram testing. One of the probands (patient 2:III:2) had 2 novel mutations in the RLBP1 gene (Arg151Trp and Gly31[2-base pair deletion], [GGA-->G-]). Segregation analysis showed that the 2 mutations were allelic and that the patient was a compound heterozygote. Both parents of the proband manifested round white deposits in the retina. The other 2 probands had no detected pathogenic mutations in RLBP1 or in the other 3 genes evaluated. CONCLUSIONS: The identification of novel RLBP1 mutations in 1 of our 3 probands, all with RPA, is further evidence of genetic (nonallelic) heterogeneity in this disease. The presence of round white deposits in the retina may be observed in those heterozygous for RLBP1. Clinical Relevance Patients with a clinical presentation of RPA can have genetically different mutations. Drusen-like lesions may be observed in heterozygotes in families with this disease and a mutation in RLBP1.

Adult↗

PubMed2003

RP2 and RPGR mutations and clinical correlations in patients with X-linked retinitis pigmentosa.

We determined the mutation spectrum of the RP2 and RPGR genes in patients with X-linked retinitis pigmentosa (XLRP) and searched for correlations between categories of mutation and severity of disease. We screened 187 unrelated male patients for mutations, including 135 with a prior clinical diagnosis of XLRP, 11 with probable XLRP, 30 isolate cases suspected of having XLRP, and 11 with cone-rod degeneration. Mutation screening was performed by single-strand conformation analysis and by sequencing of all RP2 exons and RPGR exons 1-14, ORF15, and 15a. The refractive error, visual acuity, final dark-adapted threshold, visual field area, and 30-Hz cone electroretinogram (ERG) amplitude were measured in each patient. Among the 187 patients, we found 10 mutations in RP2, 2 of which are novel, and 80 mutations in RPGR, 41 of which are novel; 66% of the RPGR mutations were within ORF15. Among the 135 with a prior clinical diagnosis of XLRP, mutations in the RP2 and RPGR genes were found in 9 of 135 (6.7%) and 98 of 135 (72.6%), respectively, for a total of 79% of patients. Patients with RP2 mutations had, on average, lower visual acuity but similar visual field area, final dark-adapted threshold, and 30-Hz ERG amplitude compared with those with RPGR mutations. Among patients with RPGR mutations, those with ORF15 mutations had, on average, a significantly larger visual field area and a borderline larger ERG amplitude than did patients with RPGR mutations in exons 1-14. Among patients with ORF15 mutations, regression analyses showed that the final dark-adapted threshold became lower (i.e., closer to normal) and that the 30-Hz ERG amplitude increased as the length of the wild-type ORF15 amino acid sequence increased. Furthermore, as the length of the abnormal amino acid sequence following ORF15 frameshift mutations increased, the severity of disease increased.

Adolescent↗

PubMed2003

Shared mutations in NR2E3 in enhanced S-cone syndrome, Goldmann-Favre syndrome, and many cases of clumped pigmentary retinal degeneration.

OBJECTIVES: To determine if enhanced s-cone syndrome (ESCS), Goldmann-Favre syndrome (GFS), and clumped pigmentary retinal degeneration (CPRD) are caused by mutations in the NR2E3 gene and to characterize the clinical findings in patients with NR2E3 mutations. Patients One patient with ESCS, one with GFS, and 20 with CPRD. METHODS: The coding regions of the NR2E3 and NRL genes and part of the THRB1 coding region were scanned for mutations using single-strand conformation and direct sequencing methods. We evaluated visual acuity, refractive error, visual fields, fundi, final dark-adaptation thresholds, and electroretinograms (ERGs). RESULTS: The patients with ESCS and GFS and 9 of the 20 unrelated patients with CPRD had mutations in the NR2E3 gene. Six mutations were found in these 11 patients, including 2 novel mutations: the missense mutation Ala256Glu and the frameshift mutation Pro276del17 (the first obviously null allele reported). Three patients were mutant homozygotes, and 8 had 2 mutations. All but one of the mutations in the patients with ESCS and GFS were also found in patients with CPRD. All NR2E3 cases were hyperopes and had retinal vascular attenuation and reduced and delayed full-field ERGs. Clumped pigment deposits were recognized in the patients with ESCS and GFS. The CPRD patients without NR2E3 mutations had no detected mutations in NRL or THRB1. CONCLUSIONS: We found that ESCS, GFS, and CPRD can all have the same genetic basis. Clinical Relevance The combination of night blindness, hyperopia, and clumped retinal pigment deposits should raise the suspicion that a patient has NR2E3 disease.

Adolescent↗

PubMed2002

Retinitis pigmentosa and allied diseases: numerous diseases, genes, and inheritance patterns.

Retinitis pigmentosa (RP) and allied diseases are heterogeneous clinically and genetically. Here we summarize the retinal cell types involved in these diseases, the large number of genes that cause them, and the variety of inheritance patterns that the affected families display. Special consideration is given to unusual inheritance patterns. The aggregate carrier frequency for recessive RP alleles may be as high as 10%.

Alleles↗

PubMed2002

Mutated alleles of the rod and cone Na-Ca+K-exchanger genes in patients with retinal diseases.

PURPOSE: To study the possible involvement of the rod (SLC24A1) and cone (SLC24A2) Na-Ca+K exchanger (NCKX) genes in retinal diseases. METHODS: DNA was collected from unrelated patients with retinal disease, mainly from North America. A human genomic library was screened with the cone NCKX cDNA, and hybridizing clones were sequenced to determine the genomic organization of the SLC24A2 gene. The single-strand conformation polymorphism (SSCP) technique and direct sequencing were used to screen the patients' DNA for mutations in SLC24A1 and SLC24A2. The effect of selected missense changes on protein function was tested by measuring potassium-dependent Na-Ca exchange of the mutant proteins expressed in insect cells. RESULTS: Twenty-seven novel sequence changes were found in the rod NCKX gene, 21 of which are unlikely to be pathogenic, because they did not cosegregate with the disease or did not affect conserved regions of the protein. Of the remaining six, two were frameshift mutations found in one patient each. If translated, these alleles would encode nonfunctional proteins. Three of the six possibly pathogenic mutations were missense changes located in conserved regions, and their protein functions were assayed. Only one (Ile992Thr) had a significantly low level of exchanger function, but it was found in two unrelated patients who were heterozygotes with different retinal diseases, and this mutation could not be unequivocally associated with either disease. The last of the six changes is likely to create a new splice acceptor site. The genomic organization of the cone NCKX gene was determined, and it contained 11 exons with a few splice variants. Fifteen novel sequence changes were identified in the cone exchanger gene in patients with a cone dysfunction or degeneration. Only three of these sequence changes, all missense changes found in heterozygous patients, were considered possibly pathogenic. Functional analysis showed only a slight reduction in the activity of the corresponding mutant proteins. CONCLUSIONS: Although variant alleles of the rod and cone NCKX genes were found, none could be definitively associated with a specific retinal disease. The human phenotype associated with mutant exchanger alleles remains unknown.

Alleles↗

PubMed2001

Profile of the genes expressed in the human peripheral retina, macula, and retinal pigment epithelium determined through serial analysis of gene expression (SAGE).

We used the serial analysis of gene expression (SAGE) technique to catalogue and measure the relative levels of expression of the genes expressed in the human peripheral retina, macula, and retinal pigment epithelium (RPE) from one or both of two humans, aged 88 and 44 years. The cone photoreceptor contribution to all transcription in the retina was found to be similar in the macula versus the retinal periphery, whereas the rod contribution was greater in the periphery versus the macula. Genes encoding structural proteins for axons were found to be expressed at higher levels in the macula versus the retinal periphery, probably reflecting the large proportion of ganglion cells in the central retina. In comparison with the younger eye, the peripheral retina of the older eye had a substantially higher proportion of mRNAs from genes encoding proteins involved in iron metabolism or protection against oxidative damage and a substantially lower proportion of mRNAs from genes encoding proteins involved in rod phototransduction. These differences may reflect the difference in age between the two donors or merely interindividual variation. The RPE library had numerous previously unencountered tags, suggesting that this cell type has a large, idiosyncratic repertoire of expressed genes. Comparison of these libraries with 100 reported nonocular SAGE libraries revealed 89 retina-specific or enriched genes expressed at substantial levels, of which 14 are known to cause a retinal disease and 53 are RPE-specific genes. We expect that these libraries will serve as a resource for understanding the relative expression levels of genes in the retina and the RPE and for identifying additional disease genes.

Adult↗