CRB1-associated Retinal Dystrophies: Genetics, Clinical Characteristics and Natural History

PURPOSE: To analyse the clinical characteristics, natural history, and genetics of CRB1-associated retinal dystrophies. DESIGN: Multicenter international retrospective cohort study. METHODS: Review of clinical notes, ophthalmic images, and genetic testing results of 104 patients (91 probands) with disease-causing CRB1 variants. Macular optical coherence tomography (OCT) parameters, visual function, fundus characteristics, and associations between variables were our main outcome measures. RESULTS: The mean age of the cohort at the first visit was 19.8 ± 16.1 (median 15) years of age, with a mean follow-up of 9.6 ± 10 years. Based on history, imaging, and clinical examination, 26 individuals were diagnosed with retinitis pigmentosa (RP, 26%), 54 with early-onset severe retinal dystrophy/Leber Congenital Amaurosis (EOSRD/LCA, 51%), and 24 with macular dystrophy (MD, 23%). Severe visual impairment was most frequent after 40 years of age for patients with RP and after 20 years of age for EOSRD/LCA. Longitudinal analysis revealed a significant difference between baseline and follow up best corrected visual acuity in the three sub-cohorts. Macular thickness decreased in most patients with EOSRD/LCA and MD, whereas the majority of patients with RP had increased perifoveal thickness. CONCLUSIONS: A subset of individuals with CRB1 variants present with mild, adult-onset RP. EOSRD/LCA phenotype was significantly associated with null variants, and 167_169 deletion was exclusively present in the MD cohort. The poor OCT lamination may have a degenerative component, as well as being congenital. Disease symmetry and reasonable window for intervention highlight CRB1 retinal dystrophies as a promising target for trials of novel therapeutics

TRPM1 Mutations are the Most Common Cause of Autosomal Recessive Congenital Stationary Night Blindness (CSNB) in the Palestinian and Israeli Populations

International audiencePrecise genetic and phenotypic characterization of congenital stationary night blindness (CSNB) patients is needed for future therapeutic interventions. The aim of this study was to estimate the prevalence of CSNB in our populations and to study clinical and genetic aspects of the autosomal recessive (AR) form of CSNB. This is a retrospective cohort study of Palestinian and Israeli CSNB patients harboring mutations in TRPM1 underwent comprehensive ocular examination. Genetic analysis was performed using homozygosity mapping and sequencing. 161 patients (from 76 families) were recruited for this study, leading to a prevalence of 1:6210 in the vicinity of Jerusalem, much higher than the worldwide prevalence. 61% of the families were consanguineous with AR inheritance pattern. Biallelic pathogenic TRPM1 mutations were identified in 36 families (72 patients). Two founder mutations explain the vast majority of cases: a nonsense mutation c.880A>T (p.Lys294*) identified in 22 Palestinian families and a large genomic deletion (36,445 bp) encompassing exons 2–7 of TRPM1 present in 13 Ashkenazi Jewish families. Most patients were myopic (with mean BCVA of 0.40 LogMAR) and all had absent rod responses in full field electroretinography. To the best of our knowledge, this is the largest report of a clinical and genetic analysis of patients affected with CSNB due to TRPM1 mutations

Towards Uncovering the Role of Incomplete Penetrance in Maculopathies through Sequencing of 105 Disease-Associated Genes.

Inherited macular dystrophies (iMDs) are a group of genetic disorders, which affect the central region of the retina. To investigate the genetic basis of iMDs, we used single-molecule Molecular Inversion Probes to sequence 105 maculopathy-associated genes in 1352 patients diagnosed with iMDs. Within this cohort, 39.8% of patients were considered genetically explained by 460 different variants in 49 distinct genes of which 73 were novel variants, with some affecting splicing. The top five most frequent causative genes were ABCA4 (37.2%), PRPH2 (6.7%), CDHR1 (6.1%), PROM1 (4.3%) and RP1L1 (3.1%). Interestingly, variants with incomplete penetrance were revealed in almost one-third of patients considered solved (28.1%), and therefore, a proportion of patients may not be explained solely by the variants reported. This includes eight previously reported variants with incomplete penetrance in addition to CDHR1:c.783G>A and CNGB3:c.1208G>A. Notably, segregation analysis was not routinely performed for variant phasing-a limitation, which may also impact the overall diagnostic yield. The relatively high proportion of probands without any putative causal variant (60.2%) highlights the need to explore variants with incomplete penetrance, the potential modifiers of disease and the genetic overlap between iMDs and age-related macular degeneration. Our results provide valuable insights into the genetic landscape of iMDs and warrant future exploration to determine the involvement of other maculopathy genes

Resolving the dark matter of ABCA4 for 1054 Stargardt disease probands through integrated genomics and transcriptomics

Purpose: Missing heritability in human diseases represents a major challenge, and this is particularly true for ABCA4-associated Stargardt disease (STGD1). We aimed to elucidate the genomic and transcriptomic variation in 1054 unsolved STGD and STGD-like probands. Methods: Sequencing of the complete 128-kb ABCA4 gene was performed using single-molecule molecular inversion probes (smMIPs), based on a semiautomated and cost-effective method. Structural variants (SVs) were identified using relative read coverage analyses and putative splice defects were studied using in vitro assays. Results: In 448 biallelic probands 14 known and 13 novel deep-intronic variants were found, resulting in pseudoexon (PE) insertions or exon elongations in 105 alleles. Intriguingly, intron 13 variants c.1938-621G>A and c.1938-514G>A resulted in dual PE insertions consisting of the same upstream, but different downstream PEs. The intron 44 variant c.6148-84A>T resulted in two PE insertions and flanking exon deletions. Eleven distinct large deletions were found, two of which contained small inverted segments. Uniparental isodisomy of chromosome 1 was identified in one proband. Conclusion: Deep sequencing of ABCA4 and midigene-based splice assays allowed the identification of SVs and causal deep-intronic variants in 25% of biallelic STGD1 cases, which represents a model study that can be applied to other inherited diseases

Resolving the dark matter of ABCA4 for 1054 Stargardt disease probands through integrated genomics and transcriptomics

Purpose: Missing heritability in human diseases represents a major challenge, and this is particularly true for ABCA4-associated Stargardt disease (STGD1). We aimed to elucidate the genomic and transcriptomic variation in 1054 unsolved STGD and STGD-like probands. Methods: Sequencing of the complete 128-kb ABCA4 gene was performed using single-molecule molecular inversion probes (smMIPs), based on a semiautomated and cost-effective method. Structural variants (SVs) were identified using relative read coverage analyses and putative splice defects were studied using in vitro assays. Results: In 448 biallelic probands 14 known and 13 novel deep-intronic variants were found, resulting in pseudoexon (PE) insertions or exon elongations in 105 alleles. Intriguingly, intron 13 variants c.1938-621G>A and c.1938-514G>A resulted in dual PE insertions consisting of the same upstream, but different downstream PEs. The intron 44 variant c.6148-84A>T resulted in two PE insertions and flanking exon deletions. Eleven distinct large deletions were found, two of which contained small inverted segments. Uniparental isodisomy of chromosome 1 was identified in one proband. Conclusion: Deep sequencing of ABCA4 and midigene-based splice assays allowed the identification of SVs and causal deep-intronic variants in 25% of biallelic STGD1 cases, which represents a model study that can be applied to other inherited diseases.Fil: Khan, Mubeen. Radboud University Nijmegen Medical Centre; Países BajosFil: Cornelis, Stéphanie S.. Radboud University Nijmegen Medical Centre; Países BajosFil: Del Pozo Valero, Marta. Hospital Universitario Fundación Jiménez Díaz; España. Radboud University Nijmegen Medical Centre; Países BajosFil: Whelan, Laura. Trinity College; Estados UnidosFil: Runhart, Esmee H.. Radboud University Nijmegen Medical Centre; Países BajosFil: Mishra, Ketan. Radboud University Nijmegen Medical Centre; Países BajosFil: Bults, Femke. Radboud University Nijmegen Medical Centre; Países BajosFil: AlSwaiti, Yahya. St John of Jerusalem Eye Hospital Group; Palestina (ANP)Fil: AlTalbishi, Alaa. St John of Jerusalem Eye Hospital Group; Palestina (ANP)Fil: De Baere, Elfride. University of Ghent; BélgicaFil: Banfi, Sandro. Seconda Universita Degli Studi Di Napoli; ItaliaFil: Banin, Eyal. The Hebrew University of Jerusalem; IsraelFil: Bauwens, Miriam. University of Ghent; BélgicaFil: Ben Yosef, Tamar. The Ruth And Bruce Rappaport Faculty Of Medicine; IsraelFil: Boon, Camiel J. F.. Leiden University. Leiden University Medical Center; Países BajosFil: van den Born, L. Ingeborgh. Rotterdam Ophthalmic Institute; Países BajosFil: Defoort, Sabine. Universite Lille; FranciaFil: Devos, Aurore. Universite Lille; FranciaFil: Dockery, Adrian. Trinity College; Estados UnidosFil: Dudakova, Lubica. Charles University and General University Hospital; República ChecaFil: Fakin, Ana. Charles University and General University Hospital; República ChecaFil: Farrar, G. Jane. Trinity College; Estados UnidosFil: Ferraz Sallum, Juliana Maria. Universidade Federal de Sao Paulo; BrasilFil: Fujinami, Kaoru. UCL Institute of Ophthalmology; Reino UnidoFil: Gilissen, Christian. Radboud University Nijmegen Medical Centre; Países BajosFil: Glavac, Damjan. University of Ljubljana; EsloveniaFil: Gorin, Michael B.. University of California at Los Angeles. School of Medicine; Estados UnidosFil: Greenberg, Jacquie. University of Cape Town; SudáfricaFil: Hayashi, Takaaki. The Jikei University School of Medicine; JapónFil: Hettinga, Ymkje M.. Bartiméus Diagnostic Center for Complex Visual Disorders; Países BajosFil: Hoischen, Alexander. Radboud University Nijmegen Medical Centre; Países BajosFil: Hoyng, Carel B.. Radboud University Nijmegen Medical Centre; Países BajosFil: Hufendiek, Karsten. University Eye Hospital Hannover Medical School; AlemaniaFil: Jägle, Herbert. University Regensburg; AlemaniaFil: Kamakari, Smaragda. OMMA Ophthalmological Institute of Athens; GreciaFil: Karali, Marianthi. Seconda Universita Degli Studi Di Napoli; ItaliaFil: Kellner, Ulrich. No especifíca;Fil: Klaver, Caroline C. W.. Radboud University Nijmegen Medical Centre; Países BajosFil: Kousal, Bohdan. Charles University and General University Hospital; República ChecaFil: Lamey, Tina M.. University of Western Australia; AustraliaFil: MacDonald, Ian M.. University of Alberta; CanadáFil: Matynia, Anna. University of California at Los Angeles. School of Medicine; Estados UnidosFil: McLaren, Terri L.. University of Western Australia; AustraliaFil: Mena, Marcela D.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Meunier, Isabelle. Université Montpellier II; FranciaFil: Miller, Rianne. Radboud University Nijmegen Medical Centre; Países BajosFil: Newman, Hadas. Universitat Tel Aviv; IsraelFil: Ntozini, Buhle. University of Cape Town; SudáfricaFil: Oldak, Monika. No especifíca;Fil: Pieterse, Marc. Radboud University Nijmegen Medical Centre; Países BajosFil: Podhajcer, Osvaldo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Puech, Bernard. Universite Lille; FranciaFil: Ramesar, Raj. University of Cape Town; SudáfricaFil: Rüther, Klaus. No especifíca;Fil: Salameh, Manar. No especifíca;Fil: Salles, Mariana Vallim. Universidade de Sao Paulo; BrasilFil: Sharon, Dror. The Hebrew University of Jerusalem; IsraelFil: Simonelli, Francesca. Seconda Universita Degli Studi Di Napoli; ItaliaFil: Spital, Georg. No especifíca;Fil: Steehouwer, Marloes. Radboud University Nijmegen Medical Centre; Países BajosFil: Szaflik, Jacek P.. No especifíca;Fil: Thompson, Jennifer A.. No especifíca;Fil: Thuillier, Caroline. Universite Lille; FranciaFil: Tracewska, Anna M.. No especifíca;Fil: van Zweeden, Martine. Radboud University Nijmegen Medical Centre; Países BajosFil: Vincent, Andrea L.. University of Auckland; Nueva ZelandaFil: Zanlonghi, Xavier. No especifíca;Fil: Liskova, Petra. Charles University and General University Hospital; República ChecaFil: Stöhr, Heidi. Universitat Regensburg; AlemaniaFil: De Roach, John N.. University of Western Australia; AustraliaFil: Ayuso, Carmen. Hospital Universitario Fundación Jiménez Díaz; EspañaFil: Roberts, Lisa. University of Cape Town; SudáfricaFil: Weber, Bernhard H. F.. Universitat Regensburg; AlemaniaFil: Dhaenens, Claire Marie. Universite Lille; FranciaFil: Cremers, Frans P. M.. Radboud University Nijmegen Medical Centre; Países Bajo