A prevalent mutation with founder effect in Spanish recessive dystrophic epidermolysis bullosa families

Background: Recessive Dystrophic Epidermolysis Bullosa (RDEB) is a genodermatosis caused by more than 500 different mutations in the COL7A1 gene and characterized by blistering of the skin following a minimal friction or mechanical trauma. The identification of a cluster of RDEB pedigrees carrying the c.6527insC mutation in a specific area raises the question of the origin of this mutation from a common ancestor or as a result of a hotspot mutation. The aim of this study was to investigate the origin of the c.6527insC mutation. Methods: Haplotypes were constructed by genotyping nine single nucleotides polymorphisms (SNPs) throughout the COL7A1 gene. Haplotypes were determined in RDEB patients and control samples, both of Spanish origin. Results: Sixteen different haplotypes were identified in our study. A single haplotype cosegregated with the c.6527insC mutation. Conclusion: Haplotype analysis showed that all alleles carrying the c.6527insC mutation shared the same haplotype cosegregating with this mutation (CCGCTCAAA_6527insC), thus suggesting the presence of a common ancestor.This work was supported in part by grants from Spanish Ministry of Science and Innovation (SAF2007-61019 and SAF2010-16976) and INTRA/08/714 from Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER)

Allelic overload and its clinical modifier effect in Bardet-Biedl syndrome

Bardet–Biedl syndrome (BBS) is an autosomal recessive ciliopathy characterized by extensive inter- and intra-familial variability, in which oligogenic interactions have been also reported. Our main goal is to elucidate the role of mutational load in the clinical variability of BBS. A cohort of 99 patients from 77 different families with biallelic pathogenic variants in a BBS-associated gene was retrospectively recruited. Human Phenotype Ontology terms were used in the annotation of clinical symptoms. The mutational load in 39 BBS-related genes was studied in index cases using different molecular and next-generation sequencing (NGS) approaches. Candidate allele combinations were analysed using the in silico tools ORVAL and DiGePred. After clinical annotation, 76 out of the 99 cases a priori fulfilled established criteria for diagnosis of BBS or BBS-like. BBS1 alleles, found in 42% of families, were the most represented in our cohort. An increased mutational load was excluded in 41% of the index cases (22/54). Oligogenic inheritance was suspected in 52% of the screened families (23/45), being 40 tested by means of NGS data and 5 only by traditional methods. Together, ORVAL and DiGePred platforms predicted an oligogenic effect in 44% of the triallelic families (10/23). Intrafamilial variable severity could be clinically confirmed in six of the families. Our findings show that the presence of more than two alleles in BBSassociated genes correlated in six families with a more severe phenotype and associated with specific findings, highlighting the role of the mutational load in the management of BBS casesInstituto de Salud Carlos III | Ref. PI15/00049Instituto de Salud Carlos III | Ref. PI16/00425Instituto de Salud Carlos III | Ref. PI19/00321Instituto de Salud Carlos III | Ref. PI19/00332CIBERER | Ref. 07/06/0036IIS-FJD BioBank | Ref. PT13/0010/0012Comunidad de Madrid | Ref. B2017/BMD-3721Xunta de Galicia | Ref. ED431G-2019/06Xunta de Galicia | Ref. ED431C-2018/54ISCIII | Ref. FI17/00192Ministerio de Educación, Cultura y Deporte | Ref. FPU 19/00175ISCIII | Ref. CP16/0011

Genetic landscape of 6089 inherited retinal dystrophies affected cases in Spain and their therapeutic and extended epidemiological implications

Inherited retinal diseases (IRDs), defined by dysfunction or progressive loss of photoreceptors, are disorders characterized by elevated heterogeneity, both at the clinical and genetic levels. Our main goal was to address the genetic landscape of IRD in the largest cohort of Spanish patients reported to date. A retrospective hospital-based cross-sectional study was carried out on 6089 IRD affected individuals (from 4403 unrelated families), referred for genetic testing from all the Spanish autonomous communities. Clinical, demographic and familiar data were collected from each patient, including family pedigree, age of appearance of visual symptoms, presence of any systemic findings and geographical origin. Genetic studies were performed to the 3951 families with available DNA using different molecular techniques. Overall, 53.2% (2100/3951) of the studied families were genetically characterized, and 1549 different likely causative variants in 142 genes were identified. The most common phenotype encountered is retinitis pigmentosa (RP) (55.6% of families, 2447/4403). The most recurrently mutated genes were PRPH2, ABCA4 and RS1 in autosomal dominant (AD), autosomal recessive (AR) and X-linked (XL) NON-RP cases, respectively; RHO, USH2A and RPGR in AD, AR and XL for non-syndromic RP; and USH2A and MYO7A in syndromic IRD. Pathogenic variants c.3386G > T (p.Arg1129Leu) in ABCA4 and c.2276G > T (p.Cys759Phe) in USH2A were the most frequent variants identified. Our study provides the general landscape for IRD in Spain, reporting the largest cohort ever presented. Our results have important implications for genetic diagnosis, counselling and new therapeutic strategies to both the Spanish population and other related populations.This work was supported by the Instituto de Salud Carlos III (ISCIII) of the Spanish Ministry of Health (FIS; PI16/00425 and PI19/00321), Centro de Investigación Biomédica en Red Enfermedades Raras (CIBERER, 06/07/0036), IIS-FJD BioBank (PT13/0010/0012), Comunidad de Madrid (CAM, RAREGenomics Project, B2017/BMD-3721), European Regional Development Fund (FEDER), the Organización Nacional de Ciegos Españoles (ONCE), Fundación Ramón Areces, Fundación Conchita Rábago and the University Chair UAM-IIS-FJD of Genomic Medicine. Irene Perea-Romero is supported by a PhD fellowship from the predoctoral Program from ISCIII (FI17/00192). Ionut F. Iancu is supported by a grant from the Comunidad de Madrid (CAM, PEJ-2017-AI/BMD7256). Marta del Pozo-Valero is supported by a PhD grant from the Fundación Conchita Rábago. Berta Almoguera is supported by a Juan Rodes program from ISCIII (JR17/00020). Pablo Minguez is supported by a Miguel Servet program from ISCIII (CP16/00116). Marta Corton is supported by a Miguel Servet program from ISCIII (CPII17/00006). The funders played no role in study design, data collection, data analysis, manuscript preparation and/or publication decisions

Overview of Five-Years of Experience Performing Non-Invasive Fetal Sex Assessment in Maternal Blood

Since the discovery of the presence of fetal DNA in maternal blood, non-invasive fetal sex determination has been the test most widely translated into clinical practice. To date there is no agreement between the different laboratories performing such tests in relation to which is the best protocol. As a consequence there are almost as many protocols as laboratories offering the service, using different methodologies and thus obtaining different diagnostic accuracies. By the end of 2007, after a validation study performed in 316 maternal samples collected between the 5th and 12th week of gestation, the fetal sex determination was incorporated into clinical practice in our Service. The test is performed in the first trimester of pregnancy, and it is offered as part of the genetic counseling process for couples at risk of X-linked disorders. As a general rule and in order to avoid misdiagnosis, two samples at different gestational ages are tested per patient. The analysis is performed by the study of the SRY gene by RT-PCR. Two hundred and twenty six pregnancies have been tested so far in these 5 years. Neither false positives nor false negatives diagnoses have been registered, thus giving a diagnostic accuracy of 100%

Frequency of CEP290 c.2991_1655A>G mutation in 175 Spanish families affected with Leber congenital amaurosis and early-onset retinitis pigmentosa

Leber congenital amaurosis (LCA; OMIM 204000) is the most severe form of inherited retinal dystrophy that presents in infancy LCA is generally inherited in an autosomal recessive manner, although some autosomal dominant families have been described The aim of the present study was to establish the prevalence of CEP290 c.2991_1655A>G in non-syndromic Spanish patients having LCA or early-onset retinitis pigmentosa (RP). METHODS A total of 175 Spanish patients with retinal dystrophy were studied for the c.2991_1655A>G mutation. Informed consent was obtained from all study participants or from their legal guardians in accordance with the tenets of the Declaration of Helsinki (Edinburgh, 2000). Of these 175 non-syndromic patients, two different cohorts were investigated individually: 49 families affected with LCA and 126 affected with early onset RP. We also recruited 50 unrelated Spanish healthy individuals and obtained DNA to use as a control panel. The difference between LCA and early-onset RP patients was established according to the age of onset. Children presenting congenital symptoms were considered as LCA phenotype, while children whose symptoms presented before they were 10 years old, but were not congenital, were classified as early-onset RP. Ophthalmic and electrophysiological evaluations were performed according to preexisting protocols, included comprehensive ophthalmological and family history, funduscopic examination after pupillary dilation, computerized testing of central and peripheral visual fields, and best corrected visual acuity. Peripheral blood samples were drawn and genomic DNA was extracted using an automated DNA extractor (BioRobot EZ1, Qiagen, Hilden, Germany). Purpose: Leber congenital amaurosis (LCA) is the most severe inherited retinopathy with the earliest age of onset. To date, eleven genes have been reported to cause the non-syndromic LCA phenotype. The CEP290 gene has been shown to account for Joubert and Senior-Loken syndromes and to represent a frequent cause of non-syndromic LCA. The aim of the present study was to establish the prevalence of CEP290 c.2991_1655A>G in non-syndromic Spanish patients having LCA or early-onset retinitis pigmentosa (RP). Methods: We used automated sequencing to examine 49 non-syndromic Spanish families with LCA and 126 Spanish families with early-onset RP for the CEP290 c.2991_1655A>G mutation. As a control, we recruited 50 unrelated Spanish healthy individuals. Results: The frequencies of mutated alleles were 6% in LCA cases and 0% in early-onset RP and healthy individual controls. These results were compared to other populations. Conclusions: The CEP290 c.2991_1655A>G mutation frequency in Spanish non-syndromic LCA families is lower than that of other countries. Correspondence to

Funduscopic photograph of a patient with autosomal recessive retinitis pigmentosa

<p><b>Copyright information:</b></p><p>Taken from "Molecular analysis of ABCA4 and CRB1 genes in a Spanish family segregating both Stargardt disease and autosomal recessive retinitis pigmentosa"</p><p></p><p>Molecular Vision 2008;14():262-267.</p><p>Published online 04 Feb 2008</p><p>PMCID:PMC2258218.</p><p></p> Funduscopy showed pigment spots homogeneously scattered through the retina with preservation of the paraarteriolar retinal pigmentary epithelium

Pedigrees from a Spanish family cosegregating Stargardt disease and early-onset retinitis pigmentosa

<p><b>Copyright information:</b></p><p>Taken from "Molecular analysis of ABCA4 and CRB1 genes in a Spanish family segregating both Stargardt disease and autosomal recessive retinitis pigmentosa"</p><p></p><p>Molecular Vision 2008;14():262-267.</p><p>Published online 04 Feb 2008</p><p>PMCID:PMC2258218.</p><p></p> : Haplotype analysis showing microsatellite markers flanking the gene (TEL-----CEN) confirmed the Stargardt disease phenotype in II:1. His affected sister (II:4) was found to be a carrier of one disease-associated allele. : Haplotype analysis with markers flanking the gene (TEL-D1S1660-- D1S2757- D1S2816-D1S408-CEN) showed cosegregation of the disease. Three brothers (II:1, II:2, II:3) were found to be carriers of the p.Cys948Tyr allele