PRPH2-Related Retinal Dystrophies: Mutational Spectrum in 103 Families from a Spanish Cohort.

PRPH2, one of the most frequently inherited retinal dystrophy (IRD)-causing genes, implies a high phenotypic variability. This study aims to analyze the PRPH2 mutational spectrum in one of the largest cohorts worldwide, and to describe novel pathogenic variants and genotype-phenotype correlations. A study of 220 patients from 103 families recruited from a database of 5000 families. A molecular diagnosis was performed using classical molecular approaches and next-generation sequencing. Common haplotypes were ascertained by analyzing single-nucleotide polymorphisms. We identified 56 variants, including 11 novel variants. Most of them were missense variants (64%) and were located in the D2-loop protein domain (77%). The most frequently occurring variants were p.Gly167Ser, p.Gly208Asp and p.Pro221_Cys222del. Haplotype analysis revealed a shared region in families carrying p.Leu41Pro or p.Pro221_Cys222del. Patients with retinitis pigmentosa presented an earlier disease onset. We describe the largest cohort of IRD families associated with PRPH2 from a single center. Most variants were located in the D2-loop domain, highlighting its importance in interacting with other proteins. Our work suggests a likely founder effect for the variants p.Leu41Pro and p.Pro221_Cys222del in our Spanish cohort. Phenotypes with a primary rod alteration presented more severe affectation. Finally, the high phenotypic variability in PRPH2 hinders the possibility of drawing genotype-phenotype correlations.

Comprehensive Genotyping and Phenotyping Analysis of GUCY2D-Associated Rod- and Cone-Dominated Dystrophies.

PURPOSE: To describe the genetic and clinical spectrum of GUCY2D-associated retinopathies and to accurately establish their prevalence in a large cohort of patients. DESIGN: Retrospective case series. METHODS: Institutional study of 47 patients from 27 unrelated families with retinal dystrophies carrying disease-causing GUCY2D variants from the Fundación Jiménez Díaz hospital dataset of 8000 patients. Patients underwent ophthalmological examination and molecular testing by Sanger or exome sequencing approaches. Statistical and principal component analyses were performed to determine genotype-phenotype correlations. RESULTS: Four clinically different associated phenotypes were identified: 66.7% of families with cone/cone-rod dystrophy, 22.2% with Leber congenital amaurosis, 7.4% with early-onset retinitis pigmentosa, and 3.7% with congenital night blindness. Twenty-three disease-causing GUCY2D variants were identified, including 6 novel variants. Biallelic variants accounted for 28% of patients, whereas most carried dominant alleles associated with cone/cone-rod dystrophy. The disease onset had statistically significant differences according to the functional variant effect. Patients carrying GUCY2D variants were projected into 3 subgroups by allelic combination, disease onset, and presence of nystagmus or night blindness. In contrast to patients with the most severe phenotype of Leber congenital amaurosis, 7 patients with biallelic GUCY2D had a later and milder rod form with night blindness in infancy as the first symptom. CONCLUSIONS: This study represents the largest GUCY2D cohort in which 4 distinctly different phenotypes were identified, including rare intermediate presentations of rod-dominated retinopathies. We established that GUCY2D is linked to about 1% of approximately 3000 molecularly characterized families of our cohort. All of these findings are critical for defining cohorts for inclusion in future clinical trials.

Análisis del rendimiento de la secuenciación del exoma clínico en hipogonadismo hipogonadotropo congénito teniendo en cuenta el grado de alteración del olfato / Diagnostic yield of clinical exome sequencing in congenital hypogonadotropic hypogonadism considering the degree of olfactory impairment

Introducción: El hipogonadismo hipogonadotropo congénito (HHC) puede presentarse de manera aislada o acompañado de anosmia o de malformaciones congénitas. Más de 30 genes han sido implicados en la patogénesis de HHC; además, se han descrito varios patrones de herencia asociados a esta entidad. La creciente disponibilidad de técnicas de secuenciación masiva (NGS) ha permitido que aumente el rendimiento diagnóstico del estudio de esta patología. Pacientes y métodos: Evaluamos el rendimiento diagnóstico del estudio mediante NGS de pacientes con HHC, usando la secuenciación del exoma clínico filtrado por paneles virtuales. Además, se analizó si el diseño de estos paneles, basándose en la presencia/ausencia de microsmia/anosmia aumentaban este rendimiento diagnóstico. Resultados: Usando un panel virtual compuesto de 34 genes pudimos confirmar el diagnóstico de HHC en cinco de nueve pacientes (55%). En dos de nueve individuos (22%) estudiados se obtuvieron resultados no concluyentes. La ausencia/presencia de microsmia para la elección de genes a estudiar no mejora el rendimiento diagnóstico. Conclusiones: El abordaje del estudio genético de pacientes con HHC puede variar en función de las técnicas disponibles en cada centro, por lo que la sensibilidad del test utilizado variará, dependiendo si se utiliza secuenciación de paneles, exoma clínico o exoma completo. El análisis de todos los genes relacionados con HHC independientemente de la presencia/ausencia de microsmia pareciera el abordaje con mejor rendimiento. (AU)

Introduction: Congenital hypogonadotropic hypogonadism (CHH) can present alone or in association with anosmia or other congenital malformations. More than 30 genes have been identified as being involved in the pathogenesis of CHH with different patterns of inheritance, and the increasing availability of next generation sequencing (NGS) has increased the diagnostic yield. Methods: We analysed the diagnostic yield of NGS in patients with CHH using the clinical exome filtered with virtual panels. We also assessed whether designing panels based on the presence/absence of microsmia increased the diagnostic yield. Results: The use of a 34-gene virtual panel confirmed the diagnosis of CHH in 5 out of 9 patients (55%). In 2 out of 9 (22%), the findings were inconclusive. Applying the presence/absence of microsmia criterion to choose genes for analysis did not improve the diagnostic yield. Conclusions: The approach to the genetic study of patients with CHH varies depending on the resources of each healthcare facility, so the sensitivity of testing may vary substantially depending on whether panels, clinical exome sequencing or whole exome sequencing (WES) are used. The analysis of every genes related to CHH regardless of the presence/absence of microsmia seems to be the best approach. (AU)

Aggregated Genomic Data as Cohort-Specific Allelic Frequencies can Boost Variants and Genes Prioritization in Non-Solved Cases of Inherited Retinal Dystrophies.

The introduction of NGS in genetic diagnosis has increased the repertoire of variants and genes involved and the amount of genomic information produced. We built an allelic-frequency (AF) database for a heterogeneous cohort of genetic diseases to explore the aggregated genomic information and boost diagnosis in inherited retinal dystrophies (IRD). We retrospectively selected 5683 index-cases with clinical exome sequencing tests available, 1766 with IRD and the rest with diverse genetic diseases. We calculated a subcohort's IRD-specific AF and compared it with suitable pseudocontrols. For non-solved IRD cases, we prioritized variants with a significant increment of frequencies, with eight variants that may help to explain the phenotype, and 10/11 of uncertain significance that were reclassified as probably pathogenic according to ACMG. Moreover, we developed a method to highlight genes with more frequent pathogenic variants in IRD cases than in pseudocontrols weighted by the increment of benign variants in the same comparison. We identified 18 genes for further studies that provided new insights in five cases. This resource can also help one to calculate the carrier frequency in IRD genes. A cohort-specific AF database assists with variants and genes prioritization and operates as an engine that provides a new hypothesis in non-solved cases, augmenting the diagnosis rate.

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 BBS-associated 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 cases.

Impact of Next Generation Sequencing in Unraveling the Genetics of 1036 Spanish Families With Inherited Macular Dystrophies.

Purpose: To assess the potential of next-generation sequencing (NGS) technologies to characterize cases diagnosed with autosomal recessive (ar) or sporadic (s) macular dystrophies (ar/sMD) and describe their mutational spectrum. Methods: A cohort of 1036 families was classified according to their suspected clinical diagnosis-Stargardt disease (STGD), cone and cone-rod dystrophy (CCRD) or other maculopathies (otherMD). Molecular studies included genotyping microarrays, Sanger sequencing, NGS, and sequencing of intronic regions of the ABCA4 gene. Clinical reclassification was done after the genetic study. Results: At the end of the study, 677 patients (65%) had a confirmed genetic diagnosis, representing 78%, 63%, and 38% of STGD, CCRD, and otherMD groups of patients, respectively. ABCA4 is the most mutated gene in all groups, and a second pathogenic variant was found in 76% of STGD patients with one previously identified mutated ABCA4 allele. Autosomal dominant or X-linked mutations were found in 5% of cases together with not-MD genes (CHM, EYS, RHO, RPGR, RLBP1, OPA1, and USH2A among others) leading to their reclassification. Novel variants in the very rare genes PLA2G5 and TTLL5 revealed additional phenotypic associations. Conclusions: This study provides for the first time a genetic landscape of 1036 ar/sMD families according to their suspected diagnosis. The analysis of >200 genes associated with retinal dystrophies and the entire locus of ABCA4 increase the rate of characterization, even regardless of available clinical and familiar data. The use of the suspected a priori diagnosis referred by the clinicians, especially in the past, could lead to clinical reclassifications to other inherited retinal dystrophies.

An evaluation of pipelines for DNA variant detection can guide a reanalysis protocol to increase the diagnostic ratio of genetic diseases.

Clinical exome (CE) sequencing has become a first-tier diagnostic test for hereditary diseases; however, its diagnostic rate is around 30-50%. In this study, we aimed to increase the diagnostic yield of CE using a custom reanalysis algorithm. Sequencing data were available for three cohorts using two commercial protocols applied as part of the diagnostic process. Using these cohorts, we compared the performance of general and clinically relevant variant calling and the efficacy of an in-house bioinformatic protocol (FJD-pipeline) in detecting causal variants as compared to commercial protocols. On the whole, the FJD-pipeline detected 99.74% of the causal variants identified by the commercial protocol in previously solved cases. In the unsolved cases, FJD-pipeline detects more INDELs and non-exonic variants, and is able to increase the diagnostic yield in 2.5% and 3.2% in the re-analysis of 78 cancer and 62 cardiovascular cases. These results were considered to design a reanalysis, filtering and prioritization algorithm that was tested by reassessing 68 inconclusive cases of monoallelic autosomal recessive retinal dystrophies increasing the diagnosis by 4.4%. In conclusion, a guided NGS reanalysis of unsolved cases increases the diagnostic yield in genetic disorders, making it a useful diagnostic tool in medical genetics.

Diagnostic yield of clinical exome sequencing in congenital hypogonadotropic hypogonadism considering the degree of olfactory impairment.

INTRODUCTION: Congenital hypogonadotropic hypogonadism (CHH) can present alone or in association with anosmia or other congenital malformations. More than 30 genes have been identified as being involved in the pathogenesis of CHH with different patterns of inheritance, and the increasing availability of next generation sequencing (NGS) has increased the diagnostic yield. METHODS: We analysed the diagnostic yield of NGS in patients with CHH using the clinical exome filtered with virtual panels. We also assessed whether designing panels based on the presence/absence of microsmia increased the diagnostic yield. RESULTS: The use of a 34-gene virtual panel confirmed the diagnosis of CHH in 5 out of 9 patients (55%) patients. In 2 out of 9 (22%), the findings were inconclusive. Applying the presence/absence of microsmia criterion to choose genes for analysis did not improve the diagnostic yield. CONCLUSIONS: The approach to the genetic study of patients with CHH varies depending on the resources of each healthcare facility, so the sensitivity of testing may vary substantially depending on whether panels, clinical exome sequencing or whole exome sequencing (WES) are used. The analysis of all genes related to CHH regardless of the presence/absence of microsmia seems to be the best approach.

Fine Breakpoint Mapping by Genome Sequencing Reveals the First Large X Inversion Disrupting the NHS Gene in a Patient with Syndromic Cataracts.

Inversions are structural variants that are generally balanced. However, they could lead to gene disruptions or have positional effects leading to diseases. Mutations in the NHS gene cause Nance-Horan syndrome, an X-linked disorder characterised by congenital cataracts and dental anomalies. Here, we aimed to characterise a balanced pericentric inversion X(p22q27), maternally inherited, in a child with syndromic bilateral cataracts by breakpoint mapping using whole-genome sequencing (WGS). 30× Illumina paired-end WGS was performed in the proband, and breakpoints were confirmed by Sanger sequencing. EdU assays and FISH analysis were used to assess skewed X-inactivation patterns. RNA expression of involved genes in the breakpoint boundaries was evaluated by droplet-digital PCR. We defined the breakpoint position of the inversion at Xp22.13, with a 15 bp deletion, disrupting the unusually large intron 1 of the canonical NHS isoform, and also perturbing topologically-associated domains (TADs). Moreover, a microhomology region of 5 bp was found on both sides. RNA analysis confirmed null and reduced NHS expression in the proband and his unaffected mother, respectively. In conclusion, we report the first chromosomal inversion disrupting NHS, fine-mapped by WGS. Our data expand the clinical spectrum and the pathogenic mechanisms underlying the NHS defects.

RPE65-related retinal dystrophy: Mutational and phenotypic spectrum in 45 affected patients.

INTRODUCTION: Biallelic pathogenic RPE65 variants are related to a spectrum of clinically overlapping inherited retinal dystrophies (IRD). Most affected individuals progress to severe disease, with 50% of patients becoming legally blind by 20 years of age. Deeper knowledge of the mutational spectrum and the phenotype-genotype correlation in RPE65-related IRD is needed. PATIENTS AND METHODS: Forty-five affected subjects from 27 unrelated families with a clinical diagnosis of RPE65-related IRD were included. Clinical evaluation consisted of self-reported ophthalmological history and objective ophthalmological examination. Patients' genotype was classified according to variant class (truncating or missense) or to variant location at different protein domains. The main phenotypic outcome measure was age at onset (AAO) of symptomatic disease and a Kaplan-Meier analysis of disease symptom event-free survival was performed. RESULTS: Twenty-nine different RPE65 variants were identified in our cohort, 7 of them novel. Patients carrying two missense alleles showed a later disease onset than those with 1 or 2 truncating variants (log-rank test p <0.05). While 60% of patients carrying a missense/missense genotype presented symptoms before or during the first year of life, almost all patients with at least 1 truncating allele (91%) had an AAO ≤1 year (p <0.05). CONCLUSION: Our findings suggest an association between the type of RPE65 variant carried and AAO. These findings provide useful data on RPE65-associated IRD phenotypes and may help improve clinical and therapeutic management of these patients.

Spotted bones in an osteopoikilosis-related disease (Buschke Ollendorff Syndrome): Identifying this rare condition from the lab to the field.

OBJECTIVE: To improve the differential diagnosis of osteopoikilosis in past populations using a clinical case as an example of this rare condition. MATERIALS: A patient referred to our Genetic Service with suspected Buschke Ollendorff Syndrome after finding a connective nevus. METHODS: Radiological images from different body regions were accompanied by a genetic study using next-generation sequencing. RESULTS: Small circular-to-ellipsoid sclerotic lesions were found in the epiphysis and metaphysis of long bones, as well as in the pelvis. These lesions were bilaterally distributed and with well-defined margins, compatible with the characteristics of Buschke Ollendorff Syndrome, bone manifestation osteopoikilosis. A heterozygous mutation on LEMD3 (NM_001167614:c.1918 + 1G > C) was identified by next-generation sequencing. Based on this confirmed case, we have discussed the most probable causes of similar bone lesions found in the archaeological record. CONCLUSION: It has been demonstrated how a current case of a rare disease can provide useful tools to improve the differential diagnosis of this disease in ancient skeletons. SIGNIFICANCE: This work underlines the great need for multidisciplinary platforms that integrates clinical research into paleopathology in order to successfully address the study of rare diseases from the past. LIMITATIONS: Since OPK is only detected by X-rays, suspected cases of this bone lesion will only be identified when radiographs are taken for other purposes. SUGGESTIONS FOR FURTHER RESEARCH: Retrospective and large-scale studies of radiographs from other research in past populations.

[Diagnostic yield of clinical exome sequencing in congenital hypogonadotropic hypogonadism considering the degree of olfactory impairment]. / Análisis del rendimiento de la secuenciación del exoma clínico en hipogonadismo hipogonadotropo congénito teniendo en cuenta el grado de alteración del olfato.

INTRODUCTION: Congenital hypogonadotropic hypogonadism (CHH) can present alone or in association with anosmia or other congenital malformations. More than 30 genes have been identified as being involved in the pathogenesis of CHH with different patterns of inheritance, and the increasing availability of next generation sequencing (NGS) has increased the diagnostic yield. METHODS: We analysed the diagnostic yield of NGS in patients with CHH using the clinical exome filtered with virtual panels. We also assessed whether designing panels based on the presence/absence of microsmia increased the diagnostic yield. RESULTS: The use of a 34-gene virtual panel confirmed the diagnosis of CHH in 5 out of 9 patients (55%). In 2 out of 9 (22%), the findings were inconclusive. Applying the presence/absence of microsmia criterion to choose genes for analysis did not improve the diagnostic yield. CONCLUSIONS: The approach to the genetic study of patients with CHH varies depending on the resources of each healthcare facility, so the sensitivity of testing may vary substantially depending on whether panels, clinical exome sequencing or whole exome sequencing (WES) are used. The analysis of every genes related to CHH regardless of the presence/absence of microsmia seems to be the best approach.

Comparison of the diagnostic yield of aCGH and genome-wide sequencing across different neurodevelopmental disorders.

Most consensus recommendations for the genetic diagnosis of neurodevelopmental disorders (NDDs) do not include the use of next generation sequencing (NGS) and are still based on chromosomal microarrays, such as comparative genomic hybridization array (aCGH). This study compares the diagnostic yield obtained by aCGH and clinical exome sequencing in NDD globally and its spectrum of disorders. To that end, 1412 patients clinically diagnosed with NDDs and studied with aCGH were classified into phenotype categories: global developmental delay/intellectual disability (GDD/ID); autism spectrum disorder (ASD); and other NDDs. These categories were further subclassified based on the most frequent accompanying signs and symptoms into isolated forms, forms with epilepsy; forms with micro/macrocephaly and syndromic forms. Two hundred and forty-five patients of the 1412 were subjected to clinical exome sequencing. Diagnostic yield of aCGH and clinical exome sequencing, expressed as the number of solved cases, was compared for each phenotype category and subcategory. Clinical exome sequencing was superior than aCGH for all cases except for isolated ASD, with no additional cases solved by NGS. Globally, clinical exome sequencing solved 20% of cases (versus 5.7% by aCGH) and the diagnostic yield was highest for all forms of GDD/ID and lowest for Other NDDs (7.1% versus 1.4% by aCGH) and ASD (6.1% versus 3% by aCGH). In the majority of cases, diagnostic yield was higher in the phenotype subcategories than in the mother category. These results suggest that NGS could be used as a first-tier test in the diagnostic algorithm of all NDDs followed by aCGH when necessary.

Prioritizing variants of uncertain significance for reclassification using a rule-based algorithm in inherited retinal dystrophies.

Inherited retinal dystrophies (IRD) are a highly heterogeneous group of rare diseases with a molecular diagnostic rate of >50%. Reclassification of variants of uncertain significance (VUS) poses a challenge for IRD diagnosis. We collected 668 IRD cases analyzed by our geneticists using two different clinical exome-sequencing tests. We identified 114 unsolved cases pending reclassification of 125 VUS and studied their genomic, functional, and laboratory-specific features, comparing them to pathogenic and likely pathogenic variants from the same cohort (N = 390). While the clinical exome used did not show differences in diagnostic rate, the more IRD-experienced geneticist reported more VUS (p = 4.07e-04). Significantly fewer VUS were reported in recessive cases (p = 2.14e-04) compared to other inheritance patterns, and of all the genes analyzed, ABCA4 and IMPG2 had the lowest and highest VUS frequencies, respectively (p = 3.89e-04, p = 6.93e-03). Moreover, few frameshift and stop-gain variants were found to be informed VUS (p = 6.73e-08 and p = 2.93e-06). Last, we applied five pathogenicity predictors and found there is a significant proof of deleteriousness when all score for pathogenicity in missense variants. Altogether, these results provided input for a set of rules that correctly reclassified ~70% of VUS as pathogenic in validation datasets. Disease- and setting-specific features influence VUS reporting. Comparison with pathogenic and likely pathogenic variants can prioritize VUS more likely to be reclassified as causal.

Genotype-Phenotype Correlations in a Spanish Cohort of 506 Families With Biallelic ABCA4 Pathogenic Variants.

PURPOSE: To define genotype-phenotype correlations in the largest cohort study worldwide of patients with biallelic ABCA4 variants, including 434 patients with Stargardt disease (STGD1) and 72 with cone-rod dystrophy (CRD). DESIGN: Cohort study. METHODS: We characterized 506 patients with ABCA4 variants using conventional genetic tools and next-generation sequencing technologies. Medical history and ophthalmologic data were obtained from 372 patients. Genotype-phenotype correlation studies were carried out for the following variables: variant type, age at symptom onset (AO), and clinical phenotype. RESULTS: A total of 228 different pathogenic variants were identified in 506 ABCA4 patients, 50 of which were novel. Genotype-phenotype correlations showed that most of the patients with biallelic truncating variants presented with CRD and that these cases had a significantly earlier AO than patients with STGD1. Three missense variants are associated with CRD for the first time (c.1804C>T; p.[Arg602Trp], c.3056C>T; p.[Thr1019Met], and c.6320G>C; p.[Arg2107Pro]). Analysis of the most prevalent ABCA4 variant in Spain, c.3386G>T; p.(Arg1129Leu), revealed that is correlated to STGD1, later AO, and foveal sparing. CONCLUSIONS: Our study, conducted in the largest ABCA4-associated disease cohort reported to date, updates the genotype-phenotype model established for ABCA4 variants and broadens the mutational spectrum of the gene. According to our observations, patients with ABCA4 presenting with 2 truncating variants may first present features of STGD1 but eventually develop rod dysfunction, and specific missense variants may be associated with a different phenotype, underscoring the importance of an accurate genetic diagnosis. Also, it is a prerequisite for enrollment in clinical trials, and to date, no other treatment has been approved for STGD1.

Genomic Landscape of Sporadic Retinitis Pigmentosa: Findings from 877 Spanish Cases.

PURPOSE: We aimed to unravel the molecular basis of sporadic retinitis pigmentosa (sRP) in the largest cohort reported to date. DESIGN: Case series. PARTICIPANTS: A cohort of 877 unrelated Spanish sporadic cases with a clinical diagnosis of retinitis pigmentosa (RP) and negative family history. METHODS: The cohort was studied by classic genotyping or targeted next-generation sequencing (NGS). Multiplex ligation-dependent probe amplification (MLPA) and array-based comparative genomic hybridization were performed to confirm copy number variations detected by NGS. Quantitative fluorescent polymerase chain reaction was assessed in sRP cases carrying de novo variants to confirm paternity. MAIN OUTCOME MEASURES: The study of the sRP cohort showed a high proportion of causal autosomal dominant (AD) and X-linked (XL) variants, most of them being de novo. RESULTS: Causative variants were identified in 38% of the patients studied, segregating recessively in 84.5% of the solved cases. Biallelic variants detected in only 6 different autosomal recessive genes explained 50% of the cases characterized. Causal AD and XL variants were found in 7.6% and 7.9% of cases, respectively. Remarkably, 20 de novo variants were confirmed after trio analysis, explaining 6% of the cases. In addition, 17% of the solved sRP cases were reclassified to a different retinopathy phenotype. CONCLUSIONS: This study highlights the clinical utility of NGS testing for sRP cases, expands the mutational spectrum, and provides accurate prevalence of mutated genes. Our findings evidence the underestimated role of de novo variants in the etiology of RP, emphasizing the importance of segregation analysis as well as comprehensive screening of genes carrying XL and AD variants in sporadic cases. Such in-depth study is essential for accurate family counseling and future enrollment in gene therapy-based treatments.

Recomendaciones para el uso de microarrays en el diagnóstico prenatal / Recommendations for the use of microarrays in prenatal diagnosis

La tecnología de microarrays, de reciente implantación en el diagnóstico prenatal internacional, se ha convertido en uno de los pilares de este diagnóstico en cuanto a su capacidad de detección y objetividad de resultados. La presente guía comprende una exposición general de la tecnología, incluyendo aspectos técnicos y diagnósticos a tener en cuenta. En concreto, se definen: los distintos tipos de muestras prenatales que se van a utilizar (biopsia de vellosidades coriónicas, líquido amniótico, sangre procedente de cordón umbilical o material procedente de restos abortivos) así como las particularidades de cada una de ellas; qué puntos hay que tener en cuenta de cara a la elaboración de un consentimiento informado y de la emisión de un informe de microarray prenatal, especialmente en el caso de la posible definición de variantes de significado incierto; las limitaciones inherentes a la técnica que deben ser tenidas en cuenta a la hora de recomendar su uso diagnóstico; así como un algoritmo pormenorizado de situaciones clínicas, donde se recomienda el uso de microarrays y su incorporación a la rutina clínica en el contexto de otras pruebas genéticas, incluyendo embarazos con antecedentes familiares o hallazgos sugerentes de un síndrome concreto, translucencia nucal incrementada en el primer trimestre o cardiopatía congénita en el segundo trimestre y hallazgos ecográficos no relacionados con un síndrome conocido o específico. Esta guía ha sido coordinada por la Asociación Española de Diagnóstico Prenatal (AEDP), la Asociación Española de Genética Humana (AEGH) y la Sociedad Española de Genética Clínica y Dismorfología (SEGCyD) (AU)

Microarray technology, recently implemented in international prenatal diagnosis systems, has become one of the main techniques in this field in terms of detection rate and objectivity of the results. This guideline attempts to provide background information on this technology, including technical and diagnostic aspects to be considered. Specifically, this guideline defines: the different prenatal sample types to be used, as well as their characteristics (chorionic villi samples, amniotic fluid, fetal cord blood or miscarriage tissue material); variant reporting policies (including variants of uncertain significance) to be considered in informed consents and prenatal microarray reports; microarray limitations inherent to the technique and which must be taken into account when recommending microarray testing for diagnosis; a detailed clinical algorithm recommending the use of microarray testing and its introduction into routine clinical practice within the context of other genetic tests, including pregnancies in families with a genetic history or specific syndrome suspicion, first trimester increased nuchal translucency or second trimester heart malformation and ultrasound findings not related to a known or specific syndrome. This guideline has been coordinated by the Spanish Association for Prenatal Diagnosis (AEDP, «Asociación Española de Diagnóstico Prenatal»), the Spanish Human Genetics Association (AEGH, «Asociación Española de Genética Humana») and the Spanish Society of Clinical Genetics and Dysmorphology (SEGCyD, «Sociedad Española de Genética Clínica y Dismorfología») (AU)

Recommendations for the use of microarrays in prenatal diagnosis. / Recomendaciones para el uso de microarrays en el diagnóstico prenatal.

Microarray technology, recently implemented in international prenatal diagnosis systems, has become one of the main techniques in this field in terms of detection rate and objectivity of the results. This guideline attempts to provide background information on this technology, including technical and diagnostic aspects to be considered. Specifically, this guideline defines: the different prenatal sample types to be used, as well as their characteristics (chorionic villi samples, amniotic fluid, fetal cord blood or miscarriage tissue material); variant reporting policies (including variants of uncertain significance) to be considered in informed consents and prenatal microarray reports; microarray limitations inherent to the technique and which must be taken into account when recommending microarray testing for diagnosis; a detailed clinical algorithm recommending the use of microarray testing and its introduction into routine clinical practice within the context of other genetic tests, including pregnancies in families with a genetic history or specific syndrome suspicion, first trimester increased nuchal translucency or second trimester heart malformation and ultrasound findings not related to a known or specific syndrome. This guideline has been coordinated by the Spanish Association for Prenatal Diagnosis (AEDP, «Asociación Española de Diagnóstico Prenatal¼), the Spanish Human Genetics Association (AEGH, «Asociación Española de Genética Humana¼) and the Spanish Society of Clinical Genetics and Dysmorphology (SEGCyD, «Sociedad Española de Genética Clínica y Dismorfología¼).

Improving molecular diagnosis of aniridia and WAGR syndrome using customized targeted array-based CGH.

Chromosomal deletions at 11p13 are a frequent cause of congenital Aniridia, a rare pan-ocular genetic disease, and of WAGR syndrome, accounting up to 30% of cases. First-tier genetic testing for newborn with aniridia, to detect 11p13 rearrangements, includes Multiplex Ligation-dependent Probe Amplification (MLPA) and karyotyping. However, neither of these approaches allow obtaining a complete picture of the high complexity of chromosomal deletions and breakpoints in aniridia. Here, we report the development and validation of a customized targeted array-based comparative genomic hybridization, so called WAGR-array, for comprehensive high-resolution analysis of CNV in the WAGR locus. Our approach increased the detection rate in a Spanish cohort of 38 patients with aniridia, WAGR syndrome and other related ocular malformations, allowing to characterize four undiagnosed aniridia cases, and to confirm MLPA findings in four additional patients. For all patients, breakpoints were accurately established and a contiguous deletion syndrome, involving a large number of genes, was identified in three patients. Moreover, we identified novel microdeletions affecting 3' PAX6 regulatory regions in three families with isolated aniridia. This tool represents a good strategy for the genetic diagnosis of aniridia and associated syndromes, allowing for a more accurate CNVs detection, as well as a better delineation of breakpoints. Our results underline the clinical importance of performing exhaustive and accurate analysis of chromosomal rearrangements for patients with aniridia, especially newborns and those without defects in PAX6 after diagnostic screening.

The p. R151C Polymorphism in MC1R Gene Modifies the Age of Onset in Spanish Huntington's Disease Patients.

The expansion of CAG repeats (≥36 CAG) in the HTT gene is the only known genetic cause of Huntington's disease (HD) and the main determinant of the course of the disease. The length of the expanded CAG repeats correlates inversely with the age of onset (AOO) but does not completely determine it. We investigated the role of the melanocortin 1 receptor (MC1R) gene as a modifier factor of AOO in 600 HD patients from Spain. We sequenced the entire region of the MC1R gene and analyzed all the nonsynonymous MC1R genetic variants with a minor allele frequency of at least 0.01 in HD patients. The variability in AOO attributable to the CAG repeats and MC1R polymorphisms was evaluated using a multiple linear regression model. We found that the loss-of-function p. R151C MC1R polymorphism has a significant influence on the AOO (P = 0.004; Bonferroni-corrected P = 0.032) which explains 1.42% of the variance in AOO that cannot be accounted for by the expanded CAG repeat. Our results suggest that the MC1R gene could modify the AOO in Spanish HD patients and encourage the evaluation of loss-of-function MC1R polymorphisms in other HD populations with a higher frequency of these MC1R polymorphisms.