High-throughput mutation detection method to scan BRCA1 and BRCA2 based on heteroduplex analysis by capillary array electrophoresis

8 páginas, 3 figuras, 2 tablas.[Background]: Scanning for mutations in BRCA1 and BRCA2 in a large number of samples is hampered by the large sizes of these genes and the scattering of mutations throughout their coding sequences. Automated capillary electrophoresis has been shown to be a powerful system to detect mutations by either single-strand conformation polymorphism or heteroduplex analysis (HA). [Methods]: We investigated the adaptation of gel-based HA of BRCA1 and BRCA2 to a fluorescent multicapillary platform to increase the throughput of this technique. We combined multiplex PCR, three different fluorescent labels, and HA in a 16-capillary DNA sequencer and tested 57 DNA sequence variants (11 insertions/deletions and 46 single-nucleotide changes) of BRCA1 and BRCA2. [Results]: We detected all 57 DNA changes in a blinded assay, and 2 additional single-nucleotide substitutions (1186 A>G of BRCA1 and 3624 A>G of BRCA2), previously unresolved by conformation-sensitive gel electrophoresis. Furthermore, different DNA changes in the same PCR fragment could be distinguished by their peak patterns. [Conclusions]: Capillary-based HA is a fast, efficient, and sensitive method that considerably reduces the amount of “hands-on” time for each sample. By this approach, the entire coding regions of BRCA1 and BRCA2 from two breast cancer patients can be scanned in a single run of 90 min.This work was supported by the Consejería de Sanidad (Junta y Castilla y León) through the regional Breast Cancer Prevention Program.Peer reviewe

Analysis of PALB2 gene in BRCA1/BRCA2 negative Spanish hereditary breast/ovarian cancer families with pancreatic cancer cases

This is an open-access article distributed under the terms of the Creative Commons Attribution License.-- et al.[Background]: The PALB2 gene, also known as FANCN, forms a bond and co-localizes with BRCA2 in DNA repair. Germline mutations in PALB2 have been identified in approximately 1% of familial breast cancer and 3–4% of familial pancreatic cancer. The goal of this study was to determine the prevalence of PALB2 mutations in a population of BRCA1/BRCA2 negative breast cancer patients selected from either a personal or family history of pancreatic cancer. [Methods]: 132 non-BRCA1/BRCA2 breast/ovarian cancer families with at least one pancreatic cancer case were included in the study. PALB2 mutational analysis was performed by direct sequencing of all coding exons and intron/exon boundaries, as well as multiplex ligation-dependent probe amplification. [Results]: Two PALB2 truncating mutations, the c.1653T>A (p.Tyr551Stop) previously reported, and c.3362del (p.Gly1121ValfsX3) which is a novel frameshift mutation, were identified. Moreover, several PALB2 variants were detected; some of them were predicted as pathological by bioinformatic analysis. Considering truncating mutations, the prevalence rate of our population of BRCA1/2-negative breast cancer patients with pancreatic cancer is 1.5%. [Conclusions]: The prevalence rate of PALB2 mutations in non-BRCA1/BRCA2 breast/ovarian cancer families, selected from either a personal or family pancreatic cancer history, is similar to that previously described for unselected breast/ovarian cancer families. Future research directed towards identifying other gene(s) involved in the development of breast/pancreatic cancer families is required.This research was supported by grants from the Xunta de Galicia (10PXIB 9101297PR) and FMM Foundation given to AV. MH was supported from the Instituto de Salud Carlos III, Fondo de Investigación Sanitaria (FIS) Research Grant 09/00859, and Fundación Mutua Madrileña (FMM) Research Grant FMM-08. SGE is supported by a Miguel Servet contract of the Instituto de Salud Carlos III. EAV was supported in part by grants BIO39/VA27/10 (Consejería de Sanidad) and CSI004A10-2 (Consejería de Educación) from the Junta de Castilla y León.Peer Reviewe

Functional analyses of a novel splice variant in the CHD7 gene, found by next generation sequencing, Confirm Its pathogenicity in a Spanish patient and diagnose him with CHARGE syndrome

Mutations in CHD7 have been shown to be a major cause of CHARGE syndrome, which presents many symptoms and features common to other syndromes making its diagnosis difficult. Next generation sequencing (NGS) of a panel of intellectual disability related genes was performed in an adult patient without molecular diagnosis. A splice donor variant in CHD7 (c.5665 + 1G > T) was identified. To study its potential pathogenicity, exons and flanking intronic sequences were amplified from patient DNA and cloned into the pSAD® splicing vector. HeLa cells were transfected with this construct and a wild-type minigene and functional analysis were performed. The construct with the c.5665 + 1G > T variant produced an aberrant transcript with an insert of 63 nucleotides of intron 28 creating a premature termination codon (TAG) 25 nucleotides downstream. This would lead to the insertion of 8 new amino acids and therefore a truncated 1896 amino acid protein. As a result of this, the patient was diagnosed with CHARGE syndrome. Functional analyses underline their usefulness for studying the pathogenicity of variants found by NGS and therefore its application to accurately diagnose patients.This work was funded by Jesús de Gangoiti Barrera Foundation (FJGB15/005). The EAV laboratory is funded by projects of the Spanish Ministry of Economy and Competitiveness, National Plan for R & D 2013–2016, ISCIII (FIS: PI13/01749) co-financed by FEDER from Regional Development European Funds (European Union) and the project CSI090U14 of the Regional ministry of Education (ORDER EDU/122/2014) (Castilla y León, Spain). This study made use of data generated by the UK10K Project. Funding for the UK10K Project was provided by the Wellcome Trust under award WT091310.Peer reviewe

Functional classification of DNA variants by hybrid minigenes: identification of 30 spliceogenic variants of BRCA2 exons 17 and 18

Mutation screening of the breast cancer genes BRCA1 and BRCA2 identifies a large fraction of variants of uncertain clinical significance (VUS) whose functional and clinical interpretations pose a challenge for genomic medicine. Likewise, an increasing amount of evidence indicates that genetic variants can have deleterious effects on pre-mRNA splicing. Our goal was to investigate the impact on splicing of a set of reported variants of BRCA2 exons 17 and 18 to assess their role in hereditary breast cancer and to identify critical regulatory elements that may constitute hotspots for spliceogenic variants. A splicing reporter minigene with BRCA2 exons 14 to-20 (MGBR2_ ex14-20) was constructed in the pSAD vector. Fiftytwo candidate variants were selected with splicing prediction programs, introduced in MGBR2_ ex14-20 by site-directed mutagenesis and assayed in triplicate in MCF-7 cells. Wild type MGBR2_ ex14-20 produced a stable transcript of the expected size (1,802 nucleotides) and structure (V1-[BRCA2_ exons_ 14-20]-V2). Functional mapping by microdeletions revealed essential sequences for exon recognition on the 3 ' end of exon 17 (c. 79447973) and the 5 ' end of exon 18 (c. 7979-7988, c. 7999-8013). Thirty out of the 52 selected variants induced anomalous splicing in minigene assays with > 16 different aberrant transcripts, where exon skipping was the most common event. A wide range of splicing motifs were affected including the canonical splice sites (15 variants), novel alternative sites (3 variants), the polypyrimidine tract (3 variants) and enhancers/silencers (9 variants). According to the guidelines of the American College of Medical Genetics and Genomics (ACMG), 20 variants could be classified as pathogenic (c. 7806-2A > G, c. 7806-1G > A, c. 7806-1G > T, c. 7806-1_ 7806-2dup, c. 7976+ 1G > A, c. 7977-3_ 7978del, c. 7977-2A > T, c. 7977-1G > T, c. 7977-1G > C, c. 8009C > A, c. 8331+ 1G > T and c. 8331+ 2T > C) or likely pathogenic (c. 78069T > G, c. 7976G > C, c. 7976G > A, c. 7977-7C > G, c. 7985C > G, c. 8023A > G, c. 8035G > T and c. 8331G > A), accounting for 30.8% of all pathogenic/likely pathogenic variants of exons 17-18 at the BRCA Share database. The remaining 8 variants (c. 7975A > G, c. 7977-6T > G, c. 7988A > T, c. 7992T > A, c. 8007A > G, c. 8009C > T, c. 8009C > G, and c. 8072C > T) induced partial splicing anomalies with important ratios of the full-length transcript (>= 70%), so that they remained classified as VUS. Aberrant splicing is therefore especially prevalent in BRCA2 exons 17 and 18 due to the presence of active ESEs involved in exon recognition. Splicing functional assays with minigenes are a valuable strategy for the initial characterization of the splicing outcomes and the subsequent clinical interpretation of variants of any disease-gene, although these results should be checked, whenever possible, against patient RNA

Germline variants of CYBA and TRPM4 predispose to familial colorectal cancer

Simple Summary Whole-genome sequencing and bioinformatics analysis on unique colorectal cancer families revealed two attractive candidate predisposition genes, CYBA and TRPM4, each with a loss-of-function variant. Supported by our functional studies, we suggest that the two gene defects mechanistically involve intestinal barrier integrity through reactive oxygen species and mucus biology, which converges in chronic bowel inflammation, a known risk factor for colorectal cancer. Abstract Familial colorectal cancer (CRC) is only partially explained by known germline predisposing genes. We performed whole-genome sequencing in 15 Polish families of many affected individuals, without mutations in known CRC predisposing genes. We focused on loss-of-function variants and functionally characterized them. We identified a frameshift variant in the CYBA gene (c.246delC) in one family and a splice site variant in the TRPM4 gene (c.25–1 G > T) in another family. While both variants were absent or extremely rare in gene variant databases, we identified four additional Polish familial CRC cases and two healthy elderly individuals with the CYBA variant (odds ratio 2.46, 95% confidence interval 0.48–12.69). Both variants led to a premature stop codon and to a truncated protein. Functional characterization of the variants showed that knockdown of CYBA or TRPM4 depressed generation of reactive oxygen species (ROS) in LS174T and HT-29 cell lines. Knockdown of TRPM4 resulted in decreased MUC2 protein production. CYBA encodes a component in the NADPH oxidase system which generates ROS and controls, e.g., bacterial colonization in the gut. Germline CYBA variants are associated with early onset inflammatory bowel disease, supported with experimental evidence on loss of intestinal mucus barrier function due to ROS deficiency. TRPM4 encodes a calcium-activated ion channel, which, in a human colonic cancer cell line, controls calcium-mediated secretion of MUC2, a major component of intestinal mucus barrier. We suggest that the gene defects in CYBA and TRPM4 mechanistically involve intestinal barrier integrity through ROS and mucus biology, which converges in chronic bowel inflammation

Minigene Splicing Assays Identify 12 Spliceogenic Variants of BRCA2 Exons 14 and 15

A relevant fraction of BRCA2 variants is associated with splicing alterations and with an increased risk of hereditary breast and ovarian cancer (HBOC). In this work, we have carried out a thorough study of variants from BRCA2 exons 14 and 15 reported at mutation databases. A total of 294 variants from exons 14 and 15 and flanking intronic sequences were analyzed with the online splicing tools NNSplice and Human Splicing Finder. Fifty-three out of these 294 variants were selected as candidate splicing variants. All variants but one, were introduced into the minigene MGBR2_ex14-20 (with exons 14–20) by site-directed mutagenesis and assayed in MCF-7 cells. Twelve of the remaining 52 variants (23.1%) impaired splicing at different degrees, yielding from 5 to 100% of aberrant transcripts. Nine variants affected the natural acceptor or donor sites of both exons and three affected putative enhancers or silencers. Fluorescent capillary electrophoresis revealed at least 10 different anomalous transcripts: (E14q5), Δ (E14p10), Δ(E14p246), Δ(E14q256), Δ(E14), Δ(E15p12), Δ(E15p13), Δ(E15p83), Δ(E15) and a 942-nt fragment of unknown structure. All transcripts, except for Δ(E14q256) and Δ(E15p12), are expected to truncate the BRCA2 protein. Nine variants induced severe splicing aberrations with more than 90% of abnormal transcripts. Thus, according to the guidelines of the American College of Medical Genetics and Genomics, eight variants should be classified as pathogenic (c.7008-2A > T, c.7008-1G > A, c.7435+1G > C, c.7436-2A > T, c.7436-2A > G, c.7617+1G > A, c.7617+1G > T, and c.7617+2T > G), one as likely pathogenic (c.7008-3C > G) and three remain as variants of uncertain clinical significance or VUS (c.7177A > G, c.7447A > G and c.7501C > T). In conclusion, functional assays by minigenes constitute a valuable strategy to primarily check the splicing impact of DNA variants and their clinical interpretation. While bioinformatics predictions of splice site variants were accurate, those of enhancer or silencer variants were poor (only 3/23 spliceogenic variants) which showed weak impacts on splicing (∼5–16% of aberrant isoforms). So, the Exonic Splicing Enhancer and Silencer (ESE and ESS, respectively) prediction algorithms require further improvement

Comprehensive Functional Characterization and Clinical Interpretation of 20 Splice-Site Variants of the RAD51C Gene

Hereditary breast and/or ovarian cancer is a highly heterogeneous disease with more than 10 known disease-associated genes. In the framework of the BRIDGES project (Breast Cancer Risk after Diagnostic Gene Sequencing), the RAD51C gene has been sequenced in 60,466 breast cancer patients and 53,461 controls. We aimed at functionally characterizing all the identified genetic variants that are predicted to disrupt the splicing process. Forty RAD51C variants of the intron-exon boundaries were bioinformatically analyzed, 20 of which were selected for splicing functional assays. To test them, a splicing reporter minigene with exons 2 to 8 was designed and constructed. This minigene generated a full-length transcript of the expected size (1062 nucleotides), sequence, and structure (Vector exon V1- RAD51C exons_2-8- Vector exon V2). The 20 candidate variants were genetically engineered into the wild type minigene and functionally assayed in MCF-7 cells. Nineteen variants (95%) impaired splicing, while 18 of them produced severe splicing anomalies. At least 35 transcripts were generated by the mutant minigenes: 16 protein-truncating, 6 in-frame, and 13 minor uncharacterized isoforms. According to ACMG/AMP-based standards, 15 variants could be classified as pathogenic or likely pathogenic variants: c.404G > A, c.405-6T > A, c.571 + 4A > G, c.571 + 5G > A, c.572-1G > T, c.705G > T, c.706-2A > C, c.706-2A > G, c.837 + 2T > C, c.905-3C > G, c.905-2A > C, c.905-2_905-1del, c.965 + 5G > A, c.1026 + 5_1026 + 7del, and c.1026 + 5G > T

Splicing predictions, minigene analyses, and ACMG-AMP clinical classification of 42 germline PALB2 splice-site variants.

PALB2 loss-of-function variants confer high risk of developing breast cancer. Here we present a systematic functional analysis of PALB2 splice-site variants detected in approximately 113,000 women in the large-scale sequencing project Breast Cancer After Diagnostic Gene Sequencing (BRIDGES; https://bridges-research.eu/). Eighty-two PALB2 variants at the intron-exon boundaries were analyzed with MaxEntScan. Forty-two variants were selected for the subsequent splicing functional assays. For this purpose, three splicing reporter minigenes comprising exons 1-12 were constructed. The 42 potential spliceogenic variants were introduced into the minigenes by site-directed mutagenesis and assayed in MCF-7/MDA-MB-231 cells. Splicing anomalies were observed in 35 variants, 23 of which showed no traces or minimal amounts of the expected full-length transcripts of each minigene. More than 30 different variant-induced transcripts were characterized, 23 of which were predicted to truncate the PALB2 protein. The pathogenicity of all variants was interpreted according to an in-house adaptation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP) variant classification scheme. Up to 23 variants were classified as pathogenic/likely pathogenic. Remarkably, three ±1,2 variants (c.49-2A>T, c.108+2T>C, and c.211+1G>A) were classified as variants of unknown significance, as they produced significant amounts of either in-frame transcripts of unknown impact on the PALB2 protein function or the minigene full-length transcripts. In conclusion, we have significantly contributed to the ongoing effort of identifying spliceogenic variants in the clinically relevant PALB2 cancer susceptibility gene. Moreover, we suggest some approaches to classify the findings in accordance with the ACMG-AMP rationale. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd on behalf of The Pathological Society of Great Britain and Ireland

NEWSHUB: Incubadora de contenidos formativos para la comunicación profesional de los resultados del Aprendizaje Basado en Proyectos (ABP)

NEWSHUB es un espacio de encuentro académico y profesional. Su principal función es cubrir necesidades específicas de formación tanto para el profesorado como para el alumnado en materia de comunicación. La finalidad es facilitar que se diseñen actividades de aprendizaje basado en proyectos orientadas a generar productos comunicativos de calidad profesional, que sirvan a un tiempo como herramienta eficiente de aprendizaje en el entorno académico además de recurso destacado en el porfolio del alumnado para la búsqueda de empleo o la formalización de proyectos emprendedores. NEWSHUB es una incubadora de proyectos. Rediseñamos actividades y prácticas de clase para que se ajusten a una aplicación eficaz de la metodología de aprendizaje basado en proyectos. Ofrecemos asesoría y acompañamiento a docentes y estudiantes para que desarrollen su actividad académica integrando estrategias y procesos de calidad propios del ámbito profesional. NEWSHUB es una plataforma de formación. Ponemos contenidos formativos sobre comunicación eficiente a disposición de la comunidad educativa e investigadora y del sector de la orientación laboral y el fomento del emprendimiento. Ofrecemos recursos educativos abiertos a través de una plataforma web modular, interoperable y accesible, que alberga contenidos digitales de producción propia y un banco de buenas prácticas. NEWSHUB es coaching digital. Con la nueva situación provocada por la pandemia tenemos que adaptar nuestra manera de enseñar y de aprender haciendo que el entorno virtual sea un espacio en el que tanto profesores como estudiantes se encuentren tan cómodos como en el aula. Para ello acompañaremos a los docentes en ese tránsito y contaremos con la opinión directa de los alumnos/as que participan en nuestro proyecto. NEWSHUB conecta asignaturas, docentes y estudiantes para que los resultados de los distintos procesos de enseñanza-aprendizaje se optimicen para el cumplimiento de los objetivos clave del proyecto: aplicar eficazmente metodologías abiertas en el aula; alimentar el porfolio y el currículum en la búsqueda de empleo y el fomento del emprendimiento; y generar recursos educativos y modelos de buenas prácticas para formar en una comunicación eficiente. NEWSHUB también permite crear un puente entre profesores/as, alumnos/as y materias de otras facultades e incluso de otros países. La virtualización permite deslocalizar y ponernos en contacto para intercambiar experiencias, programas y recursos educativos proporcionando una visión más rica y abierta en diferentes contextos culturales y de diversidad. Como principal novedad, en esta segunda parte del proyecto, NEWSHUB se vuelve más internacional incorporando a profesores y profesoras de facultades de Comunicación y Diseño que imparten materiales similares. El objetivo de esta internacionalización es comparar el proceso de enseñanza y aprendizaje basada en proyectos en diferentes contextos culturales