A Yeast Recombination Assay to Characterize Human BRCA1 Missense Variants of Unknown Pathological Significance

The BRCA1 tumor suppressor gene is found mutated in familial breast cancer. Although many of the mutations are clearly pathological because they give rise to truncated proteins, several missense variants of uncertain pathological consequences have been identified. A novel functional assay to screen for BRCA1 missense variants in a simple genetic system could be very useful for the identification of potentially deleterious mutations. By using two prediction computer programs, Sorting Intolerant from Tolerant (SIFT) and Polymorphism Phenotyping (PolyPhen), seven nonsynonymous missense BRCA1 variants likely disrupting the gene function were selected as potentially deleterious. The budding yeast Saccharomyces cerevisiae (S. cerevisiae) was used to test these cancer-related missense mutations for their ability to affect cell growth and homologous recombination (HR) at the HIS3 and ADE2 loci. The variants localized in the BRCA1 C-Terminus (BRCT) domain did not show any growth inhibition when overexpressed in agreement with previous results. Overexpression of either wild-type BRCA1 or two neutral missense variants did not increase yeast HR but when cancer-related variants were overexpressed a significant increase in recombination was observed. Results clearly showed that this genetic system can be useful to discriminate between neutral and deleterious BRCA1 missense variants

A recombination-based method to characterize human BRCA1 missense variants

Purpose. Many missense variants in BRCA1 are of unclear clinical significance. Functional and genetic approaches have been proposed for elucidating the clinical significance of such variants. The purpose of the present study was to evaluate BRCA1 missense variants for their effect on both Homologous Recombination (HR) and Non Homologous End Joining (NHEJ). Methods. HR frequency evaluation: HeLaG1 cells, containing a stably integrated plasmid that allows to measure HR events by gene conversion events were transfected with the pcDNA3β expression vector containing the BRCA1-wild type (BRCA1-WT) or the BRCA1-Unclassified Variants (BRCA1-UCVs). The NHEJ was measured by a random plasmid integration assay. Results. This assays suggested a BRCA1 involvement mainly in the NHEJ. As a matter of fact, the Y179C and the A1789T variant altered significantly the NHEJ activity as compared to the wild type, suggesting that they may be related to BRCA1 associated pathogenicity by affecting this function. The variants N550H and I1766S, and the mutation M1775R did not alter the NHEJ frequency. Conclusions. These data, beside proposing a method for the study of BRCA1 variants effect on HR and NHEJ, highlighted the need for a range of functional assays to be performed in order to identify variants with altered function

Effects on human transcriptome of mutated BRCA1 BRCT domain: A microarray study

BACKGROUND: BRCA1 (breast cancer 1, early onset) missense mutations have been detected in familial breast and ovarian cancers, but the role of these variants in cancer predisposition is often difficult to ascertain. In this work, the molecular mechanisms affected in human cells by two BRCA1 missense variants, M1775R and A1789T, both located in the second BRCT (BRCA1 C Terminus) domain, have been investigated. Both these variants were isolated from familial breast cancer patients and the study of their effect on yeast cell transcriptome has previously provided interesting clues to their possible role in the pathogenesis of breast cancer. METHODS: We compared by Human Whole Genome Microarrays the expression profiles of HeLa cells transfected with one or the other variant and HeLa cells transfected with BRCA1 wild-type. Microarray data analysis was performed by three comparisons: M1775R versus wild-type (M1775RvsWT-contrast), A1789T versus wild-type (A1789TvsWT-contrast) and the mutated BRCT domain versus wild-type (MutvsWT-contrast), considering the two variants as a single mutation of BRCT domain. RESULTS: 201 differentially expressed genes were found in M1775RvsWT-contrast, 313 in A1789TvsWT-contrast and 173 in MutvsWT-contrast. Most of these genes mapped in pathways deregulated in cancer, such as cell cycle progression and DNA damage response and repair. CONCLUSIONS: Our results represent the first molecular evidence of the pathogenetic role of M1775R, already proposed by functional studies, and give support to a similar role for A1789T that we first hypothesized based on the yeast cell experiments. This is in line with the very recently suggested role of BRCT domain as the main effector of BRCA1 tumor suppressor activity

Characterisation of gene expression profiles of yeast cells expressing BRCA1 missense variants

Germline mutations in breast cancer susceptibility gene 1 (BRCA1) confer high risk of developing breast and ovarian cancers. Even though most BRCA1 cancer-predisposing mutations produce a non-functional truncated protein, 5-10% of them cause single amino acid substitutions. This second type of mutations represents a useful tool for examining BRCA1 molecular functions. Human BRCA1 inhibits cell proliferation in transformed Saccharomyces cerevisiae cells and this effect is abolished by disease-associated mutations in the BRCT domain. Moreover, BRCA1 mutations located both inside and outside the BRCT domain may induce an increase in the homologous recombination frequency in yeast cells. Here we present a microarray analysis of gene expression induced in yeast cells transformed with five BRCA1 missense variants, in comparison with gene expression induced by wildtype BRCA1. Data analysis was performed by grouping the BRCA1 variants into three sets: Recombination (R)-set (Y179C and S1164I), Recombination and Proliferation (RP)-set(I1766S and M1775R) and Proliferation (P)-set (A1789T), according to their effects on yeast cell phenotype. We found 470, 740 and 1136 differentially expressed genes in R-, P- and RP-set, respectively. Our results point to some molecular mechanisms critical for the control of cell proliferation and of genome integrity providing support to a possible pathogenic role of the analysed mutations. They also confirm that yeast, despite the absence of a BRCA1 homologue, represents a valid model system to examine BRCA1 molecular functions, as the molecular pathways activated by BRCA1 variants are conserved in humans

Autosomal recessive LRP1-related syndrome featuring cardiopulmonary dysfunction, bone dysmorphology, and corneal clouding.

We provide the first study of two siblings with a novel autosomal recessive LRP1-related syndrome identified by rapid genome sequencing and overlapping multiple genetic models. The patients presented with respiratory distress, congenital heart defects, hypotonia, dysmorphology, and unique findings, including corneal clouding and ascites. Both siblings had compound heterozygous damaging variants, c.11420G \u3e C (p.Cys3807Ser) and c.12407T \u3e G (p.Val4136Gly) i

NOTAS E RESENHAS

RESULTADOS TEXTURAIS DA ANÁLISE DE AMOSTRAS DE PLATAFORMA CONTINENTAL INTERNA COLETADAS DURANTE A OPERAÇÃO GEOMAR X ENTRE A BAÍA DE GUANABARA E PONTA NEGRA – RJ - Dieter Muche e Jorge Luiz Barbosa DIMENSÕES DA AGRICULTURA REGIONALIZAÇÃO DA MODERNIZAÇÃO NO MATO CROSSO DE GOIÁS – 1975 - Maria José Rezende Barreto e Lucia Helena de Oliveira Gerardi A MIGRAÇÃO EM ESCALA ESPACIAL MICRO: A MIGRAÇÃO INTRA-URBANA - Odeibler Santo Guidugli MEIO AMBIENTE: A ABORDAGEM DE ESPECIALISTAS DE DIVERSOS – RAMOS DO SABER - Antonio José Teixeira Guerra METODOLOGIA PARA VISÃO TRIDIMENSIONAL DAS IMAGENS "LANDSAT" - Jairo Roberto Jimenez Rueda e Antonio Misson Godoy CLIMATOLOGlA DO BRASIL - Maria Juraci Zani dos Santos  PANORAMA AVALIATIVO DA CONTRIBUIÇÃO INGLESA À QUANTIFICAÇAO EM GEOGRAFIA - Antonio Christofoletti ANÁLISE GEOGRÁFICA DO COMPORTAMENTO HUMANO - Antonio Christofoletti ERODOLOGIA E GEOGRAFIA DOS SOLOS - Antonio Christofoletti CARACTERISTICAS E BASES FÍSICAS DAS ESTRUTURAS SEDIMENTARES – Antonio Christofoletti SEMINÁRIO INTERNACIONAL SOBRE PROCESSOS DE LATERIZAÇÃO - Antonio Christofoletti A ANÁLISE POLÍTICA DO ESPAÇO EM GEOGRAFIA - Odeibler Santo Guidugli QUANTIFICAÇAO EM GEOGRAFIA - José Alexandre Felizola Dini

DNA Glycosylases Involved in Base Excision Repair May Be Associated with Cancer Risk in BRCA1 and BRCA2 Mutation Carriers

Peer reviewe

IN VIVO AND IN VITRO ANALYSIS OF THE BRCA1 UNCLASSIFIED VARIANTS (VUSs)

BRCA1 acts a tumor suppressor gene and germ-line mutations which disrupt its functions culminate, after the loss of the wild type allele, in breast and ovarian cancer development. Although the precise biochemical functions of BRCA1 relevant for tumor suppression still remains to be clarified, it has been demonstrated to play a role in several cellular processes including: DNA DSBs repair, transcriptional regulation, chromatin remodeling, cell cycle checkpoints, ubiquitination and centrosome replication. An increasing number of mutations leading to an amino acidic substitution in the protein (missense mutations) have been identified in hereditary breast/ovarian cancer patients and the pathogenetic role of such missense mutations remains largely undefined. We studied some BRCA1 variants of uncertain significance (VUSs) both by in vivo analysis and by in vitro analysis. In particular we carried out an in vivo molecular study on the tumor tissue from patients carrier of the VUSs and we performed three in vitro functional assays based on two BRCA1 cellular function: the repair of DNA double strand break by Homologous Recombination and Non Homologous End Joining; the transcriptional control. It is important to perform systematic studies of the VUSs to assess pathogenicity of these variants found during genetic testing for BRCA1 hereditary breast and ovarian cancers

A recombination-based method to characterize human BRCA1 missense variants

International audienceMany missense variants in BRCA1 are of unclear clinical significance. Functional and genetic approaches have been proposed for elucidating the clinical significance of such variants. The purpose of this study was to evaluate BRCA1 missense variants for their effect on both homologous recombination (HR) and non homologous end joining (NHEJ). HR frequency evaluation: HeLaG1 cells, containing a stably integrated plasmid that allows us to measure HR events by gene conversion events, were transfected with the pcDNA3β expression vector containing the BRCA1-wild-type () or the BRCA1-unclassified variants (BRCA1-UCVs). The NHEJ was measured by a random plasmid integration assay. The assays suggested a BRCA1 involvement mainly in the NHEJ. As a matter of fact, the Y179C and the A1789T variant significantly altered the NHEJ activity as compared to the wild type, suggesting that they may be related to BRCA1-associated pathogenicity by affecting this function. The variants N550H and I1766S, and the mutation M1775R did not alter the NHEJ frequency. These data, besides proposing a method for the study of BRCA1 variants' effect on HR and NHEJ, highlighted the need for a range of functional assays to be performed to identify variants with altered function