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Detection of mutations and intragenic rearrangements in BRCA1 and BRCA2 genes by sequencing and MLPA method
PECHOVÁ, Kristýna
In my bachelor thesis I dealt with the detection of mutations in BRCA genes and their effect on the development of breast cancer. Nowadays, this topic is very important, because breast cancer is the most common cancer among women in the Czech Republic (Weinberger a Zikán, 2016). In the theoretical part I focused on breast cancer, particularly on its diagnosis and consequent treatment. I also dedicated genetic counselling and examination, which is very important for the diagnosis of hereditary forms of cancer. I mentioned basic information about BRCA genes, and their protein products and I summarized the issue of mutations in these genes and their relationship to cancer, particularly breast and ovarian. In the practical part, I focused on the examination of selected areas of BRCA genes by the Sanger sequencing method. At present, BRCA genes are examined by the NGS method, because it allows for the analysis of all exons of one particular gene at once, but this testing wasn't possible to realize in my laboratory conditions, therefore I have chosen the method of Sanger sequencing, which does, however, have certain capacity limitations. By using the PCR method, I prepared samples for testing by Sanger sequencing. This testing was conducted by the firm Genseq s.r.o. In the last part of my thesis I processed the obtained sequences and I evaluated the results. I examined a total of 20 anonymized samples using the sequencing method. Mutation was present in 4 samples of the total amount - one was pathogenic, one benign and two of uncertain significance.
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Gene sequencing in patients with cancer anamnesis
MARKOVÁ, Iveta
Cancer is the second most common cause of death in the Czech Republic, of which 5-10% are occupied by hereditary cancer syndromes. They are caused by a congenital - hereditary mutation in one of the alleles of the genes, when after the second random intervention in the other allele hereditary cancer develops. It is important to distinguish between hereditary and sporadic carcinomas due to the high risk of inheritance of mutated alleles in the family. The indication may be, for example, the onset of the disease at a young age or the recurrence of the cancer in the family In my work I focused on the analysis and evaluation of data obtained by Sanger sequencing. The aim was to find mutations in the genes mentioned below and to evaluate their pathogenicity by comparison with databases. In the theoretical part of the bachelor thesis I deal with cancer in general and hereditary cancer. I specify the hereditary breast and ovarian cancer syndrome, including genes, that may cause this syndrome - BRCA1, BRCA2, TP53, PTEN, ATM, PALB2, I also deal with Lynch syndrome and the MMR gene system. Last but not least, I describe a familial adenomatous polyposis associated with the APC gene. In the research part I focused on the examination of selected areas of 18 anonymized samples in the gene PALB2 - exon 13 and in the gene BRCA2 - exon 10/4 and exon 11/12. Using the PCR method, I prepared the samples for Sanger sequencing, which then took place in GenSeq s.r.o. In the last part of my work I deal with the analysis and evaluation of the results using the BioEdit program and the NCBI database. I found a mutation in 5 samples - in 4 it was a deletion of one nucleotide with a conflicting interpretation of pathogenicity, the last mutation was pathogenic - causes hereditary breast and ovarian cancer syndrome, it was a nucleotide duplication.
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Structure, function and importace of BRCA 1protein
Hojný, Jan ; Kleibl, Zdeněk (advisor) ; Falk, Martin (referee)
Studies of factors contributed to the development of hereditary breast and ovary cancers lead to the discovery of Breast Cancer 1 gene (BRCA1). The protein product of this tumor suppressor gene is nuclear phosphoprotein that plays a critical role in DNA repair and it is required for genome integrity control. The BRCA1 protein is the key component for correct assembly of reparation complexes formed in sites of DNA double strand breaks. Furthermore, BRCA1 protein is implicated in regulation of cell cycle checkpoints and it is also involved in regulation of gene expression in response to DNA damage. These activities suggest that BRCA1 protein plays a crucial role in orchestration of intracellular response to genotoxic DNA damage. Loss of BRCA1 functions leads to the DNA-damage repair mechanisms failure resulting in genomic instability and a tolerance of genomic alterations in affected cells. The genomic instability is the initial step toward early malignant transformation of cells lacking BRCA1 proteins. The aim of this work is to summarize the information about structure, functions known and the importance of BRCA1 protein with respect to the current discoveries enabling elucidation of versatile BRCA1-containing multiprotein complexes in which BRCA1 protein acts as the multiplatform interacting...
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Study of population specific alterations of breast cancer predisposition genes in Czech Republic.
Judasová, Kristýna ; Ševčík, Jan (advisor) ; Holá, Dana (referee)
Breast cancer is the most frequent malignant disease in the female population worldvide. About 10 % of all cases are of hereditary origin. The inactivation of tumor suppressor gene BRCA1 is the main genetic predisposing factor in breast cancer in the Czech Republic. Primarily, BRCA1 participates in DNA double strand break repair. Depending on cell cycle phase, the damage is repaired by homologous recombination or non-homologous end joining. Alternative splicing variants of BRCA1 are frequently detected during the genetic screening of high risk patients. The clinical significance of these variants is unknown. Understanding of the nature of breast cancer genetics is the critical factor for early diagnosis. Based on earlier studies from the Institute of Biochemistry and Experimental Oncology 1st Faculty of Medicine Charles University, two alternative splicing variants which were repeatedly detected in patients, were chosen for functional analysis. The aim of this work is to investigate the impact of alternative splicing variants BRCA1Δ5 and BRCA1Δ10 on DNA double strand breaks repair. Particular variants were over- expressed in the cells of model system. Activity of homologous recombination (HR) and non-homologous end joining (NHEJ) was scored by in vitro DNA repair assay. The cellular localization of...
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The functional in vitro analysis of the BRCA1alternative splicing variants
Ševčík, Jan ; Kleibl, Zdeněk (advisor) ; Stopka, Tomáš (referee) ; Macůrek, Libor (referee)
BACKGROUND: The inactivation of the tumor suppressor gene BRCA1 is a predisposing factor for a breast/ovarian cancer development. Formation of cancer-specific alternative splicing variants with aberrant biological properties can represent additional mechanism decreasing the overall BRCA1 activity in DNA double strand break (DDSB) repair. In this study, we analyzed BRCA1 alternative splicing variants BRCA114-15 and 17-19 ascertained previously during the screening of high-risk breast cancer individuals. METHODS: We established a stable MCF-7 cell line-based model system for an in vitro analysis of BRCA1 variants. Using this system, we analyzed the impact of BRCA114-15 and 17-19 variants on DNA repair kinetics using comet assay and confocal immunomicroscopy. The capacity of DNA repair was assessed directly by an in vitro NHEJ assay and indirectly by a mitomycin C sensitivity test. The proliferation activities were determined by a clonogenic assay and growth curves. RESULTS: Overexpression of BRCA114-15 and 17-19 increases the endogenous level of DNA damage, slows down the DDSB repair, and decelerates the initial phase of radiation-induced foci formation and prolongs their persistence. Moreover, BRCA114-15 and 17-19 differentially influence the activity of HR and NHEJ and sensitivity of MCF-7 cells to ionizing...
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Clinical and genetic aspects of familial breast cancer: Frequency of recurrent mutations in BRCA1 and BRCA2 genes in Czech republic and the role of NBN gene
Matějů, Martin ; Novotný, Jan (advisor) ; Konopásek, Bohuslav (referee) ; Vaňásek, Jaroslav (referee)
Summary: Background: An increased risk for development of hereditary breast cancer is associated with germline mutations in BRCA1/2 and the influence of NBN mutations is also supposed. The aim of this study is to specify the frequency of recurrent mutations in BRCA1/2 in unselected breast cancer patients and the frequency of most common pathogenic mutations in NBN in Czech republic, to assess current criteria for genetic testing and to consider the addition of NBN to the tested genes. Methods: Screening for recurrent mutations 5382insC and 300T>G in BRCA1 was performed by RFLP, screening for mutations in exon 11 of BRCA1 was performed by PTT, screening for mutations in a selected region of exon 11 of BRCA2 by DHPLC, and screening for mutations in exon 6 of NBN by HRMA. All the mutations were confirmed by direct sequencing. Results: In 679 unselected breast cancer patients 7 carriers of 5382insC, 3 of 300T>G, and 4 of other mutations in BRCA1 were identified. 2 locally prevalent mutations were found in BRCA2. In 730 controls only one 5382insC BRCA1 mutation was identified. Out of 5 NBN mutations found in 600 high-risk patients two were 657del5 and one R215W. A total of 8 NBN mutation carriers were identified among 703 breast cancer patients, 2 of them 657del5 carriers and three R215W carriers. In 915...
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Analysis of pre-mRNA alternative splicing products and their importance in breast cancer oncogenesis.
Hojný, Jan ; Kleiblová, Petra (advisor) ; Malík, Radek (referee) ; Boušková, Veronika (referee)
Breast cancer is the most common tumor disease diagnosed in women worldwide. The hereditary character of this disease is observed in 5-10 % of all cases, and it is usually caused by a pathogenic mutation in one of the predisposition genes. Although a variety of pathogenic mutations in the coding sequences of these genes was described, the cause of the disease is still unknown in many familial cases (> 50%). A great number of identified pathogenic mutations were localized in the consensus splicing sites, which results in the formation of aberrant mRNA splicing variants and their damaged protein isoforms. However, little is known about mutations affecting regulatory splicing sites, which can result in the translation of similarly affected mRNAs. In this work, we proposed a method for indirect detection of mutations affecting the natural splicing pattern of any gene of our interest based on multiplex PCR and NGS with high sensitivity. Verification of this method on the BRCA1 model gene revealed the presence of the total of 94 splicing variants in peripheral leucocytes and healthy breast and adjacent fat tissues. This is the most detailed catalogue of physically occurring BRCA1 mRNA variants thus far. The most commonly occurring variants, maintaining open reading frame, were quantified by RT-qPCR which...
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Role of human RECQ5 helicase in the resolution of conflicts between transcription and replication complexes
Fryzelková, Jana ; Dobrovolná, Jana (advisor) ; Vopálenský, Václav (referee)
The progression of replication forks can be slowed down or paused by various external and internal factors during DNA replication. This phenomenon is referred to as replication stress and substantially contributes to genomic instability that is a hallmark of cancer. Transcription complex belongs to the internal replication-interfering factors and represents a barrier for progression of the replication complex. The replication forks are slowed down or paused while passing through the transcriptionally active regions of the genome that can lead to subsequent collapse of stalled forks and formation of DNA double-strand breaks, especially under conditions of increased replication stress. DNA helicase RECQ5 is significantly involved in maintenance of genomic stability during replication stress, but the mechanisms of its action are not clear. In this diploma theses, we have shown that RECQ5 helicase, in collaboration with BRCA1 protein, participates in the resolution of collisions between replication and transcription complexes. BRCA1 protein is a key factor in the homologous recombination process, which is essential for the restart of stalled replication forks. Furthermore, we have shown that RECQ5 helicase is involved in ubiquitination of PCNA protein at stalled replication forks. Key words DNA...
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Study of population specific alterations of breast cancer predisposition genes in Czech Republic.
Judasová, Kristýna ; Ševčík, Jan (advisor) ; Holá, Dana (referee)
Breast cancer is the most frequent malignant disease in the female population worldvide. About 10 % of all cases are of hereditary origin. The inactivation of tumor suppressor gene BRCA1 is the main genetic predisposing factor in breast cancer in the Czech Republic. Primarily, BRCA1 participates in DNA double strand break repair. Depending on cell cycle phase, the damage is repaired by homologous recombination or non-homologous end joining. Alternative splicing variants of BRCA1 are frequently detected during the genetic screening of high risk patients. The clinical significance of these variants is unknown. Understanding of the nature of breast cancer genetics is the critical factor for early diagnosis. Based on earlier studies from the Institute of Biochemistry and Experimental Oncology 1st Faculty of Medicine Charles University, two alternative splicing variants which were repeatedly detected in patients, were chosen for functional analysis. The aim of this work is to investigate the impact of alternative splicing variants BRCA1Δ5 and BRCA1Δ10 on DNA double strand breaks repair. Particular variants were over- expressed in the cells of model system. Activity of homologous recombination (HR) and non-homologous end joining (NHEJ) was scored by in vitro DNA repair assay. The cellular localization of...
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