Ana Paula M Silva

Ludwig Institute for Cancer Research Brazil, San Paulo, São Paulo, Brazil

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Publications (4)28.62 Total impact

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    ABSTRACT: Although patterns of somatic alterations have been reported for tumor genomes, little is known on how they compare with alterations present in non-tumor genomes. A comparison of the two would be crucial to better characterize the genetic alterations driving tumorigenesis. We sequenced the genomes of a lymphoblastoid (HCC1954BL) and a breast tumor (HCC1954) cell line derived from the same patient and compared the somatic alterations present in both. The lymphoblastoid genome presents a comparable number and similar spectrum of nucleotide substitutions to that found in the tumor genome. However, a significant difference in the ratio of non-synonymous to synonymous substitutions was observed between both genomes (P = 0.031). Protein-protein interaction analysis revealed that mutations in the tumor genome preferentially affect hub-genes (P = 0.0017) and are co-selected to present synergistic functions (P < 0.0001). KEGG analysis showed that in the tumor genome most mutated genes were organized into signaling pathways related to tumorigenesis. No such organization or synergy was observed in the lymphoblastoid genome. Our results indicate that endogenous mutagens and replication errors can generate the overall number of mutations required to drive tumorigenesis and that it is the combination rather than the frequency of mutations that is crucial to complete tumorigenic transformation.
    Nucleic Acids Research 04/2011; 39(14):6056-68. · 8.81 Impact Factor
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    ABSTRACT: Serial Analysis of Gene Expression (SAGE) and Massively Parallel Signature Sequencing (MPSS) are powerful techniques for gene expression analysis. A crucial step in analyzing SAGE and MPSS data is the assignment of experimentally obtained tags to a known transcript. However, tag to transcript assignment is not a straightforward process since alternative tags for a given transcript can also be experimentally obtained. Here, we have evaluated the impact of Single Nucleotide Polymorphisms (SNPs) on the generation of alternative SAGE and MPSS tags. This was achieved through the construction of a reference database of SNP-associated alternative tags, which has been integrated with SAGE Genie. A total of 2020 SNP-associated alternative tags were catalogued in our reference database and at least one SNP-associated alternative tag was observed for approximately 8.6% of all known human genes. A significant fraction (61.9%) of these alternative tags matched a list of experimentally obtained tags, validating their existence. In addition, the origin of four out of five SNP-associated alternative MPSS tags was experimentally confirmed through the use of the GLGI-MPSS protocol (Generation of Long cDNA fragments for Gene Identification). The availability of our SNP-associated alternative tag database will certainly improve the interpretation of SAGE and MPSS experiments.
    Nucleic Acids Research 02/2004; 32(20):6104-10. · 8.81 Impact Factor
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    ABSTRACT: Massively Parallel Signature Sequencing (MPSS) is a powerful technique for genome-wide gene expression analysis, which, similar to SAGE, relies on the production of short tags proximal to the 3'end of transcripts. A single MPSS experiment can generate over 10(7) tags, providing a 10-fold coverage of the transcripts expressed in a human cell. A significant fraction of MPSS tags cannot be assigned to known transcripts (orphan tags) and are likely to be derived from transcripts expressed at very low levels (approximately 1 copy per cell). In order to explore the potential of MPSS for the characterization of the human transcriptome, we have adapted the GLGI protocol (Generation of Longer cDNA fragments from SAGE tags for Gene Identification) to convert MPSS tags into their corresponding 3' cDNA fragments. GLGI-MPSS was applied to 83 orphan tags and 41 cDNA fragments were obtained. The analysis of these 41 fragments allowed the identification of novel transcripts, alternative tags generated from polymorphic and alternatively spliced transcripts, as well as the detection of artefactual MPSS tags. A systematic large-scale analysis of the genome by MPSS, in combination with the use of GLGI-MPSS protocol, will certainly provide a complementary approach to generate the complete catalog of human transcripts.
    Nucleic Acids Research 02/2004; 32(12):e94. · 8.81 Impact Factor
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    ABSTRACT: We applied a systematic bioinformatics approach, followed by careful manual inspection and experimental validation to identify additional expressed sequences located at the Hereditary Prostate Cancer Region (HPC1) between D1S2818 and D1S1642 on chromosome 1q25. All transcripts already described for the 1q25 region were identified and we were able to define 11 additional expressed sequences within this region (three full-length cDNA clone sequences and eight ESTs), increasing the total number of gene count in this region by 38%. Five out of the 11 expressed sequences identified were shown to be expressed in prostate tissue and thus represent novel disease gene candidates for the HPC1 region. Here, we report a detailed characterization of these five novel disease gene candidates, their expression pattern in various tissues, their genomic organization and functional annotation. Two candidates (RGSL1 and RGSL2) correspond to novel members of the RGS family, which is involved in the regulation of G-protein signaling. RGSL1 and RGLS2 expression was detected by real-time polymerase chain reaction in normal prostate tissue, but could not be detected in prostate tumor cell lines, suggesting they might have a role in prostate cancer.
    Gene 06/2003; 310:49-57. · 2.20 Impact Factor