Germline MLH1, MSH2 and MSH6 variants in Brazilian patients with colorectal cancer and clinical features suggestive of Lynch Syndrome.

Lynch syndrome (LS) is the most common hereditary colorectal cancer syndrome, caused by germline mutations in one of the major genes involved in mismatch repair (MMR): MLH1, MSH2, MSH6 and more rarely, PMS2. Recently, germline deletions in EPCAM have been also associated to the syndrome. Most of the pathogenic MMR mutations found in LS families occur in MLH1 or MSH2. Gene variants include missense, nonsense, frameshift mutations, large genomic rearrangements and splice-site variants and most of the studies reporting the molecular characterization of LS families have been conducted outside South America. In this study, we analyzed 60 unrelated probands diagnosed with colorectal cancer and LS criteria. Testing for germline mutations and/or rearrangements in the most commonly affected MMR genes (MLH1, MSH2, EPCAM and MSH6) was done by Sanger sequencing and MLPA. Pathogenic or likely pathogenic variants were identified in MLH1 or MSH2 in 21 probands (35.0%). Of these, approximately one-third were gene rearrangements. In addition, nine variants of uncertain significance (VUS) were identified in 10 (16.6%) of the sixty probands analyzed. Other four novel variants were identified, only in MLH1. Our results suggest that MSH6 pathogenic variants are not common among Brazilian LS probands diagnosed with CRC and that MMR gene rearrangements account for a significant proportion of the germline variants in this population underscoring the need to include rearrangement analysis in the molecular testing of Brazilian individuals with suspected Lynch syndrome.

ß-Globin polymorphisms in Amerindian populations from the Brazilian Amazon.

OBJECTIVES: This investigation was performed to examine genetic variation at the ß-globin locus in a sample of 30 healthy individuals from native populations in South America. The patterns of haplotypic variation were compared with those of previous studies including samples for various worldwide populations in an attempt to make inferences about the occupation of the Americas from a deeper temporal perspective than is typically available with haploid markers. METHODS: A 2.67-kb segment containing the ß-globin gene and its flanking regions was examined for genetic variation in a sample of 60 chromosomes from native populations in South America. The fragment was PCR-amplified and directly sequenced. To determine linkage relationships in compound heterozygotes, we used the amplification refractory mutation system. In addition, we assessed genetic variability and differentiation among populations, and we performed tests of selective neutrality. These analyses were performed for Brazilian Amerindian group and other worldwide populations previously studied. RESULTS: Eleven polymorphic sites were found in the studied fragment, which distinguished eight different haplotypes, three recombinants haplotypes (present as single copies) and five previously described haplotypes, including some of those most highly differentiated. Genetic variation found in the pooled sample is substantial. CONCLUSIONS: Although only five known haplotypes are observed in Amazonia, some of these are highly divergent, resulting in patterns of molecular polymorphism equal to or higher than those from other world regions.

Human aging and somatic point mutations in mtDNA: a comparative study of generational differences (grandparents and grandchildren)

The accumulation of somatic mutations in mtDNA is correlated with aging. In this work, we sought to identify somatic mutations in the HVS-1 region (D-loop) of mtDNA that might be associated with aging. For this, we compared 31 grandmothers (mean age: 63 ± 2.3 years) and their 62 grandchildren (mean age: 15 ± 4.1 years), the offspring of their daughters. Direct DNA sequencing showed that mutations absent in the grandchildren were detected in a presumably homoplasmic state in three grandmothers and in a heteroplasmic state in an additional 13 grandmothers; no mutations were detected in the remaining 15 grandmothers. However, cloning followed by DNA sequencing in 12 grandmothers confirmed homoplasia in only one of the three mutations previously considered to be homoplasmic and did not confirm heteroplasmy in three out of nine grandmothers found to be heteroplasmic by direct sequencing. Thus, of 12 grandmothers in whom mtDNA was analyzed by cloning, eight were heteroplasmic for mutations not detected in their grandchildren. In this study, the use of genetically related subjects allowed us to demonstrate the occurrence of age-related (> 60 years old) mutations (homoplasia and heteroplasmy). It is possible that both of these situations (homoplasia and heteroplasmy) were a long-term consequence of mitochondrial oxidative phosphorylation that can lead to the accumulation of mtDNA mutations throughout life.

Antenas ligadas para preservar a biodiversidade: concepções alternativas no ensino de ciências / On antennas to preserve biodiversity: alternative conceptions in the education of sciences

Este trabalho foi realizado durante o ano letivo de 2004; com alunos de uma escola pública no município de Nilópolis, Baixada Fluminense,RJ com intuito de verificar as percepções dos estudantes de ensino fundamental, com idades entre 9 e 17 anos, sobre a importância dos insetos e a interação com o homem e o ambiente em que vivem. Objetivamos...a cidadania. A princípio, foram aplicados 115 questionários semi-abertos para os alunos do segundo segmento do ensino fundamental com idades entre 10 a 17 anos, 57 questionarios abertos para alunos de 13 a 17 anos das sétima e oitava séries e analisados os desenhos dos alunos do primeiro segmento com idade entre 9 e 11 anos com intuito de verificar suas concepções sobre os insetos para fornecer subsídios a implementação de novas metodologias de ensino. Foi possível verificar que os alunos têm mais nojo que medo de insetos transmissores de doenças e que não dão a real importância aos mesmos quer seja no controle de vetores ou no processo de polinização. No caso da Dengue, os entrevistados têm medo da doença e não do vetor, o mosquito, e em nenhum momento mencionam o vírus como causador da doença. Observamos que as concepções errôneas construídas no âmbito escolar convivem com concepções do cotidiano influenciadas pela mídia e por pré-conceitos já incutidos no ambiente familiar, ou seja, no cotidiano. Foi possível...já que os insetos são abordados principalmente nesta fase do ensino e a constatação de erros, tanto na parte textual como na parte visual dos livros. Em relação aos insetos e em suas relações com o homem e o ambiente, verificamos que o material de campanhas locais sobre dengue também induz ao erro sobre o vetor da doença corroborando para a formação de concepções errôneas. A partir daí tentamos estabelecer 3 metodologias: montagem de insetário, aulas práticas com auxílio de lupa manual e oficina de desenho, permitindo que os alunos identifiquem insetos quanto à possibilidade de causar danos ou benefícios a com...