Mitochondrial DNA-like sequence in the nuclear genome of Saguinus (Callitrichinae, Primates): transfer estimation

Seqüências tipo mitocondriais têm comumente sido encontradas no genoma nuclear de diversos organismos. Quando acidentalmente incluídas em estudos de seqüências mitocondriais, diversas conclusões errôneas podem ser obtidas. No entanto, estes pseudogenes nucleares tipo mitocondriais podem ser usados para a estimativa da taxa relativa de evolução de genes mitocondriais e também como grupo externo em análises filogenéticas. No presente trabalho, seqüências mitocondriais com características do tipo de pseudogene, tais como deleções e/ou inserções e códons de parada, foram encontradas em tamarins (Saguinus spp., Callitrichinae, Primates). A análise filogenética permitiu a estimativa do tempo da migração da seqüência mitocondrial para o genoma nuclear e algumas inferências filogenéticas. A escolha de um grupo externo não adequado (Aotus infulatus) não permitiu uma reconstrução filogenética confiável da subfamília Callitrichinae. A divergência bastante antiga de Cebidae (Callitrichinae, Aotinae e Cebinae) pode ter favorecido o aparecimento de homoplasias, obscurecendo a análise.

Molecular phylogeny of the genus Saguinus (Platyrrhini, Primates) based on the ND1 mitochondrial gene and implications for conservation

The systematics of the subfamily Callitrichinae (Platyrrhini, Primates), a group of small monkeys from South America and Panama, remains an area of considerable discussion despite many investigations, there being continuing controversy over subgeneric taxonomic classifications based on morphological characters. The purpose of our research was to help elucidate the phylogenetic relationships within the monkey genus Saguinus (Callitrichinae) using a molecular approach to discover whether or not the two different sections containing hairy-faced and bare-faced species are monophyletic, whether Saguinus midas midas and Saguinus bicolor are more closely related than are S. midas midas and Saguinus midas niger, and if Saguinus fuscicollis melanoleucus and Saguinus fuscicollis weddelli really are different species. We sequenced the 957 bp ND1 mitochondrial gene of 21 Saguinus monkeys (belonging to six species and nine morphotypes) and one Cebus monkey (the outgroup) and constructed phylogenetic trees using maximum parsimony, neighbor joining, and maximum likelihood methods. The phylogenetic trees obtained divided the genus Saguinus into two groups, one containing the small-bodied species S. fuscicollis and the other, the large-bodied species S. mystax, S. leucopus, S. oedipus, S. midas, S. bicolor. The most derived taxa, S. midas and S. bicolor, grouped together, while S. fuscicollis melanoleucus and S. f. weddelli showed divergence values that did not support the division of these morphotypes into subspecies. On the other hand, S. midas individuals showed divergence compatible with the existence of three subspecies, two of them with the same morphotype as the subspecies S. midas niger. The results of our study suggest that there is at least one Saguinus subspecies that has not yet been described and that the conservation status of Saguinus species and subspecies should be carefully revised using modern molecular approaches.

Low levels of genetic diversity depicted from mitochondrial DNA sequences in a heavily exploited marine fish (Cynoscion acoupa, Sciaenidae) from the Northern coast of Brazil

The acoupa weakfish (Cynoscion acoupa - Sciaenidae) is a marine species of croaker with estuarine-dependent behavior, found in the western Atlantic from Panama to Argentina. It is one of the most exploited food fish on the northern coast of Brazil. In this study, DNA sequences were determined from the entire control region (D-loop) of the mitochondrial genome of 297 individuals collected during seven different months between December 2003 and August 2005 on the northern coast of Brazil (Amapá and Pará). Genetic variability expressed by haplotype (h = 0,892) and nucleotide (p = 0,003) diversities were low compared to other heavily exploited marine fish species from the western Atlantic and eastern Asia. AMOVA depicted a lack of genetic structuring among the samples from different years, indicating the presence of a single stock of C. acoupa within the sample area. The possible reasons for the low levels of genetic diversity are discussed. These results demonstrate a need for the monitoring of C. acoupa harvesting and the preservation of the estuaries within its geographic range, considering that this large fish depends on estuarine ecosystems during part of its life cycle.

Sciaenidae fish of the Caeté River estuary, Northern Brazil: mitochondrial DNA suggests explosive radiation for the Western Atlantic assemblage

Sciaenids are fish which are normally abundant in tropical estuaries of the western Atlantic. Studies on the Caeté river estuary in the northern Brazilian state of Pará have revealed that in this area Sciaenidae is the dominant family, comprising almost 50% of all teleosts sampled. In this paper we present the results of the first phylogenetic study on South American estuarine sciaenids, during which we obtained mitochondrial gene 16S sequences from 15 species belonging to eight genera occurring in the Caeté estuary. Intergeneric nucleotide divergences varied from 5 to 15%, Lonchurus and Menticirrhus being the most divergent lineages. Nucleotide divergences were quite variable amongst species of the same genus, ranging from 1.2% (Stellifer microps x Stellifer naso) to 8.4% (Menticirrhus americanus x Menticirrhus littoralis). Cladograms based on maximum parsimony, minimum evolution and maximum likelihood depicted an explosive diversification pattern for the western Atlantic sciaenid assemblage. Our analysis further reveals a very close relationship between Bairdiella and Stellifer, a monophyletic clade which emerged during the more recent diversification events of the Sciaenidae family. The phylogenetic reconstruction suggests the need for a revision of the taxonomy and nomenclature of the Bairdiella/Stellifer group.

Phylogenetic analysis of 16S mitochondrial DNA data in sloths and anteaters

We sequenced part of the 16S rRNA mitochondrial gene in 17 extant taxa of Pilosa (sloths and anteaters) and used these sequences along with GenBank sequences of both extant and extinct sloths to perform phylogenetic analysis based on parsimony, maximum-likelihood and Bayesian methods. By increasing the taxa density for anteaters and sloths we were able to clarify some points of the Pilosa phylogenetic tree. Our mitochondrial 16S results show Bradypodidae as a monophyletic and robustly supported clade in all the analysis. However, the Pleistocene fossil Mylodon darwinii does not group significantly to either Bradypodidae or Megalonychidae which indicates that trichotomy best represents the relationship between the families Mylodontidae, Bradypodidae and Megalonychidae. Divergence times also allowed us to discuss the taxonomic status of Cyclopes and the three species of three-toed sloths, Bradypus tridactylus, Bradypus variegatus and Bradypus torquatus. In the Bradypodidae the split between Bradypus torquatus and the proto-Bradypus tridactylus / B. variegatus was estimated as about 7.7 million years ago (MYA), while in the Myrmecophagidae the first offshoot was Cyclopes at about 31.8 MYA followed by the split between Myrmecophaga and Tamandua at 12.9 MYA. We estimate the split between sloths and anteaters to have occurred at about 37 MYA.

Alterações oxidativas em portadores de doença de Parkinson: correlação com critérios clínicos e estágios da doença

A doença de Parkinson (DP) constitui uma das mais prevalentes doenças neurológicas. Nesta doença, ocorre a neurodegeneração do sistema nigroestriatal com alteração da circuitaria neuronal dos núcleos da base levando ao comprometimento motor característico da doença. Os sintomas clássicos são o tremor de repouso, rigidez, acinesia ou bradicinesia e instabilidade postural. A patogênese da DP ainda permanece obscura. No entanto, estima-se que a disfunção mitocondrial e o desenvolvimento de estresse oxidativo na substância negra tenham papel relevante neste processo. O diagnóstico da DP é clinico e normalmente acontece tardiamente, quando a maioria dos neurônios nigrais está degenerada. Alguns trabalhos mostram o efeito neuroprotetor de medicações antiparkinsonianas e isto demonstra que quanto mais precoce a introdução do tratamento melhor o prognóstico à longo prazo da doença. Portanto o desenvolvimento de marcadores periféricos que ajudem no diagnóstico precoce da doença é importante para que se inicie o tratamento a tempo de retardar o avanço da morte neuronal. O objetivo deste trabalho foi verificar a existência de alterações em parâmetros oxidantes e antioxidantes no sangue de pacientes parkinsonianos e sua relação com o estágio da doença e critérios clínicos. Foram avaliados 30 portadores de DP e 30 indivíduos sem a doença. Para avaliar o estágio da doença e caracteres clínicos foram aplicadas as escalas de Hoehn & Yahr e a UPDRS (escala unificada para doença de Parkinson) nos pacientes parkinsonianos. Para avaliar a atividade oxidativa no plasma dos individuos, foi analisada a peroxidação lipídica através da mensuração de produtos da ação de Espécies Reativas de Oxigênio e Nitrogênio (ERON; TBARS) e para avaliar a resposta antioxidante foi feita a avaliação da Capacidade Antioxidante Total (TEAC). Nos grupos DP leve e DP moderado foi encontrado maior valor do TBARS e menor valor do TEAC em relação aos controles e DP grave (p<0,05), confirmando a presença de estresse oxidativo nas fases precoces da DP. Nesta pesquisa esses parâmetros demonstraram serem bons marcadores periféricos do estresse oxidativo, colaborando para um diagnóstico precoce da DP.

Cytogenetic description of breast fibroadenomas: alterations related solely to proliferation?

Twelve breast fibroadenomas were analyzed cytogenetically and only four were found to have clonal alterations. The presence of chromosomal alterations in fibroadenomas must be the consequence of the proliferating process and must not be related to the etiology of this type of lesion. In contrast, the few fibroadenomas that exhibit chromosomal alterations are likely to be those presenting a risk of neoplastic transformation. Clonal numerical alterations involved chromosomes 8, 18, 19, and 21. Of the chromosomal alterations found in the present study, only monosomy of chromosomes 19 and 21 has been reported in breast fibroadenomas. The loss of chromosome 21 was the most frequent alteration found in our sample. The study of benign proliferations and their comparison with chromosome alterations in their malignant counterparts ought to result in a better understanding of the genes acting on cell proliferation alone, and of the genes that cause these cells to exhibit varied behaviors such as recurrences, spontaneous regression and fast growth.

Mitochondrial DNA mapping of social-biological interactions in Brazilian Amazonian African-descendant populations

ABSTRACT: The formation of the Brazilian Amazonian population has historically involved three main ethnic groups, Amerindian, African and European. This has resulted in genetic investigations having been carried out using classical polymorphisms and molecular markers. To better understand the genetic variability and the micro-evolutionary processes acting in human groups in the Brazilian Amazon region we used mitochondrial DNA to investigate 159 maternally unrelated individuals from five Amazonian African-descendant communities. The mitochondrial lineage distribution indicated a contribution of 50.2% from Africans (L0, L1, L2, and L3), 46.6% from Amerindians (haplogroups A, B, C and D) and a small European contribution of 1.3%. These results indicated high genetic diversity in the Amerindian and African lineage groups, suggesting that the Brazilian Amazonian African-descendant populations reflect a possible population amalgamation of Amerindian women from different Amazonian indigenous tribes and African women from different geographic regions of Africa who had been brought to Brazil as slaves. The present study partially mapped the historical biological and social interactions that had occurred during the formation and expansion of Amazonian African-descendant communities.

Epigenetic alterations in human brain tumors in a Brazilian population

Aberrant methylation of CpG islands located in promoter regions represents one of the major mechanisms for silencing cancer-related genes in tumor cells. We determined the frequency of aberrant CpG island methylation for several tumor-associated genes: DAPK, MGMT, p14^ARF, p16^INK4a, TP73, RB1 and TIMP-3 in 55 brain tumors, consisting of 26 neuroepithelial tumors, 6 peripheral nerve tumors, 13 meningeal tumors and 10 metastatic brain tumors. Aberrant methylation of at least one of the seven genes studied was detected in 83.6% of the cases. The frequencies of aberrant methylation were: 40% for p14^ARF, 38.2% for MGMT, 30.9% for, p16^INK4a, 14.6% for TP73 and for TIMP-3, 12.7% for DAPK and 1.8% for RB1. These data suggest that the hypermethylation observed in the genes p14^ARF, MGMT and p16^INK4a is a very important event in the formation or progression of brain tumors, since the inactivation of these genes directly interferes with the cell cycle or DNA repair. The altered methylation rate of the other genes has already been reported to be related to tumorigenesis, but the low methylation rate of RB1 found in tumors in our sample is different from that so far reported in the literature, suggesting that perhaps hypermethylation of the promoter is not the main event in the inactivation of this gene. Our results suggest that hypermethylation of the promoter region is a very common event in nervous system tumors.