Mitochondrial haplogroups, control region polymorphisms and malignant melanoma: a study in middle European Caucasians

Background

Because mitochondria play an essential role in energy metabolism, generation of reactive oxygen species (ROS), and apoptosis, sequence variation in the mitochondrial genome has been postulated to be a contributing factor to the etiology of multifactorial age-related diseases, including cancer. The aim of the present study was to compare the frequencies of mitochondrial DNA (mtDNA) haplogroups as well as control region (CR) polymorphisms of patients with malignant melanoma (n = 351) versus those of healthy controls (n = 1598) in Middle Europe.

Methodology and Principal Findings

Using primer extension analysis and DNA sequencing, we identified all nine major European mitochondrial haplogroups and known CR polymorphisms. The frequencies of the major mitochondrial haplogroups did not differ significantly between patients and control subjects, whereas the frequencies of the one another linked CR polymorphisms A16183C, T16189C, C16192T, C16270T and T195C were significantly higher in patients with melanoma compared to the controls. Regarding clinical characteristics of the patient cohort, none of the nine major European haplogroups was associated with either Breslow thickness or distant metastasis. The CR polymorphisms A302CC-insertion and T310C-insertion were significantly associated with mean Breslow thickness, whereas the CR polymorphism T16519C was associated with metastasis.

Conclusions and Significance

Our results suggest that mtDNA variations could be involved in melanoma etiology and pathogenesis, although the functional consequence of CR polymorphisms remains to be elucidated.     

Cytoplasmic thioredoxin reductase is essential for embryogenesis but dispensable for cardiac development

Two distinct thioredoxin/thioredoxin reductase systems are present in the cytosol and the mitochondria of mammalian cells. Thioredoxins (Txn), the main substrates of thioredoxin reductases (Txnrd), are involved in numerous physiological processes, including cell-cell communication, redox metabolism, proliferation, and apoptosis. To investigate the individual contribution of mitochondrial (Txnrd2) and cytoplasmic (Txnrd1) thioredoxin reductases in vivo, we generated a mouse strain with a conditionally targeted deletion of Txnrd1. We show here that the ubiquitous Cre-mediated inactivation of Txnrd1 leads to early embryonic lethality. Homozygous mutant embryos display severe growth retardation and fail to turn. In accordance with the observed growth impairment in vivo, Txnrd1-deficient embryonic fibroblasts do not proliferate in vitro. In contrast, ex vivo-cultured embryonic Txnrd1-deficient cardiomyocytes are not affected, and mice with a heart-specific inactivation of Txnrd1 develop normally and appear healthy. Our results indicate that Txnrd1 plays an essential role during embryogenesis in most developing tissues except the heart.     

Diversification of Neoaves: integration of molecular sequence data and fossils

Patterns of diversification and timing of evolution within Neoaves, which includes almost 95% of all bird species, are virtually unknown. On the other hand, molecular data consistently indicate a Cretaceous origin of many neoavian lineages and the fossil record seems to support an Early Tertiary diversification. Here, we present the first well-resolved molecular phylogeny for Neoaves, together with divergence time estimates calibrated with a large number of stratigraphically and phylogenetically well-documented fossils. Our study defines several well-supported clades within Neoaves. The calibration results suggest that Neoaves, after an initial split from Galloanseres in Mid-Cretaceous, diversified around or soon after the K/T boundary. Our results thus do not contradict palaeontological data and show that there is no solid molecular evidence for an extensive pre-Tertiary radiation of Neoaves.     

New specimens of the early Eocene stem group galliform Paraortygoides (Gallinuloididae), with comments on the evolution of a crop in the stem lineage of Galliformes

Two new specimens of the fossil stem group galliform Paraortygoides messelensis Mayr 2000 (Gallinuloididae) are described from the Middle Eocene of Messel in Germany, including a complete skeleton in which the hitherto unknown skull of this species is preserved. The shorter and more protruding crista deltopectoralis of the humerus, also for the first time visible in one of the new specimens, shows gallinuloidids to be the sister taxon of all other, extinct and extant, galliform birds. Gallinuloidids distinctly differ from modern Galliformes in several other plesiomorphic osteological features, mainly of the pectoral girdle, of which the absence of a spina interna on the sternum is here reported for the first time. It is assumed that major evolutionary transformations in the stem lineage of Galliformes are related to the evolution of a large crop, which appears to have been absent in gallinuloidids. The vegetarian food component of gallinuloidids thus probably mainly consisted of soft plant matter rather than coarse material such as seeds.     

Readout technologies for highly miniaturized kinase assays applicable to high-throughput screening in a 1536-well format

This article discusses the development of homogeneous, miniaturized assays for the identification of novel kinase inhibitors from very large compound collections. In particular, the suitability of time-resolved fluorescence resonance energy transfer (TR-RET) based on phospho-specific antibodies, an antibody-independent fluorescence polarization (FP) approach using metal-coated beads (IMAP technology), and the determination of adenosine triphosphate consumption through chemiluminescence is evaluated. These readouts are compared with regard to assay sensitivity, compound interference, reagent consumption, and performance in a 1536-well format, and practical considerations for their application in primary screening or in the identification of kinase substrates are discussed. All of the tested technologies were found to be suitable for miniaturized high-throughput screening (HTS) in principle, but each of them has distinct limitations and advantages. Therefore, the target-specific selection of the most appropriate readout technology is recommended to ensure maximal relevance of HTS campaigns.     

Expression of the carbohydrate tumour marker Sialyl Lewis A, Sialyl Lewis X, Lewis Y and Thomsen-Friedenreich antigen in normal squamous epithelium of the uterine cervix, cervical dysplasia and cervical cancer

The carbohydrate molecules Sialyl Lewis X (SLeX), Sialyl Lewis A (SLeA), Lewis Y (LeY) and Thomsen-Friedenreich antigen (TF) are known to mediate the adhesion between tumor cells and endothelium. They are used as serum markers in diagnosis and treatment in a broad spectrum of human carcinomas, but their expression profile and role in the development of cervical cancer remains unclear. The aim of this study was to investigate the expression of SLeX, SLeA, LeY and TF in normal cervical squamous epithelium, cervical dysplasia and cervical cancer. Slides of paraffin-embedded tissue were fixed and incubated with monoclonal antibodies against SLeX, SLeA, LeY and TF. Immunohistochemical staining was evaluated by using a semi-quantitative score (IRS Score). We found a significant difference of SLeA expression in invasive cervical cancer compared to normal epithelium (p=0.006) and all grades of dysplasia (p=0.002). The expression of SLeX in normal epithelium was less intense than in carcinoma in situ (p=0.036). Staining for LeY showed the weakest results of the investigated markers. Significant differences were found when normal epithelium was compared to CIN I (p=0.011), to CIN II (p=0.013) and to invasive cervical cancer (p=0.005). For TF, significant differences were found in normal epithelium compared to CIN I (p=0.011), CIN II (p=0.013) and compared to invasive cervical cancer (p=0.005). This is the first study on the expression of SLeA, SLeX, LeY and TF in normal cervical endothelium, cervical dysplasia, carcinoma in situ and invasive cervical cancer. Further studies and higher numbers are desirable.     

A toolkit for graded expression of green fluorescent protein fusion proteins in mammalian cells

Green fluorescent protein (GFP) and GFP-like proteins of different colors are important tools in cell biology. In many studies, the intracellular targeting of proteins has been determined by transiently expressing GFP fusion proteins and analyzing their intracellular localization by fluorescence microscopy. In most vectors, expression of GFP is driven by the enhancer/promoter cassette of the immediate early gene of human cytomegalovirus (hCMV). This cassette generates high levels of protein expression in most mammalian cell lines. Unfortunately, these nonphysiologically high protein levels have been repeatedly reported to artificially alter the intracellular targeting of proteins fused to GFP. To cope with this problem, we generated a multitude of attenuated GFP expression vectors by modifying the hCMV enhancer/promoter cassette. These modified vectors were transiently expressed, and the expression levels of enhanced green fluorescent protein (EGFP) alone and enhanced yellow fluorescent protein (EYFP) fused to another protein were determined by fluorescence microscopy and/or Western blotting. As shown in this study, we were able to (i) clearly reduce the expression of EGFP alone and (ii) reduce expression of an EYFP fusion protein down to the level of the endogenous protein, both in a graded manner.