Surprisingly long survival of premature conclusions about naked mole-rat biology

Naked mole-rats express many unusual traits for such a small rodent. Their morphology, social behaviour, physiology, and ageing have been well studied over the past half-century. Many early findings and speculations about this subterranean species persist in the literature, although some have been repeatedly questioned or refuted. While the popularity of this species as a natural-history curiosity, and oversimplified story-telling in science journalism, might have fuelled the perpetuation of such misconceptions, an accurate understanding of their biology is especially important for this new biomedical model organism. We review 28 of these persistent myths about naked mole-rat sensory abilities, ecophysiology, social behaviour, development and ageing, and where possible we explain how these misunderstandings came about.     

Influence of environmental exposure to PAHs on the susceptibility of lymphocytes to DNA-damage induction and on their repair capacity

The influence of occupational exposure to environmental carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) on DNA damage detected in lymphocytes of exposed people (city policemen) was studied. The cellular susceptibility to the induction of the DNA damage and the repair capacity of exposed donors are presented in comparison with matched controls. Monitoring was performed and blood samples (164 donors) were collected in Prague, Czech Republic, during the winter and summer seasons. The single-cell gel electrophoresis (SCGE) assay with an internal standard was applied to evaluate the DNA damage. A challenging dose of 2Gy of X-rays was used to study cellular capacities. In the results of studies of the DNA damage induced in vivo or as an immediate response to the challenging treatment no significant difference was found between exposed and unexposed subgroups. The percentage of non-repaired X-ray-induced DNA damage (residual damage, RD) overall in both seasons was significantly higher in lymphocytes of policemen exposed to c-PAHs than in matched controls (RD(T-DNA), %DNA in the comet tail: winter 36.4+/-22.1 versus 22.7+/-10.8, p < 0.001; summer 47.7+/-22.9 versus 34.7+/-15.2, p < 0.001). The results suggest that occupational exposure to environmental c-PAHs significantly reduces the cellular capacity to repair the DNA damage induced by a challenging treatment. A significant decrease of repair efficiency in donors occupationally exposed to environmental c-PAHs was also observed when subgroups were stratified according to smoking history. In conclusion, our results suggest that environmental exposure to c-PAHs affects the cellular repair processes and can lead to harmful effects hazardous to human health.     

Fundamentally different repetitive element composition of sex chromosomes in Rumex acetosa

Background and AimsDioecious species with well-established sex chromosomes are rare in the plant kingdom. Most sex chromosomes increase in size but no comprehensive analysis of the kind of sequences that drive this expansion has been presented. Here we analyse sex chromosome structure in common sorrel (Rumex acetosa), a dioecious plant with XY₁Y₂ sex determination, and we provide the first chromosome-specific repeatome analysis for a plant species possessing sex chromosomes.MethodsWe flow-sorted and separately sequenced sex chromosomes and autosomes in R. acetosa using the two-dimensional fluorescence in situ hybridization in suspension (FISHIS) method and Illumina sequencing. We identified and quantified individual repeats using RepeatExplorer, Tandem Repeat Finder and the Tandem Repeats Analysis Program. We employed fluorescence in situ hybridization (FISH) to analyse the chromosomal localization of satellites and transposons.Key ResultsWe identified a number of novel satellites, which have, in a fashion similar to previously known satellites, significantly expanded on the Y chromosome but not as much on the X or on autosomes. Additionally, the size increase of Y chromosomes is caused by non-long terminal repeat (LTR) and LTR retrotransposons, while only the latter contribute to the enlargement of the X chromosome. However, the X chromosome is populated by different LTR retrotransposon lineages than those on Y chromosomes.ConclusionsThe X and Y chromosomes have significantly diverged in terms of repeat composition. The lack of recombination probably contributed to the expansion of diverse satellites and microsatellites and faster fixation of newly inserted transposable elements (TEs) on the Y chromosomes. In addition, the X and Y chromosomes, despite similar total counts of TEs, differ significantly in the representation of individual TE lineages, which indicates that transposons proliferate preferentially in either the paternal or the maternal lineage.     

Regulation of Rac1 activation by the low density lipoprotein receptor-related protein

The low density lipoprotein receptor-related protein (LRP-1) binds and mediates the endocytosis of multiple ligands, transports the urokinase-type plasminogen activator receptor (uPAR) and other membrane proteins into endosomes, and binds intracellular adaptor proteins involved in cell signaling. In this paper, we show that in murine embryonic fibroblasts (MEFs) and L929 cells, LRP-1 functions as a major regulator of Rac1 activation, and that this activity depends on uPAR. LRP-1-deficient MEFs demonstrated increased Rac1 activation compared with LRP-1-expressing MEFs, and this property was reversed by expressing the VLDL receptor, a member of the same gene family as LRP-1, with overlapping ligand-binding specificity. Neutralizing the activity of LRP-1 with receptor-associated protein (RAP) increased Rac1 activation and cell migration in MEFs and L929 cells. The same parameters were unaffected by RAP in uPAR-/- MEFs, prepared from uPAR gene knockout embryos, and in uPAR-deficient LM-TK- cells. Untreated uPAR+/+ MEFs demonstrated substantially increased Rac1 activation compared with uPAR-/- MEFs. In addition to Rac1, LRP-1 suppressed activation of extracellular signal-regulated kinase (ERK) in MEFs; however, it was Rac1 (and not ERK) that was responsible for the effects of LRP-1 on MEF migration. Thus, LRP-1 regulates two signaling proteins in the same cell (Rac1 and ERK), both of which may impact on cell migration. In uPAR-negative cells, LRP-1 neutralization does not affect Rac1 activation, and other mechanisms by which LRP-1 may regulate cell migration are not unmasked.     

Uphill distributional shift of an endangered habitat specialist

The rove beetle Emus hirtus (Linnaeus, 1758) is an endangered habitat specialist, which occurs in long-term cattle pastures where it forages on cattle dung. We studied this species’ historical and recent altitudinal distribution and habitat requirements in the centre of its distributional range in the Czech Republic. The species had experienced a sharp decline and was for nearly 20 years considered as regionally extinct within the Czech Republic. Nowadays, Emus hirtus is present and occurs in relatively high population densities. However, the beetle has shown an uphill shift and is distributed at significantly higher altitudes in sun-exposed localities in foothills and mountains compared to its historical distribution in the lowlands. Emus hirtus is one of many organisms that seem to indicate the openness of the pastured woodland landscape in the past. The main reason for its uphill shift could be habitat loss in densely populated and intensively managed lowlands and restoration of grazing at higher elevations due to agricultural subsidies.     

Population-specific responses to an invasive species

Predicting the impacts of non-native species remains a challenge. As populations of a species are genetically and phenotypically variable, the impact of non-native species on local taxa could crucially depend on population-specific traits and adaptations of both native and non-native species. Bitterling fishes are brood parasites of unionid mussels and unionid mussels produce larvae that parasitize fishes. We used common garden experiments to measure three key elements in the bitterling–mussel association among two populations of an invasive mussel (Anodonta woodiana) and four populations of European bitterling (Rhodeus amarus). The impact of the invasive mussel varied between geographically distinct R. amarus lineages and between local populations within lineages. The capacity of parasitic larvae of the invasive mussel to exploit R. amarus was higher in a Danubian than in a Baltic R. amarus lineage and in allopatric than in sympatric R. amarus populations. Maladaptive oviposition by R. amarus into A. woodiana varied among populations, with significant population-specific consequences for R. amarus recruitment. We suggest that variation in coevolutionary states may predispose different populations to divergent responses. Given that coevolutionary relationships are ubiquitous, population-specific attributes of invasive and native populations may play a critical role in the outcome of invasion. We argue for a shift from a species-centred to population-centred perspective of the impacts of invasions.     

Effects of polycyclic aromatic hydrocarbons (PAHs) in environmental pollution on exogenous and oxidative DNA damage (EXPAH project): description of the population under study

The EXPAH project was a molecular epidemiology study whose aims were to evaluate the hypothesis that polycyclic aromatic hydrocarbons (PAHs) are a major source of genotoxic activities of organic mixtures associated with air pollution. Biomarkers of exposure, effects and susceptibility, and oxidative DNA damage were measured in three PAH-exposed populations from Prague (Czech Republic), Kosice (Slovakia) and Sofia (Bulgaria). Control populations were included from each city. In total 356 individuals were enrolled. A questionnaire was used to determine life style/dietary factors. Ambient air exposure was measured by stationary monitoring, and personal exposure monitoring was also carried out. The characteristics of the population are described in this paper together with their personal exposure to carcinogenic PAHs (c-PAHs). The dose of c-PAH exposure was found to vary between the occupationally exposed (e.g. policemen and bus drivers) and the control populations in each country, and also varied from country to country.     

Incidence of nontuberculous mycobacteria in four hot water systems using various types of disinfection

The objective of this study was to determine the incidence of nontuberculous mycobacteria (NTM) in hot water systems of 4 selected hospital settings. The hospitals provided the following types of disinfection for their hot water systems: hydrogen peroxide and silver, thermal disinfection, chlorine dioxide, and no treatment (control). In each building, 6 samples were collected from 5 sites during a 3 month period. NTM were detected in 56 (46.7%) of 120 samples; the CFU counts ranged from 10 to 1625 CFU/L. The detected NTM species were the pathogens Mycobacterium kansasii, Mycobacterium xenopi, and Mycobacterium fortuitum and the saprophyte Mycobacterium gordonae. The most common to be isolated was M. xenopi, which was present in 51 samples. The hot water systems differed significantly in the incidence of NTM. NTM were not detected in the system treated by thermal disinfection, and a relatively low incidence (20% positive samples) was found in the system disinfected with chlorine dioxide. However, a high incidence was found in the control system with no additional disinfection (70% positives) and in the system using hydrogen peroxide and silver (97% positives). Water temperatures above 50 degrees C significantly limited the occurrence of NTM.     

Possible genetic damage in the Czech nuclear power plant workers

The aim of our study was to identify occupational risk of irradiation exposure in the Czech nuclear power plant workers. We analyzed levels of chromosomal aberrations, a well-known biomarker of early biological effects and a predictor of cancer risk. We applied the conventional method of cytogenetic analysis and fluorescence in situ hybridization (FISH, whole chromosome painting for chromosomes 1 and 4, combined with a pancentromeric probe) to three groups: 123 subjects in the Temelin nuclear power plant (2 years in use), 114 subjects in the Dukovany nuclear power plant (20 years in use), and 53 matched controls from Ceske Budejovice. Nuclear power plant workers were divided into two groups: subjects with admittance into the monitored zone, and others. Following factors were also analyzed: GSTM1, GSTT1, GSTP1, XPD, XRCC1, hOGG1, p53, MTHFR, and MS gene polymorphisms, levels of vitamins A, C, E, and folate in plasma, and level of cotinine in urine. Long-term exposure to ionizing radiation in the monitored zone was 0.47+/-1.50 mSv (miliSievert) in the Temelin nuclear power plant and 5.74+/-9.57 mSv in the Dukovany nuclear power plant. Using the conventional cytogenetic analysis, we observed 1.90+/-0.95 and 1.82+/-1.19% AB.C. (percent of aberrant cells) in the Temelin nuclear power plant, and 2.39+/-1.01 and 2.33+/-1.04% AB.C. in the Dukovany nuclear power plant, for monitored zone workers and others, respectively. In the control group, we found 2.25+/-0.82% AB.C. Genomic frequency of translocations F(G)/100 measured by FISH was 1.89+/-1.40 and 2.01+/-1.68 in the Temelin nuclear power plant, and 2.48+/-1.93 and 2.14+/-1.62 in the Dukovany nuclear power plant for monitored zone workers and others, respectively. In the control group, F(G)/100 was 1.83+/-1.19. Following factors were identified as potential confounders by the conventional cytogenetic analysis: XPD-6, by the FISH: age, GSTP1 and p53Bst genotypes, long-term use of medication, alcohol consumption, and smoking. No association between the dose of irradiation and the level of chromosomal aberrations in any nuclear power plant was detected either by the conventional cytogenetic analysis or by FISH.