Role of Sonic hedgehog signaling in cell cycle,oxidative stress,and autophagy of temozolomide resistant glioblastoma

The first-line chemotherapy treatment for Glioblastoma (GBM) - the most aggressive and frequent brain tumor - is temozolomide (TMZ). The Sonic hedgehog (SHH) pathway is involved with GBM tumorigenesis and TMZ chemoresistance. The role of SHH pathway inhibition in the potentiation of TMZ's effects using T98G, U251, and GBM11 cell lines is investigated herein. The combination of GANT-61 and TMZ over 72 hr suggested a synergistic effect. All TMZ-resistant cell lines displayed a significant decrease in cell viability, increased DNA fragmentation and loss of membrane integrity. For T98G cells, G₂/M arrest was observed, while U251 cells presented a significant increase in reactive oxygen species production and catalase activity. All the cell lines presented acidic vesicles formation correlated to Beclin-1 overexpression. The combined treatment also enhanced GLI1 expression, indicating the presence of select resistant cells. The selective inhibition of the SHH pathway potentiated the cytotoxic effect of TMZ, thus becoming a promising in vitro strategy for GBM treatment.     

MuPIT interactive: webserver for mapping variant positions to annotated, interactive 3D structures

Mutation position imaging toolbox (MuPIT) interactive is a browser-based application for single-nucleotide variants (SNVs), which automatically maps the genomic coordinates of SNVs onto the coordinates of available three-dimensional (3D) protein structures. The application is designed for interactive browser-based visualization of the putative functional relevance of SNVs by biologists who are not necessarily experts either in bioinformatics or protein structure. Users may submit batches of several thousand SNVs and review all protein structures that cover the SNVs, including available functional annotations such as binding sites, mutagenesis experiments, and common polymorphisms. Multiple SNVs may be mapped onto each structure, enabling 3D visualization of SNV clusters and their relationship to functionally annotated positions. We illustrate the utility of MuPIT interactive in rationalizing the impact of selected polymorphisms in the PharmGKB database, somatic mutations identified in the Cancer Genome Atlas study of invasive breast carcinomas, and rare variants identified in the exome sequencing project. MuPIT interactive is freely available for non-profit use at http://mupit.icm.jhu.edu.     

End‐joining inhibition at telomeres requires the translocase and polySUMO‐dependent ubiquitin ligase Uls1

In eukaryotes, permanent inhibition of the non‐homologous end joining (NHEJ) repair pathway at telomeres ensures that chromosome ends do not fuse. In budding yeast, binding of Rap1 to telomere repeats establishes NHEJ inhibition. Here, we show that the Uls1 protein is required for the maintenance of NHEJ inhibition at telomeres. Uls1 protein is a non‐essential Swi2/Snf2‐related translocase and a Small Ubiquitin‐related Modifier (SUMO)‐Targeted Ubiquitin Ligase (STUbL) with unknown targets. Loss of Uls1 results in telomere–telomere fusions. Uls1 requirement is alleviated by the absence of poly‐SUMO chains and by rap1 alleles lacking SUMOylation sites. Furthermore, Uls1 limits the accumulation of Rap1 poly‐SUMO conjugates. We propose that one of Uls1 functions is to clear non‐functional poly‐SUMOylated Rap1 molecules from telomeres to ensure the continuous efficiency of NHEJ inhibition. Since Uls1 is the only known STUbL with a translocase activity, it can be the general molecular sweeper for the clearance of poly‐SUMOylated proteins on DNA in eukaryotes.     

Genetic diversity within vertebrate species is greater at lower latitudes

The latitudinal gradient of species diversity is one of the oldest recognized patterns in biology. While the cause of the pattern remains debated, the global signal of greater diversity toward the tropics is widely established. Whether the pattern holds for genetic diversity within species, however, has received much less attention. We examine latitudinal variation of intraspecific genetic diversity by contrasting nucleotide distance within low- and high-latitude animal groups. Using mitochondrial DNA markers across 72 vertebrate species that together span six continents, two oceans, and 129 degrees of latitude, we found significantly greater genetic diversity at low latitudes within mammalian species, and trends consistent with this pattern in reptiles, amphibians, fish, and birds. The signal held even after removing species whose current geographic ranges include areas recently covered by glaciers during the late Pleistocene and which presumably have experienced colonization bottlenecks in high latitudes. Higher genetic diversity within species was found at low latitudes also for genera that do not possess higher species richness toward the tropics. Moreover, examination of a subset of species with sufficient sampling across a broad geographic range revealed that genetic variation demonstrates a typical gradient, with mid-latitude populations intermediate in genetic diversity between high and low latitude ones. These results broaden the pattern of the global latitudinal diversity gradient, to now include variation within species. These results are also concordant with other studies indicating that low latitude populations and species are on different evolutionary trajectories than high latitude ones, and we speculate that higher rates of evolution toward the equator are driving the pattern for genetic diversity within species.     

Hypersomnolence and Accidents in Truck Drivers: A Cross‐Sectional Study

Truck drivers are more likely to suffer severe injury and death due to certain truck driving characteristics. Identifying and preventing factors associated with accidents in this population is important to minimize damage and improve road safety. Excessive daytime sleepiness is a major public health problem, leading to impaired cognitive function, reduced alertness, and increased risk of motor vehicle crashes. The aim of this cross‐sectional study was to determine the prevalence and predictors of hypersomnolence (defined as an Epworth Sleepiness Scale score greater than 10) among truck drivers. Three hundred male truck drivers were studied. Quality of sleep was assessed by the Pittsburgh Sleep Quality Index, and the association between demographic, clinical, and occupational data with excessive sleepiness was analyzed. The mean daily sleep duration was 5.6±1.3 h, and poor quality of sleep was found in 46.3% of the individuals. Hypersomnolence was found in 46% of the drivers and was associated with younger age, snoring, and working >10 h without rest. A positive correlation between hypersomnolence and previous accidents was detected (p=0.005). These results show that sleep deprivation and hypersomnolence are frequent among truck drivers. The treatment of sleep‐disordered breathing and the implementation of educational programs, particularly targeting younger drivers and promoting increased awareness of the deleterious effects of sleep loss and work overload, may help to reduce hypersomnolence and accidents among truck drivers.     

Estimating population size by spatially explicit capture–recapture

The number of animals in a population is conventionally estimated by capture–recapture without modelling the spatial relationships between animals and detectors. Problems arise with non‐spatial estimators when individuals differ in their exposure to traps or the target population is poorly defined. Spatially explicit capture–recapture (SECR) methods devised recently to estimate population density largely avoid these problems. Some applications require estimates of population size rather than density, and population size in a defined area may be obtained as a derived parameter from SECR models. While this use of SECR has potential benefits over conventional capture–recapture, including reduced bias, it is unfamiliar to field biologists and no study has examined the precision and robustness of the estimates. We used simulation to compare the performance of SECR and conventional estimators of population size with respect to bias and confidence interval coverage for several spatial scenarios. Three possible estimators for the sampling variance of realised population size all performed well. The precision of SECR estimates was nearly the same as that of the null‐model conventional population estimator. SECR estimates of population size were nearly unbiased (relative bias 0–10%) in all scenarios, including surveys in randomly generated patchy landscapes. Confidence interval coverage was near the nominal level. We used SECR to estimate the population of a species of skink Oligosoma infrapunctatum from pitfall trapping. The estimated number in the area bounded by the outermost traps differed little between a homogeneous density model and models with a quadratic trend in density or a habitat effect on density, despite evidence that the latter models fitted better. Extrapolation of trend models to a larger plot may be misleading. To avoid extrapolation, a large region of interest should be sampled throughout, either with one continuous trapping grid or with clusters of traps dispersed widely according to a probability‐based and spatially representative sampling design.     

Measuring carbon and N2 fixation in field populations of colonial and free‐living unicellular cyanobacteria using nanometer‐scale secondary ion mass spectrometry1

Unicellular cyanobacteria are now recognized as important to the marine N and C cycles in open ocean gyres, yet there are few direct in situ measurements of their activities. Using a high‐resolution nanometer scale secondary ion mass spectrometer (nanoSIMS), single cell N₂ and C fixation rates were estimated for unicellular cyanobacteria resembling N₂ fixer Crocosphaera watsonii. Crocosphaera watsonii‐like cells were observed in the subtropical North Pacific gyre (22°45′ N, 158°0′ W) as 2 different phenotypes: colonial and free‐living. Colonies containing 3–242 cells per colony were observed and cell density in colonies increased with incubation time. Estimated C fixation rates were similarly high in both phenotypes and unexpectedly for unicellular cyanobacteria 85% of the colonial cells incubated during midday were also enriched in ¹⁵N above natural abundance. Highest ¹⁵N enrichment and N₂ fixation rates were found in cells incubated overnight where up to 64% of the total daily fixed N in the upper surface waters was attributed to both phenotypes. The colonial cells retained newly fixed C in a sulfur‐rich matrix surrounding the cells and often cells of both phenotypes possessed areas (<1 nm) of enriched ¹⁵N and ¹³C resembling storage granules. The nanoSIMS imaging of the colonial cells also showed evidence for a division of N₂ and C fixation activity across the colony where few individual cells (<34%) in a given colony were enriched in both ¹⁵N and ¹³C above the colony average. Our results provide new insights into the ecophysiology of unicellular cyanobacteria.