5,6-Dihydro-5-aza-2′-deoxycytidine potentiates the anti-HIV-1 activity of ribonucleotide reductase inhibitors

The nucleoside analog 5,6-dihydro-5-aza-2′-deoxycytidine (KP-1212) has been investigated as a first-in-class lethal mutagen of human immunodeficiency virus type-1 (HIV-1). Since a prodrug monotherapy did not reduce viral loads in Phase II clinical trials, we tested if ribonucleotide reductase inhibitors (RNRIs) combined with KP-1212 would improve antiviral activity. KP-1212 potentiated the activity of gemcitabine and resveratrol and simultaneously increased the viral mutant frequency. G-to-C mutations predominated with the KP-1212-resveratrol combination. These observations represent the first demonstration of a mild anti-HIV-1 mutagen potentiating the antiretroviral activity of RNRIs and encourage the clinical translation of enhanced viral mutagenesis in treating HIV-1 infection.     

Structure of a mosaic hybrid zone between the field crickets Gryllus firmus and G. pennsylvanicus

Hybrid zones provide insight into the nature of species boundaries and the evolution of barriers to gene exchange. Characterizing multiple regions within hybrid zones is essential for understanding both their history and current dynamics. Here, we describe a previously uncharacterized region of a well‐studied hybrid zone between two species of field crickets, Gryllus pennsylvanicus and G. firmus. We use a combination of mitochondrial DNA sequencing, morphological data, and modeling of environmental variables to identify the ecological factors structuring the hybrid zone and define patterns of hybridization and introgression. We find an association between species distribution and natural habitat; Gryllus pennsylvanicus occupies natural habitat along forest edges and natural clearings, whereas G. firmus occupies more disturbed areas in agricultural and suburban environments. Hybridization and introgression occur across patch boundaries; there is evidence of substantial admixture both in morphological characters and mtDNA, over a broad geographic area. Nonetheless, the distribution of morphological types is bimodal. Given that F₁ hybrids are viable and fertile in the lab, this suggests that strong pre‐zygotic barriers are operating in this portion of the hybrid zone.     

Characterizing genic and nongenic molecular markers: comparison of microsatellites and SNPs

The implications of transitioning to single nucleotide polymorphism (SNPs) from microsatellite markers (MSs) have been investigated in a number of population genetics studies, but the effect of genomic location on the amount of information each type of marker reveals has not been explored in detail. We developed novel SNP markers flanking 1 kb regions of 13 genic (within gene or <1 kb away from gene) and 13 nongenic (>10 kb from annotated gene) MSs in the threespine stickleback genome to obtain comparable data for both types of markers. We analysed patterns of genetic diversity and divergence on various geographic scales after converting the SNP loci within each genomic region into haplotypes. Marker type (SNP haplotype or MS) and location (genic or nongenic) significantly affected most estimates of population diversity and divergence. Between‐lineage divergence was significantly higher in SNP haplotypes (genic and nongenic), however, within‐lineage divergence was similar between marker types. Most divergence and diversity measures were uncorrelated between markers, except for population differentiation which was correlated between MSs and SNP haplotypes (both genic and nongenic). Broad‐scale population structure and assignment were similarly resolved by both marker types, however, only the MSs were able to delimit fine‐scale population structuring, particularly when genic and nongenic markers were combined. These results demonstrate that estimates of genetic variability and differentiation among populations can be strongly influenced by marker type, their genomic location in relation to genes and by the interaction of these two factors. This highlights the importance of having an awareness of the inherent strengths and limitations associated with different molecular tools to select the most appropriate methods for accurately addressing various ecological and evolutionary questions.     

Clozapine-Induced Mitochondria Alterations and Inflammation in Brain and Insulin-Responsive Cells

Background

Metabolic syndrome (MetS) is a constellation of factors including abdominal obesity, hyperglycemia, dyslipidemias, and hypertension that increase morbidity and mortality from diabetes and cardiovascular diseases and affects more than a third of the population in the US. Clozapine, an atypical antipsychotic used for the treatment of schizophrenia, has been found to cause drug-induced metabolic syndrome (DIMS) and may be a useful tool for studying cellular and molecular changes associated with MetS and DIMS. Mitochondria dysfunction, oxidative stress and inflammation are mechanisms proposed for the development of clozapine-related DIMS. In this study, the effects of clozapine on mitochondrial function and inflammation in insulin responsive and obesity-associated cultured cell lines were examined.

Methodology/Principal Findings

Cultured mouse myoblasts (C2C12), adipocytes (3T3-L1), hepatocytes (FL-83B), and monocytes (RAW 264.7) were treated with 0, 25, 50 and 75 µM clozapine for 24 hours. The mitochondrial selective probe TMRM was used to assess membrane potential and morphology. ATP levels from cell lysates were determined by bioluminescence assay. Cytokine levels in cell supernatants were assessed using a multiplex array. Clozapine was found to alter mitochondria morphology, membrane potential, and volume, and reduce ATP levels in all cell lines. Clozapine also significantly induced the production of proinflammatory cytokines IL-6, GM-CSF and IL12-p70, and this response was particularly robust in the monocyte cell line.

Conclusions/Significance

Clozapine damages mitochondria and promotes inflammation in insulin responsive cells and obesity-associated cell types. These phenomena are closely associated with changes observed in human and animal studies of MetS, obesity, insulin resistance, and diabetes. Therefore, the use of clozapine in DIMS may be an important and relevant tool for investigating cellular and molecular changes associated with the development of these diseases in the general population.     

Impact of Laminitis on the Canonical Wnt Signaling Pathway in Basal Epithelial Cells of the Equine Digital Laminae

The digital laminae is a two layer tissue that attaches the distal phalanx to the inner hoof wall, thus suspending the horse''s axial skeleton in the hoof capsule. This tissue fails at the epidermal:dermal junction in laminitic horses, causing crippling disease. Basal epithelial cells line the laminar epidermal:dermal junction, undergo physiological change in laminitic horses, and lose versican gene expression. Versican gene expression is purportedly under control of the canonical Wnt signaling pathway and is a trigger for mesenchymal-to-epithelial transition; thus, its repression in laminar epithelial cells of laminitic horses may be associated with suppression of the canonical Wnt signaling pathway and loss of the epithelial cell phenotype. In support of the former contention, we show, using laminae from healthy horses and horses with carbohydrate overload-induced laminitis, quantitative real-time polymerase chain reaction, Western blotting after sodium dodecylsulfate polyacrylamide gel electrophoresis, and immunofluorescent tissue staining, that positive and negative regulatory components of the canonical Wnt signaling pathway are expressed in laminar basal epithelial cells of healthy horses. Furthermore, expression of positive regulators is suppressed and negative regulators elevated in laminae of laminitic compared to healthy horses. We also show that versican gene expression in the epithelial cells correlates positively with that of β-catenin and T-cell Factor 4, consistent with regulation by the canonical Wnt signaling pathway. In addition, gene and protein expression of β-catenin correlates positively with that of integrin β4 and both are strongly suppressed in laminar basal epithelial cells of laminitic horses, which remain E-cadherin⁺/vimentin⁻, excluding mesenchymal transition as contributing to loss of the adherens junction and hemidesmosome components. We propose that suppression of the canonical Wnt signaling pathway, and accompanying reduced expression of β catenin and integrin β4 in laminar basal epithelial cells reduces cell:cell and cell:basement membrane attachment, thus, destabilizing the laminar epidermal:dermal junction.     

Origins and Evolution of the Etruscans’ mtDNA

The Etruscan culture is documented in Etruria, Central Italy, from the 8^th to the 1^st century BC. For more than 2,000 years there has been disagreement on the Etruscans’ biological origins, whether local or in Anatolia. Genetic affinities with both Tuscan and Anatolian populations have been reported, but so far all attempts have failed to fit the Etruscans’ and modern populations in the same genealogy. We extracted and typed the hypervariable region of mitochondrial DNA of 14 individuals buried in two Etruscan necropoleis, analyzing them along with other Etruscan and Medieval samples, and 4,910 contemporary individuals from the Mediterranean basin. Comparing ancient (30 Etruscans, 27 Medieval individuals) and modern DNA sequences (370 Tuscans), with the results of millions of computer simulations, we show that the Etruscans can be considered ancestral, with a high degree of confidence, to the current inhabitants of Casentino and Volterra, but not to the general contemporary population of the former Etruscan homeland. By further considering two Anatolian samples (35 and 123 individuals) we could estimate that the genetic links between Tuscany and Anatolia date back to at least 5,000 years ago, strongly suggesting that the Etruscan culture developed locally, and not as an immediate consequence of immigration from the Eastern Mediterranean shores.     

Evaluating environmental DNA‐based quantification of ranavirus infection in wood frog populations

A variety of challenges arise when monitoring wildlife populations for disease. Sampling tissues can be invasive to hosts, and obtaining sufficient sample sizes can be expensive and time‐consuming, particularly for rare species and when pathogen prevalence is low. Environmental DNA (eDNA)‐based detection of pathogens is an alternative approach to surveillance for aquatic communities that circumvents many of these issues. Ranaviruses are emerging pathogens of ectothermic vertebrates linked to die‐offs of amphibian populations. Detecting ranavirus infections is critical, but nonlethal methods have the above issues and are prone to false negatives. We report on the feasibility and effectiveness of eDNA‐based ranavirus detection in the field. We compared ranavirus titres in eDNA samples collected from pond water to titres in wood frog (Lithobates sylvaticus; n = 5) tadpoles in sites dominated by this one species (n = 20 pond visits). We examined whether ranavirus DNA can be detected in eDNA from pond water when infections are present in the pond and if viral titres detected in eDNA samples correlate with the prevalence or intensity of ranavirus infections in tadpoles. With three 250 mL water samples, we were able to detect the virus in all visits with infected larvae (0.92 diagnostic sensitivity). Also, we found a strong relationship between the viral eDNA titres and titres in larval tissues. eDNA titres increased prior to observed die‐offs and declined afterwards, and were two orders of magnitude higher in ponds with a die‐off. Our results suggest that eDNA is useful for detecting ranavirus infections in wildlife and aquaculture.     

Rearing Temperature Influences Adult Response to Changes in Mating Status

Rearing environment can have an impact on adult behavior, but it is less clear how rearing environment influences adult behavior plasticity. Here we explore the effect of rearing temperature on adult mating behavior plasticity in the butterfly Bicyclus anynana, a species that has evolved two seasonal forms in response to seasonal changes in temperature. These seasonal forms differ in both morphology and behavior. Females are the choosy sex in cohorts reared at warm temperatures (WS butterflies), and males are the choosy sex in cohorts reared at cooler temperatures (DS butterflies). Rearing temperature also influences mating benefits and costs. In DS butterflies, mated females live longer than virgin females, and mated males live shorter than virgin males. No such benefits or costs to mating are present in WS butterflies. Given that choosiness and mating costs are rearing temperature dependent in B. anynana, we hypothesized that temperature may also impact male and female incentives to remate in the event that benefits and costs of second matings are similar to those of first matings. We first examined whether lifespan was affected by number of matings. We found that two matings did not significantly increase lifespan for either WS or DS butterflies relative to single matings. However, both sexes of WS but not DS butterflies experienced decreased longevity when mated to a non-virgin relative to a virgin. We next observed pairs of WS and DS butterflies and documented changes in mating behavior in response to changes in the mating status of their partner. WS but not DS butterflies changed their mating behavior in response to the mating status of their partner. These results suggest that rearing temperature influences adult mating behavior plasticity in B. anynana. This developmentally controlled behavioral plasticity may be adaptive, as lifespan depends on the partner’s mating status in one seasonal form, but not in the other.