Characterization and expression analysis of P5CS (Δ1-pyrroline-5-carboxylate synthase) gene in two distinct populations of the Atlantic Forest native species Eugenia uniflora L.

Molecular Biology Reports - Eugenia uniflora is an Atlantic Forest native species, occurring in contrasting edaphoclimatic environments. The identification of genes involved in response to abiotic...     

Modulation of bone marrow mesenchymal stem cell secretome by ECM-like hydrogels

It has been demonstrated that bone marrow mesenchymal stem cell (BM-MSCs) transplantation has beneficial effects on several central nervous system (CNS) debilitating conditions. Growing evidence indicate that trophic factors secreted by these cells are the key mechanism by which they are acting. These cells are frequently used in combination with 3D artificial matrices, for instance hydrogels, in tissue engineering-based approaches. However, so far, no study has been reported on the influence of such matrices, namely the presence or absence of extracellular matrix motifs, on BM-MSCs secretome and its effects in neuronal cell populations. In this sense, we herein studied the impact of a hydrogel, gellan gum, on the behavior and secretome of BM-MSCs, both in its commercial available form (commonly used in tissue engineering) and in a fibronectin peptide-modified form. The results showed that in the presence of a peptide in the gellan gum hydrogel, BM-MSCs presented higher proliferation and metabolic activity than in the regular hydrogel. Moreover, the typical spindle shape morphology of BM-MSCs was only observed in the modified hydrogel. The effects of the secretome of BM-MSCs were also affected by the chemical nature of the extracellular matrix. BM-MSCs cultured in the modified hydrogel were able to secrete factors that induced higher metabolic viabilities and neuronal cell densities, when compared to those of the unmodified hydrogel. Thus adding a peptide sequence to the gellan gum had a significant effect on the morphology, activity, proliferation and secretome of BM-MSCs. These results highlight the importance of mimicking the extracellular matrix when BM-MSCs are cultured in hydrogels for CNS applications.     

Synthetic Condensed 1,4-naphthoquinone Derivative Shifts Neural Stem Cell Differentiation by Regulating Redox State

Naphthoquinones are bioactive compounds widespread in nature that impact on several cellular pathways, including cell proliferation and survival, by acting as prooxidants and electrophiles. We have previously described the role of the synthetic isoxazole condensed 1,4-naphthoquinone derivative 1a in preventing apoptosis induced by distinct stimuli in several cell models. In addition, apoptosis regulators and executioners may control neural stem cell (NSC) fate, without involving cell death per se. Here, we hypothesize that 1a might also play a role in NSC fate decision. We found that exposure to 1a shifts NSC differentiation potential from neurogenic to gliogenic lineage and involves the generation of reactive oxygen species, without increasing cell death. Modulation of caspases and calpains, using cysteine protease inhibitors, failed to mimic 1a effects. In addition, incubation with the naphthoquinone derivative resulted in upregulation and nuclear translocation of antioxidant responsive proteins, Nrf2 and Sirt1, which in turn may mediate 1a-directed shift in NSC differentiation. In fact, antioxidants halted the shift in NSC differentiation potential from neurogenic to gliogenic lineage, while strongly reducing reactive oxygen species generation and Nrf2 and Sirt1 nuclear translocation in NSC exposed to 1a. Collectively, these data support a new role for a specific naphthoquinone derivative in NSC fate decision and underline the importance of redox environment control.     

UCP2 and ANT differently modulate proton-leak in brain mitochondria of long-term hyperglycemic and recurrent hypoglycemic rats

A growing body of evidence suggests that mitochondrial proton-leak functions as a regulator of reactive oxygen species production and its modulation may limit oxidative injury to tissues. The main purpose of this work was to characterize the proton-leak of brain cortical mitochondria from long-term hyperglycemic and insulin-induced recurrent hypoglycemic rats through the modulation of the uncoupling protein 2 (UCP2) and adenine nucleotide translocator (ANT). Streptozotocin-induced diabetic rats were treated subcutaneously with twice-daily insulin injections during 2 weeks to induce the hypoglycemic episodes. No differences in the basal proton-leak, UCP2 and ANT protein levels were observed between the experimental groups. Mitochondria from recurrent hypoglycemic rats presented a decrease in proton-leak in the presence of GDP, a specific UCP2 inhibitor, while an increase in proton-leak was observed in the presence of linoleic acid, a proton-leak activator, this effect being reverted by the simultaneous addition of GDP. Mitochondria from long-term hyperglycemic rats showed an enhanced susceptibility to ANT modulation as demonstrated by the complete inhibition of basal and linoleic acid-induced proton-leak caused by the ANT specific inhibitor carboxyatractyloside. Our results show that recurrent-hypoglycemia renders mitochondria more susceptible to UCPs modulation while the proton-leak of long-term hyperglycemic rats is mainly modulated by ANT, which suggest that brain cortical mitochondria have distinct adaptation mechanisms in face of different metabolic insults.     

Deregulation of excitatory neurotransmission underlying synapse failure in Alzheimer's disease

Alzheimer′s disease (AD) is the most common form of dementia in the elderly. Memory loss in AD is increasingly attributed to soluble oligomers of the amyloid‐β peptide (AβOs), toxins that accumulate in AD brains and target particular synapses. Glutamate receptors appear to be centrally involved in synaptic targeting by AβOs. Once bound to neurons, AβOs dysregulate the activity and reduce the surface expression of both N‐methyl‐d ‐aspartate (NMDA) and 2‐amino‐3‐(3‐hydroxy‐5‐methyl‐isoxazol‐4‐yl)propanoic acid (AMPA) types of glutamate receptors, impairing signaling pathways involved in synaptic plasticity. In the extracellular milieu, AβOs promote accumulation of the excitatory amino acids, glutamate and d ‐serine. This leads to overactivation of glutamate receptors, triggering abnormal calcium signals with noxious impacts on neurons. Here, we review key findings linking AβOs to deregulated glutamate neurotransmission and implicating this as a primary mechanism of synapse failure in AD. We also discuss strategies to counteract the impact of AβOs on excitatory neurotransmission. In particular, we review evidence showing that inducing neuronal hyperpolarization via activation of inhibitory GABA_A receptors prevents AβO‐induced excitotoxicity, suggesting that this could comprise a possible therapeutic approach in AD.     

Forest cover, extinction thresholds and time lags in woody plants (Myrtaceae) in the Brazilian Atlantic Forest: resources for conservation

Efforts to conserve tropical forests could be strengthened based on ecological knowledge, such as extinction thresholds in ecological processes. Many studies of extinction thresholds associated with habitat reduction have focused on animals, generally at the patch scale. However, certain plant groups are very interesting models with which to study this type of relationship, such as Myrtaceae in Neotropical forests. Because trees are long-lived organisms, local extinctions in response to habitat loss may occur in different ways due to a time lag. In this study, our objective was to assess the occurrence of extinction thresholds at the landscape scale for Myrtaceae in a large biome and the pattern of species reduction in different tree size classes. We studied nine landscapes with different amounts of available habitat (between 5 and 55 % forest cover) in different parts of the Atlantic Forest in Bahia, Brazil, and in each landscape, we evaluated four plant classes based on tree circumference: saplings (CBH between 8 and 15 cm), young (CBH between 15 and 30 cm) adults (CBH ≥30 cm) and total (all individuals with CBH ≥8 cm). Landscapes with forest cover less than 25 % presented an approximately sixfold reduction in Myrtaceae total species richness compared with landscapes with forest cover greater than 40 %. We identified a relationship with a threshold between the amount of available habitat at the landscape level and Myrtaceae richness, with a reduction in total, sapling and young species below a threshold of 40 % forest cover, whereas adults had an extinction threshold at 30 % forest cover. We discuss the differences among the categories of plants associated with a time lag and the possibilities and limitations in applying these results in environmental management.     

Molecular mechanisms beyond glucose transport in diabetes-related male infertility

Diabetes mellitus (DM) is one of the greatest public health threats in modern societies. Although during a few years it was suggested that DM had no significant effect in male reproductive function, this view has been challenged in recent years. The increasing incidence of DM worldwide will inevitably result in a higher prevalence of this pathology in men of reproductive age and subfertility or infertility associated with DM is expected to dramatically rise in upcoming years. From a clinical perspective, the evaluation of semen parameters, as well as spermatozoa deoxyribonucleic acid (DNA) integrity, are often studied due to their direct implications in natural and assisted conception. Nevertheless, recent studies based on the molecular mechanisms beyond glucose transport in testicular cells provide new insights in DM-induced alterations in male reproductive health. Testicular cells have their own glucose sensing machinery that react to hormonal fluctuations and have several mechanisms to counteract hyper- and hypoglycemic events. Moreover, the metabolic cooperation between testicular cells is crucial for normal spermatogenesis. Sertoli cells (SCs), which are the main components of blood–testis barrier, are not only responsible for the physical support of germ cells but also for lactate production that is then metabolized by the developing germ cells. Any alteration in this tied metabolic cooperation may have a dramatic consequence in male fertility potential. Therefore, we present an overview of the clinical significance of DM in the male reproductive health with emphasis on the molecular mechanisms beyond glucose fluctuation and transport in testicular cells.     

Preferential Duplication of Intermodular Hub Genes: An Evolutionary Signature in Eukaryotes Genome Networks

Whole genome protein-protein association networks are not random and their topological properties stem from genome evolution mechanisms. In fact, more connected, but less clustered proteins are related to genes that, in general, present more paralogs as compared to other genes, indicating frequent previous gene duplication episodes. On the other hand, genes related to conserved biological functions present few or no paralogs and yield proteins that are highly connected and clustered. These general network characteristics must have an evolutionary explanation. Considering data from STRING database, we present here experimental evidence that, more than not being scale free, protein degree distributions of organisms present an increased probability for high degree nodes. Furthermore, based on this experimental evidence, we propose a simulation model for genome evolution, where genes in a network are either acquired de novo using a preferential attachment rule, or duplicated with a probability that linearly grows with gene degree and decreases with its clustering coefficient. For the first time a model yields results that simultaneously describe different topological distributions. Also, this model correctly predicts that, to produce protein-protein association networks with number of links and number of nodes in the observed range for Eukaryotes, it is necessary 90% of gene duplication and 10% of de novo gene acquisition. This scenario implies a universal mechanism for genome evolution.     

New Insights into the Phylogeny and Worldwide Dispersion of Two Closely Related Nematode Species,Bursaphelenchus xylophilus and Bursaphelenchus mucronatus

The pinewood nematode, Bursaphelenchus xylophilus, is one of the greatest threats to coniferous forests worldwide, causing severe ecological damage and economic loss. The biology of B. xylophilus is similar to that of its closest relative, B. mucronatus, as both species share food resources and insect vectors, and have very similar morphological characteristics, although little pathogenicity to conifers has been associated with B. mucronatus. Using both nuclear and mitochondrial DNA markers, we show that B. xylophilus and B. mucronatus form distinct phylogenetic groups with contrasting phylogeographic patterns. B. xylophilus presents lower levels of intraspecific diversity than B. mucronatus, as expected for a species that evolved relatively recently through geographical or reproductive isolation. Genetic diversity was particularly low in recently colonised areas, such as in southwestern Europe. By contrast, B. mucronatus displays high levels of genetic diversity and two well-differentiated clades in both mitochondrial and nuclear DNA phylogenies. The lack of correlation between genetic and geographic distances in B. mucronatus suggests intense gene flow among distant regions, a phenomenon that may have remained unnoticed due to the reduced pathogenicity of the species. Overall, our findings suggest that B. xylophilus and B. mucronatus have different demographic histories despite their morphological resemblance and ecological overlap. These results suggest that Bursaphelenchus species are a valuable model for understanding the dispersion of invasive species and the risks posed to native biodiversity and ecosystems.     

DNAdigest and Repositive: Connecting the World of Genomic Data

There is no unified place where genomics researchers can search through all available raw genomic data in a way similar to OMIM for genes or Uniprot for proteins. With the recent increase in the amount of genomic data that is being produced and the ever-growing promises of precision medicine, this is becoming more and more of a problem. DNAdigest is a charity working to promote efficient sharing of human genomic data to improve the outcome of genomic research and diagnostics for the benefit of patients. Repositive, a social enterprise spin-out of DNAdigest, is building an online platform that indexes genomic data stored in repositories and thus enables researchers to search for and access a range of human genomic data sources through a single, easy-to-use interface, free of charge.