VEGF inhibition alters neurotrophin signalling pathways and induces caspase-3 activation and autophagy in rabbit retina

This study sought to evaluate the prospective role exerted by vascular endothelial growth factor (VEGF) in the modulation of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) signalling pathways in the rabbit retina. To reach this aim, the anti-VEGF agents aflibercept and ranibizumab were used as a pharmacological approach to evaluate the putative consequences elicited by VEGF inhibition on neurotrophin signalling. VEGF inhibition determined a marked imbalance in proneurotrophin expression, a significant reduction in TrkA and TrkB phosphorylation states and a decrease in the pan-neurotrophin receptor p75. Importantly, VEGF blockade also caused a strong increase in cleaved caspase-3, beclin-1 and lipidated LC3. The effects were more pronounced in the aflibercept group when compared with ranibizumab-treated rabbits, particularly 1 week after injection. This study demonstrates that VEGF exerts pivotal physiological roles in regulating NGF and BDNF pathways in the retina, as its inhibition by anti-VEGF agents deeply impacts neurotrophin homeostasis. These events are accompanied by a sustained induction of apoptotic and autophagic markers, suggesting that anti-VEGF-dependent impairments in neurotrophin signalling could be responsible for the activation of retinal cell death pathways.     

Competition between DivIVA and the nucleoid for ParA binding promotes segrosome separation and modulates mycobacterial cell elongation

Although mycobacteria are rod shaped and divide by simple binary fission, their cell cycle exhibits unusual features: unequal cell division producing daughter cells that elongate with different velocities, as well as asymmetric chromosome segregation and positioning throughout the cell cycle. As in other bacteria, mycobacterial chromosomes are segregated by pair of proteins, ParA and ParB. ParA is an ATPase that interacts with nucleoprotein ParB complexes – segrosomes and non‐specifically binds the nucleoid. Uniquely in mycobacteria, ParA interacts with a polar protein DivIVA (Wag31), responsible for asymmetric cell elongation, however the biological role of this interaction remained unknown. We hypothesised that this interaction plays a critical role in coordinating chromosome segregation with cell elongation. Using a set of ParA mutants, we determined that disruption of ParA‐DNA binding enhanced the interaction between ParA and DivIVA, indicating a competition between the nucleoid and DivIVA for ParA binding. Having identified the ParA mutation that disrupts its recruitment to DivIVA, we found that it led to inefficient segrosomes separation and increased the cell elongation rate. Our results suggest that ParA modulates DivIVA activity. Thus, we demonstrate that the ParA‐DivIVA interaction facilitates chromosome segregation and modulates cell elongation.     

Endocrine control of sexual behavior in sneaker males of the peacock blenny Salaria pavo: effects of castration, aromatase inhibition, testosterone and estradiol

The effects of castration and sex steroid manipulations on the expression of sexual behavior were investigated in a small fish, the peacock blenny, Salaria pavo. In this species, large males defend nests and attract females while small "sneaker" males reproduce by imitating the female morphology and courtship behavior in order to approach nests during spawning events and parasitically fertilize eggs. Sneakers switch into nest holders in their second breeding season, thus displaying both male and female-like sexual behavior during their lifetime. We tested the effects of castration and of an aromatase inhibitor (Fadrozole, F), testosterone (T) or 17beta-estradiol (E(2)) implants on the expression of male and female-like behavior in sneakers. Sneakers were either sham-operated, castrated or castrated and implanted with vehicle, F, T+F or E(2)+F. Seven days after the treatment, sneakers were placed in a tank with a nesting male, two ripe females and an available nest. Castrated fish had lower levels of circulating T and increased the time spent displaying female typical nuptial coloration. T implants had the opposite effect, inhibiting the expression of female-like behavior and coloration. E(2) implants had no significant effect on the display of sexual behavior but the frequency of aggressive displays decreased. The results agree with previous findings in sneakers of S. pavo that demonstrated an inhibition of female-like behavior by 11-ketotestosterone (11-KT). The reported increase in T and 11-KT production when sneakers change into nest holders may thus contribute to behaviorally defeminize sneakers. Contrarily, both T and E(2) failed to promote male-like behavior, suggesting that behavioral masculization during tactic switching depends on other neuroendocrine mechanisms or that the time length of the experiment was insufficient to induce male-like behavioral changes in sneakers.     

Synthesis, structural characterization, and catalytic activity of chiral diamine and diimine Pd(II)-complexes

A combined catalytic and crystallographic investigation on the effectiveness of chiral diamino-bithiophene (2) and the corresponding diimino molecules (1) as chiral ligands for Pd(II) catalyzed transformations is presented. In particular, a systematic X-ray characterization of the [Pd]-pre-catalytic species provided valuable rationales for the different behavior of the two classes of ligands, underlining the key role played by sterical as well as electronic factors in controlling the oxidative addition of the starting racemic allylcarbonate to the chiral Pd(0) intermediate. Moreover, the versatility of the synthetic strategy for the preparation of enantiopure oligothienyl systems allowed us to synthesize a new type of mixed thiophene/pyridine ligands (2d) that have been effectively employed in asymmetric allylic alkylations (AAA).     

Characterization of the mechanisms by which gelatinase A, neutrophil collagenase, and membrane-type metalloproteinase MMP-14 recognize collagen I and enzymatically process the two alpha-chains

The turnover of native collagen has been ascribed to different members of the matrix metalloproteinase (MMP) family. Here, the mechanisms by which neutrophil collagenase (MMP-8), gelatinase A (MMP-2), and the ectodomain of MT1-MMP (ectMMP-14) degrade fibrillar collagen were examined. In particular, the hydrolysis of type I collagen at 37 degrees C was investigated to identify functional differences in the processing of the two alpha-chain types of fibrillar collagen. Thermodynamic and kinetic parameters were used for a quantitative comparison of the binding, unwinding, and hydrolysis of triple helical collagen. We demonstrate that the MMP family has developed at least two distinct mechanisms for collagen unwinding and cleavage. MMP-8 and ectMMP-14 display a similar mechanism (although with different catalytic parameters), which is characterized by binding (likely through the hemopexin-like domain) and cleavage of alpha-1 and/or alpha-2 chains without distinguishing between them and keeping the gross conformation of the triple helix (at least during the first cleavage step). On the other hand, MMP-2 binds preferentially the alpha-1 chains (likely through the fibronectin-like domain, which is not present in MMP-8 and ectMMP-14), grossly altering the whole triple helical arrangement of the collagen molecule and cleaving preferentially the alpha-2 chain. These distinctive mechanisms underly a drastically different mode of interaction with triple helical fibrillar collagen I, according to which the MMP domain is involved in binding. These findings can be related to the different role exerted by these MMPs on collagen homeostasis in the extracellular matrix.     

The assessment of inter-individual variation of whole-genome DNA sequence in 32 cows

Despite the growing number of sequenced bovine genomes, the knowledge of the population-wide variation of sequences remains limited. In many studies, statistical methodology was not applied in order to relate findings in the sequenced samples to a population-wide level. Our goal was to assess the population-wide variation in DNA sequence based on whole-genome sequences of 32 Holstein–Friesian cows. The number of SNPs significantly varied across individuals. The number of identified SNPs increased with coverage, following a logarithmic curve. A total of 15,272,427 SNPs were identified, 99.16 % of them being bi-allelic. Missense SNPs were classified into three categories based on their genomic location: housekeeping genes, genes undergoing strong selection, and genes neutral to selection. The number of missense SNPs was significantly higher within genes neutral to selection than in the other two categories. The number of variants located within 3′UTR and 5′UTR regions was also significantly different across gene families. Moreover, the number of insertions and deletions differed significantly among cows varying between 261,712 and 330,103 insertions and from 271,398 to 343,649 deletions. Results not only demonstrate inter-individual variation in the number of SNPs and indels but also show that the number of missense SNPs differs across genes representing different functional backgrounds.

     

Groundwater Macrocrustaceans as Natural Indicators of the Ariège Alluvial Aquifer

The macrocrustacean fauna from an alluvial aquifer in the French Pyrénées was investigated using 15 wells scattered over the floodplain. Wells were sampled at three contrasting periods for faunal, phy‐sical and chemical variables to investigate relationships between amphipod, isopod distributions and environmental factors. The assemblages, dominated by stygobite amphipod species, showed an overall persistence between the sampling dates. Groundwater quality exhibited between‐site variations related to agriculturally‐induced pollution. Low correlations existed between water quality and fauna distribution patterns. At the scale of the aquifer, groundwater contamination did not influence the macrocrustacean distribution. The spatial distribution of amphipods and isopods was clearly related to hydrogeology and hydrodynamics: strong relationships were found between the assemblages composition and the hydrological context of the stations (wells from the alluvial plain and from the alluvial terrace). With respect to spatial and temporal scales and providing adequate sampling methods, macrocrustaceans then constitute natural indicators of groundwater hydrodynamics in the Ariège aquifer.