Activation processing of cathepsin H impairs recognition by its propeptide

Free propeptides are known to function as inhibitors of the parental mature cysteine cathepsins. This general rule, however, does not apply to the aminopeptidase cathepsin H. Screening of propeptide fragments for their inhibitory potency revealed no significant effect on the native mature cathepsin H. On the other hand, inhibitory interaction was established with recombinant cathepsin H that displays endopeptidase activity due to a lack of the mini-chain. This finding suggests that the propeptide-binding region is structurally rearranged during maturation processing and mini-chain formation, which impairs the effective recognition of mature cathepsin H by its own propeptide.     

Skin structure and hair morphology of different body parts in the Common Pipistrelle (Pipistrellus pipistrellus)

The bat skin shows an unusual morphology that corresponds to flying adaptations but also performs multiple functions including a protective barrier against microbes and parasites. Here, we compare the microscopic structure of the skin and hairs collected from the membranes with other body parts in the Common Pipistrelle (Pipistrellus pipistrellus) in relation to parasite availability. Statistical analysis of whole‐skin thickness revealed two main groups according to body regions; the first with thin skin (wing and tail membrane) and the second with thick skin (head and dorsum, abdomen, footpad). The density of hair was evaluated by a novel method, and it revealed that the density was significantly higher in the head region than in dorsal and ventral body parts. These differences possibly play a role for bat ectoparasites when choosing the preferred region of their host. Along the axis of each hair, the scale morphology was found to be variable. Hair morphology, however, did not vary among body regions. Mast cells were numerous in the hairy areas around vessels and hair follicles of the dorsum and abdomen, which are easily accessible to ectoparasites. Increased numbers of mast cells in hair‐bearing skin are part of the host adaptation system in parasite‐preferred locations.     

An imputed genotype resource for the laboratory mouse

We have created a high-density SNP resource encompassing 7.87 million polymorphic loci across 49 inbred mouse strains of the laboratory mouse by combining data available from public databases and training a hidden Markov model to impute missing genotypes in the combined data. The strong linkage disequilibrium found in dense sets of SNP markers in the laboratory mouse provides the basis for accurate imputation. Using genotypes from eight independent SNP resources, we empirically validated the quality of the imputed genotypes and demonstrated that they are highly reliable for most inbred strains. The imputed SNP resource will be useful for studies of natural variation and complex traits. It will facilitate association study designs by providing high-density SNP genotypes for large numbers of mouse strains. We anticipate that this resource will continue to evolve as new genotype data become available for laboratory mouse strains. The data are available for bulk download or query at /. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Increased xerotolerance of Saccharomyces cerevisiae during an osmotic pressure ramp over several generations

Although mechanisms involved in response of Saccharomyces cerevisiae to osmotic challenge are well described for low and sudden stresses, little is known about how cells respond to a gradual increase of the osmotic pressure (reduced water activity; a_w) over several generations as it could encounter during drying in nature or in food processes. Using glycerol as a stressor, we propagated S. cerevisiae through a ramp of the osmotic pressure (up to high molar concentrations to achieve testing-to-destruction) at the rate of 1.5 MPa day^-1 from 1.38 to 58.5 MPa (0.990–0.635 a_w). Cultivability (measured at 1.38 MPa and at the harvest osmotic pressure) and glucose consumption compared with the corresponding sudden stress showed that yeasts were able to grow until about 10.5 MPa (0.926 a_w) and to survive until about 58.5 MPa, whereas glucose consumption occurred until 13.5 MPa (about 0.915 a_w). Nevertheless, the ramp conferred an advantage since yeasts harvested at 10.5 and 34.5 MPa (0.778 a_w) showed a greater cultivability than glycerol-shocked cells after a subsequent shock at 200 MPa (0.234 a_w) for 2 days. FTIR analysis revealed structural changes in wall and proteins in the range 1.38–10.5 MPa, which would be likely to be involved in the resistance at extreme osmotic pressure.     

Amnion and ocular surface problems

The amniotic membrane, the most internal placental membrane, has various properties useful in ophthalmology. Collected on delivery by elective Caesarean section, the amnion is prepared under sterile conditions, and, usually, cryopreserved until its use as a biological bandage or as a substrate for epithelial growth in the management of various ocular surface conditions. Specifically, the amnion is used to : (1) limit formation of adhesive bands between eyelids and eyeball (symblepharon) or the progression of a fibrovascular outgrowth towards the cornea (pterygium) or to (2) facilitate the healing of corneal ulcers, bullous keratopathy, and corneal stem cell deficiency. In this last condition, either hereditary or acquired after a thermal or a chemical burn, corneal stem cells, located at a transitional zone between the cornea and conjunctiva, are lost. These cells are essential for renewal of corneal epithelium in normal and in diseased states. The loss of these cells leaves the corneal surface free for invasion by conjunctival epithelium. Not only, does conjunctival epithelium support the development of vascularisation on the normally avascular cornea, but some conjunctival cells differentiate into mucus secreting goblet cells. Such a change in phenotype leads to loss of corneal transparency and visual disability. The removal of this fibro-vascular outgrowth in combination with transplantation of both amniotic membrane and corneal stem cells are used to treat this condition. The amnion stimulates the proliferation of less differentiated cells which have the potential to reconstruct the cornea. This potential is at the origin of the hypothesis that the amnion may provide an alternative niche for limbal stem cells of the corneal epithelium. It abounds in cytokines and has antalgic, anti-bacterial, anti-inflammatory and anti-immunogenic properties, in addition to allowing, like fetal skin does, wound healing with minimal scar formation. These desirable properties are responsible for the increasing use of amniotic membrane in ophthalmology. The complete understanding of the mechanisms of action of amniotic membrane for ocular surface diseases has yet to be understood. Once revealed by research, they may provide new pharmacological avenues to treat ocular surface diseases.     

Community disassembly under global change: Evidence in favor of the stress‐dominance hypothesis

Ecological theory suggests that communities are not random combinations of species but rather the results of community assembly processes filtering and sorting species that are able to coexist together. To date, such processes (i.e., assembly rules) have been inferred from observed spatial patterns of biodiversity combined with null model approaches, but relatively few attempts have been made to assess how these processes may be changing through time. Specifically, in the context of the ongoing biodiversity crisis and global change, understanding how processes shaping communities may be changing and identifying the potential drivers underlying these changes become increasingly critical. Here, we used time series of 460 French freshwater fish communities and assessed both functional and phylogenetic diversity patterns to determine the relative importance of two key assembly rules (i.e., habitat filtering and limiting similarity) in shaping these communities over the last two decades. We aimed to (a) describe the temporal changes in both functional and phylogenetic diversity patterns, (b) determine to what extent temporal changes in processes inferred through the use of standardized diversity indices were congruent, and (c) test the relationships between the dynamics of assembly rules and both climatic and biotic drivers. Our results revealed that habitat filtering, although already largely predominant over limiting similarity, became more widespread over time. We also highlighted that phylogenetic and trait‐based approaches offered complementary information about temporal changes in assembly rules. Finally, we found that increased environmental harshness over the study period (especially higher seasonality of temperature) led to an increase in habitat filtering and that biological invasions increased functional redundancy within communities. Overall, these findings underlie the need to develop temporal perspectives in community assembly studies, as understanding ongoing temporal changes could provide a better vision about the way communities could respond to future global changes.     

Exploring nucleo-cytoplasmic large DNA viruses in Tara Oceans microbial metagenomes

Nucleo-cytoplasmic large DNA viruses (NCLDVs) constitute a group of eukaryotic viruses that can have crucial ecological roles in the sea by accelerating the turnover of their unicellular hosts or by causing diseases in animals. To better characterize the diversity, abundance and biogeography of marine NCLDVs, we analyzed 17 metagenomes derived from microbial samples (0.2–1.6 μm size range) collected during the Tara Oceans Expedition. The sample set includes ecosystems under-represented in previous studies, such as the Arabian Sea oxygen minimum zone (OMZ) and Indian Ocean lagoons. By combining computationally derived relative abundance and direct prokaryote cell counts, the abundance of NCLDVs was found to be in the order of 10⁴–10⁵ genomes ml⁻¹ for the samples from the photic zone and 10²–10³ genomes ml⁻¹ for the OMZ. The Megaviridae and Phycodnaviridae dominated the NCLDV populations in the metagenomes, although most of the reads classified in these families showed large divergence from known viral genomes. Our taxon co-occurrence analysis revealed a potential association between viruses of the Megaviridae family and eukaryotes related to oomycetes. In support of this predicted association, we identified six cases of lateral gene transfer between Megaviridae and oomycetes. Our results suggest that marine NCLDVs probably outnumber eukaryotic organisms in the photic layer (per given water mass) and that metagenomic sequence analyses promise to shed new light on the biodiversity of marine viruses and their interactions with potential hosts.