Inflammation-associated enterotypes,host genotype,cage and inter-individual effects drive gut microbiota variation in common laboratory mice

Background

Murine models are a crucial component of gut microbiome research. Unfortunately, a multitude of genetic backgrounds and experimental setups, together with inter-individual variation, complicates cross-study comparisons and a global understanding of the mouse microbiota landscape. Here, we investigate the variability of the healthy mouse microbiota of five common lab mouse strains using 16S rDNA pyrosequencing.

Results

We find initial evidence for richness-driven, strain-independent murine enterotypes that show a striking resemblance to those in human, and which associate with calprotectin levels, a marker for intestinal inflammation. After enterotype stratification, we find that genetic, caging and inter-individual variation contribute on average 19%, 31.7% and 45.5%, respectively, to the variance in the murine gut microbiota composition. Genetic distance correlates positively to microbiota distance, so that genetically similar strains have more similar microbiota than genetically distant ones. Specific mouse strains are enriched for specific operational taxonomic units and taxonomic groups, while the ''cage effect'' can occur across mouse strain boundaries and is mainly driven by Helicobacter infections.

Conclusions

The detection of enterotypes suggests a common ecological cause, possibly low-grade inflammation that might drive differences among gut microbiota composition in mammals. Furthermore, the observed environmental and genetic effects have important consequences for experimental design in mouse microbiome research.     

Formation of an Antral Follicle-Like Structure by Bovine Cumulus-Oocyte Complexes Embedded with Fragmin/Protamine Microparticles

Fragmin/protamine microparticles (F/P MPs) approximately 0.5-1 µM in diameter were prepared by the simple mixing of fragmin with protamine. This study investigated the effects of F/P MP-containing collagen gels as a hormone carrier on the formation of antral follicle-like structures and on the development of growing bovine oocytes. The supplementation of F/P MPs in collagen gels contributed to the beneficial effects of follicle stimulating hormone (FSH) on the formation and size of antral follicle-like structures. The F/P MPs may serve as potential hormone carriers for the growth of cultured bovine oocytes from early antral follicles.     

Persistent expression of Nqo1 by p62-mediated Nrf2 activation facilitates p53-dependent mitotic catastrophe

Prolonged mitosis due to aberrant chromosome segregation permits cells to enter the G1 phase without cytokinesis and subsequently triggers the p53-dependent cell death program, known as mitotic catastrophe. Cells which fail to go through mitotic catastrophe create aneuploidy, posing a risk of oncogenesis. In the present report, we show that p62-mediated non-canonical activation of Nrf2 leads to the persistent expression of Nqo1, which plays a critical role for p53 stabilization during mitotic catastrophe. With prolonged exposure to nocodazole, a microtubule-depolymerizing agent, p62-deficient HCT116 cells exhibited an accumulation of a polyploid population with a limited appearance of apoptotic cells, which was attributable to the attenuated stabilization of p53. Combinatorial gene manipulation analysis verified that the regulatory cascade with a hierarchy of p62–Keap1–Nrf2–Nqo1 is required for p53 stabilization for mitotic catastrophe. This is consistent with the role of Nqo1 as a gatekeeper for proteasomal degradation of p53. Thus, we demonstrate for the first time the functional connection between the non-canonical Nrf2 pathway and p53-dependent cell death program upon prolonged mitosis.     

Studies on the anorectic effect of N-acylphosphatidylethanolamine and phosphatidylethanolamine in mice

N-acyl-phosphatidylethanolamine is a precursor phospholipid for anandamide, oleoylethanolamide, and other N-acylethanolamines, and it may in itself have biological functions in cell membranes. Recently, N-palmitoyl-phosphatidylethanolamine (NAPE) has been reported to function as an anorectic hormone secreted from the gut and acting on the brain (Gillum et al., [5]). In the current study, two of our laboratories independently investigated whether NAPE metabolites may be involved in mediating the anorectic action of NAPE i.p. injected in mice. Thus, the anorectic activity of a non-hydrolysable NAPE analogue, having ether bonds instead of ester bonds at sn1 and sn2 was compared with that of NAPE in molar equivalent doses. Furthermore, the anorectic effect of NAPE in NAPE-hydrolysing phospholipase D knockout animals was investigated. As negative controls, the NAPE precursor phosphatidylethanolamine and the related phospholipids phosphatidylcholine and phosphatidic acid were also tested. All compounds except one were found to inhibit food intake, raising the possibility that the effect of NAPE is non-specific.     

Fitness cost of pheromone production in signaling female moths

A secondary sexual character may act as an honest signal of the quality of the individual if the trait bears a cost and if its expression is phenotypically condition dependent. The cost of increasing the trait should be tolerable for individuals in good condition but not for those in a poor condition. The trait thus provides an honest signal of quality that enables the receiver to choose higher quality mates. Evidence for sex pheromones, which play a major role in shaping sexual evolution, inflicting a signaling cost is scarce. Here, we demonstrate that the amount of the major component of the pheromone in glands of Lobesia botrana (Lepidoptera) females at signaling time was significantly greater in large than in small females, that male moths preferred larger females as mates when responding to volatile signals, and small virgin females, but not large ones, exposed to conspecific pheromone, produced, when mated, significantly fewer eggs than nonexposed females. The latter indicates a condition-dependent cost of signaling. These results are in accordance with the predictions of condition-dependent honest signals. We therefore suggest that female signaling for males using sex pheromones bears a cost and thus calling may serve as honest advertisement for female quality.     

Effect of an asparagine-to-serine mutation at position 294 in neuraminidase on the pathogenicity of highly pathogenic H5N1 influenza A virus

Like the histidine-to-tyrosine substitution at position 274 in neuraminidase (NA H274Y), an asparagine-to-serine mutation at position 294 in this protein (NA N294S) confers oseltamivir resistance to highly pathogenic H5N1 influenza A viruses. However, unlike viruses with the NA H274Y mutation, the properties of viruses possessing NA N294S are not well understood. Here, we assessed the effect of the NA N294S substitution on the replication and pathogenicity of human H5N1 viruses and on the efficacy of the NA inhibitors oseltamivir and zanamivir in mouse and ferret models. Although NA N294S-possessing H5N1 viruses were attenuated in mice and ferrets compared to their oseltamivir-sensitive counterparts, one of the infected ferrets died from systemic infection, demonstrating the potential lethality in ferrets of oseltamivir-resistant H5N1 viruses with the NA N294S substitution. The efficacy of oseltamivir, but not that of zanamivir, against an NA N294S-possessing virus was substantially impaired both in ferrets and in vitro. These results demonstrate the considerable pathogenicity of NA N294S substitution-possessing H5N1 viruses and underscore the importance of monitoring the emergence of the NA N294S mutation in circulating H5N1 viruses.     

Additional effects of silver nanoparticles on bactericidal efficiency depend on calcination temperature and dip-coating speed

There is an increasing interest in the application of photocatalytic properties for disinfection of surfaces, air, and water. Titanium dioxide is widely used as a photocatalyst, and the addition of silver reportedly enhances its bactericidal action. However, the synergy of silver nanoparticles and TiO(2) is not well understood. The photocatalytic elimination of Bacillus atrophaeus was examined under different calcination temperatures, dip-coating speeds, and ratios of TiO(2), SiO(2), and Ag to identify optimal production conditions for the production of TiO(2)- and/or TiO(2)/Ag-coated glass for surface disinfection. Photocatalytic disinfection of pure TiO(2) or TiO(2) plus Ag nanoparticles was dependent primarily on the calcination temperature. The antibacterial activity of TiO(2) films was optimal with a high dip-coating speed and high calcination temperature (600°C). Maximal bacterial inactivation using TiO(2)/Ag-coated glass was also observed following high-speed dip coating but with a low calcination temperature (250°C). Scanning electron microscopy (SEM) showed that the Ag nanoparticles combined together at a high calcination temperature, leading to decreased antibacterial activity of TiO(2)/Ag films due to a smaller surface area of Ag nanoparticles. The presence of Ag enhanced the photocatalytic inactivation rate of TiO(2), producing a more pronounced effect with increasing levels of catalyst loading.     

WD repeat-containing protein 5, a ubiquitously expressed histone methyltransferase adaptor protein, regulates smooth muscle cell-selective gene activation through interaction with pituitary homeobox 2

WD repeat-containing protein 5 (WDR5) is a common component of mammalian mixed lineage leukemia methyltransferase family members and is important for histone H3 lysine 4 methylation (H3K4me), which has been implicated in control of activation of cell lineage genes during embryogenesis. However, WDR5 has not been considered to play a specific regulatory role in epigenetic programming of cell lineage because it is ubiquitously expressed. Previous work from our laboratory showed the appearance of histone H3K4me within smooth muscle cell (SMC)-marker gene promoters during the early stages of development of SMC from multipotential embryonic cells but did not elucidate the underlying mechanisms that mediate SMC-specific and locus-selective H3K4me. Results presented herein show that knockdown of WDR5 significantly decreased SMC-marker gene expression in cultured SMC differentiation systems and in Xenopus laevis embryos in vivo. In addition, we showed that WDR5 complexes within SMC progenitor cells contained H3K4 methyltransferase enzymatic activity and that knockdown of WDR5 selectively decreased H3K4me1 and H3K4me3 enrichment within SMC-marker gene promoter loci. Moreover, we present evidence that it is recruited to these gene promoter loci through interaction with a SMC-selective pituitary homeobox 2 (Pitx2). Taken together, studies provide evidence for a novel mechanism for epigenetic control of SMC-marker gene expression during development through interaction of WDR5, homeodomain proteins, and chromatin remodeling enzymes.