Hepatic stellate cells function as regulatory bystanders

Regulatory T cells (Tregs) contribute significantly to the tolerogenic nature of the liver. The mechanisms, however, underlying liver-associated Treg induction are still elusive. We recently identified the vitamin A metabolite, retinoic acid (RA), as a key controller that promotes TGF-β-dependent Foxp3(+) Treg induction but inhibits TGF-β-driven Th17 differentiation. To investigate whether the RA producing hepatic stellate cells (HSC) are part of the liver tolerance mechanism, we investigated the ability of HSC to function as regulatory APC. Different from previous reports, we found that highly purified HSC did not express costimulatory molecules and only upregulated MHC class II after in vitro culture in the presence of exogenous IFN-γ. Consistent with an insufficient APC function, HSC failed to stimulate naive OT-II TCR transgenic CD4(+) T cells and only moderately stimulated α-galactosylceramide-primed invariant NKT cells. In contrast, HSC functioned as regulatory bystanders and promoted enhanced Foxp3 induction by OT-II TCR transgenic T cells primed by spleen dendritic cells, whereas they greatly inhibited the Th17 differentiation. Furthermore, the regulatory bystander capacity of the HSC was completely dependent on their ability to produce RA. Our data thus suggest that HSC can function as regulatory bystanders, and therefore, by promoting Tregs and suppressing Th17 differentiation, they might represent key players in the mechanism that drives liver-induced tolerance.     

Bovine Brain Myelin Glycerophosphocholine Choline Phosphodiesterase is an Alkaline Lysosphingomyelinase of the eNPP-Family, Regulated by Lysosomal Sorting

Glycerophosphocholine choline phosphodiesterase (GPC-Cpde) is a glycosylphosphatidylinositol (GPI)-anchored alkaline hydrolase that is expressed in the brain and kidney. In brain the hydrolase is synthesized by the oligodendrocytes and expressed on the myelin membrane. There are two forms of brain GPC-Cpde, a membrane-linked (mGPC-Cpde) and a soluble (sGPC-Cpde). Here we report the characterisation sGPC-Cpde from bovine brain. The amino acid sequence was identical to ectonucleotide pyrophosphatase/phosphodiesterase 6 (eNPP6) precursor, lacking the N-terminal signal peptide region and a C-terminal stretch, suggesting that the hydrolase was solubilised by C-terminal proteolysis, releasing the GPI-anchor. sGPC-Cpde existed as two isoforms, a homodimer joined by a disulfide bridge linking C414 from each monomer, and a monomer resulting from proteolysis N-terminally to this disulfide bond. The only internal disulfide bridge, linking C142 and C154, stabilises the choline-binding pocket. sGPC-Cpde was specific for lysosphingomyelin, displaying 1 to 2 orders of magnitude higher catalytic activity than towards GPC and lysophosphatidylcholine, suggesting that GPC-Cpde may function in the sphingomyelin signaling, rather than in the homeostasis of acylglycerophosphocholine metabolites. The truncated high mannose and bisected hybrid type glycans linked to N118 and N341 of sGPC-Cpde is a hallmark of glycans in lysosomal glycoproteins, subjected to GlcNAc-1-phosphorylation en route through Golgi. Thus, sGPC-Cpde may originate from the lysosomes, suggesting that lysosomal sorting contributes to the level of mGPC-Cpde on the myelin membrane.     

Root engineering in maize by increasing cytokinin degradation causes enhanced root growth and leaf mineral enrichment

Plant Molecular Biology - Root-specific expression of a cytokinin-degrading CKX gene in maize roots causes formation of a larger root system leading to higher element content in shoot organs. The...     

The geometry and genetics of hybridization

When divergent populations form hybrids, hybrid fitness can vary with genome composition, current environmental conditions, and the divergence history of the populations. We develop analytical predictions for hybrid fitness, which incorporate all three factors. The predictions are based on Fisher's geometric model, and apply to a wide range of population genetic parameter regimes and divergence conditions, including allopatry and parapatry, local adaptation, and drift. Results show that hybrid fitness can be decomposed into intrinsic effects of admixture and heterozygosity, and extrinsic effects of the (local) adaptedness of the parental lines. Effect sizes are determined by a handful of geometric distances, which have a simple biological interpretation. These distances also reflect the mode and amount of divergence, such that there is convergence toward a characteristic pattern of intrinsic isolation. We next connect our results to the quantitative genetics of line crosses in variable or patchy environments. This means that the geometrical distances can be estimated from cross data, and provides a simple interpretation of the “composite effects.” Finally, we develop extensions to the model, involving selectively induced disequilibria, and variable phenotypic dominance. The geometry of fitness landscapes provides a unifying framework for understanding speciation, and wider patterns of hybrid fitness.     

Follicular 17β-estradiol and progesterone concentrations and degree of cumulus cell expansion as predictors of in vivo-matured oocyte developmental competence in superstimulated heifers

The quality of an oocyte is crucial for successful generation of offspring, but few selection parameters have been identified that reliably predict oocyte developmental competence. The objective of the present study was to determine whether the developmental competence of in vivo-matured oocytes derived from superstimulated heifers could be predicted by 17β-estradiol and progesterone concentrations in follicular fluid, degree of cumulus cell expansion, and follicular diameter. Cumulus oocyte complexes were individually collected from follicles ≥8 mm 22 hours after an induced LH peak and individually fertilized and cultured in vitro. Only oocytes that originated from follicles with 17β-estradiol ≤0.25 μM and progesterone ≥0.26 μM developed into blastocysts. When a combination of these cutoff values was evaluated as a predictor of oocyte competence, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 75%, 49%, and 100%, respectively. Hormone concentrations in follicular fluid were also associated with the degree of cumulus cell expansion and only cumulus oocyte complexes with full expansion developed into blastocysts; sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 71%, 45%, and 100%, respectively, when full expansion was used as the predictive criterion for blastocyst production. Follicular diameter was not a good predictor of oocyte competence. In conclusion, concentrations of 17β-estradiol and progesterone in the preovulatory follicle and the degree of cumulus cell expansion are predictors of blastocyst production in superstimulated heifers and can be used as selection markers for oocyte developmental competency.     

Food security versus biodiversity protection: an example of land-sharing from East Africa

The recent controversial debate on land-sharing versus land-sparing is clearly exemplified in the East African mountains, one of the most diverse biodiversity hotspots on our planet. In these areas, species richness is particularly concentrated in the mountain cloud forests which are surrounded by a sea of dry lowland savannas heavily encroached on by local communities. Sustainable land use practices in the lowlands, however, are necessary to safeguard the natural capital at higher elevations. The interdependence between sustainable land-use and conservation of biodiversity hotspots was underlined during a workshop held in the rural areas of Kenya, East Africa, early spring 2013. It was concluded that close links between livelihoods, natural capital and poverty remains a fundamental challenge in East Africa’s forest conservation efforts.     

Increased Cardiac Myocyte PDE5 Levels in Human and Murine Pressure Overload Hypertrophy Contribute to Adverse LV Remodeling

Background

The intracellular second messenger cGMP protects the heart under pathological conditions. We examined expression of phosphodiesterase 5 (PDE5), an enzyme that hydrolyzes cGMP, in human and mouse hearts subjected to sustained left ventricular (LV) pressure overload. We also determined the role of cardiac myocyte-specific PDE5 expression in adverse LV remodeling in mice after transverse aortic constriction (TAC).

Methodology/Principal Findings

In patients with severe aortic stenosis (AS) undergoing valve replacement, we detected greater myocardial PDE5 expression than in control hearts. We observed robust expression in scattered cardiac myocytes of those AS patients with higher LV filling pressures and BNP serum levels. Following TAC, we detected similar, focal PDE5 expression in cardiac myocytes of C57BL/6NTac mice exhibiting the most pronounced LV remodeling. To examine the effect of cell-specific PDE5 expression, we subjected transgenic mice with cardiac myocyte-specific PDE5 overexpression (PDE5-TG) to TAC. LV hypertrophy and fibrosis were similar as in WT, but PDE5-TG had increased cardiac dimensions, and decreased dP/dt_max and dP/dt_min with prolonged tau (P<0.05 for all). Greater cardiac dysfunction in PDE5-TG was associated with reduced myocardial cGMP and SERCA2 levels, and higher passive force in cardiac myocytes in vitro.

Conclusions/Significance

Myocardial PDE5 expression is increased in the hearts of humans and mice with chronic pressure overload. Increased cardiac myocyte-specific PDE5 expression is a molecular hallmark in hypertrophic hearts with contractile failure, and represents an important therapeutic target.