The common rs9939609 gene variant of the fat mass- and obesity-associated gene FTO is related to fat cell lipolysis

We investigated the rs9939609 single nucleotide polymorphism of the FTO gene in relation to fat cell function and adipose tissue gene expression in 306 healthy women with a wide range in body mass index (18-53 kg/m(2)). Subcutaneous adipose tissue biopsies were taken for fat cell metabolism studies and in a subgroup (n = 90) for gene expression analyses. In homozygous carriers of the T-allele, the in vitro basal (spontaneous) adipocyte glycerol release was increased by 22% (P = 0.007) and the in vivo plasma glycerol level was increased by approximately 30% (P = 0.037) compared with carriers of the A allele. In contrast, there were no genotype effects on catecholamine-stimulated lipolysis or basal or insulin-induced lipogenesis. We found no difference between genotypes for adipose tissue mRNA levels of FTO, hormone-sensitive lipase, adipose triglyceride lipase, perilipin, or CGI-58. Finally, the adipose tissue level of FTO mRNA was increased in obesity (P = 0.002), was similar in subcutaneous and omental adipose tissue, was higher in fat cells than in fat tissue (P = 0.0007), and was induced at an early stage in the differentiation process (P = 0.004). These data suggest a role of the FTO gene in fat cell lipolysis, which may be important in explaining why the gene is implicated in body weight regulation.     

Hepoxilin A3 (HXA3) synthase deficiency is causative of a novel ichthyosis form

Non-bullous congenital ichthyosis erythroderma (NCIE) and lamellar ichthyosis (LI) are characterized by mutations in 12R-lipoxygenase (12R-LOX) and/or epidermal lipoxygenase 3 (eLOX3) enzymes. The eLOX3 lacks oxygenase activity, but is capable of forming hepoxilin-type products from arachidonic acid-derived hydroperoxide from 12R-LOX, termed 12R-hydroperoxyeicosa-5,8,10,14-tetraenoic acid (12R-HpETE). Mutations in either of two enzymes lead to NCIE or LI. Moreover, 12R-LOX-deficient mice exhibit severe phenotypic water barrier dysfunctions. Here, we demonstrate that 12R-HpETE can also be transformed to 8R-HXA(3) by hepoxilin A(3) (HXA(3)) synthase (12-lipoxygenase), which exhibits oxygenase activity. We also presented a novel form of ichthyosis in a patient, termed hepoxilin A(3) synthase-linked ichthyosis (HXALI), whose scales expressed high levels of 12R-LOX, but were deficient of HXA(3) synthase.     

The nuclear Dbf2-related kinase COT1 and the mitogen-activated protein kinases MAK1 and MAK2 genetically interact to regulate filamentous growth, hyphal fusion and sexual development in Neurospora crassa

Ndr kinases, such as Neurospora crassa COT1, are important for cell differentiation and polar morphogenesis, yet their input signals as well as their integration into a cellular signaling context are still elusive. Here, we identify the cot-1 suppressor gul-4 as mak-2 and show that mutants of the gul-4/mak-2 mitogen-activated protein (MAP) kinase pathway suppress cot-1 phenotypes along with a concomitant reduction in protein kinase A (PKA) activity. Furthermore, mak-2 pathway defects are partially overcome in a cot-1 background and are associated with increased MAK1 MAPK signaling. A comparative characterization of N. crassa MAPKs revealed that they act as three distinct modules during vegetative growth and asexual development. In addition, common functions of MAK1 and MAK2 signaling during maintenance of cell-wall integrity distinguished the two ERK-type pathways from the p38-type OS2 osmosensing pathway. In contrast to separate functions during vegetative growth, the concerted activity of the three MAPK pathways is essential for cell fusion and for the subsequent formation of multicellular structures that are required for sexual development. Taken together, our data indicate a functional link between COT1 and MAPK signaling in regulating filamentous growth, hyphal fusion, and sexual development.     

Specific TRPC6 channel activation, a novel approach to stimulate keratinocyte differentiation

The protective epithelial barrier in our skin undergoes constant regulation, whereby the balance between differentiation and proliferation of keratinocytes plays a major role. Impaired keratinocyte differentiation and proliferation are key elements in the pathophysiology of several important dermatological diseases, including atopic dermatitis and psoriasis. Ca(2+) influx plays an essential role in this process presumably mediated by different transient receptor potential (TRP) channels. However, investigating their individual role was hampered by the lack of specific stimulators or inhibitors. Because we have recently identified hyperforin as a specific TRPC6 activator, we investigated the contribution of TRPC6 to keratinocyte differentiation and proliferation. Like the endogenous differentiation stimulus high extracellular Ca(2+) concentration ([Ca(2+)](o)), hyperforin triggers differentiation in HaCaT cells and in primary cultures of human keratinocytes by inducing Ca(2+) influx via TRPC6 channels and additional inhibition of proliferation. Knocking down TRPC6 channels prevents the induction of Ca(2+)- and hyperforin-induced differentiation. Importantly, TRPC6 activation is sufficient to induce keratinocyte differentiation similar to the physiological stimulus [Ca(2+)](o). Therefore, TRPC6 activation by hyperforin may represent a new innovative therapeutic strategy in skin disorders characterized by altered keratinocyte differentiation.     

Modulation by D1 and D2 dopamine receptors of ATP-induced release of intracellular Ca2+ in cultured rat striatal neurons

The aim of the present study was to investigate, whether dopamine D1 and/or D2 receptors are able to interfere with the ATP-induced increase of the intracellular Ca2+ concentration ([Ca2+]i) in cultured striatal neurons identified by their morphological characteristics and their [Ca2+]i transients in response to a high-K+ superfusion medium. ATP appeared to release Ca2+ mostly from an intracellular pool, since its effect was markedly depressed in the presence of cyclopiazonic acid, which is known to deplete such storage sites [Rubini, P., Pinkwart, C., Franke, H., Gerevich, Z., N?renberg, W., Illes, P., 2006. Regulation of intracellular Ca2+ by P2Y1 receptors may depend on the developmental stage of cultured rat striatal neurons. J. Cell. Physiol. 209, 81-93]. The mixed D1/D2 receptor agonist dopamine increased the ATP-induced [Ca2+]i transients in a subpopulation of neurons. At the same time, dopamine did not alter the responses to K+ in these cells. The selective D1 (SKF 83566) and D2 (sulpiride) receptor antagonists failed to modify the effect of ATP, but unmasked in the previously unresponsive neurons an inhibitory and facilitatory effect of dopamine, respectively. A combination of the two antagonists resulted in a failure of dopamine to modulate the [Ca2+]i responses in any cell investigated. In conclusion, D1 and D2 receptors may modulate in an opposite manner the signalling pathways of P2Y1 receptors in striatal neurons and thereby alter their development/growth or their cellular excitability and/or the release of GABA from their terminals.     

AlphaPIX Rho GTPase guanine nucleotide exchange factor regulates lymphocyte functions and antigen receptor signaling

AlphaPIX is a Rho GTPase guanine nucleotide exchange factor domain-containing signaling protein that associates with other proteins involved in cytoskeletal-membrane complexes. It has been shown that PIX proteins play roles in some immune cells, including neutrophils and T cells. In this study, we report the immune system phenotype of alphaPIX knockout mice. We extended alphaPIX expression experiments and found that whereas alphaPIX was specific to immune cells, its homolog betaPIX was expressed in a wider range of cells. Mice lacking alphaPIX had reduced numbers of mature lymphocytes and defective immune responses. Antigen receptor-directed proliferation of alphaPIX(-) T and B cells was also reduced, but basal migration was enhanced. Accompanying these defects, formation of T-cell-B-cell conjugates and recruitment of PAK and Lfa-1 integrin to the immune synapse were impaired in the absence of alphaPIX. Proximal antigen receptor signaling was largely unaffected, with the exception of reduced phosphorylation of PAK and expression of GIT2 in both T cells and B cells. These results reveal specific roles for alphaPIX in the immune system and suggest that redundancy with betaPIX precludes a more severe immune phenotype.     

The genetic consequences of dog breed formation—Accumulation of deleterious genetic variation and fixation of mutations associated with myxomatous mitral valve disease in cavalier King Charles spaniels

Selective breeding for desirable traits in strictly controlled populations has generated an extraordinary diversity in canine morphology and behaviour, but has also led to loss of genetic variation and random entrapment of disease alleles. As a consequence, specific diseases are now prevalent in certain breeds, but whether the recent breeding practice led to an overall increase in genetic load remains unclear. Here we generate whole genome sequencing (WGS) data from 20 dogs per breed from eight breeds and document a ~10% rise in the number of derived alleles per genome at evolutionarily conserved sites in the heavily bottlenecked cavalier King Charles spaniel breed (cKCs) relative to in most breeds studied here. Our finding represents the first clear indication of a relative increase in levels of deleterious genetic variation in a specific breed, arguing that recent breeding practices probably were associated with an accumulation of genetic load in dogs. We then use the WGS data to identify candidate risk alleles for the most common cause for veterinary care in cKCs–the heart disease myxomatous mitral valve disease (MMVD). We verify a potential link to MMVD for candidate variants near the heart specific NEBL gene in a dachshund population and show that two of the NEBL candidate variants have regulatory potential in heart-derived cell lines and are associated with reduced NEBL isoform nebulette expression in papillary muscle (but not in mitral valve, nor in left ventricular wall). Alleles linked to reduced nebulette expression may hence predispose cKCs and other breeds to MMVD via loss of papillary muscle integrity.     

Distribution and effects of tree leaf litter on vegetation composition and biomass in a forest-grassland ecotone

Aims After abandonment of grasslands, secondary succession leads to the invasion by woody species. This process begins with the accumulation of tree litter in the forest–grassland ecotone. Our objectives were to determine the relationships between litter amounts and vegetation composition and cover along natural forest–grassland ecotones and to experimentally study the initial effects of tree litter accumulation on grassland vegetation and on microsite conditions.Methods We established 11 transects varying from 12 to 15 m in length in different forest–grassland ecotones in the Lahn-Dill highlands, Germany, and measured the mass and cover of tree litter and the cover and composition of vegetation at five sequential positions along each transect by using 1 m 2 plots with five replications. In a field experiment, we established plots subjected to different litter amounts (0, 200 and 600g m ?2) and evaluated changes in grassland vegetation, soil temperature and soil nutrient availability below the litter layer.Important findings Tree litter amounts decrease from 650 to 65g m ?2 across the forest–grassland ecotone. Vegetation changed from shrubs and annual species (adapted to more stressful conditions) in the forests edge to grasses, rosettes and hemirosette species (with higher competitive abilities) in the grassland. These anthropogenic forest–grassland ecotones showed abrupt edges, and the two adjacent ecosystems were characterized by different species pools and functional groups. In the field experiment, the presence of a litter layer reduced vegetation biomass and cover; the species richness was only reduced in the treatment with high litter (600g m ?2). Additionally, adding litter on top of vegetation also reduced thermal amplitude and the number of frost days, while increasing the availability of some nutrients, such as nitrogen and aluminium, the latter being an indicator of soil acidification. Adding a tree litter layer of 600g m ?2 in grassland areas had strong effects on the composition and diversity of grassland vegetation by reducing the cover of several key grassland species. In, or near, forest edges, litter accumulation rapidly changes established vegetation, microsite conditions and soil nutrients.