E-cadherin is essential for in vivo epidermal barrier function by regulating tight junctions

Cadherin adhesion molecules are key determinants of morphogenesis and tissue architecture. Nevertheless, the molecular mechanisms responsible for the morphogenetic contributions of cadherins remain poorly understood in vivo. Besides supporting cell-cell adhesion, cadherins can affect a wide range of cellular functions that include activation of cell signalling pathways, regulation of the cytoskeleton and control of cell polarity. To determine the role of E-cadherin in stratified epithelium of the epidermis, we have conditionally inactivated its gene in mice. Here we show that loss of E-cadherin in the epidermis in vivo results in perinatal death of mice due to the inability to retain a functional epidermal water barrier. Absence of E-cadherin leads to improper localization of key tight junctional proteins, resulting in permeable tight junctions and thus altered epidermal resistance. In addition, both Rac and activated atypical PKC, crucial for tight junction formation, are mislocalized. Surprisingly, our results indicate that E-cadherin is specifically required for tight junction, but not desmosome, formation and this appears to involve signalling rather than cell contact formation.     

A functional link between hyphal maintenance and quorum sensing in Candida albicans

Morphogenesis in Candida albicans requires hyphal initiation and maintenance, and both processes are regulated by the fungal quorum sensing molecule (QSM) farnesol. We show that deletion of C. albicans EED1, which is crucial for hyphal extension and maintenance, led to a dramatically increased sensitivity to farnesol, and thus identified the first mutant hypersensitive to farnesol. Furthermore, farnesol decreased the transient filamentation of an eed1Δ strain without inducing cell death, indicating that two separate mechanisms mediate quorum sensing and cell lysis by farnesol. To analyze the cause of farnesol hypersensitivity we constructed either hyperactive or deletion mutants of factors involved in farnesol signaling, by introducing the hyperactive RAS1^G13V or pADH1‐CYR1^CAT allele, or deleting CZF1 or NRG1 respectively. Neither of the constructs nor the exogenous addition of dB‐cAMP was able to rescue the farnesol hypersensitivity, highlighting that farnesol mediates its effects not only via the cAMP pathway. Interestingly, the eed1Δ strain also displayed increased farnesol production. When eed1Δ was grown under continuous medium flow conditions, to remove accumulating QSMs from the supernatant, maintenance of eed1Δ filamentation, although not restored, was significantly prolonged, indicating a link between farnesol sensitivity, production, and the hyphal maintenance‐defect in the eed1Δ mutant strain.     

Genetic structure in the European endemic seabird,Phalacrocorax aristotelis,shaped by a complex interaction of historical and contemporary,physical and nonphysical drivers

Geographically separated populations tend to be less connected by gene flow, as a result of physical or nonphysical barriers preventing dispersal, and this can lead to genetic structure. In this context, highly mobile organisms such as seabirds are interesting because the small effect of physical barriers means nonphysical ones may be relatively more important. Here, we use microsatellite and mitochondrial data to explore the genetic structure and phylogeography of Atlantic and Mediterranean populations of a European endemic seabird, the European shag, Phalacrocorax aristotelis, and identify the primary drivers of their diversification. Analyses of mitochondrial markers revealed three phylogenetic lineages grouping the North Atlantic, Spanish/Corsican and eastern Mediterranean populations, apparently arising from fragmentation during the Pleistocene followed by range expansion. These traces of historical fragmentation were also evident in the genetic structure estimated by microsatellite markers, despite significant contemporary gene flow among adjacent populations. Stronger genetic structure, probably promoted by landscape, philopatry and local adaptation, was found among distant populations and those separated by physical and ecological barriers. This study highlights the enduring effect of Pleistocene climatic changes on shag populations, especially within the Mediterranean Basin, and suggests a role for cryptic northern refugia, as well as known southern refugia, on the genetic structure of European seabirds. Finally, it outlines how contemporary ecological barriers and behavioural traits may maintain population divergence, despite long‐distance dispersal triggered by extreme environmental conditions (e.g. population crashes).     

Global Mental Health and Adolescent Anxiety: Kin,Care and Struggle in New Mexico

While recent developments within the field of global mental health have illuminated the reality of serious mental health difficulties worldwide, particularly in low-income settings, research that focuses on children and adolescents remains underdeveloped. This is especially the case with respect to ethnographic studies of lived experience of adolescents diagnosed with serious mental health conditions. Drawing from an interdisciplinary study of adolescents in New Mexico who were afflicted with a broad range of disorders according to contemporary research diagnostic criteria, this article focuses on anxiety-related conditions with respect to subjective experience and social–ecological contexts of living with such conditions. We offer preliminary observations regarding the value of linking ethnographic and research diagnostic data to address questions of resilience, endurance, capacity and struggle. These observations are intended as the basis for the formulation of more precise hypotheses about adolescent anxiety, kin, and care under conditions of structural violence marked by psychological, residential, and intergenerational adversity.     

Advances in NANI and NAPI accounting for the Baltic drainage basin: spatial and temporal trends and relationships to watershed TN and TP fluxes

In order to assess the progress toward eutrophication management goals, it is important to understand trends in land-based nutrient use. Here we present net anthropogenic nitrogen and phosphorus inputs (NANI and NAPI, respectively) for 2000 and 2010 for the Baltic Sea watershed. Overall, across the entire Baltic, between the 5-year periods centered on 2000 and 2010, NANI and NAPI decreased modestly by ?6 and ?4%, respectively, but with substantial regional variation, including major increases in the Gulf of Riga drainage basin (+19 and +58%, respectively) and decreases in the Danish Straits drainage basin (?25 and ?40% respectively). The changes were due primarily to changes in mineral fertilizer use. Mineral fertilizers dominated inputs, at 57% of both NANI and NAPI in 2000, increasing to 68 and 70%, respectively, by 2010. Net food and feed imports declined over that period, corresponding to increased crop production; either fewer imports of food and feedstocks were required to feed humans and livestock, or more of these commodities were exported. A strong linear relationship exists between regional net nutrient inputs and riverine nutrient fluxes for both periods. About 17% of NANI and 4.7% of NAPI were exported to the sea in 2000; these relationships did not significantly differ from those for 2010. Changes in NANI from 2000 to 2010 across basins were directly proportional rather than linearly related to changes in total N (TN) fluxes to the sea (i.e., no change in NANI suggests no change in TN flux). Similarly, for all basins except those draining to the Baltic Proper, changes in NAPI were proportional to changes in total P (TP) fluxes. The Danish Straits decreased most between 2000 and 2010, where NANI and NAPI declined by 25 and 40%, respectively, and corresponding fluxes of TN and TP declined 31 and 18%, respectively. For the Baltic Proper, NAPI was relatively unchanged between 2000 and 2010, while riverine TP fluxes decreased 25%, due possibly to lagged effects of fertilizer reduction resulting from socio-political changes in the early 1990s or improvements in sewage treatment capabilities. For most regions, further reductions in NANI and NAPI could be achieved by more efficient production and greater substitution of manure for imported mineral fertilizers.     

Ignoring spatial effects results in inadequate models for variation in littoral macroinvertebrate diversity

Studies focusing on the effects of spatial processes versus environmental filtering on aquatic metacommunities have so far been focused almost entirely on relatively isolated systems, such as sets of different lakes or streams. In contrast, metacommunity patterns and underlying processes within a single aquatic system have received less attention. In this study, we aimed to examine how strongly variations in different diversity indices are affected by spatial processes (dispersal) versus local environmental conditions (species sorting) within a large lake system. Modern biodiversity research focuses on multiple diversity facets because different indices may be uncorrelated within and between facets, and they may thus describe different phenomena. We investigated the relationship of littoral macroinvertebrate diversity with environmental and spatial factors using 10 indices of species, functional and taxonomic diversity. Using spatial factors as proxies of dispersal, we decomposed variation in diversity indices into fractions attributable to environmental and spatial factors. Our results highlighted generally equal or higher importance of spatial processes in controlling the variation in diversity indices when compared to local environmental variables. Local environmental conditions accounted for higher proportion of variation only in a single index (i.e. taxonomic diversity). These findings suggest that the effects of high dispersal rates (mass effects) may override the influences of local environmental conditions (species sorting) on the diversity in highly‐connected aquatic system, such as large lakes and marine coastal systems. Our results further suggest that biodiversity assessment and environmental monitoring in highly‐connected systems cannot rely solely on the idea of environmental control. We hence recommend that the roles of both environmental and spatial processes should be integrated in basic and applied ecological research of aquatic systems.     

Global biogeography of mating system variation in seed plants

Latitudinal gradients in biotic interactions have been suggested as causes of global patterns of biodiversity and phenotypic variation. Plant biologists have long speculated that outcrossing mating systems are more common at low than high latitudes owing to a greater predictability of plant–pollinator interactions in the tropics; however, these ideas have not previously been tested. Here, we present the first global biogeographic analysis of plant mating systems based on 624 published studies from 492 taxa. We found a weak decline in outcrossing rate towards higher latitudes and among some biomes, but no biogeographic patterns in the frequency of self‐incompatibility. Incorporating life history and growth form into biogeographic analyses reduced or eliminated the importance of latitude and biome in predicting outcrossing or self‐incompatibility. Our results suggest that biogeographic patterns in mating system are more likely a reflection of the frequency of life forms across latitudes rather than the strength of plant–pollinator interactions.