Organ-specific functions of tissue-resident macrophages in the steady-state heart are unknown. Here, we show that cardiac macrophages facilitate electrical conduction through the distal ...atrioventricular node, where conducting cells densely intersperse with elongated macrophages expressing connexin 43. When coupled to spontaneously beating cardiomyocytes via connexin-43-containing gap junctions, cardiac macrophages have a negative resting membrane potential and depolarize in synchrony with cardiomyocytes. Conversely, macrophages render the resting membrane potential of cardiomyocytes more positive and, according to computational modeling, accelerate their repolarization. Photostimulation of channelrhodopsin-2-expressing macrophages improves atrioventricular conduction, whereas conditional deletion of connexin 43 in macrophages and congenital lack of macrophages delay atrioventricular conduction. In the Cd11bDTR mouse, macrophage ablation induces progressive atrioventricular block. These observations implicate macrophages in normal and aberrant cardiac conduction.
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•Tissue-resident macrophages abound in the mouse and human AV nodes•Connexin 43 connects macrophages with cardiomyocytes•Macrophages modulate the electrical activity of cardiomyocytes•Macrophages assist normal AV nodal conduction
Heart-resident macrophages directly modulate the electrical properties of cardiomyocytes.
Limited scope for latitudinal extension of reef corals Muir, Paul R.; Wallace, Carden C.; Done, Terence ...
Science (American Association for the Advancement of Science),
06/2015, Letnik:
348, Številka:
6239
Journal Article
Recenzirano
An analysis of present-day global depth distributions of reef-building corals and underlying environmental drivers contradicts a commonly held belief that ocean warming will promote tropical coral ...expansion into temperate latitudes. Using a global data set of a major group of reef corals, we found that corals were confined to shallower depths at higher latitudes (up to 0.6 meters of predicted shallowing per additional degree of latitude). Latitudinal attenuation of the most important driver of this phenomenon—the dose of photosynthetically available radiation over winter—would severely constrain latitudinal coral range extension in response to ocean warming. Latitudinal gradients in species richness for the group also suggest that higher winter irradiance at depth in low latitudes allowed a deep-water fauna that was not viable at higher latitudes.
Mass bleaching associated with unusually high sea temperatures represents one of the greatest threats to corals and coral reef ecosystems. Deeper reef areas are hypothesized as potential refugia, but ...the susceptibility of Scleractinian species over depth has not been quantified. During the most severe bleaching event on record, we found up to 83% of coral cover severely affected on Maldivian reefs at a depth of 3–5 m, but significantly reduced effects at 24–30 m. Analysis of 153 species' responses showed depth, shading and species identity had strong, significant effects on susceptibility. Overall, 73.3% of the shallow-reef assemblage had individuals at a depth of 24–30 m with reduced effects, potentially mitigating local extinction and providing a source of recruits for population recovery. Although susceptibility was phylogenetically constrained, species-level effects caused most lineages to contain some partially resistant species. Many genera showed wide variation between species, including Acropora, previously considered highly susceptible. Extinction risk estimates showed species and lineages of concern and those likely to dominate following repeated events. Our results show that deeper reef areas provide refuge for a large proportion of Scleractinian species during severe bleaching events and that the deepest occurring individuals of each population have the greatest potential to survive and drive reef recovery.
Neurodegeneration in Alzheimer's disease (AD) is closely associated with the accumulation of pathologic tau aggregates in the form of neurofibrillary tangles. We found that a p.Asp395Gly mutation in
...(valosin-containing protein) was associated with dementia characterized neuropathologically by neuronal vacuoles and neurofibrillary tangles. Moreover, VCP appeared to exhibit tau disaggregase activity in vitro, which was impaired by the p.Asp395Gly mutation. Additionally, intracerebral microinjection of pathologic tau led to increased tau aggregates in mice in which p.Asp395Gly
mice was knocked in, as compared with injected wild-type mice. These findings suggest that p.Asp395Gly
is an autosomal-dominant genetic mutation associated with neurofibrillary degeneration in part owing to reduced tau disaggregation, raising the possibility that VCP may represent a therapeutic target for the treatment of AD.
Reductions in genetic diversity can have widespread ecological consequences: populations with higher genetic diversity are more stable, productive and resistant to disturbance or disease than ...populations with lower genetic diversity. These ecological effects of genetic diversity differ from the more familiar evolutionary consequences of depleting genetic diversity, because ecological effects manifest within a single generation. If common, genetic diversity effects have the potential to change the way we view and manage populations, but our understanding of these effects is far from complete, and the role of genetic diversity in sexually reproducing animals remains unclear. Here, we examined the effects of genetic diversity in a sexually reproducing marine invertebrate in the field. We manipulated the genetic diversity of experimental populations and then measured individual survival, growth, and fecundity, as well as the size of offspring produced by individuals in high and low genetic diversity populations. Overall, we found greater genetic diversity increased performance across all metrics, and that complementarity effects drove the increased productivity of our high-diversity populations. Our results show that differences in genetic diversity among populations can have pervasive effects on population productivity within remarkably short periods of time.
Metamorphosis is common in animals, yet the genetic associations between life cycle stages are poorly understood. Given the radical changes that occur at metamorphosis, selection may differ before ...and after metamorphosis, and the extent that genetic associations between pre- and post-metamorphic traits constrain evolutionary change is a subject of considerable interest. In some instances, metamorphosis may allow the genetic decoupling of life cycle stages, whereas in others, metamorphosis could allow complementary responses to selection across the life cycle. Using a diallel breeding design, we measured viability at four ontogenetic stages (embryo, larval, juvenile and adult viability), in the ascidian Ciona intestinalis and examined the orientation of additive genetic variation with respect to the metamorphic boundary. We found support for one eigenvector of G (gobsmax), which contrasted larval viability against embryo viability and juvenile viability. Target matrix rotation confirmed that while gobsmax shows genetic associations can extend beyond metamorphosis, there is still considerable scope for decoupled phenotypic evolution. Therefore, although genetic associations across metamorphosis could limit that range of phenotypes that are attainable, traits on either side of the metamorphic boundary are capable of some independent evolutionary change in response to the divergent conditions encountered during each life cycle stage.
The production of reactive oxygen species (ROS) in a highly regulated fashion is a hallmark of members of the NADPH oxidase (Nox) family of enzymes. Nox enzymes are present in most eukaryotic groups ...such as the amebozoid, fungi, algae and plants, and animals, in which they are involved in seemingly diverse biological processes. However, a comprehensive survey of Nox functions throughout biology reveals common functional themes. Noxes are often activated in response to stressful conditions such as nutrient starvation, physical damage, or pathogen attack. Although the end result varies depending on the organism and tissue, Nox-produced ROS mediate the response to the adverse stimuli, such as innate immunity responses in plants and animals or cell differentiation in
Dictyostelium, fungi, and plants. These responses involve ROS-mediated signaling mechanisms occurring at intracellular or cell-to-cell levels and sometimes involve cell wall or extracellular matrix cross-linking. Indeed, Noxes are involved in local and systemic signaling from plants to fish and in cross-linking of the plant hair-cell wall, synthesis of the nematode cuticle, and formation of the sea urchin fertilization envelope. The extensive use of Nox enzymes in biology to regulate cell-to-cell signaling and morphogenesis suggests that additional functions in mammalian signaling and development remain to be discovered.
The individuals of many species shift habitats at different stages in their lives. Sometimes, these habitat shifts coincide with an ontogenetic transition. These ontogenetic habitat shifts can allow ...species to access nutritional resources, avoid conspecific aggression or predation, or secure breeding opportunities when it is advantageous to do so. The Kermadec Islands giant limpet
Scutellastra kermadecensis
is a protandrous hermaphrodite endemic to Rangitāhua, the Kermadec Islands. These limpets have an unusual habit whereby small limpets (piggies) piggy-back on the shells of larger individuals rather than living on the rocky substrate. We investigated whether the ontogenetic habitat shift between the piggy-backing and rock-attached limpets was determined by the availability of free space on the rock or whether the ontogenetic habitat shift was a response to the properties of the surrounding limpet population. We found that the available rock space did not influence the size at which an individual transitioned from being a piggy to being rock-attached. Furthermore, larger rock-attached limpets were more likely to have piggies, they had more piggies, and the piggies were larger. Overall, our results suggest that Kermadec giant limpets are motivated to piggy-back by the properties of the social environment rather than space constraints. The piggy-backing behaviour may be a mechanism to avoid bulldozing by larger limpets, to access grazing opportunities on the shells of larger limpets, and/or to monopolise breeding opportunities with larger rock-attached females. We discuss the repercussions of this life-history strategy for this extremely range-restricted species, with reference to how these populations may be monitored and maintained.
Genetic correlations between traits can concentrate genetic variance into fewer phenotypic dimensions that can bias evolutionary trajectories along the axis of greatest genetic variance and away from ...optimal phenotypes, constraining the rate of evolution. If genetic correlations limit adaptation, rapid adaptive divergence between multiple contrasting environments may be difficult. However, if natural selection increases the frequency of rare alleles after colonization of new environments, an increase in genetic variance in the direction of selection can accelerate adaptive divergence. Here, we explored adaptive divergence of an Australian native wildflower by examining the alignment between divergence in phenotype mean and divergence in genetic variance among four contrasting ecotypes. We found divergence in mean multivariate phenotype along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with much of the divergence in phenotype among ecotypes associated with changes in trait combinations containing substantial levels of genetic variance. Overall, our results suggest that natural selection can alter the distribution of genetic variance underlying phenotypic traits, increasing the amount of genetic variance in the direction of natural selection and potentially facilitating rapid adaptive divergence during an adaptive radiation.
Genetic variance is not equal for all multivariate combinations of traits. This inequality, in which some combinations of traits have abundant genetic variation while others have very little, biases ...the rate and direction of multivariate phenotypic evolution. However, we still understand little about what causes genetic variance to differ among trait combinations. Here, we investigate the relative roles of mutation and selection in determining the genetic variance of multivariate phenotypes. We accumulated mutations in an outbred population of
and analyzed wing shape and size traits for over 35,000 flies to simultaneously estimate the additive genetic and additive mutational (co)variances. This experimental design allowed us to gain insight into the phenotypic effects of mutation as they arise and come under selection in naturally outbred populations. Multivariate phenotypes associated with more (less) genetic variance were also associated with more (less) mutational variance, suggesting that differences in mutational input contribute to differences in genetic variance. However, mutational correlations between traits were stronger than genetic correlations, and most mutational variance was associated with only one multivariate trait combination, while genetic variance was relatively more equal across multivariate traits. Therefore, selection is implicated in breaking down trait covariance and resulting in a different pattern of genetic variance among multivariate combinations of traits than that predicted by mutation and drift. Overall, while low mutational input might slow evolution of some multivariate phenotypes, stabilizing selection appears to reduce the strength of evolutionary bias introduced by pleiotropic mutation.
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