Developmental constraints enforce altruism and avert the tragedy of the commons in a social microbe.

Organisms often cooperate through the production of freely available public goods. This can greatly benefit the group but is vulnerable to the "tragedy of the commons" if individuals lack the motivation to make the necessary investment into public goods production. Relatedness to groupmates can motivate individual investment because group success ultimately benefits their genes' own self-interests. However, systems often lack mechanisms that can reliably ensure that relatedness is high enough to promote cooperation. Consequently, groups face a persistent threat from the tragedy unless they have a mechanism to enforce investment when relatedness fails to provide adequate motivation. To understand the real threat posed by the tragedy and whether groups can avert its impact, we determine how the social amoeba Dictyostelium discoideum responds as relatedness decreases to levels that should induce the tragedy. We find that, while investment in public goods declines as overall within-group relatedness declines, groups avert the expected catastrophic collapse of the commons by continuing to invest, even when relatedness should be too low to incentivize any contribution. We show that this is due to a developmental buffering system that generates enforcement because insufficient cooperation perturbs the balance of a negative feedback system controlling multicellular development. This developmental constraint enforces investment under the conditions expected to be most tragic, allowing groups to avert a collapse in cooperation. These results help explain how mechanisms that suppress selfishness and enforce cooperation can arise inadvertently as a by-product of constraints imposed by selection on different traits.

Inferring Adaptive Codon Preference to Understand Sources of Selection Shaping Codon Usage Bias.

Alternative synonymous codons are often used at unequal frequencies. Classically, studies of such codon usage bias (CUB) attempted to separate the impact of neutral from selective forces by assuming that deviations from a predicted neutral equilibrium capture selection. However, GC-biased gene conversion (gBGC) can also cause deviation from a neutral null. Alternatively, selection has been inferred from CUB in highly expressed genes, but the accuracy of this approach has not been extensively tested, and gBGC can interfere with such extrapolations (e.g., if expression and gene conversion rates covary). It is therefore critical to examine deviations from a mutational null in a species with no gBGC. To achieve this goal, we implement such an analysis in the highly AT rich genome of Dictyostelium discoideum, where we find no evidence of gBGC. We infer neutral CUB under mutational equilibrium to quantify "adaptive codon preference," a nontautologous genome wide quantitative measure of the relative selection strength driving CUB. We observe signatures of purifying selection consistent with selection favoring adaptive codon preference. Preferred codons are not GC rich, underscoring the independence from gBGC. Expression-associated "preference" largely matches adaptive codon preference but does not wholly capture the influence of selection shaping patterns across all genes, suggesting selective constraints associated specifically with high expression. We observe patterns consistent with effects on mRNA translation and stability shaping adaptive codon preference. Thus, our approach to quantifying adaptive codon preference provides a framework for inferring the sources of selection that shape CUB across different contexts within the genome.

Mutant resources for functional genomics in Dictyostelium discoideum using REMI-seq technology.

BACKGROUND: Genomes can be sequenced with relative ease, but ascribing gene function remains a major challenge. Genetically tractable model systems are crucial to meet this challenge. One powerful model is the social amoeba Dictyostelium discoideum, a eukaryotic microbe widely used to study diverse questions in the cell, developmental and evolutionary biology. RESULTS: We describe REMI-seq, an adaptation of Tn-seq, which allows high throughput, en masse, and quantitative identification of the genomic site of insertion of a drug resistance marker after restriction enzyme-mediated integration. We use REMI-seq to develop tools which greatly enhance the efficiency with which the sequence, transcriptome or proteome variation can be linked to phenotype in D. discoideum. These comprise (1) a near genome-wide resource of individual mutants and (2) a defined pool of 'barcoded' mutants to allow large-scale parallel phenotypic analyses. These resources are freely available and easily accessible through the REMI-seq website that also provides comprehensive guidance and pipelines for data analysis. We demonstrate that integrating these resources allows novel regulators of cell migration, phagocytosis and macropinocytosis to be rapidly identified. CONCLUSIONS: We present methods and resources, generated using REMI-seq, for high throughput gene function analysis in a key model system.

Strategic investment explains patterns of cooperation and cheating in a microbe.

Contributing to cooperation is typically costly, while its rewards are often available to all members of a social group. So why should individuals be willing to pay these costs, especially if they could cheat by exploiting the investments of others? Kin selection theory broadly predicts that individuals should invest more into cooperation if their relatedness to group members is high (assuming they can discriminate kin from nonkin). To better understand how relatedness affects cooperation, we derived the ?Collective Investment" game, which provides quantitative predictions for patterns of strategic investment depending on the level of relatedness. We then tested these predictions by experimentally manipulating relatedness (genotype frequencies) in mixed cooperative aggregations of the social amoeba Dictyostelium discoideum, which builds a stalk to facilitate spore dispersal. Measurements of stalk investment by natural strains correspond to the predicted patterns of relatedness-dependent strategic investment, wherein investment by a strain increases with its relatedness to the group. Furthermore, if overall group relatedness is relatively low (i.e., no strain is at high frequency in a group) strains face a scenario akin to the "Prisoner's Dilemma" and suffer from insufficient collective investment. We find that strains employ relatedness-dependent segregation to avoid these pernicious conditions. These findings demonstrate that simple organisms like D. discoideum are not restricted to being ?cheaters" or ?cooperators" but instead measure their relatedness to their group and strategically modulate their investment into cooperation accordingly. Consequently, all individuals will sometimes appear to cooperate and sometimes cheat due to the dynamics of strategic investing.

Coenzyme A and protein CoAlation levels are regulated in response to oxidative stress and during morphogenesis in Dictyostelium discoideum.

Dictyostelium discoideum (D. discoideum) is a simple eukaryote with a unique life cycle in which it differentiates from unicellular amoebae into a fruiting body upon starvation. Reactive oxygen species (ROS) have been associated with bacterial predation, as well as regulatory events during D. discoideum development and differentiation. Coenzyme A (CoA) is a key metabolic integrator in all living cells. A novel function of CoA in redox regulation, mediated by covalent attachment of CoA to cellular proteins in response to oxidative or metabolic stress, has been recently discovered and termed protein CoAlation. In this study, we report that the level of CoA and protein CoAlation in D. discoideum are developmentally regulated, and correlate with the temporal expression pattern of genes implicated in CoA biosynthesis during morphogenesis. Furthermore, treatment of growing D. discoideum cells with oxidising agents results in a dose-dependent increase of protein CoAlation. However, much higher concentrations were required when compared to mammalian cells and bacteria. Increased resistance of D. discoideum to oxidative stress induced by H2O2 has previously been attributed to high levels of catalase activity. In support of this notion, we found that H2O2-induced protein CoAlation is significantly increased in CatA-deficient D. discoideum cells. Collectively, this study provides insights into the role of CoA and protein CoAlation in the maintenance of redox homeostasis in amoeba and during D. discoideum morphogenesis.

Assessment of lymphatic impairment and interstitial protein accumulation in patients with breast cancer treatment-related lymphedema using CEST MRI.

PURPOSE: Lymphatic impairment is known to reduce quality of life in some of the most crippling diseases of the 21st century, including obesity, lymphedema, and cancer. However, the lymphatics are not nearly as well-understood as other bodily systems, largely owing to a lack of sensitive imaging technologies that can be applied using standard clinical equipment. Here, proton exchange-weighted MRI is translated to the lymphatics in patients with breast cancer treatment-related lymphedema (BCRL). METHODS: Healthy volunteers (N = 8) and BCRL patients (N = 7) were scanned at 3 Tesla using customized structural MRI and amide proton transfer (APT) chemical exchange saturation transfer (CEST) MRI in sequence with the hypothesis that APT effects would be elevated in lymphedematous tissue. APT contrast, lymphedema stage, symptomatology, and histology information were evaluated. RESULTS: No significant difference between proton-weighted APT contrast in the right and left arms of healthy controls was observed. An increase in APT contrast in the affected arms of patients was found (P = 0.025; Cohen's d = 2.4), and variability among patients was consistent with documented damage to lymphatics as quantified by lymphedema stage. CONCLUSION: APT CEST MRI may have relevance for evaluating lymphatic impairment in patients with BCRL, and may extend to other pathologies where lymphatic compromise is evident.

Prevalence and impact of preoperative moderate/severe tricuspid regurgitation on patients undergoing transcatheter aortic valve replacement.

OBJECTIVES: Significant tricuspid regurgitation (TR) is a marker for late-stage myocardial and valvular heart disease. Whether preoperative TR affects clinical outcomes of patients undergoing transcatheter aortic valve replacement (TAVR) has never been investigated. This study sought to identify the impact of moderate and severe TR on outcomes after TAVR. METHODS: All patients undergoing TAVR from January 2007 to August 2012 at St. Paul's Hospital, Vancouver, Canada, (n = 518) were dichotomized according to the severity of preoperative TR (moderate/severe vs. none/mild). All clinical outcomes were defined according to the valve academic research consortium-2 definitions. RESULTS: At baseline, moderate or severe TR was reported in 79 patients (15.2%). At 30 days, moderate/severe TR had improved in 12 patients (15.2%), was unchanged in 46 patients (58.3%), and worsened in 7 patients (8.9%). Of those with none/mild TR at baseline, 35 (7.9%) patients had moderate TR at 30-day follow-up. Two-year all-cause (38.4% vs. 20.0%, Log-rank test, P = 0.001) and cardiac mortality (12.9% vs. 4.6%, Log-rank test, P = 0.004) as estimated by Kaplan-Meier analysis were considerably higher in patients with significant TR. However, significant TR did not emerge as independent risk factor for 2-year all-cause mortality (adjusted OR: 1.55, 95% confidence interval (CI): 0.91-2.64, P = 0.105). Pre-specified subgroups showed an interaction between TR and left ventricular systolic function (Pinteraction = 0.047). Indeed, moderate/severe TR was significantly related to mortality only in patients with left ventricular ejection fraction (LVEF) > 40% (adjusted OR: 2.01, CI: 1.05-3.84, P = 0.036). In patients with LVEF ≤ 40%, TR had no significant impact on all-cause mortality (adjusted OR: 1.04, CI: 0.34-3.16, P = 0.946). No significant interactions were identified regarding patients with perioperative moderate/severe mitral regurgitation (Pinteraction = 0.829) and patients with baseline systolic pulmonary artery pressure ≥ 60 mm Hg (Pinteraction = 0.669). CONCLUSIONS: In patients undergoing TAVR, significant preoperative TR was present in 15% of patients and associated with more comorbidities. Despite being associated with a doubling of mortality rate, after a robust adjustment, significant TR was not an independent predictor of 2-year mortality. However, a significant interaction between TR and left ventricular systolic function was found. The response of TR to TAVR was extremely variable.

Functional properties of five Dictyostelium discoideum P2X receptors.

The Dictyostelium discoideum genome encodes five proteins that share weak sequence similarity with vertebrate P2X receptors. Unlike vertebrate P2X receptors, these proteins are not expressed on the surface of cells, but populate the tubules and bladders of the contractile vacuole. In this study, we expressed humanized cDNAs of P2XA, P2XB, P2XC, P2XD, and P2XE in human embryonic kidney cells and altered the ionic and proton environment in an attempt to reflect the situation in amoeba. Recording of whole-cell membrane currents showed that four receptors operated as ATP-gated channels (P2XA, P2XB, P2XD, and P2XE). At P2XA receptors, ATP was the only effective agonist of 17 structurally related putative ligands that were tested. Extracellular sodium, compared with potassium, strongly inhibited ATP responses in P2XB, P2XD, and P2XE receptors. Increasing the proton concentration (pH 6.2) accelerated desensitization at P2XA receptors and decreased currents at P2XD receptors, but increased the currents at P2XB and P2XE receptors. Dictyostelium lacking P2XA receptors showed impaired regulatory volume decrease in hypotonic solution. This phenotype was readily rescued by overexpression of P2XA and P2XD receptors, partially rescued by P2XB and P2XE receptors, and not rescued by P2XC receptors. The failure of the nonfunctional receptor P2XC to restore the regulatory volume decrease highlights the importance of ATP activation of P2X receptors for a normal response to hypo-osmotic shock, and the weak rescue by P2XB and P2XE receptors indicates that there is limited functional redundancy among Dictyostelium P2X receptors.

Impact of preoperative moderate/severe mitral regurgitation on 2-year outcome after transcatheter and surgical aortic valve replacement: insight from the Placement of Aortic Transcatheter Valve (PARTNER) Trial Cohort A.

BACKGROUND: The effect of preoperative mitral regurgitation (MR) on clinical outcomes of patients undergoing transcatheter aortic valve replacement (TAVR) is controversial. This study sought to examine the impact of moderate and severe MR on outcomes after TAVR and surgical aortic valve replacement (SAVR). METHODS AND RESULTS: Data were drawn from the randomized Placement of Aortic Transcatheter Valve (PARTNER) Trial cohort A patients with severe, symptomatic aortic stenosis undergoing either TAVR (n=331) or SAVR (n=299). Both TAVR and SAVR patients were dichotomized according to the degree of preoperative MR (moderate/severe versus none/mild). At baseline, moderate or severe MR was reported in 65 TAVR patients (19.6%) and 63 SAVR patients (21.2%). At 30 days, among survivors who had isolated SAVR/TAVR, moderate/severe MR had improved in 25 SAVR patients (69.4%) and 30 TAVR patients (57.7%), was unchanged in 10 SAVR patients (27.8%) and 19 TAVR patients (36.5%), and worsened in 1 SAVR patient (2.8%) and 4 TAVR patients (5.8%; all P=NS). Mortality at 2 years was higher in SAVR patients with moderate or severe MR than in those with mild or less MR (49.8% versus 28.1%; adjusted hazard ratio, 1.73; 95% confidence interval, 1.01-2.96; P=0.04). In contrast, MR severity at baseline did not affect mortality in TAVR patients (37.0% versus 32.7%, moderate/severe versus none/mild; hazard ratio, 1.14; 95% confidence interval, 0.72-1.78; P=0.58; P for interaction=0.05). CONCLUSIONS: Both TAVR and SAVR were associated with a significant early improvement in MR in survivors. However, moderate or severe MR at baseline was associated with increased 2-year mortality after SAVR but not after TAVR. TAVR may be a reasonable option in selected patients with combined aortic and mitral valve disease. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT00530894.

Sociogenomics of self vs. non-self cooperation during development of Dictyostelium discoideum.

BACKGROUND: Dictyostelium discoideum, a microbial model for social evolution, is known to distinguish self from non-self and show genotype-dependent behavior during chimeric development. Aside from a small number of cell-cell recognition genes, however, little is known about the genetic basis of self/non-self recognition in this species. Based on the key hypothesis that there should be differential expression of genes if D. discoideum cells were interacting with non-clone mates, we performed transcriptomic profiling study in this species during clonal vs. chimeric development. The transcriptomic profiles of D. discoideum cells in clones vs. different chimeras were compared at five different developmental stages using a customized microarray. Effects of chimerism on global transcriptional patterns associated with social interactions were observed. RESULTS: We find 1,759 genes significantly different between chimera and clone, 1,144 genes associated significant strain differences, and 6,586 genes developmentally regulated over time. Principal component analysis showed a small amount of the transcriptional variance to chimerism-related factors (Chimerism: 0.18%, Chimerism × Timepoint: 0.03%). There are 162 genes specifically regulated under chimeric development, with continuous small differences between chimera vs. clone over development. Almost 60% of chimera-associated differential genes were differentially expressed at the 4 h aggregate stage, which corresponds to the initial transition of D. discoideum from solitary life to a multicellular phase. CONCLUSIONS: A relatively small proportion of over-all variation in gene expression is explained by differences between chimeric and clonal development. The relatively small modifications in gene expression associated with chimerism is compatible with the high level of cooperation observed among different strains of D. discoideum; cells of distinct genetic backgrounds will co-aggregate indiscriminately and co-develop into fruiting bodies. Chimeric development may involve re-programming of the transcriptome through small modifications of the developmental genetic network, which may also indicate that response to social interaction involves many genes with individually small transcriptional effect.

Cell type-specific filamin complex regulation by a novel class of HECT ubiquitin ligase is required for normal cell motility and patterning.

Differential cell motility, which plays a key role in many developmental processes, is perhaps most evident in examples of pattern formation in which the different cell types arise intermingled before sorting out into discrete tissues. This is thought to require heterogeneities in responsiveness to differentiation-inducing signals that result in the activation of cell type-specific genes and 'salt and pepper' patterning. How differential gene expression results in cell sorting is poorly defined. Here we describe a novel gene (hfnA) that provides the first mechanistic link between cell signalling, differential gene expression and cell type-specific sorting in Dictyostelium. HfnA defines a novel group of evolutionarily conserved HECT ubiquitin ligases with an N-terminal filamin domain (HFNs). HfnA expression is induced by the stalk differentiation-inducing factor DIF-1 and is restricted to a subset of prestalk cells (pstO). hfnA(-) pstO cells differentiate but their sorting out is delayed. Genetic interactions suggest that this is due to misregulation of filamin complex activity. Overexpression of filamin complex members phenocopies the hfnA(-) pstO cell sorting defect, whereas disruption of filamin complex function in a wild-type background results in pstO cells sorting more strongly. Filamin disruption in an hfnA(-) background rescues pstO cell localisation. hfnA(-) cells exhibit altered slug phototaxis phenotypes consistent with filamin complex hyperactivity. We propose that HfnA regulates filamin complex activity and cell type-specific motility through the breakdown of filamin complexes. These findings provide a novel mechanism for filamin regulation and demonstrate that filamin is a crucial mechanistic link between responses to differentiation signals and cell movement in patterning based on 'salt and pepper' differentiation and sorting out.

A simple mechanism for complex social behavior.

The evolution of cooperation is a paradox because natural selection should favor exploitative individuals that avoid paying their fair share of any costs. Such conflict between the self-interests of cooperating individuals often results in the evolution of complex, opponent-specific, social strategies and counterstrategies. However, the genetic and biological mechanisms underlying complex social strategies, and therefore the evolution of cooperative behavior, are largely unknown. To address this dearth of empirical data, we combine mathematical modeling, molecular genetic, and developmental approaches to test whether variation in the production of and response to social signals is sufficient to generate the complex partner-specific social success seen in the social amoeba Dictyostelium discoideum. Firstly, we find that the simple model of production of and response to social signals can generate the sort of apparent complex changes in social behavior seen in this system, without the need for partner recognition. Secondly, measurements of signal production and response in a mutant with a change in a single gene that leads to a shift in social behavior provide support for this model. Finally, these simple measurements of social signaling can also explain complex patterns of variation in social behavior generated by the natural genetic diversity found in isolates collected from the wild. Our studies therefore demonstrate a novel and elegantly simple underlying mechanistic basis for natural variation in complex social strategies in D. discoideum. More generally, they suggest that simple rules governing interactions between individuals can be sufficient to generate a diverse array of outcomes that appear complex and unpredictable when those rules are unknown.

Facultative cheater mutants reveal the genetic complexity of cooperation in social amoebae.

Cooperation is central to many major transitions in evolution, including the emergence of eukaryotic cells, multicellularity and eusociality. Cooperation can be destroyed by the spread of cheater mutants that do not cooperate but gain the benefits of cooperation from others. However, cooperation can be preserved if cheaters are facultative, cheating others but cooperating among themselves. Several cheater mutants have been studied before, but no study has attempted a genome-scale investigation of the genetic opportunities for cheating. Here we describe such a screen in a social amoeba and show that cheating is multifaceted by revealing cheater mutations in well over 100 genes of diverse types. Many of these mutants cheat facultatively, producing more than their fair share of spores in chimaeras, but cooperating normally when clonal. These findings indicate that phenotypically stable cooperative systems may nevertheless harbour genetic conflicts. The opportunities for evolutionary moves and countermoves in such conflicts may select for the involvement of multiple pathways and numerous genes.

Contractile reserve induced with dobutamine echocardiography predicts outcome in patients with left ventricular dysfunction and mitral regurgitation.

BACKGROUND AND AIM OF THE STUDY: The appropriate management of patients with mitral regurgitation (MR) and left ventricular dysfunction (LVD) is controversial. The study aim was to determine whether the presence of contractile reserve (CR) assessed by dobutamine stress echocardiography (DSE) was associated with improved outcomes. METHODS: Death and heart transplantation were analyzed as the primary outcomes associated with the presence of CR. A total of 125 consecutive patients (96 males, 29 females; mean age 60 +/- 12 years) with left ventricular ejection fraction (LVEF) < or = 35% and hemodynamically significant MR underwent DSE between 1999 and 2005. CR was defined as an increase in LVEF of > or = 10% during dobutamine infusion. RESULTS: Among 125 patients, 55 (43.0%) showed evidence of CR. Within five years after DSE, 24 patients (34.3%) in the CR- group and seven (12.7%) in the CR+ group had died or required heart transplantation (p < 0.01, log rank). After adjusting for age, baseline LVEF, NYHA class and moderate/severe tricuspid regurgitation (TR), CR remained an independent predictor of time to death or heart transplantation (HR 0.34; 95% CI: 0.15-0.76, p < 0.01). Improvement in the degree of MR was present at one year in 85.0% of CR+ patients, and in 62.5% of CR- patients (p = 0.03). An improvement of 5% in LVEF was noted in the CR+ group, compared to 0% in the CR- group (p = 0.04). CONCLUSION: In patients with advanced LVD and severe MR, CR detected by DSE was associated with significant reductions in the risk of death and heart transplantation.

Functional mechanism study of the allelochemical myrigalone A identifies a group of ultrapotent inhibitors of ethylene biosynthesis in plants.

Allelochemicals represent a class of natural products released by plants as root, leaf, and fruit exudates that interfere with the growth and survival of neighboring plants. Understanding how allelochemicals function to regulate plant responses may provide valuable new approaches to better control plant function. One such allelochemical, Myrigalone A (MyA) produced by Myrica gale, inhibits seed germination and seedling growth through an unknown mechanism. Here, we investigate MyA using the tractable model Dictyostelium discoideum and reveal that its activity depends on the conserved homolog of the plant ethylene synthesis protein 1-aminocyclopropane-1-carboxylic acid oxidase (ACO). Furthermore, in silico modeling predicts the direct binding of MyA to ACO within the catalytic pocket. In D. discoideum, ablation of ACO mimics the MyA-dependent developmental delay, which is partially restored by exogenous ethylene, and MyA reduces ethylene production. In Arabidopsis thaliana, MyA treatment delays seed germination, and this effect is rescued by exogenous ethylene. It also mimics the effect of established ACO inhibitors on root and hypocotyl extension, blocks ethylene-dependent root hair production, and reduces ethylene production. Finally, in silico binding analyses identify a range of highly potent ethylene inhibitors that block ethylene-dependent response and reduce ethylene production in Arabidopsis. Thus, we demonstrate a molecular mechanism by which the allelochemical MyA reduces ethylene biosynthesis and identify a range of ultrapotent inhibitors of ethylene-regulated responses.

Not lost in translation: neural responses shared across languages.

How similar are the brains of listeners who hear the same content expressed in different languages? We directly compared the fMRI response time courses of English speakers and Russian speakers who listened to a real-life Russian narrative and its English translation. In the translation, we tried to preserve the content of the narrative while reducing the structural similarities across languages. The story evoked similar brain responses, invariant to the structural changes across languages, beginning just outside early auditory areas and extending through temporal, parietal, and frontal cerebral cortices. The similarity of responses across languages was nearly equal to the similarity of responses within each language group. The present results demonstrate that the human brain processes real-life information in a manner that is largely insensitive to the language in which that information is conveyed. The methods introduced here can potentially be used to quantify the transmission of meaning across cultural and linguistic boundaries.

An intracellular P2X receptor required for osmoregulation in Dictyostelium discoideum.

P2X receptors are membrane ion channels gated by extracellular ATP that are found widely in vertebrates, but not previously in microbes. Here we identify a weakly related gene in the genome of the social amoeba Dictyostelium discoideum, and show, with the use of heterologous expression in human embryonic kidney cells, that it encodes a membrane ion channel activated by ATP (30-100 muM). Site-directed mutagenesis revealed essential conservation of structure-function relations with P2X receptors of higher organisms. The receptor was insensitive to the usual P2X antagonists but was blocked by nanomolar concentrations of Cu2+ ions. In D. discoideum, the receptor was found on intracellular membranes, with prominent localization to an osmoregulatory organelle, the contractile vacuole. Targeted disruption of the gene in D. discoideum resulted in cells that were unable to regulate cell volume in hypotonic conditions. Cell swelling in these mutant cells was accompanied by a marked inhibition of contractile vacuole emptying. These findings demonstrate a new functional role for P2X receptors on intracellular organelles, in this case in osmoregulation.

Two-Year Outcomes After Pediatric In-Office Tympanostomy Using Lidocaine/Epinephrine Iontophoresis and an Automated Tube Delivery System.

OBJECTIVE: Evaluate 2-year outcomes after lidocaine/epinephrine iontophoresis and tympanostomy using an automated tube delivery system for pediatric tube placement in-office. STUDY DESIGN: Prospective, single-arm. SETTING: Eighteen otolaryngology practices. METHODS: Children age 6 months to 12 years indicated for tympanostomy were enrolled between October 2017 and February 2019. Local anesthesia of the tympanic membrane was achieved via lidocaine/epinephrine iontophoresis and tympanostomy was completed using an automated tube delivery system (the Tula® System). An additional Lead-In cohort of patients underwent tube placement in the operating room (OR) under general anesthesia using only the tube delivery system. Patients were followed for 2 years or until tube extrusion, whichever occurred first. Otoscopy and tympanometry were performed at 3 weeks, and 6, 12, 18, and 24 months. Tube retention, patency, and safety were evaluated. RESULTS: Tubes were placed in-office for 269 patients (449 ears) and in the OR for 68 patients (131 ears) (mean age, 4.5 years). The median and mean times to tube extrusion for the combined OR and In-Office cohorts were 15.82 (95% confidence interval [CI]: 15.41-19.05) and 16.79 (95% CI: 16.16-17.42) months, respectively. Sequelae included ongoing perforation for 1.9% of ears (11/580) and medial tube displacement for 0.2% (1/580) observed at 18 months. Over a mean follow-up of 14.3 months, 30.3% (176/580) of ears had otorrhea and 14.3% (83/580) had occluded tubes. CONCLUSION: In-office pediatric tympanostomy using lidocaine/epinephrine iontophoresis and automated tube delivery results in tube retention within the ranges described for similar grommet-type tubes and complication rates consistent with traditional tube placement in the OR.

Structured growth and genetic drift raise relatedness in the social amoeba Dictyostelium discoideum.

One condition for the evolution of altruism is genetic relatedness between altruist and beneficiary, often achieved through active kin recognition. Here, we investigate the power of a passive process resulting from genetic drift during population growth in the social amoeba Dictyostelium discoideum. We put labelled and unlabelled cells of the same clone in the centre of a plate, and allowed them to proliferate outward. Zones formed by genetic drift owing to the small population of actively growing cells at the colony edge. We also found that single cells could form zones of high relatedness. Relatedness increased at a significantly higher rate when food was in short supply. This study shows that relatedness can be significantly elevated before the social stage without a small founding population size or recognition mechanism.

The genetic architecture underlying prey-dependent performance in a microbial predator.

Natural selection should favour generalist predators that outperform specialists across all prey types. Two genetic solutions could explain why intraspecific variation in predatory performance is, nonetheless, widespread: mutations beneficial on one prey type are costly on another (antagonistic pleiotropy), or mutational effects are prey-specific, which weakens selection, allowing variation to persist (relaxed selection). To understand the relative importance of these alternatives, we characterised natural variation in predatory performance in the microbial predator Dictyostelium discoideum. We found widespread nontransitive differences among strains in predatory success across different bacterial prey, which can facilitate stain coexistence in multi-prey environments. To understand the genetic basis, we developed methods for high throughput experimental evolution on different prey (REMI-seq). Most mutations (~77%) had prey-specific effects, with very few (~4%) showing antagonistic pleiotropy. This highlights the potential for prey-specific effects to dilute selection, which would inhibit the purging of variation and prevent the emergence of an optimal generalist predator.