The emergence of division of labour in forced associations of normally solitary ant queens

ABSTRACT We tested the hypothesis that division of labour is an inescapable property of social groups, rather than an evolutionary event separate from sociality. We propose a variance-based emergent property model in which division of labour can spontaneously emerge when (1) individuals in a group vary in their intrinsic sensitivity to stimuli for a given task, and (2) the performance of a task by individuals with higher task sensitivities reduces performance of the task by the other group members. Under these conditions, the individuals with higher sensitivity become the task specialists. To determine if division of labour can occur in the absence of direct selection, we created artificial foundress associations (groups of queens during nest establishment) of the ant Pogonomyrmex barbatus, which has no history of cooperative colony founding. We compared the incidence of task specialization in this species to that in Pogonomyrmex californicus, in which foundress associations commonly occur. Levels of task specialization for nest excavation were high in both species, arguing that division of labour emerges in groups regardless of evolutionary history. Consistent with the variance-based model, the role of nest excavation specialist in P. barbatus foundress associations could be predicted by both (1) differences in excavation roles in prior pairs and (2) variation in excavation activity while solitary. Furthermore, the assumption of the excavator role by one foundress dramatically reduced the performance of that task by the other foundress of the pair. We also found a strong negative relationship between excavation activity and foundress survival in P. barbatus, suggesting that division of labour in this context may act as a constraint on social evolution

Treatment outcome in early diffuse cutaneous systemic sclerosis: the European Scleroderma Observational Study (ESOS).

OBJECTIVES: The rarity of early diffuse cutaneous systemic sclerosis (dcSSc) makes randomised controlled trials very difficult. We aimed to use an observational approach to compare effectiveness of currently used treatment approaches. METHODS: This was a prospective, observational cohort study of early dcSSc (within three years of onset of skin thickening). Clinicians selected one of four protocols for each patient: methotrexate, mycophenolate mofetil (MMF), cyclophosphamide or 'no immunosuppressant'. Patients were assessed three-monthly for up to 24 months. The primary outcome was the change in modified Rodnan skin score (mRSS). Confounding by indication at baseline was accounted for using inverse probability of treatment (IPT) weights. As a secondary outcome, an IPT-weighted Cox model was used to test for differences in survival. RESULTS: Of 326 patients recruited from 50 centres, 65 were prescribed methotrexate, 118 MMF, 87 cyclophosphamide and 56 no immunosuppressant. 276 (84.7%) patients completed 12 and 234 (71.7%) 24 months follow-up (or reached last visit date). There were statistically significant reductions in mRSS at 12 months in all groups: -4.0 (-5.2 to -2.7) units for methotrexate, -4.1 (-5.3 to -2.9) for MMF, -3.3 (-4.9 to -1.7) for cyclophosphamide and -2.2 (-4.0 to -0.3) for no immunosuppressant (p value for between-group differences=0.346). There were no statistically significant differences in survival between protocols before (p=0.389) or after weighting (p=0.440), but survival was poorest in the no immunosuppressant group (84.0%) at 24 months. CONCLUSIONS: These findings may support using immunosuppressants for early dcSSc but suggest that overall benefit is modest over 12 months and that better treatments are needed. TRIAL REGISTRATION NUMBER: NCT02339441

Heavy and light roles: myosin in the morphogenesis of the heart

Myosin is an essential component of cardiac muscle, from the onset of cardiogenesis through to the adult heart. Although traditionally known for its role in energy transduction and force development, recent studies suggest that both myosin heavy-chain and myosin lightchain proteins are required for a correctly formed heart. Myosins are structural proteins that are not only expressed from early stages of heart development, but when mutated in humans they may give rise to congenital heart defects. This review will discuss the roles of myosin, specifically with regards to the developing heart. The expression of each myosin protein will be described, and the effects that altering expression has on the heart in embryogenesis in different animal models will be discussed. The human molecular genetics of the myosins will also be reviewed

Somatic mutations affect key pathways in lung adenocarcinoma

Determining the genetic basis of cancer requires comprehensive analyses of large collections of histopathologically well- classified primary tumours. Here we report the results of a collaborative study to discover somatic mutations in 188 human lung adenocarcinomas. DNA sequencing of 623 genes with known or potential relationships to cancer revealed more than 1,000 somatic mutations across the samples. Our analysis identified 26 genes that are mutated at significantly high frequencies and thus are probably involved in carcinogenesis. The frequently mutated genes include tyrosine kinases, among them the EGFR homologue ERBB4; multiple ephrin receptor genes, notably EPHA3; vascular endothelial growth factor receptor KDR; and NTRK genes. These data provide evidence of somatic mutations in primary lung adenocarcinoma for several tumour suppressor genes involved in other cancers - including NF1, APC, RB1 and ATM - and for sequence changes in PTPRD as well as the frequently deleted gene LRP1B. The observed mutational profiles correlate with clinical features, smoking status and DNA repair defects. These results are reinforced by data integration including single nucleotide polymorphism array and gene expression array. Our findings shed further light on several important signalling pathways involved in lung adenocarcinoma, and suggest new molecular targets for treatment.National Human Genome Research InstituteWe thank A. Lash, M.F. Zakowski, M.G. Kris and V. Rusch for intellectual contributions, and many members of the Baylor Human Genome Sequencing Center, the Broad Institute of Harvard and MIT, and the Genome Center at Washington University for support. This work was funded by grants from the National Human Genome Research Institute to E.S.L., R.A.G. and R.K.W.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62885/1/nature07423.pd

Social regulatory networks.

<p>Triad significance profiles compare the characteristic network motifs across a diverse range of network types and sizes by plotting standardized Z-scores which quantify the extent to which each subgraph is observed more or less frequently than expected in networks of a similar size and global structure but with randomized edge connections. The observed <i>P. californicus</i> social insect networks exhibit a distinct pattern of social regulatory structure combining elements found in previously identified major network superfamilies <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040337#pone.0040337-Milo2" target="_blank">[22]</a>.</p

Network motif analysis results.

<p>This table summarizes the classification of subgraphs as network motifs. (1) The number of observed networks containing each respective subgraph. (2) The number of networks in which the observed density for a subgraph is significantly greater than its density in the random networks and in which the subgraph appears more than once in the observed network. (3) The number of networks in which the average observed density for a subgraph is significantly greater than its density in the random networks and in which the subgraph density is at least one percent in the observed network.</p

Ant colony interaction networks.

<p>(<b>A</b>) The development of a directed network of interactions between workers in a single <i>P. californicus</i> colony over a period of 60 s. Nodes represent individual workers or queens within a colony and arrows represent interactions between individuals. (<b>B</b>) Example <i>P. californicus</i> interaction network based on 26 s of colony behavior. (<b>C</b>) Photograph of queens and workers within a seed harvester colony; individuals have been painted with unique color combinations to track their interactions.</p

Summary of out-degree scaling analysis.

<p>(1) This is the OLS-estimated slope for the relationship describing how the number of nodes with a given number of out-degree edges scales with out-degree. The data (x) were transformed prior to regression according to log₁₀(x+1). The absolute value of the slope is an estimate for the degree distribution power law exponent (alpha).</p