Experimentally Manipulated Growth Rate in Threespine Sticklebacks: Assessing Trade Offs with Developmental Stability

The evolution of adaptive growth rate and its influence on how other life history traits evolve is a neglected topic in biology. Growth rate influences life history because size strongly influences age-specific survival and fecundity, and because growth rate defines the relationship between age and size. Improved predictions about the evolution of life history traits may be possible with a greater understanding of the factors that influence the evolution of growth rate. We experimentally tested the hypothesis that a trade off may exist between growth rate and developmental stability in freshwater threespine sticklebacks, Gasterosteus aculeatus. We compared the degree of developmental instability (measured as fluctuating asymmetry = FA) in four lateral plate and two fin traits of fish reared under a high vs. low growth regime in response to food ration and temperature. We found evidence that symmetry was reduced (FA increased) in fast growing compared to slow growing fish, suggesting that a trade off between developmental stability and growth is possible. FA plausibly reflected developmental instability because of significant associations between rank FA levels across traits in individuals. These results are preliminary because of the possible confounding effects of temperature and food ration on asymmetry, and because we do not know if this trade off has fitness or other life history consequences. Our results also do not support the hypothesis of honest signaling sometimes invoked in studies of sexual selection because greater symmetry was found under poorer rather than better resource levels.     

Heterogeneity of the tumorigenic phenotype expressed by Madin-Darby canine kidney cells

The mechanisms by which cells spontaneously immortalized in tissue culture develop the capacity to form tumors in vivo likely embody fundamental processes in neoplastic development. The evolution of Madin-Darby canine kidney (MDCK) cells from presumptively normal kidney cells to immortalized cells that become tumorigenic represents an example of neoplastic development in vitro. Studies of the mechanisms by which spontaneously immortalized cells develop the capacity to form tumors would benefit from quantitative in vivo assays. Most mechanistic correlations are evaluated by using single-dose tumor-induction experiments, which indicate only whether cells are or are not tumorigenic. Here we used quantitative tumorigenicity assays to measure dose-and time-dependent tumor development in nude mice of 3 lots of unmodified MDCK cells. The results revealed lot-to-lot variations in the tumorigenicity of MDCK cells, which were reflected by their tumor-inducing efficiency (threshold cell dose represented by mean tumor-producing dose; log(10) 50% endpoints of 5.2 for vial 1 and 4.4 for vial 2, and a tumor-producing dose of 5.8 for vial 3) and mean tumor latency (vial 1,6.6 wk; vial 2,2.9 wk; and vial 3,3.8 wk). These studies provide a reference for further characterization of the MDCK cell neoplastic phenotype and may be useful in delineating aspects of neoplastic development in vitro that determine tumor-forming capacity. Such data also are useful when considering MDCK cells as a reagent for vaccine manufacture.     

De novo formation and ultra-structural characterization of a fiber-producing human hair follicle equivalent in vitro

Across many tissues and organs, the ability to create an organoid, the smallest functional unit of an organ, in vitro is the key both to tissue engineering and preclinical testing regimes. The hair follicle is an organoid that has been much studied based on its ability to grow quickly and to regenerate after trauma. But hair follicle formation in vitro has been elusive. Replacing hair lost due to pattern baldness or more severe alopecia, including that induced by chemotherapy, remains a significant unmet medical need.By carefully analyzing and recapitulating the growth conditions of hair follicle formation, we recreated human hair follicles in tissue culture that were capable of producing hair. Our microfollicles contained all relevant cell types and their structure and orientation resembled in some ways excised hair follicle specimens from human skin. This finding offers a new window onto hair follicle development. Having a robust culture system for hair follicles is an important step towards improved hair regeneration as well as to an understanding of how marketed drugs or drug candidates, including cancer chemotherapy, will affect this important organ.     

Blood autoantibody and cytokine profiles predict response to anti-tumor necrosis factor therapy in rheumatoid arthritis

Introduction

Anti-TNF therapies have revolutionized the treatment of rheumatoid arthritis (RA), a common systemic autoimmune disease involving destruction of the synovial joints. However, in the practice of rheumatology approximately one-third of patients demonstrate no clinical improvement in response to treatment with anti-TNF therapies, while another third demonstrate a partial response, and one-third an excellent and sustained response. Since no clinical or laboratory tests are available to predict response to anti-TNF therapies, great need exists for predictive biomarkers.

Methods

Here we present a multi-step proteomics approach using arthritis antigen arrays, a multiplex cytokine assay, and conventional ELISA, with the objective to identify a biomarker signature in three ethnically diverse cohorts of RA patients treated with the anti-TNF therapy etanercept.

Results

We identified a 24-biomarker signature that enabled prediction of a positive clinical response to etanercept in all three cohorts (positive predictive values 58 to 72%; negative predictive values 63 to 78%).

Conclusions

We identified a multi-parameter protein biomarker that enables pretreatment classification and prediction of etanercept responders, and tested this biomarker using three independent cohorts of RA patients. Although further validation in prospective and larger cohorts is needed, our observations demonstrate that multiplex characterization of autoantibodies and cytokines provides clinical utility for predicting response to the anti-TNF therapy etanercept in RA patients.     

Circulating immune complexes contain citrullinated fibrinogen in rheumatoid arthritis

Introduction  

There is increasing evidence that autoantibodies and immune complexes (ICs) contribute to synovitis in rheumatoid arthritis (RA), yet the autoantigens incorporated in ICs in RA remain incompletely characterised.     

Experimental evidence that competition between stickleback species favours adaptive character divergence

The ecological character displacement hypothesis assumes that the effects of interspecific resource competition cause divergent selection to favour phenotypes that exploit non-shared resources. This model predicts that interspecific competition declines with increased divergence. Direct tests of this decline are rare despite much comparative evidence for character displacement. We tested this prediction using a pair of divergent brook sticklebacks. Brook sticklebacks sympatric with ninespine sticklebacks have diverged from local allopatric brook populations, and so the two types of brook sticklebacks potentially represent pre- and post-displacement forms. We used enclosures placed in a lake to compare short-term fitness (growth) of sympatric (post-displacement) and allopatric (pre-displacement) brook forms in the presence and absence of ninespine sticklebacks. Brook sticklebacks grew less in the presence vs. absence of ninespine sticklebacks, indicating that interspecific competition occurred. As expected, allopatric brook forms had lower growth than sympatric forms when ninespine sticklebacks were present. This result suggests that ecological character displacement has occurred.     

Contemporary and historical evolutionary processes interact to shape patterns of within-lake phenotypic divergences in polyphenic pumpkinseed sunfish, Lepomis gibbosus

Historical and contemporary evolutionary processes can both contribute to patterns of phenotypic variation among populations of a species. Recent studies are revealing how interactions between historical and contemporary processes better explain observed patterns of phenotypic divergence than either process alone. Here, we investigate the roles of evolutionary history and adaptation to current environmental conditions in structuring phenotypic variation among polyphenic populations of sunfish inhabiting 12 postglacial lakes in eastern North America. The pumpkinseed sunfish polyphenism includes sympatric ecomorphs specialized for littoral or pelagic lake habitats. First, we use population genetic methods to test the evolutionary independence of within-lake phenotypic divergences of ecomorphs and to describe patterns of genetic structure among lake populations that clustered into three geographical groupings. We then used multivariate analysis of covariance (MANCOVA) to partition body shape variation (quantified with geometric morphometrics) among the effects of evolutionary history (reflecting phenotypic variation among genetic clusters), the shared phenotypic response of all populations to alternate habitats within lakes (reflecting adaptation to contemporary conditions), and unique phenotypic responses to habitats within lakes nested within genetic clusters. All effects had a significant influence on body form, but the effects of history and the interaction between history and contemporary habitat were larger than contemporary processes in structuring phenotypic variation. This highlights how divergence can be better understood against a known backdrop of evolutionary history.     

Ecological and morphological differentiation of pumpkinseed sunfish in lakes without bluegill sunfish

Summary Over the last three decades, sunfish of the familyCentrarchidae have become recognized as a model system in which the ecological consequences of species interactions can be observed and tested. The evolutionary consequences of species interactions in sunfish have received less attention. Bluegill (Lepomis machrochirus) and pumpkinseed (Lepomis gibbosus) sunfish are two common and well-studied species that occupy separate ecological niches. Adult bluegill are generalists that feed in the open water on zooplankton during much of the year, while adult pumpkinseeds specialize on crushing hard-bodied prey such as snails. These species coexist over much of their geographical ranges, but bluegill are historically absent from several large drainage basins in the northeastern US. Here we show that pumpkinseeds from an Adirondack lake without bluegills have differentiated into two morphological forms, one of which is planktivorous. Differentiation is independent of sex and occurs over a broad range of sizes. Thus, the ecological diversity that exists between the bluegill and pumpkinseeds in sympatry has been replaced by a comparable degree of diversity within pumpkinseeds in allopatry.     

Invertebrate predation predicts variation in an autotomy-related trait in larval damselfly

Autotomy, the discarding of a prey appendage grasped by a predator, may evolve when the benefits of immediate survival outweigh the costs of appendage loss. In larval damselflies, joints connecting lamellae to the abdomen vary in size and shape within and among taxa suggesting that they may evolve under selection by invertebrate predators, such as dragonfly larvae. Assuming that joint width is proportional to the force required for autotomy, we tested if invertebrate predation favours smaller lamellar joints for autotomy or larger joints for structural support of lamellae for swimming. We compared the maximum joint widths of larval Lestes and Enallagma among ponds that varied in risk of invertebrate predation. Relative predation risk estimated as the frequency of regenerated lamellae within ponds was weakly and positively related to the relative abundance of larval dragonflies. The allometry of lamellar joint size decreased with increasing risk of invertebrate predation across ponds after controlling for variation in body size in Lestes congener but not in Enallagma species. Both species of Lestes had larger joint sizes than the five species of Enallagma, suggesting that the ancestral divergence of lamellar joints between these genera may influence contemporary responses to invertebrate predation.     

Analyzing nested variation in the body form of Lepomid sunfishes

Phylogenetic hierarchies are often composed of younger diverging lineages nested within older diverging lineages. Comparing phenotypic variation among several hierarchical levels can be used to test hypotheses about selection, phenotypic evolution and speciation. Such hierarchical comparisons have only been performed in threespine stickleback, and so here we use a hierarchical pattern of divergences between near-shore littoral and off-shore pelagic habitats to test for selection on the evolution of body form in Lepomis sunfish in lakes. We compare variation in external body form between fish from littoral and pelagic habitats at three levels: among ecomorphs within individual lake populations (intrapopulation), among populations of the same species in different lakes (interpopulation), and between bluegill and pumpkinseed sunfish species (interspecifically). Using geometric morphometric methods, we first demonstrate that interpopulation variation in mean body form of pumpkinseed sunfish varies with the presence of pelagic habitat. We then incorporate these results with existing data in order to test the similarity of phenotypic divergence between littoral and pelagic habitats at different hierarchical levels. Parallel relationships between certain body form traits (head length, caudal length and pectoral length) and habitat occur at all three levels suggesting that selection persistently acts at all levels to diversify these traits and so may contribute to species formation. For other traits (caudal depth and pectoral altitude), divergence between habitats is inconsistent at different hierarchical levels. Thus, nested biological variation in Lepomid body form reflects a history of deterministic selection and historical contingency, and also identifies traits that likely have likely influenced fitness and so serve important functions.