44 Works

Was bietet die IFLA der VÖB? – Warum Bibliothekar*innen international aktiv sein sollten - Statement

Patrick Danowski
75 Jahre VÖB. 1946–2021, Hg. v. Alker-Windbichler, Bauer und Köstner-Pemsel, 2021, S. 143–145

Clines on the seashore: The genomic architecture underlying rapid divergence in the face of gene flow

Anja Marie Westram, Anja M. Westram, Marina Rafajlović, Pragya Chaube, Rui Faria, Tomas Larsson, Marina Panova, Mark Ravinet, Anders Blomberg, Bernhard Mehlig, Kerstin Johannesson & Roger Butlin
Adaptive divergence and speciation may happen despite opposition by gene flow. Identifying the genomic basis underlying divergence with gene flow is a major task in evolutionary genomics. Most approaches (e.g., outlier scans) focus on genomic regions of high differentiation. However, not all genomic architectures potentially underlying divergence are expected to show extreme differentiation. Here, we develop an approach that combines hybrid zone analysis (i.e., focuses on spatial patterns of allele frequency change) with system-specific simulations...

High-dimensional expansion and crossing numbers of simplicial complexes

Pascal Wild
In this dissertation we study coboundary expansion of simplicial complex with a view of giving geometric applications. Our main novel tool is an equivariant version of Gromov's celebrated Topological Overlap Theorem. The equivariant topological overlap theorem leads to various geometric applications including a quantitative non-embeddability result for sufficiently thick buildings (which partially resolves a conjecture of Tancer and Vorwerk) and an improved lower bound on the pair-crossing number of (bounded degree) expander graphs. Additionally, we...

Translation-invariant quantum systems with effectively broken symmetry

Morris Brooks
The scope of this thesis is to study quantum systems exhibiting a continuous symmetry that is broken on the level of the corresponding effective theory. In particular we are going to investigate translation-invariant Bose gases in the mean field limit, effectively described by the Hartree functional, and the Fröhlich Polaron in the regime of strong coupling, effectively described by the Pekar functional. The latter is a model describing the interaction between a charged particle and...

Data from: Transformation of stimulus correlations by the retina

Kristina D. Simmons, Jason S. Prentice, Gašper Tkačik, Jan Homann, Heather K. Yee, Stephanie E. Palmer, Philip C. Nelson & Vijay Balasubramanian
Redundancies and correlations in the responses of sensory neurons may seem to waste neural resources, but they can also carry cues about structured stimuli and may help the brain to correct for response errors. To investigate the effect of stimulus structure on redundancy in retina, we measured simultaneous responses from populations of retinal ganglion cells presented with natural and artificial stimuli that varied greatly in correlation structure; these stimuli and recordings are publicly available online....

Data from: Selection history and epistatic interactions impact dynamics of adaptation to novel environmental stresses

Mato Lagator, Nick Colegrave & Paul Neve
In rapidly changing environments, selection history may impact the dynamics of adaptation. Mutations selected in one environment may result in pleiotropic fitness trade-offs in subsequent novel environments, slowing the rates of adaptation. Epistatic interactions between mutations selected in sequential stressful environments may slow or accelerate subsequent rates of adaptation, depending on the nature of that interaction. We explored the dynamics of adaptation during sequential exposure to herbicides with different modes of action in Chlamydomonas reinhardtii....

Data from: A sting in the spit: widespread cross-infection of multiple RNA viruses across wild and managed bees

Dino P. McMahon, Matthias A. Fürst, Jesicca Caspar, Panagiotis Theodorou, Mark J. F. Brown & Robert J. Paxton
1.Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood. 2.This study aims to attain a detailed understanding of the current and on going risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses....

Data from: Is embryo abortion a postzygotic barrier to gene flow between Littorina ecotypes?

Kerstin Johannesson, Zuzanna Zagrodzka, Rui Faria, Anja Westram & Roger Butlin
Genetic incompatibilities contribute to reproductive isolation between many diverging populations, but it is still unclear to what extent they play a role if divergence happens with gene flow. In contact zones between the "Crab" and "Wave" ecotypes of the snail Littorina saxatilis divergent selection forms strong barriers to gene flow, while the role of postzygotic barriers due to selection against hybrids remains unclear. High embryo abortion rates in this species could indicate the presence of...

Data from: CRISPR-based herd immunity limits phage epidemics in bacterial populations

Pavel Payne, Lukas Geyrhofer, Nick H Barton, Jonathan P Bollback & Nicholas H Barton
Herd immunity, a process in which resistant individuals limit the spread of a pathogen among susceptible hosts has been extensively studied in eukaryotes. Even though bacteria have evolved multiple immune systems against their phage pathogens, herd immunity in bacteria remains unexplored. Here we experimentally demonstrate that herd immunity arises during phage epidemics in structured and unstructured Escherichia coli populations consisting of differing frequencies of susceptible and resistant cells harboring CRISPR immunity. In addition, we develop...

BayesW time-to-event analysis posterior outputs and summary statistics

Sven Erik Ojavee & Matthew Robinson
Here, we develop a Bayesian approach (BayesW) that provides probabilistic inference of the genetic architecture of age-at-onset phenotypes in a hybrid-parallel sampling scheme that facilitates Bayesian time-to-event large-scale biobank analyses. We show in extensive simulation work that BayesW achieves a greater number of discoveries, better model performance and improved genomic prediction as compared to other approaches. In the UK Biobank, we find many thousands of common genomic regions underlying the age-at-onset of high blood pressure...

Probabilistic inference of the genetic architecture of functional enrichment of complex traits

Matthew Robinson
We develop a Bayesian model (BayesRR-RC) that provides robust SNP-heritability estimation, an alternative to marker discovery, and accurate genomic prediction, taking 22 seconds per iteration to estimate 8.4 million SNP-effects and 78 SNP-heritability parameters in the UK Biobank. We find that only $\leq$ 10\% of the genetic variation captured for height, body mass index, cardiovascular disease, and type 2 diabetes is attributable to proximal regulatory regions within 10kb upstream of genes, while 12-25% is attributed...

Wolbachia frequency data from: Why did the Wolbachia transinfection cross the road? Drift, deterministic dynamics and disease control

Michael Turelli & Nicholas Barton
Maternally inherited Wolbachia transinfections are being introduced into natural mosquito populations to reduce the transmission of dengue, Zika and other arboviruses. Wolbachia-induced cytoplasmic incompatibility provides a frequency-dependent reproductive advantage to infected females that can spread transinfections within and among populations. However, because transinfections generally reduce host fitness, they tend to spread within populations only after their frequency exceeds a critical threshold. This produces bistability with stable equilibrium frequencies at both 0 and 1, analogous to...

Data from: Genetic architecture of repeated phenotypic divergence in Littorina saxatilis ecotype evolution

Eva L Koch, Mark Ravinet, Anja M Westram, Kerstin Johannesson & Roger K. Butlin
Chromosomal inversions have been shown to play a major role in local adaptation by suppressing recombination between alternative arrangements and maintaining beneficial allele combinations. However, so far, their importance relative to the remaining genome remains largely unknown. Understanding the genetic architecture of adaptation requires better estimates of how loci of different effect sizes contribute to phenotypic variation. Here, we used three Swedish islands where the marine snail Littorina saxatilis has repeatedly evolved into two distinct...

Modulation of auxin transport via ZF proteins adjust plant response to high ambient temperature

Christina Artner
As the overall global mean surface temperature is increasing due to climate change, plant adaptation to those stressful conditions is of utmost importance for their survival. Plants are sessile organisms, thus to compensate for their lack of mobility, they evolved a variety of mechanisms enabling them to flexibly adjust their physiological, growth and developmental processes to fluctuating temperatures and to survive in harsh environments. While these unique adaptation abilities provide an important evolutionary advantage, overall...

Homogenizing yarn simulations: Large-scale mechanics, small-scale detail, and quantitative fitting

Georg Sperl
The complex yarn structure of knitted and woven fabrics gives rise to both a mechanical and visual complexity. The small-scale interactions of yarns colliding with and pulling on each other result in drastically different large-scale stretching and bending behavior, introducing anisotropy, curling, and more. While simulating cloth as individual yarns can reproduce this complexity and match the quality of real fabric, it may be too computationally expensive for large fabrics. On the other hand, continuum-based...

Using replicate hybrid zones to understand the genomic basis of adaptive divergence

Anja Marie Westram, Rui Faria, Kerstin Johannesson & Roger Butlin
Combining hybrid zone analysis with genomic data is a promising approach to understanding the genomic basis of adaptive divergence. It allows for the identification of genomic regions underlying barriers to gene flow. It also provides insights into spatial patterns of allele frequency change, informing about the interplay between environmental factors, dispersal and selection. However, when only a single hybrid zone is analysed, it is difficult to separate patterns generated by selection from those resulting from...

Chimeric G protein-coupled receptors mimic distinct signaling pathways and modulate microglia function

Rouven Schulz
G protein-coupled receptors (GPCRs) respond to specific ligands and regulate multiple processes ranging from cell growth and immune responses to neuronal signal transmission. However, ligands for many GPCRs remain unknown, suffer from off-target effects or have poor bioavailability. Additional challenges exist to dissect cell-type specific responses when the same GPCR is expressed on several cell types within the body. Here, we overcome these limitations by engineering DREADD-based GPCR chimeras that selectively bind their agonist clozapine-N-oxide...

Improving genome-wide association discovery and genomic prediction accuracy in biobank data

Matthew Robinson, Etienne J. Orliac, Daniel Trejo Banos, Sven E. Ojavee, Kristi Läll, Reedik Mägi, Peter M. Visscher & Matthew R. Robinson
Genetically informed, deep-phenotyped biobanks are an important research resource and it is imperative that the most powerful, versatile, and efficient analysis approaches are used. Here, we apply our recently developed Bayesian grouped mixture of regressions model (GMRM) in the UK and Estonian Biobanks and obtain the highest genomic prediction accuracy reported to date across 21 heritable traits. When compared to other approaches, GMRM accuracy was greater than annotation prediction models run in the LDAK or...

MorphOMICs, a tool for mapping microglial morphology, reveals brain region- and sex-dependent phenotypes

Gloria Colombo
Environmental cues influence the highly dynamic morphology of microglia. Strategies to characterize these changes usually involve user-selected morphometric features, which preclude the identification of a spectrum of context-dependent morphological phenotypes. Here, we develop MorphOMICs, a topological data analysis approach, which enables semiautomatic mapping of microglial morphology into an atlas of cue-dependent phenotypes, overcomes feature-selection bias and minimizes biological variability. First, with MorphOMICs we derive the morphological spectrum of microglia across seven brain regions during postnatal...

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