Biology subjects

Olsson, A.

Publications and source records attributed to Olsson, A..

At least 19 recordsLinked to original sources

bioRxiv2026

Genetic determinants of intraspecific variation in crossover frequencies in the honeybee, Apis mellifera

Meiotic recombination facilitates natural selection and is necessary for correct chromosomal segregation in most sexually reproducing species. Crossover rates vary greatly both within and among species, but the determinants of this variation are not fully understood. The honeybee Apis mellifera has extremely high recombination rates. Honeybee males (drones) are haploid, which enables the distribution of crossovers to be directly estimated from the progeny of a single reproductive female (queen). Here we map crossover events in the honeybee using whole genome sequencing of 1509 drone progeny of 184 queens. This allows us to assay intra-specific variation in recombination rate and its genetic and non-genetic determinants. We estimate the average crossover rate as 23 cM/Mb, with between 22 and 88 crossovers events detected in individual offspring. We estimate 28% of this variation is additive heritable variation among queens. There is no effect of queen age or genetic background on crossover rate. A genome-wide association study identifies variation in the gene mlh1 as associated with mean crossover rate. We estimate that variation in the gene is associated with a 10% difference in crossover rate between the two homozygous genotypes at the most significant SNP. This gene has a well-established role in recombination and variation in the gene could affect crossover rates by affecting resolution of Holliday junctions as crossovers. This is the first gene discovered to be associated with recombination rate variation in an insect. Adaptive evolution of this gene could potentially underlie the extremely high recombination rates in honeybees.

genomics↗

bioRxiv2026

A new lineage of Ranavirus micropterus1 infects ornamental wrasses from the Great Barrier Reef and causes severe disease in captivity

The Great Barrier Reef (GBR) supports remarkable vertebrate diversity but is among the most fragile ecosystems globally, and diseases affecting reef fishes remain poorly understood. We employed traditional veterinary diagnostic techniques and metatranscriptomics to investigate a disease outbreak with 100% mortality in captive wrasses (Macropharyngodon choati) from the GBR. Histopathology revealed multifocal necrosis of renal tubules, and cytopathic effect was observed in bluegill fry cell lines. A novel ranavirus isolate, Macropharyngodon choati ranavirus (McRV), was identified at exceptionally high transcript abundance across different host tissues, alongside strong expression of host genes linked to cellular stress and immune function. Phylogenetic analysis placed McRV in a distinct clade of wrasse ranaviruses, clustering with a virus previously identified on the GBR, suggesting that wild wrasses serve as natural hosts. These data emphasise the need for enhanced pathogen monitoring in marine wildlife increasingly threatened by anthropogenic change.

microbiology↗

bioRxiv2025

Genetic mapping in the red mason bee Osmia bicornis implicates ANTSR as an ancient sex-determining locus in bees and ants

Haplodiploid inheritance, in which females are diploid and males are haploid, is found in all species of Hymenoptera. Sex in haplodiploids is commonly determined by the alleles present at a complementary sex determination (CSD) locus, with heterozygosity triggering the female developmental pathway. The identity of this locus differs among taxa and is only known in a few species. Here, we map a single CSD locus to a 2 kbp region in the genome of the red mason bee Osmia bicornis. It overlaps the long noncoding RNA ANTSR, which has been identified as the sex-determining gene in the invasive ant Linepithema humile. This locus is homozygous in diploid males and exhibits extremely high levels of haplotype diversity, consistent with the action of frequency-dependent selection. The elevated levels of heterozygosity in the CSD locus enable us to fine-map potentially functional genetic variation within it. We also identify elevated levels of genetic diversity in the ortholog of the CSD locus in five other bee and ant genera, suggesting that it may govern sex determination widely in Hymenoptera. Our data are consistent with the hypothesis that ANTSR evolved a role in sex determination over 150 million years ago and is the ancestral sex-determination locus of bees and ants.

evolutionary biology↗

bioRxiv2025

In vitro model of human subcutaneous adipocyte spheroids for studying mitochondrial dysfunction and mitochondria activating compounds

Mitochondrial abnormalities drive subcutaneous white adipose tissue dysfunction in obesity, leading to metabolic complications. A key challenge in obesity research is the lack of in vitro models to study human adipocyte mitochondria. Here, we establish a human subcutaneous adipocyte spheroid model to characterize mitochondrial metabolism under obesity-relevant conditions and drug exposure. Human preadipocyte spheroids were differentiated in ultra-low attachment plates for 3 weeks in media free of thiazolidinediones. The differentiated adipocyte spheroids showed increased lipid accumulation, adipogenic gene expression, mitochondrial respiration and adiponectin secretion, and a proper response to hormonal stimulation. Lipid mixture administration during differentiation induced metabolic disturbances including mitochondrial respiration failure associated with increased mitochondrial biogenesis. Post-differentiation treatment with rosiglitazone, a peroxisome proliferator-activated receptor {gamma} agonist, improved mitochondrial bioenergetics and adiponectin secretion in lipid mixture-administered adipocyte spheroids. Our model enables precise measurement of adipocyte mitochondria under various conditions, providing a platform for mitochondria-related research and drug discovery in obesity.

molecular biology↗

bioRxiv2025

Diverse Viral Pathogens in Australian Canines: Limited Geographic Structure and the First Detection of an RNA Virus in Dingoes

Viruses impose a substantial disease burden on dogs and the close relationship between dogs and humans may facilitate zoonotic disease emergence. Australias geographic isolation, strict biosecurity measures and native dingo populations present a unique model for understanding the spread and evolution of canine viruses. However, aside from a few well-characterised pathogens, genomic data are scarce for many common dog viruses, limiting our understanding of their evolution and disease ecology. Using a metatranscriptomic approach we identified the viruses in dogs and dingoes from various geographical locations across mainland Australia and sample types, revealing 86 vertebrate-associated viruses belonging to 16 distinct species, including a new vesivirus-like species. Many of the viruses identified here have not previously been sequenced in Australia. We identified important dog pathogens associated with canine infectious respiratory disease syndrome--such as canine pneumovirus, canine herpesvirus, and canine respiratory coronavirus--and gastroenteritis, including canine parvovirus, canine coronavirus, and rotavirus A. The sequences of Australian canine viruses often occupied multiple distinct clades phylogenetically and had little geographic structure, suggesting multiple virus introductions and subsequent spread across the country. Notably, we identified the first RNA virus - rotavirus A - in a dingo. This virus was phylogenetically distinct from dog-associated rotavirus A sequences and more closely related to viruses found in humans and bats, indicative of the past cross-species transmission of a reassortant virus into dingoes, and shows dingoes and domestic dogs may have distinct viromes. Our findings expand the knowledge of viral diversity in Australian canines, improving our understanding of viral movement into and within Australia, as well as the potential zoonotic risks associated with dogs and dingoes.

microbiology↗

bioRxiv2024

Detection of exotic biosecurity threat ribgrass mosaic virus and novel tobamoviruses through metatranscriptomic sequencing of animal gut content

Ribgrass mosaic virus (RMV) and related viruses of the genus Tobamovirus (Virgaviridae) are cruciferous plant pathogens that represent a threat to global horticultural systems. In Australia, they are considered exotic biosecurity threats, and an incursion of these viruses would require rapid and strict control efforts. However, current surveillance methods for these viruses are limited. We examined whether RMV and related tobamoviruses could be detected by deep sequencing of gut metatranscriptomes of vertebrate animals and ticks. Using this method, we discovered that RMV, as well as a novel relative of RMV, and two highly diverse novel tobamoviruses are present in Australia. RMV was detected in multiple sites in both the Australian Capital Territory (ACT) and Tasmania, two regions separated by approximately 700km of land and 200km of water. The novel relative of RMV was detected in the ACT and New South Wales (NSW), while the highly divergent novel tobamoviruses were each detected in a single state, NSW and Queensland (QLD). In addition, Tobacco mild green mosaic virus, which is already known to be present in Australia, was detected in QLD using this method. This work highlights the potential utility of metatranscriptomic sequencing of wild animal gut for the surveillance of biosecurity threats to native and agricultural plant species. ImportancePlant viruses can have devastating impacts on global horticulture. Tobamoviruses (family Virgaviridae, genus Tobamovirus) are among the most damaging seed-borne viruses in horticultural crops, and Australia is free of many of the tobamoviruses that cause major crop losses in other countries. These viruses are extremely difficult to eradicate. Consequently, early detection of incursions is key to the control of these viruses in Australia, alongside rapid deployment of eradication and management plans. Current biosecurity surveillance methods in Australia rely on visual inspection, immunological assays, and molecular methods such as screening of imported seed lots. This study introduces a complementary approach that utilises unbiased metatranscriptomic sequencing of animal gut material to detect cryptic plant viruses circulating in nature. Using this approach, we detected five different tobamovirus circulating in Australia, including a virus thought to be exotic and three novel viruses. This unique approach highlights alternative options for surveillance/detection of exotic crop viruses.

microbiology↗

bioRxiv2024

Unexpectedly low recombination rates and presence of hotspots in termite genomes

Meiotic recombination is a fundamental evolutionary process that facilitates adaptation and the removal of deleterious genetic variation. Social Hymenoptera exhibit some of the highest recombination rates among metazoans, whereas high recombination rates have not been found among non-social species from this insect order. It is unknown whether elevated recombination rates are a ubiquitous feature of all social insects. In many metazoan taxa, recombination is mainly restricted to hotspots a few kilobases in length. However, little is known about the prevalence of recombination hotspots in insect genomes. Here we infer recombination rate and its fine-scale variation across the genomes of two social species from the insect order Blattodea: the termites Macrotermes bellicosus and Cryptotermes secundus. We used linkage-disequilibrium-based methods to infer recombination rate. We infer that recombination rates are close to 1 cM/Mb in both species, similar to the average metazoan rate. We also observed a highly punctate distribution of recombination in both termite genomes, indicative of the presence of recombination hotspots. We infer the presence of full-length PRDM9 genes in the genomes of both species, which suggests recombination hotspots in termites might be determined by PRDM9, as they are in mammals. We also find that recombination rates in genes are correlated with inferred levels of germline DNA methylation. The finding of low recombination rates in termites indicates that eusociality is not universally connected to elevated recombination rate. We speculate that the elevated recombination rates in social Hymenoptera are instead promoted by intense selection among haploid males.

genomics↗

bioRxiv2023

Validation of the in-house designed one-trial inhibitory avoidance test for two strains of adult zebrafish

Open-source validated tools are important for affordable high-quality science. Zebrafish model is often used in behavioral sciences, thus validated tools must be developed for this species. We aimed to implement the memory task one-trial inhibitory avoidance test in our laboratory by creating a custom-built 3D printed apparatus and custom-made hardware and software using microcontrollers; this decreases the costs and increases methodological flexibility. In this task, a mild electric shock (3.3 {+/-} 0.3V and 2A for 5sec) is used as an aversive stimulus for the one-trial inhibitory avoidance task based on classical conditioning. For this study we used 72-adult zebrafish from the AB and TU strain. The aversive stimulus caused a robust and long-lasting memory that was learned in one session. The apparatus consisted in one aquarium with two compartments (white and black) where, during the conditioning session, the shock was delivered in the preferred side (black), followed by 30min of immersion in 20M MK-801, a compound known for inducing amnesia (amnesic group, n= 20 for AB and 17 for TU), or in clean water (control, n= 20 for AB and 15 for TU). Both the AB and TU strain animals from the control group took more time to enter in the black compartment after conditioning (p[≤]0.039), indicating avoidance for the black side, while the latency was not altered in the MK-801 group, demonstrating impaired memory. In summary, this open-source apparatus is an affordable and validated option for memory assessment for the two most used strains of zebrafish in research.

animal behavior and cognition↗

bioRxiv2023

Ecological genomics in the Northern krill uncovers loci for local adaptation across ocean basins

Krill is a vital food source for many marine animals but also strongly impacted by climate change. Genetic adaptation could support populations, but remains uncharacterized. We assembled the 19 Gb Northern krill genome and compared genome-scale variation among 74 specimens from the colder Atlantic Ocean and warmer Mediterranean Sea. The genome is dominated by methylated transposable elements and contains many duplicated genes implied in molting and vision. Analysis of 760 million SNPs indicates extensive homogenizing gene-flow among populations. Nevertheless, we detect extreme divergence across hundreds of genes, governing ecophysiological functions like photoreception, circadian regulation, reproduction and thermal tolerance. Such standing variation may be essential for resilience in zooplankton, necessitating insight into adaptive variation to forecast their roles in future marine ecosystems and support ocean conservation. One-Sentence SummaryGenome-scans of Northern krill link genes for photoreception, reproduction and thermal tolerance to ecological adaptation.

evolutionary biology↗

bioRxiv2021

Help or flight: Neural defensive circuits promote helping under threat in humans

Empathy for others distress has long been considered the driving force of helping. However, when deciding to help others in danger, one must consider not only their distress, but also the risk to oneself. Whereas the role of self-defence in helping has been overlooked in human research, studies in other animals indicate defensive responses are necessary for the protection of conspecifics. In this pre-registered study (N=49), we demonstrate that human defensive neural circuits are implicated in helping others under threat. Participants underwent fMRI scanning while deciding whether to help another participant avoid aversive electrical shocks, at the risk of also being shocked. We found that higher engagement of neural circuits that coordinate fast escape from self-directed danger (including the insula, PAG and ACC) facilitated decisions to help others. Importantly, using Representational Similarity Analysis, we found that the strength with which the amygdala and insula uniquely represented the threat to oneself (and not the others distress) predicted helping. Our findings indicate that in humans, as other mammals, defensive mechanisms play a greater role in helping behaviour than previously understood.

neuroscience↗

bioRxiv2021

Learning about threat from friends and strangers is equally effective: an fMRI study on observational fear conditioning

Humans often benefit from social cues when learning about the world. For instance, learning about threats from others can save the individual from dangerous first-hand experiences. Familiarity is believed to increase the effectiveness of social learning, but it is not clear whether it plays a role in learning about threats. Using functional magnetic resonance imaging, we undertook a naturalistic approach and investigated whether there was a difference between observational fear learning from friends and strangers. Participants (observers) witnessed either their friends or strangers (demonstrators) receiving aversive (shock) stimuli paired with colored squares (observational learning stage). Subsequently, participants watched the same squares, but without receiving any shocks (direct-expression stage). We observed a similar pattern of brain activity in both groups of observers. Regions related to threat responses (amygdala, anterior insula, anterior cingulate cortex) and social perception (fusiform gyrus, posterior superior temporal sulcus) were activated during the observational phase, reflecting the fear contagion process. The anterior insula and anterior cingulate cortex were also activated during the subsequent stage, indicating the expression of learned threat. Because there were no differences between participants observing friends and strangers, we argue that social threat learning is independent of the level of familiarity with the demonstrator. HighlightsO_LIWe compared observational learning of fear from friends and strangers C_LIO_LIFamiliarity does not enhance social learning of fear in humans C_LIO_LIBayesian statistics confirm absence of differences between friends and strangers C_LIO_LIObservational fear learning activates social and fear networks including amygdala C_LIO_LIAmygdala activations are absent when learned fear is recalled C_LI

neuroscience↗

bioRxiv2021

Genome sequencing and morphometric analysis of alpine bumblebees experiencing climate change reveal ongoing phenotypic shifts and a lack of population structure

Over the last six decades, populations of the bumblebees Bombus sylvicola and Bombus balteatus in Colorado have experienced decreases in tongue length, a trait important for plant-pollinator mutualisms. It has been hypothesized that this observation reflects selection resulting from shifts in floral composition under climate change. Here we used morphometrics and population genomics to determine whether morphological change is ongoing, investigate the genetic basis of morphological variation, and analyze population structure in these populations. We generated a genome assembly of B. balteatus. We then analyzed whole-genome sequencing data and morphometric measurements of 580 samples of both species from seven high-altitude localities. Out of 281 samples originally identified as B. sylvicola, 67 formed a separate genetic cluster comprising a newly-discovered cryptic species ("incognitus"). However, an absence of genetic structure within species suggests that gene flow is common between mountains. We found a significant decrease in tongue length between bees collected between 2012-2014 and in 2017, indicating that morphological shifts are ongoing. We did not discover any genetic associations with tongue length, but a SNP related to production of a proteolytic digestive enzyme was implicated in body size variation. We identified evidence of covariance between kinship and both tongue length and body size, which is suggestive of a genetic component of these traits, although it is possible that shared environmental effects between colonies are responsible. Our results provide evidence for ongoing modification of a morphological trait important for pollination and indicate that this trait likely has a complex genetic and environmental basis.

evolutionary biology↗

bioRxiv2021

Adult zebrafish anaesthesia: a study of efficacy and behavioural recovery of different anaesthetics

The use of proper anaesthesia in zebrafish research is essential to ensure fish welfare and data reliability. However, anaesthesia long-term side effects remain poorly understood. The purpose of this study was to assess anaesthesia quality and recovery in adult zebrafish using different anaesthetic protocols and to determine possible long-term effects on the fish activity and anxiety-like behaviours after anaesthesia. Mixed sex adult AB zebrafish were randomly assigned to 5 different groups (control, 175mg/L MS222, 45 mg/L clove oil, 2 mg/L etomidate and 5mg/L propofol combined with 150mg/L lidocaine) and placed in the respective anaesthetic bath. Time to lose the equilibrium, response to touch and to tail pinch stimuli, and recovery after anaesthesia administration were evaluated. In addition, after stopping anaesthesia, respiratory rate, activity and anxiety-like behaviours in the novel tank test were studied. Overall, all protocols proved to be adequate for zebrafish anaesthesia research as they showed full recovery at 1h, and only etomidate had minor effects on fish behaviour in the novel tank, a validated test for anxiety.

animal behavior and cognition↗

bioRxiv2021

Caprin-1 binding to the critical stress granule protein G3BP1 is regulated by pH

G3BP is the central hub within the protein-RNA interaction network of stress-induced bio-molecular condensates known as stress granules (SG). The SG-associated proteins Caprin-1 and USP10 exhibit mutually exclusive binding to the structured NTF2-domain of G3BP1, thereby regulating G3BP1-mediated condensation, but with opposite effects: Caprin-1 promotes but USP10 inhibits SG formation. Herein, we present the crystal structure of G3BP1-NTF2 in complex with a Caprin-1 derived short linear motif (SLiM), which provides a molecular understanding for the mutually exclusive binding of USP10 and Caprin-1 to G3BP1. Caprin-1 but not USP10 contacts two G3BP1-NTF2 histidine residues, which was confirmed using biochemical, biophysical and cellular biological binding assays. G3BP1/Caprin-1 interactions disrupted via point mutations resulted in fewer and smaller SG condensates. In addition, biochemical binding assays demonstrated reduced binding of Caprin-1 to G3BP1 at lower pH values. Finally, ratiometric pH sensitive measurements of SGs revealed a substantial drop in pH compared to the adjacent cytosol, suggesting that reduced pH can fine-tune and regulate the G3BP1-mediated interaction network via a NTF2-mediated pH-sensitive SLiM-selection mechanism.

biochemistry↗

bioRxiv2020

Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19

ABSTRACTSARS-CoV-2-specific memory T cells will likely prove critical for long-term immune protection against COVID-19. We systematically mapped the functional and phenotypic landscape of SARS-CoV-2-specific T cell responses in a large cohort of unexposed individuals as well as exposed family members and individuals with acute or convalescent COVID-19. Acute phase SARS-CoV-2-specific T cells displayed a highly activated cytotoxic phenotype that correlated with various clinical markers of disease severity, whereas convalescent phase SARS-CoV-2-specific T cells were polyfunctional and displayed a stem-like memory phenotype. Importantly, SARS-CoV-2-specific T cells were detectable in antibody-seronegative family members and individuals with a history of asymptomatic or mild COVID-19. Our collective dataset shows that SARS-CoV-2 elicits robust memory T cell responses akin to those observed in the context of successful vaccines, suggesting that natural exposure or infection may prevent recurrent episodes of severe COVID-19 also in seronegative individuals.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2020

Shared safety abolishes the recovery of learned threat

Social learning offers an efficient route to transmit information about threat and safety. To better isolate the processes that contribute to the efficacy of social safety learning, we developed a novel dyadic model of associative threat and extinction learning. In three separate social groups, we manipulated whether safety information during extinction was acquired via direct exposure to the conditioned stimulus (CS) in the presence of another individual (Direct exposure), via observation of other’s safety behavior (Vicarious exposure), or via the combination of both (Shared exposure). These groups were contrasted against a fourth group receiving direct CS exposure alone (Asocial exposure). Based on skin conductance responses, we observed that all social groups outperformed asocial learning in inhibiting the recovery of threat, but only Shared exposure abolished threat recovery. These results suggest that social safety learning is optimized by a combination of direct exposure and vicariously transmitted safety signals.Statement of relevance Humans, like other social animals, learn about threats and safety in the environment through social cues. Yet, the processes that contribute to the efficacy of social safety learning during threat transmission remain unknown. Here, we used a two-person approach to analyze skin conductance responses as participants engaged in a standard fear conditioning procedure (acquisition, extinction, and reinstatement). We found that during extinction, both (i) direct (conditioned stimulus) exposure in the presence of another individual and (ii) vicarious safety signals alone is sufficient to inhibit subsequent threat recovery, but that abolishing the recovery of conditioned threat responses requires a combination of both. This study has relevance for understanding how social information can optimize standard, asocial safety learning procedures to augment the effects of exposure on previously acquired fears. Thus, our work might help identify psychological and social strategies that can be used to counteract maladaptive fears in humans.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2020

Three-dimensional mapping identifies distinct vascular niches for myelopoiesis

In contrast to virtually all other tissues in the body the anatomy of differentiation in the bone marrow remains unknown. This is due to the lack of strategies to examine blood cell production in situ, which are required to better understand differentiation, lineage commitment decisions, and to define how spatial organizing cues inform tissue function. Here we developed imaging approaches to map all myeloid cells in whole bones and generated 3D atlases of granulocyte and monocyte/dendritic cell differentiation during homeostasis. We found that myeloid progenitors leave the hematopoietic stem cell niche during differentiation. Granulocyte and monocyte dendritic cell progenitors (MDP) do not interact, instead they localize to different sinusoids where they give rise to clusters of immature cells. MDP cluster with Ly6Clo monocytes and conventional dendritic cells; these localize to a unique subset of colony stimulating factor 1 (CSF1, the major regulator of monopoiesis1) -expressing sinusoids. Csf1 deletion in the vasculature disrupted the MDP clusters and their interaction with sinusoids, leading to reduced MDP numbers and differentiation ability, with subsequent loss of peripheral Ly6Clo monocytes and dendritic cells. These data indicate that there is a specific spatial organization of definitive hematopoiesis and that local cues produced by distinct blood vessels are responsible for this organization. These maps provide a blueprint for in situ analyses of hematopoiesis in blood disorders.

immunology↗

bioRxiv2020

High laboratory mouse pre-weaning mortality associated with litter overlap, advanced mother age, small and large litters

High and variable pre-weaning mortality is a persistent problem among the main mouse strains used in biomedical research. If a modest 15% mortality rate is assumed across all mouse strains used in the EU, approximately 1 million more pups must be produced yearly to compensate for those which die. A few environmental and social factors have been identified as affecting pup mortality, but optimizing these factors does not cease the problem. This study is the first large study to mine data records from 219,975 pups from two breeding facilities to determine the major risk factors associated with mouse pre-weaning mortality. It was hypothesized that litter overlap (i.e. the presence of older siblings in the cage when new pups are born), a recurrent social configuration in trio-housed mice, is associated with increased newborn mortality, along with high mother age, large litter size, as well as a high number and age of older siblings in the cage. The estimated probability of pup death was two to seven percentage points higher in cages with compared to those without litter overlap. Litter overlap was associated with an increase in percentage of litter losses of 19% and 103%, respectively, in the two breeding facilities. Increased number and age of older siblings, high mother age, small litter size (less than four pups born) and large litter size (over 11 pups born) were associated with increased probability of pup death. Results suggest that common social cage configurations at breeding facilities are dangerous for the survivability of young mouse pups. The underlying mechanisms and strategies to avoid these situations should be further investigated.

animal behavior and cognition↗