Biology subjects

Olsson, M.

Publications and source records attributed to Olsson, M..

7 recordsLinked to original sources

bioRxiv2026

Genomic consequences of admixture in an experimentally founded sand lizard population

Conservation interventions are increasingly required for species threatened by population declines and isolation due to anthropogenic pressures. Small, isolated populations are particularly vulnerable to the loss of genetic diversity, increased inbreeding, and the accumulation of deleterious mutations. Translocations or supplementation of allopatric individuals for genetic rescue may be the only way to increase genetic diversity to increase population persistence via increased adaptive potential. Here, we use an experimentally admixed population of sand lizards on a small island in Sweden as a valuable model of genetic rescue. This population was established approximately 20 years ago (5-6 generations) resulting in increased fecundity and hatchling viability. This population was founded from crossings between individuals from an inbred population from the nearby mainland and individuals sourced from populations in southern Sweden. Low-coverage whole-genome sequencing revealed elevated genetic diversity and reduced realized genetic load in this admixed population relative to the source populations. Ancestry analyses indicated a greater contribution of southern Swedish genetic variation, potentially reflecting contribution of beneficial adaptive variation from this region that may underlie the positive population effects. This system provides valuable empirical insights into the long-term genomic consequences of genetic rescue in this model vertebrate population.

genomics↗

bioRxiv2025

Large scale, low coverage population genomics approach to assess genetic variation and structure across vulnerable Swedish sand lizard populations

Genomics has emerged as a powerful tool in conservation biology, offering valuable insights into the genetic diversity, population connectivity and adaptive potential of threatened species. Here, we apply a large-scale, low-coverage whole genome sequencing approach to the conservation genomics of the Swedish sand lizard (Lacerta agilis). Sand lizards occur in fragmented populations across Sweden, with varying population sizes and degrees of isolation, and face significant threats from habitat degradation and land use change. In this study, we sequenced 139 individuals to investigate genetic diversity, population structure and genetic load. We reveal strong population structure among Swedish sand lizards and identify populations with low genetic diversity and realised high genetic load. Genetic diversity in populations declined with increasing latitude, likely reflecting the historical northward expansion process and the subsequent population fragmentation and isolation. We observe strong population structure and reveal genetic distinctiveness of populations; findings with significant conservation implications. For example, the Sormon population, a relict population in central Sweden, appears genetically distinct from all other populations. Further, the northern-most populations in Dalarna appear relatively small, with high genetic load, and thus may require intensive management via e.g., restored open successional habitat to aid population recovery. Our study adds to the growing field of conservation genomics and demonstrates the value of high-resolution whole genome approaches to the conservation efforts for threatened populations. Finally, our research contributes crucial insights for the conservation management of this vulnerable species in Sweden.

genomics↗

bioRxiv2025

Slow Wave Sleep Reduces CSF Concentrations of Beta-amyloid and Tau: A Randomized Crossover Study in Healthy Adults

BackgroundSlow-wave sleep has been proposed to facilitate the removal of proteins, implicated in neurodegeneration, from the brain. While mechanistic evidence from animal models is accumulating, direct human data on how slow-wave sleep shapes cerebrospinal fluid (CSF) proteostasis remain limited, constraining our understanding of physiological resilience to neurodegenerative disease. MethodsTwelve healthy adults (aged 20-40 years) underwent CSF sampling following three controlled sleep conditions in a randomized crossover design; (1) one night of sleep followed by afternoon CSF sampling, (2) one night of sleep followed by morning CSF sampling, and (3) one night of total sleep deprivation followed by morning CSF sampling. Sleep and wakefulness were verified using polysomnography and actigraphy, with >4-week washout periods between conditions. Measured CSF biomarkers included Alzheimers disease-related proteins: beta-amyloid isoforms (A{beta}38, A{beta}40, and A{beta}42), total and phosphorylated tau, glial fibrillary acidic protein (GFAP), and neurofilament light, as well as orexin, albumin (also measured in serum), and osmolality. Differences between conditions were assessed using Friedman tests with Dunns post hoc correction. ResultsCSF levels of A{beta} and tau tended to be consistently lower after sleep compared with both afternoon sampling and post-sleep deprivation. Concurrently, CSF albumin levels increased after sleep, while neurofilament light and GFAP remained unchanged. Orexin levels rose markedly during sleep deprivation but showed no circadian variation. ConclusionsThese findings support a model in which slow wave sleep enhances CSF turnover, reducing concentrations of specific proteins, including A{beta} and tau. Understanding how sleep regulates the homeostasis of neurodegeneration-related proteins may inform strategies to mitigate disease progression.

neuroscience↗

bioRxiv2023

Tau in cerebrospinal fluid induces neuronal hyperexcitability and alters hippocampal theta oscillations

Alzheimers disease (AD) and other tauopathies are characterized by the aggregation of tau into soluble and insoluble forms (including tangles and neuropil threads). In humans, a fraction of both phosphorylated and non-phosphorylated N-terminal to mid-domain tau species, including the aggregated forms, are secreted into cerebrospinal fluid (CSF). Some of these CSF tau species can be measured as diagnostic and prognostic biomarkers, starting from early stages of disease. While in animal models of AD pathology, soluble tau aggregates have been shown to disrupt neuronal function, it is unclear whether the tau species present in CSF will modulate neural activity. Here, we have developed and applied a novel approach to examine the electrophysiological effects of CSF from patients with a tau-positive biomarker profile. The method involves incubation of acutely-isolated wild-type mouse hippocampal brain slices with small volumes of diluted human CSF, followed by a suite of electrophysiological recording methods to evaluate their effects on neuronal function from single cells through to the network level. Comparison of the toxicity profiles of the same CSF samples, with and without immuno-depletion for tau, has enabled a pioneering demonstration that CSF-tau potently modulates neuronal function. We demonstrate that CSF-tau mediates an increase in neuronal excitability in single cells. We then observed, at the network level, increased input-output responses and enhanced paired-pulse facilitation as well as an increase in long-term potentiation. Finally, we show that CSF-tau modifies the generation and maintenance of hippocampal theta oscillations, which have important roles in learning and memory and are known to be altered in AD patients. Together, we describe a novel method for screening human CSF-tau to understand functional effects on neuron and network activity, which could have far-reaching benefits in understanding tau pathology, thus allowing for the development of better targeted treatments for tauopathies in the future. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/525362v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@13f564forg.highwire.dtl.DTLVardef@13b75cborg.highwire.dtl.DTLVardef@b27dbaorg.highwire.dtl.DTLVardef@5c68c0_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

An agnostic study of associations between ABO and RhD blood group and phenome-wide disease risk

There are multiple known associations between the ABO and RhD blood groups and disease. However, no systematic population-based studies elucidating associations between a large number of disease states and blood group have been conducted. Using SCANDAT3-S, a comprehensive nationwide blood donation-transfusion database, we modelled outcomes for 1,217 disease categories including 70 million person-years of follow-up, accruing from 5.1 million unique individuals. We discovered 49 and 1 associations between a disease and ABO and RhD blood group, respectively, after adjustment for multiple testing. We identified new associations such as kidney stones and blood group B as compared to O. We also expanded previous knowledge on other associations such as pregnancy-induced hypertension and blood group A and AB as compared to O and RhD positive as compared to negative. Our findings generate strong further support for previously known associations, but also indicate new interesting relations.

physiology↗

bioRxiv2020

Exercise training in a color-polymorphic lizard reveals differential effects of mating tactics and color morphs on telomere, body condition and growth dynamics

Alternative reproductive tactics (ARTs) are correlated suites of sexually selected traits that are likely to impose differential physiological costs on different individuals. While some level of activity might be beneficial, animals living in the wild are often working at the margins of their resources and performance limits. Individuals using ARTs may have divergent capacities for activity, and when pushed beyond their capacity, they may experience condition loss, oxidative stress, and molecular damage that must be repaired with limited resources. We used the Australian painted dragon lizard that exhibits color-polymorphims with corresponding alternative reproductive tactics (ARTs) as a model to experimentally test the effect of exercise on body condition, growth, reactive oxygen species (ROS), and telomere dynamics--a potential marker of stress and aging and a correlate of longevity. For most males, ROS tended to be lower with greater exercise; however, males with yellow throat patches--or bibs-- had higher ROS than non-bibbed males. At the highest level of exercise, bibbed males exhibited telomere loss, while non-bibbed males gained telomere length; the opposite pattern was observed in the no-exercise controls. Growth was positively related to food intake but negatively correlated with telomere length at the end of the experiment. Body condition was not related to food intake but was positively correlated with increases in telomere length. These results, along with our previous work, suggest that aggressive bibbed males suffer physiological costs that may reduce longevity.

evolutionary biology↗

bioRxiv2019

Condition-dependent SOD activity attenuates morph-specific superoxide effects on sperm performance

Sperm competition theory predicts a negative correlation between somatic investment in traits that aid in pre- and postcopulatory sexual selection. Sperm performance is critical for postcopulatory success but are susceptible to damage by free radicals such as superoxide radicals generated during mitochondrial respiration (mtSOx). Males can ameliorate damage to spermatozoa by investing in the production of antioxidants, like superoxide dismutase (SOD), which may act as a mechanistic link for pre and postcopulatory trade-offs. Some male Australian, colour-polymorphic painted dragon lizards (Ctenophorus pictus) possess a yellow throat patch (bib) that females prefer over non-bibbed males and are also more likely to win male-male contests indicating that males with bibs are better at monopolizing females. We tested whether the sperm performance in non-bibbed males was superior to that of bibbed males as predicted by sperm competition theory. We show that blood cell mtSOx levels are negatively correlated with SOD activity in the plasma in all males early in the breeding season but SOD was lower in bibbed males. Non-bibbed males maintain a positive correlation between body condition and SOD activity over time while bibbed males do not. Overall sperm performance was not different between the bib-morphs, however, higher mtSOx levels were negatively correlated with sperm performance in bibbed males, but not of non-bibbed males. Together these data suggest physiological associations between body condition, SOD activity and sperm performance are linked to the expression of a yellow gular patch, which may be related to intrinsic differences in metabolism of bibbed versus non-bibbed males. Lay summaryDamage-inducing reactive oxygen species (ROS) are a by-product of oxygen-based energy production that are quenched by energetically expensive antioxidants. Male sexual colouration requires investment of energy and resources, which may constrain allocation to other functions like antioxidant production or spermatogenesis. Here we explored whether the body condition of colourful male lizards reflected their investment in antioxidants and reduction of ROS, which may influence sperm performance. We found that drab males in better condition had more antioxidants. Colourful males had lower levels of antioxidants and their sperm performed poorly at higher ROS levels. These results suggest a trade-off between colour maintenance and sperm performance.

evolutionary biology↗