Bestrophin-like protein 4 is involved in photosynthetic acclimation to light fluctuations in Chlamydomonas.

In many eukaryotic algae, CO2 fixation by Rubisco is enhanced by a CO2-concentrating mechanism, which utilizes a Rubisco-rich organelle called the pyrenoid. The pyrenoid is traversed by a network of thylakoid membranes called pyrenoid tubules, which are proposed to deliver CO2. In the model alga Chlamydomonas (Chlamydomonas reinhardtii), the pyrenoid tubules have been proposed to be tethered to the Rubisco matrix by a bestrophin-like transmembrane protein, BST4. Here, we show that BST4 forms a complex that localizes to the pyrenoid tubules. A Chlamydomonas mutant impaired in the accumulation of BST4 (bst4) formed normal pyrenoid tubules, and heterologous expression of BST4 in Arabidopsis (Arabidopsis thaliana) did not lead to the incorporation of thylakoids into a reconstituted Rubisco condensate. Chlamydomonas bst4 mutants did not show impaired growth under continuous light at air level CO2 but were impaired in their growth under fluctuating light. By quantifying the non-photochemical quenching (NPQ) of chlorophyll fluorescence, we propose that bst4 has a transiently lower thylakoid lumenal pH during dark-to-light transition compared to control strains. We conclude that BST4 is not a tethering protein but is most likely a pyrenoid tubule ion channel involved in the ion homeostasis of the lumen with particular importance during light fluctuations.

Resolution of tuberculosis blood RNA signatures fails to discriminate persistent sputum culture positivity after eight weeks of anti-tuberculous treatment.

BACKGROUND: Concerted efforts aim to reduce the burden of 6 months anti-tuberculous treatment for tuberculosis (TB). Treatment cessation at 8 weeks is effective for most but incurs increased risk of disease relapse. We tested the hypothesis that blood RNA signatures or C-reactive protein (CRP) measurements discriminate 8-week sputum culture status, as a prerequisite for a biomarker to stratify risk of relapse following treatment cessation at this time point. METHODS: We identified blood RNA signatures of TB disease or cure by systematic review. We evaluated these signatures and CRP measurements in a pulmonary TB cohort, pre-treatment, at 2 and 8 weeks of treatment, and sustained cure after treatment completion. We tested biomarker discrimination of 8-week sputum culture status using area under the receiver operating characteristic curve (AUROC) analysis and, secondarily, assessed correlation of biomarker scores with time-to-culture positivity at 8 weeks of treatment. RESULTS: 12 blood RNA signatures were reproduced in the dataset from 44 individuals with sputum culture positive pulmonary TB. These normalised over time from TB treatment initiation. 11/44 cases with blood RNA, CRP and sputum culture results were sputum culture positive at 8 weeks of treatment. None of the contemporary blood RNA signatures discriminated sputum culture status at this time point or correlated with bacterial load. CRP achieved modest discrimination with AUROC of 0.69 (95% confidence interval 0.52-0.87). CONCLUSIONS: Selected TB blood RNA signatures and CRP do not provide biomarkers of microbiological clearance to support TB treatment cessation at 8 weeks. Resolution of blood transcriptional host-responses in sputum culture-positive individuals suggests Mycobacterium tuberculosis may colonise the respiratory tract without triggering a detectable immune response.

ANXIOLYTICS: Origins, drug discovery, and mechanisms.

Anxiety is a part of the human condition and has been managed by psychoactive substances for centuries. The current medical need and societal demand for anxiolytic medicines has not abated. The present overview provides a brief historical introduction to the discovery of modern age anxiolytics that include the benzodiazepines together with a discussion of the continuing medical need for new antianxiety medications. The paper also discusses the use and impact of behavioral pharmacology in the preclinical development of anxiolytics. The review then highlights the diversity of mechanisms for creating a new generation of anxiolytics through mechanisms beyond the potentiation of GABAA receptors and the blockade of monoamine uptake. A discussion then follows on the behavioral specificity of action of anxiolytics that includes the concept of creating an anxioselective drug, one that targets anxiety without producing untoward effects that include sedation and dependence. The use of anxiolytics in the treatment of other conditions such as substance use disorder is also briefly reviewed. Finally, a brief summary of the current status of anxiolytic drug development is provided. The review concludes with the idea that despite a host of anxiolytic drugs, the lack of efficacy in some patients and the side-effects and safety issues associated with some of these medications demands alternative medicines. Current preclinical and clinical research is ongoing with the goal of identifying such compounds.

Population structure of Dugong dugon across the Indo-Pacific revealed by historical mitogenomes.

Sirenia, an iconic marine taxon with a tropical and subtropical worldwide distribution, face an uncertain future. All species are designated 'Vulnerable' to extinction by the IUCN. Nonetheless, a comprehensive understanding of geographic structuring across the global range is lacking, impeding our ability to highlight particularly vulnerable populations for conservation priority. Here, we use ancient DNA to investigate dugong (Dugong dugon) population structure, analysing 56 mitogenomes from specimens comprising the known historical range. Our results reveal geographically structured and distinct monophyletic clades characterized by contrasting evolutionary histories. We observe deep-rooted and divergent lineages in the East (Indo-Pacific) and obtain new evidence for the relatively recent dispersal of dugongs into the western Indian Ocean. All populations are significantly differentiated from each other with western populations having approximately 10-fold lower levels of genetic variation than eastern Indo-Pacific populations. Additionally, we find a significant temporal loss of genetic diversity in western Indian Ocean dugongs since the mid-twentieth century, as well as a decline in population size beginning approximately 1000 years ago. Our results add to the growing body of evidence that dugong populations are becoming ever more susceptible to ongoing human action and global climate change.

Molecular Pathway Changes Associated with Different Post-Conditioning Exercise Interventions After Experimental TBI.

Traumatic brain injury (TBI) causes complex, time-dependent molecular and cellular responses, which include adaptive changes that promote repair and recovery, as well as maladaptive processes such as chronic inflammation that contribute to chronic neurodegeneration and neurological dysfunction. Hormesis is a well-established biological phenomenon in which exposure to low-dose toxins or stressors results in protective responses to subsequent higher-level stressors or insults. Hormetic stimuli show a characteristic U-shaped or inverted J-shaped dose-response curve, as well as being time and exposure-frequency dependent, similar to pre-conditioning and post-conditioning actions. Voluntary exercise interventions, before or after injury, appear to follow these general hormetic principles. But the molecular alterations associated with exercise interventions or more general hormetic responses have received only limited attention. In this study, we used a well-characterized mouse TBI model to assess the effects of different post-conditioning exercise-intervention paradigms on diverse molecular pathways, including neuroinflammation regulators, and post-traumatic neurological deficits. We generated high-throughput gene expression data and associated molecular pathway analyses to assess the potential molecular mechanisms associated with time- and duration-dependent voluntary exercise intervention, as well as time after treatment. Importantly, we also used newer analytical methods to more broadly assess the impact of exercise on diverse molecular pathways. TBI caused long-term changes in multiple neuroinflammation markers and chronic cognitive dysfunction. Notably, all delayed, post-conditioning exercise interventions reduced post-traumatic neuroinflammation and/or attenuated the related cognitive changes, albeit with different pathway specificity and effects magnitude. Exercise comprehensively reversed injury-associated effects in the hippocampus across both activated inflammatory and inhibited neuronal pathways, consistent with a return toward the noninjured, homeostatic state. In contrast, the cortex showed a less consistent pattern with more limited attenuation of inflammatory pathway activation and an amplification in the injury-dependent inhibition of select noninflammatory pathways, indicating less effective and potentially detrimental responses to exercise. Exercise intervention beginning 2 weeks after injury and lasting 2 weeks was less effective than exercise continuing for 4 weeks. Exercise initiated at a more delayed timepoint of 6 weeks after injury and continuing for 4 weeks was more effective than that during the acute phase. The delayed paradigm was also more effective than exercise initiated at 10 weeks after injury and continuing for 8 weeks, consistent with hormetic responses in other models and species. Overall, our study delineates regional and interventional parameters, as well as related molecular pathway changes, associated with post-conditioning exercise treatment, which may help inform future translational interventional strategies.

Archaeological evidence of resource utilisation of walrus, Odobenus rosmarus, over the past two millennia: A systematic review protocol.

The walrus, Odobenus rosmarus, is an iconic pinniped and predominant molluscivore that is well adapted to Arctic and subarctic environments. Its circumpolar distribution, large body size and ivory tusks facilitated its vital role as food, raw material (for tools and art), income, and cultural influence on many Arctic Indigenous communities for millennia. Intensification of hunting (often due to the arrival of Europeans, especially between the 16 th and 19 th centuries) to obtain ivory, hide, blubber and meat, resulted in diminished, sometimes extirpated, walrus populations. Zooarchaeological, artefactual and documentary evidence of walrus material has been collated at local and regional scales and is frequently focused on a specific culture or period of time. Systematic collation of this evidence across the Northern Hemisphere will provide insight into the chronology and circumpolar distribution of walrus hunting and provide a tool to document societal change in walrus resource use. Here, we lay out a systematic review protocol to collate records of archaeological walrus artefacts, tusks and bones that have been documented primarily within published literature to archive when and where (as feasible) walrus extractions occurred between 1 CE and 2000 CE. These data will be openly available for the scientific community. The resulting dataset will be the first to provide spatiotemporal information (including the recognition of knowledge gaps) regarding past walrus populations and extirpations on a circumpolar scale. Our protocol is published to ensure reproducibility and comparability in the future, and to encourage the adoption of systematic review methodology (including pre-published protocols) in archaeology.

Predicting Rubisco-Linker Condensation from Titration in the Dilute Phase.

The condensation of Rubisco holoenzymes and linker proteins into "pyrenoids," a crucial supercharger of photosynthesis in algae, is qualitatively understood in terms of "sticker-and-spacer" theory. We derive semianalytical partition sums for small Rubisco-linker aggregates, which enable the calculation of both dilute-phase titration curves and dimerization diagrams. By fitting the titration curves to surface plasmon resonance and single-molecule fluorescence microscopy data, we extract the molecular properties needed to predict dimerization diagrams. We use these to estimate typical concentrations for condensation, and successfully compare these to microscopy observations.

Cervical cancer screening using DNA methylation triage in a real-world population.

Cervical cancer (CC) screening in women comprises human papillomavirus (HPV) testing followed by cytology triage of positive cases. Drawbacks, including cytology's low reproducibility and requirement for short screening intervals, raise the need for alternative triage methods. Here we used an innovative triage technique, the WID-qCIN test, to assess the DNA methylation of human genes DPP6, RALYL and GSX1 in a real-life cohort of 28,017 women aged ≥30 years who attended CC screening in Stockholm between January and March 2017. In the analysis of all 2,377 HPV-positive samples, a combination of WID-qCIN (with a predefined threshold) and HPV16 and/or HPV18 (HPV16/18) detected 93.4% of cervical intraepithelial neoplasia grade 3 and 100% of invasive CCs. The WID-qCIN/HPV16/18 combination predicted 69.4% of incident cervical intraepithelial neoplasia grade 2 or worse compared with 18.2% predicted by cytology. Cytology or WID-qCIN/HPV16/18 triage would require 4.1 and 2.4 colposcopy referrals to detect one cervical intraepithelial neoplasia grade 2 or worse, respectively, during the 6 year period. These findings support the use of WID-qCIN/HPV16/18 as an improved triage strategy for HPV-positive women.

A historical perspective and recent advances on the evolution of the relationship between acute and chronic pain and cardiovascular disease.

The relationship between acute pain and the cardiovascular system was recognized approximately 50 years ago following the initial observation, along with several subsequent experimental studies, that hypertension can result in decreases in the perception of pain. These studies provided a strong impetus to study potential mechanisms to clarify commonalities between the regulatory pathways associated with pain and the cardiovascular system. Attention subsequently shifted to an emphasis on the impact of chronic pain on cardiovascular diseases and mortality with several large meta-analyses of longitudinal studies providing clear evidence that chronic widespread pain increases the risk for developing cardiovascular disease and is associated with excess morbidity and mortality. Cardiovascular associated mortality from myocardial infarction and stroke appears to be directly related to the duration and severity of chronic pain, a result often characterized as a 'dose-response' relationship. The availability and reproducibility of extensive large-scale observational and retrospective studies have emphasized the critical need for more research, including prospective studies, along with the need for the development of preclinical animal models, to better understand the relationship(s) and underlying mechanisms between chronic pain, associated comorbidities, and cardiovascular disease. Elucidation and a deeper understanding of these relationships, including a focus on the link between chronic pain, cardiovascular disease, and depression, could provide valuable information to guide the development of potential treatment interventions to aid in attenuating pain while preventing pain-associated cardiovascular disease, comorbidities, and mortality.

Share of Adult Suicides After Recent Jail Release.

Importance: Although people released from jail have an elevated suicide risk, the potentially large proportion of this population in all adult suicides is unknown. Objective: To estimate what percentage of adults who died by suicide within 1 year or 2 years after jail release could be reached if the jail release triggered community suicide risk screening and prevention efforts. Design, Setting, and Participants: This cohort modeling study used estimates from meta-analyses and jail census counts instead of unit record data. The cohort included all adults who were released from US jails in 2019. Data analysis and calculations were performed between June 2021 and February 2024. Main Outcomes and Measures: The outcomes were percentage of total adult suicides within years 1 and 2 after jail release and associated crude mortality rates (CMRs), standardized mortality ratios (SMRs), and relative risks (RRs) of suicide in incarcerated vs not recently incarcerated adults. Taylor expansion formulas were used to calculate the variances of CMRs, SMRs, and other ratios. Random-effects restricted maximum likelihood meta-analyses were used to estimate suicide SMRs in postrelease years 1 and 2 from 10 jurisdictions. Alternate estimate was computed using the ratio of suicides after release to suicides while incarcerated. Results: Included in the analysis were 2019 estimates for 7 091 897 adults (2.8% of US adult population; 76.7% males and 23.3% females) who were released from incarceration at least once, typically after brief pretrial stays. The RR of suicide was 8.95 (95% CI, 7.21-10.69) within 1 year after jail release and 6.98 (95% CI, 4.21-9.76) across 2 years after release. A total of 27.2% (95% CI, 18.0%-41.7%) of all adult suicide deaths occurred in formerly incarcerated individuals within 2 years of jail release, and 19.9% (95% CI, 16.2%-24.1%) of all adult suicides occurred within 1 year of release (males: 23.3% [95% CI, 20.8%-25.6%]; females: 24.0% [95% CI, 19.7%-36.8%]). The alternate method yielded slightly larger estimates. Another 0.8% of adult suicide deaths occurred during jail stays. Conclusions and Relevance: This cohort modeling study found that adults who were released from incarceration at least once make up a large, concentrated population at greatly elevated risk for death by suicide; therefore, suicide prevention efforts focused on return to the community after jail release could reach many adults within 1 to 2 years of jail release, when suicide is likely to occur. Health systems could develop infrastructure to identify these high-risk adults and provide community-based suicide screening and prevention.

High performance of the DNA methylation-based WID-qEC test for detecting uterine cancers independent of sampling modalities.

Endometrial cancer (EC) is the most prevalent gynaecological cancer in high-income countries and its incidence is continuing to rise sharply. Simple and objective tools to reliably detect women with EC are urgently needed. We recently developed and validated the DNA methylation (DNAme)-based women's cancer risk identification-quantitative polymerase chain reaction test for endometrial cancer (WID-qEC) test that could address this need. Here, we demonstrate that the stability of the WID-qEC test remains consistent regardless of: (i) the cervicovaginal collection device and sample media used (Cervex brush and PreservCyt or FLOQSwab and eNAT), (ii) the collector of the specimen (gynaecologist- or patient-based), and (iii) the precise sampling site (cervical, cervicovaginal and vaginal). Furthermore, we demonstrate sample stability in eNAT medium for 7 days at room temperature, greatly facilitating the implementation of the test into diagnostic laboratory workflows. When applying FLOQSwabs (Copan) in combination with the eNAT (Copan) sample collection media, the sensitivity and specificity of the WID-qEC test to detect uterine (i.e., endometrial and cervical) cancers in gynaecologist-taken samples was 92.9% (95% confidence interval [CI] = 75.0%-98.8%) and 98.6% (95% CI = 91.7%-99.9%), respectively, whilst the sensitivity and specificity in patient collected self-samples was 75.0% (95% CI = 47.4%-91.7%) and 100.0% (95% CI = 93.9%-100.0%), respectively. Taken together these data confirm the robustness and clinical potential of the WID-qEC test.

Interaction of high-fat diet and brain trauma alters adipose tissue macrophages and brain microglia associated with exacerbated cognitive dysfunction.

Obesity increases the morbidity and mortality of traumatic brain injury (TBI). Detailed analyses of transcriptomic changes in the brain and adipose tissue were performed to elucidate the interactive effects between high-fat diet-induced obesity (DIO) and TBI. Adult male mice were fed a high-fat diet (HFD) for 12 weeks prior to experimental TBI and continuing after injury. High-throughput transcriptomic analysis using Nanostring panels of the total visceral adipose tissue (VAT) and cellular components in the brain, followed by unsupervised clustering, principal component analysis, and IPA pathway analysis were used to determine shifts in gene expression patterns and molecular pathway activity. Cellular populations in the cortex and hippocampus, as well as in VAT, during the chronic phase after combined TBI-HFD showed amplification of central and peripheral microglia/macrophage responses, including superadditive changes in selected gene expression signatures and pathways. Furthermore, combined TBI and HFD caused additive dysfunction in Y-Maze, Novel Object Recognition (NOR), and Morris water maze (MWM) cognitive function tests. These novel data suggest that HFD-induced obesity and TBI can independently prime and support the development of altered states in brain microglia and VAT, including the disease-associated microglia/macrophage (DAM) phenotype observed in neurodegenerative disorders. The interaction between HFD and TBI promotes a shift toward chronic reactive microglia/macrophage transcriptomic signatures and associated pro-inflammatory disease-altered states that may, in part, underlie the exacerbation of cognitive deficits. Thus, targeting of HFD-induced reactive cellular phenotypes, including in peripheral adipose tissue immune cell populations, may serve to reduce microglial maladaptive states after TBI, attenuating post-traumatic neurodegeneration and neurological dysfunction.

Archaeological evidence of resource utilisation of the great whales over the past two millennia: A systematic review protocol.

Archaeological faunal remains provide key insights into human societies in the past, alongside information on previous resource utilisation and exploitation of wildlife populations. The great whales (Mysticete and sperm whales) were hunted unsustainably throughout the 16th - 20th centuries (herein defined as the modern period) leading to large population declines and variable recovery patterns among species. Humans have utilised whales as a resource through carcass scavenging for millennia; however, increasing local and regional ethnographic and archaeological evidence suggests that, prior to the modern period, hunting of the great whales was more common than previously thought; impacts of earlier hunting pressures on the population ecology of many whale species remains relatively unknown. Hunting guided by traditional ecological knowledge may have been sustainable and likely originated in societies that also incorporated opportunistic use of stranded individuals. The collation of georeferenced zooarchaeological data of the great whales between the 1st - 20th centuries CE worldwide will provide insight into the timescale and distribution of resource utilisation of the great whales and how this varied within and between societies, and may have changed over time. By comparing regions of known resource utilisation and breeding and feeding grounds of current-day whale populations, this information will subsequently be used to infer regions where whale populations were possibly lost or extirpated prior to detailed historical records. This systematic review protocol also provides a template for archaeologists, ecologists, and historians interested in using faunal remains to infer historical ecology and resource use of wild animal populations. The transparency of our data collection approach provides opportunities for reproducibility and comparability with future datasets.

The impact of Longitudinal Integrated Foundation Training: preliminary experiences in the United Kingdom.

BACKGROUND: The United Kingdom health system is challenged with retaining doctors entering specialty training directly after their second foundation year. Improving doctors' training experience during the foundation programme may aid such retention. The Longitudinal Integrated Foundation Training (LIFT) pilot scheme aimed to provide a programme that improves the quality of their foundation training experience, advance patient-centred care and provide doctors with more experience in the primary care settings. METHODS: During this pilot study, three methods were employed to evaluate and compare doctors' experiences across their 2-year foundation training programme: Horus ePortfolio assessment of six domains for good medical practice analysed using a T-test, online survey assessments analysed using a 2-tailed chi-square test, and focus group feedback sessions with thematic analysis. RESULTS: Doctors completing LIFT (n = 47) scored a higher but non-significant mean score on all six domains for good medical practice versus doctors completing traditional foundation training (n = 94). By the end of foundation training, 100% of LIFT doctors rated their understanding of how primary and secondary care work together as high versus 78.7% of traditional doctors (p < 0.05). Improvements in wellbeing were observed among LIFT doctors, along with a reduction in the proportion of doctors considering leaving medical training. A significantly greater number of LIFT doctors versus traditional doctors rated their compassion for patients as high (100% versus 86.8%; p < 0.05), intended to become general practitioners (23.1% versus 13.5%; p < 0.05) and rated the extent to which they felt well informed and able to consider a general practice career rather than a hospital career as high (91.7% versus 72.3%, respectively; p < 0.05). Some LIFT doctors felt they had reduced exposure to secondary care, received less on-call experience and considered working a half-day to be problematic; challenges ameliorated by the end of the 2-year foundation programme. CONCLUSION: The LIFT programme enhanced the quality of foundation training and improved doctors' experiences and competencies, generating valuable insights for the future of education and healthcare delivery. Applying the principles of LIFT to foundation training helps doctors to be more compassionate and patient-centred, leading to enhanced individualised patient care.

The role of BST4 in the pyrenoid of Chlamydomonas reinhardtii.

In many eukaryotic algae, CO2 fixation by Rubisco is enhanced by a CO2-concentrating mechanism, which utilizes a Rubisco-rich organelle called the pyrenoid. The pyrenoid is traversed by a network of thylakoid-membranes called pyrenoid tubules, proposed to deliver CO2. In the model alga Chlamydomonas reinhardtii (Chlamydomonas), the pyrenoid tubules have been proposed to be tethered to the Rubisco matrix by a bestrophin-like transmembrane protein, BST4. Here, we show that BST4 forms a complex that localizes to the pyrenoid tubules. A Chlamydomonas mutant impaired in the accumulation of BST4 (bst4) formed normal pyrenoid tubules and heterologous expression of BST4 in Arabidopsis thaliana did not lead to the incorporation of thylakoids into a reconstituted Rubisco condensate. Chlamydomonas bst4 mutant did not show impaired growth at air level CO2. By quantifying the non-photochemical quenching (NPQ) of chlorophyll fluorescence, we show that bst4 displays a transiently lower thylakoid lumenal pH during dark to light transition compared to control strains. When acclimated to high light, bst4 had sustained higher NPQ and elevated levels of light-induced H2O2 production. We conclude that BST4 is not a tethering protein, but rather is an ion channel involved in lumenal pH regulation possibly by mediating bicarbonate transport across the pyrenoid tubules.

Young persons and healthcare professionals experience of virtual gastroenterology consultations: a multicentre survey conducted during the COVID-19 pandemic.

Objective: To explore Young Persons (YP) and healthcare professionals (HCP) experiences of virtual consultations (VC) and establish whether developmentally appropriate healthcare can be delivered virtually. Method: YP and HCP questionnaire surveys were designed and piloted. Electronic questionnaire links were sent by post, email or text message January-April 2021 to YP aged 13-25 years old, with predefined chronic gastrointestinal conditions, attending a gastroenterology/hepatology VC. HCP undertaking VC were invited to complete staff questionnaire. Results were anonymous and collated using Excel version 2302. Results: Five UK hospital trusts participated, with 35 HCP responses. Of the 100 YP completing the survey 66% were female and 34% male aged between 13 years and 25 years (median: 18 years). 13% were new appointments and 87% follow ups, 29% were by video, 69% by phone and 2% gave no response. 80% of HCP spoke to YP directly but not privately (69%). 87% of YP and 88% HCP found VC useful. 83% of YP want VC again, although 20% preferred face to face. 43% of HCP required improved phone/internet connection. 77% of YP required hospital appointments for tests following VC. Conclusions: Overall respondents were satisfied with VC, finding them useful, convenient and time saving. Successful VC rely on appropriate patient selection and availability of reliable technology. Patient preference is key which may alter with time.

Holocene deglaciation drove rapid genetic diversification of Atlantic walrus.

Rapid global warming is severely impacting Arctic ecosystems and is predicted to transform the abundance, distribution and genetic diversity of Arctic species, though these linkages are poorly understood. We address this gap in knowledge using palaeogenomics to examine how earlier periods of global warming influenced the genetic diversity of Atlantic walrus (Odobenus rosmarus rosmarus), a species closely associated with sea ice and shallow-water habitats. We analysed 82 ancient and historical Atlantic walrus mitochondrial genomes (mitogenomes), including now-extinct populations in Iceland and the Canadian Maritimes, to reconstruct the Atlantic walrus' response to Arctic deglaciation. Our results demonstrate that the phylogeography and genetic diversity of Atlantic walrus populations was initially shaped by the last glacial maximum (LGM), surviving in distinct glacial refugia, and subsequently expanding rapidly in multiple migration waves during the late Pleistocene and early Holocene. The timing of diversification and establishment of distinct populations corresponds closely with the chronology of the glacial retreat, pointing to a strong link between walrus phylogeography and sea ice. Our results indicate that accelerated ice loss in the modern Arctic may trigger further dispersal events, likely increasing the connectivity of northern stocks while isolating more southerly stocks putatively caught in small pockets of suitable habitat.