Universal DNA methylation age across mammalian tissues

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

High-energy photoemission final states beyond the free-electron approximation

Three-dimensional (3D) electronic band structure is fundamental for understanding a vast diversity of physical phenomena in solid-state systems, including topological phases, interlayer interactions in van der Waals materials, dimensionality-driven phase transitions, etc. Interpretation of ARPES data in terms of 3D electron dispersions is commonly based on the free-electron approximation for the photoemission final states. Our soft-X-ray ARPES data on Ag metal reveals, however, that even at high excitation energies the final states can be a way more complex, incorporating several Bloch waves with different out-of-plane momenta. Such multiband final states manifest themselves as a complex structure and added broadening of the spectral peaks from 3D electron states. We analyse the origins of this phenomenon, and trace it to other materials such as Si and GaN. Our findings are essential for accurate determination of the 3D band structure over a wide range of materials and excitation energies in the ARPES experiment.

Fate of charge order in overdoped La-based cuprates

In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering study of weak charge correlations in La2-xSrxCuO4 and La1.8-xEu0.2SrxCuO4. Ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes. Long-range temperature-dependent stripe order is only found below optimal doping. At higher doping, short-range temperature-independent correlations are present up to the highest doping measured. This transformation is distinct from and preempts the pseudogap critical doping. We argue that the doping and temperature-independent short-range correlations originate from unresolved electron-phonon coupling that broadly peaks at the stripe ordering vector. In La2-xSrxCuO4, long-range static stripe order vanishes around optimal doping and we discuss both quantum critical and crossover scenarios.

Phase Ib/IIa trial of CEND‐1 in combination with neoadjuvant FOLFIRINOX-based therapies in pancreatic, colorectal, and appendiceal cancers (CENDIFOX)

TPS4195

Background: The efficacy of chemotherapy is often compromised due to poor penetration of drugs in solid tumors. The tumor microenvironment, which is characterized by dense extracellular matrix‐rich stroma that creates a physical barrier to penetration of anti‐cancer drugs, is especially pronounced in Pancreatic Ductal Adenocarcinoma (PDAC) and in peritoneal metastases from Colorectal/Appendiceal Adenocarcinoma. CEND‐1 is a tumor‐penetrating peptide (scientifically also known as iRGD) that has preclinically demonstrated to enhance the tumor penetration of chemotherapy agents through binding and activation of alphav-integrins and neuropilin‐1 (NRP-1). The 2-step mechanism leads to a higher delivery and concentration of chemotherapeutics selectively in the tumor, while sparing normal tissue. Hence CEND-1 therapy has the potential to improve the efficacy of anti‐cancer therapies and reduce side effects through increased tumor access, specificity, and sensitivity. We hypothesize that CEND‐1 may become a powerful adjuvant that safely enhances standard anti‐neoplastic therapy in the neoadjuvant setting for the above populations. Methods: A safety lead-in 6-9 patients (Phase Ib) will be followed by an open label, single arm, parallel (3 cohorts) Phase IIa study. A total of 50 patients (20 PDAC, 15 colorectal/appendiceal with peritoneal metastases, 15 oligometastatic colorectal) will be enrolled. A starting CEND-1 dose of 3.2 mg/kg in combination with the standard doses of FOLFIRINOX (+/- Panitumumab if RAS/RAF wild type) will be used for the safety lead-in. CEND-1 dose will be lowered for Phase IIa if > 1/6 patients experienced DLTs. Participants enrolled will receive standard doses of FOLFIRINOX q2w +/- Panitumumab q2w 6mg/kg IV q2w (14-day cycles) for Cycles 1-3. After a subsequent research biopsy, the CEND-1 + chemotherapy combo will be continued at RP2D q2w for cycles 4-6, followed by CEND-1 +/- Panitumumab ̃72h prior to resection. Assessment of tumor response using RECIST v1.1 will be done every 3 cycles. Up to 10 patients may receive Panitumumab. Eligible Pts are untreated, newly diagnosed, resectable/borderline resectable PDAC or colorectal/appendiceal adenocarcinoma with peritoneal metastases or oligometastases eligible for cytoreductive surgery, as determined by multidisciplinary evaluation. Inclusion criteria also include ECOG PS 0-1, adequate organ function, measurable or evaluable disease. Primary objectives are safety and biological activity of CEND‐1. Secondary objectives include ORR, R0 resection rate, DFS, OS. Exploratory objectives include pathologic response, tissue immune response, EGFR expression, tumor tissue-to-plasma concentration of Panitumumab pre and post CEND-1 treatment. Enrollment to the CENDIFOX trial is currently ongoing. Clinical trial information: NCT05121038.

Association of pathologic response and survival after peri-operative therapy in resected pancreatic adenocarcinoma: KU cancer center experience

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Background: Neo-adjuvant therapy (NAT) and associated pathologic complete response (pCR) rates have correlated with improved survival in resected pancreatic ductal adenocarcinoma (PDAC). In this study, we explored the relationship between pathologic response, peri-operative therapy, and survival, especially the impact of change in adjuvant therapy in patients with no/poor path response to NAT. Methods: Retrospectively reviewed 66 PDAC patients who received NAT ± radiation and underwent resection at KU Cancer Center between 2011-2022. We compared DFS and OS between Path Responders vs Non-Responders based on standard Tumor Regression Scores from pathology reports. A subanalysis was performed in path non-responders based on switch in adjuvant therapy (AT) versus not. Results: Patient characteristics are summarized in the table. Among 66 PDAC patients, 50 (75.8%) achieved a path response (G0-G2), 16 (24.2%) experienced no/poor path response (G3). Of the 50 pts who achieved a path response, 4 (8.0%) had a complete path response (pCR; G0), 5 (10%) marked response (G1), 41 (82%) moderate response (G2). Median DFS (mDFS) was 17.3 months (95% CI: 12.7-22.4) in Path Responders vs 15.9m (95% CI: 9.6-35.8) in Non-Responders [p=0.59]. Median OS (mOS) was 32.9m (95% CI: 23.4-41.5) vs 27.7m (95% CI: 15.2-38.2), respectively [p=0.39). A sub-analysis in the Non-Responders (n=16) based on switch in AT (n=8) vs not (n=3), revealed mDFS 16.4m (95% CI: 9.6-41.8) when AT was switched vs mDFS 11.3m (95% CI: 5.9-16.6) when AT was not switched [p=0.24]; and mOS 30.6m (95% CI: 15.7-60.3) vs 17.2 months (95% CI: 6.7-27.7), respectively [p=0.18]. Conclusions: Our study found no statistical difference in DFS and OS between Pathologic Responders and Non-Responders to neo-adjuvant therapy. However, a sub-analysis within Pathologic Non-Responders revealed a longer DFS and OS after switching adjuvant therapy without reaching statistical significance, likely due to small sample size. Our findings warrant validation in a larger cohort as switch in adjuvant therapy could potentially change the treatment landscape for Pathologic Non-Responders.[Table: see text]

Human desmocollin 3-specific IgG antibodies are pathogenic in a humanized HLA-class II transgenic mouse model of pemphigus

Pemphigus is a potentially lethal autoimmune bullous skin disorder, which is associated with IgG autoantibodies against desmoglein 3 (Dsg3) and Dsg1. Notably, a subset of pemphigus patients presents with a similar clinical phenotype in the absence of anti-Dsg IgG, suggesting the presence of serum IgG reactive with desmosomal components other than Dsg1 or Dsg3. We and others have previously shown that such patients have serum IgG autoantibodies against desmocollin 3 (Dsc3), a component of desmosomes, that induce loss of keratinocyte adhesion ex vivo. Moreover, Dsc3 hypomorphic mice show a severe blistering phenotype of the mucous membrane which is highly characteristic in pemphigus. These findings prompted us to study induction and regulation of anti-human Dsc3 IgG in humanized mice transgenic for HLA-DRB1*04:02, which is a highly prevalent haplotype in pemphigus. We show that IgG from sera of immunized mice induce acantholysis in a dispase-based keratinocyte dissociation assay via the activation of p38 mitogen-activated protein kinases and epidermal growth factor receptor. Passive IgG transfer from mice immunized with recombinant human Dsc3 into neonates did not induce intraepidermal loss of adhesion presumably due to the lack of homology between human and mouse Dsc3. Ex vivo stimulation of splenocytes from Dsc3-immunized mice with human Dsc3 leads to a significant proliferative interferon-γ and interleukin 4 T cell response, which is restricted by HLA-DR/DQ. These findings suggest that induction of pathogenic anti-Dsc3 IgG is associated with Dsc3-specific T cells that recognize Dsc3 in association with HLA-DRB1*04:02.

Ca2+ signalling is critical for autoantibody-induced blistering of human epidermis in pemphigus

BACKGROUND

Pemphigus is a severe bullous autoimmune skin disease. Pemphigus foliaceus (PF) is characterized by antidesmoglein (Dsg) 1 IgG causing epidermal blistering; mucosal pemphigus vulgaris (mPV) by anti-Dsg3 IgG inducing erosions in the mucosa; and mucocutaneous pemphigus vulgaris (PV) by affecting both, with autoantibodies targeting Dsg1 and Dsg3.

OBJECTIVES

To characterize the Ca²⁺ flux pathway and delineate its importance in pemphigus pathogenesis and clinical phenotypes caused by different antibody profiles.

METHODS

Immunoprecipitation, Ca²⁺ flux analysis, Western blotting, immunofluorescence staining, dissociation assays and a human skin ex vivo model were used.

RESULTS

PV IgG and PF IgG, but neither Dsg3-specific monoclonal antibody (AK23) nor mPV IgG, caused Ca²⁺ influx in primary human keratinocytes. Phosphatidylinositol 4-kinase α interacts with Dsg1 but not with Dsg3. Its downstream target - phospholipase-C-γ1 (PLC) - was activated by PV IgG and PF IgG but not AK23 or mPV IgG. PLC releases inositol 1,4,5-trisphosphate (IP3) causing IP3 receptor (IP3R) activation and Ca²⁺ flux from the endoplasmic reticulum into the cytosol, which stimulates Ca²⁺ release-activated channels (CRAC)-mediated Ca²⁺ influx. Inhibitors against PLC, IP3R and CRAC effectively blocked PV IgG and PF IgG-induced Ca²⁺ influx; ameliorated alterations of Dsg1 and Dsg3 localization, and reorganization of keratin and actin filaments; and inhibited loss of cell adhesion in vitro. Finally, inhibiting PLC or IP3R was protective against PV IgG-induced blister formation and redistribution of Dsg1 and Dsg3 in human skin ex vivo.

CONCLUSIONS

Ca²⁺ -mediated signalling is important for epidermal blistering and dependent on the autoantibody profile, which indicates different roles for signalling complexes organized by Dsg1 and Dsg3. Interfering with PLC and Ca²⁺ signalling may be a promising approach to treat epidermal manifestations of pemphigus.

Publisher Correction: Electronic structure of the parent compound of superconducting infinite-layer nickelates

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

High-Temperature Charge-Stripe Correlations in La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4}

We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4}. By differentiating elastic from inelastic scattering, it is demonstrated that charge-stripe correlations precede both the structural low-temperature tetragonal phase and the transport-defined pseudogap onset. The scattering peak amplitude from charge stripes decays approximately as T^{-2} towards our detection limit. The in-plane integrated intensity, however, remains roughly temperature independent. Therefore, although the incommensurability shows a remarkably large increase at high temperature, our results are interpreted via a single scattering constituent. In fact, direct comparison to other stripe-ordered compounds (La_{1.875}Ba_{0.125}CuO_{4}, La_{1.475}Nd_{0.4}Sr_{0.125}CuO_{4}, and La_{1.875}Sr_{0.125}CuO_{4}) suggests a roughly constant integrated scattering intensity across all these compounds. Our results therefore provide a unifying picture for the charge-stripe ordering in La-based cuprates. As charge correlations in La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4} extend beyond the low-temperature tetragonal and pseudogap phase, their emergence heralds a spontaneous symmetry breaking in this compound.

Electronic structure of the parent compound of superconducting infinite-layer nickelates

The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors^1-10. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO₂ (refs. ^11,12) has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO₂ and NdNiO₂, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with [Formula: see text] symmetry in the NiO₂ layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics^13-15, which are well known for heavy fermion behaviour, where the NiO₂ correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like 'oxide-intermetallic' replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.

Survival outcomes of pancreatic intraepithelial neoplasm (PanIN) versus intraductal papillary mucinous neoplasm (IPMN) associated pancreatic adenocarcinoma

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Background: Pancreatic intraepithelial neoplasms (PanINs) and intraductal papillary mucinous neoplasms (IPMNs) are common pancreatic adenocarcinoma precursor lesions. However, data regarding their respective associations with prognosis is lacking. Methods: We retrospectively evaluated 72 resected pancreatic adenocarcinoma cases at the KU Cancer Center between Aug 2009 and March 2019. Patients were divided into either one of two groups, PanIN or IPMN, based on the results of the surgical path report. We compared baseline characteristics, overall and progression free survival between the two groups, as well as OS and PFS based on local or distant tumor recurrence. Results: 52 patients had PanIN and 20 patients had IPMN. Demographic and baseline characteristics are as follows (PanIN/IPMN): Median age 62.5/69; Gender (male) 63%/65%; ECOG status (0-1) 98%/85%; pancreatic head tumors 87%/70%; pancreatic body tumors 6%/15%; pancreatic tail tumors 7%/15%; Abnormal CA19-9 at diagnosis 79%/67%; Comorbidity Index 5/5 respectively. Median PFS was 26.2 months (95% CI: 21.4-31.0) for PanIN and 74.3 months (95% CI: 15.7-132.9) for IPMN [p = 0.004]. Median OS was 70.3 months (95% CI: 35.4-105.2) for PanIN and 78.8 months (95% CI: 33.2-124.4) for IPMN [p = 0.013]. Within the PanIN group, median OS after recurrence was 71.3 months (95% CI: 68.8.-73.4) for local recurrence and 46.7 months (95% CI: 39.2-54.2) for distant recurrence [p = 0.330]. Conclusions: Patients who had a IPMN associated pancreatic cancer had better PFS and OS when compared to patients with PanIN associated pancreatic cancer. In patients with PanIN associated cancer that recurred, OS was better with local recurrence compared to distant recurrence but did not meet statistical significance. The results need to be validated in a larger cohort. [Table: see text]

Strategies and practical examples

Various tools and mechanisms can help to increase the use of scientific evidence in policy development by making policymakers appreciate, understand and incorporate such scientific information into policy decisions. As part of this process, it is crucial that researchers and public health practitioners acquire the ability to translate their knowledge and become skilled on communicating the evidence effectively.

The European Observatory on Health Systems and Policies supports and promotes evidence-based health policy-making through comprehensive and rigorous analysis of the dynamics of health-care systems in Europe. It engages directly with policy-makers and experts, and works in partnership with research centers, governments and international organizations to analyze health systems and policy trends.

In this presentation, concrete strategies will be given for advocating scientific evidence. The focus will lie particularly on the process of real-life applications of evidence-informed policy-making. By this way, it will help the participants to analyze to whom they are targeting, what are their interests and how to communicate scientific information to a decision-maker effectively based on specific examples from the European Observatory on Health Systems and Policies.

Niraparib in metastatic pancreatic cancer after previous chemotherapy (NIRA-PANC): A phase 2 trial

TPS4168

Background: Attempts to improve therapy for patients with pancreatic adenocarcinoma with traditional chemotherapy have largely failed to meaningfully improve survival. Therefore, there is a critical need for identification of specific molecular changes that define prognosis and potentially guide therapy decisions. Defective DNA damage response pathways in pancreatic cancer represent a targeted opportunity for treatment. PARP inhibitors exert activity in tumor cells that may not be effectively able to repair initially single-stranded and cumulatively double-stranded DNA breaks and can have a heightened susceptibility in tumor cells over normal tissue. This concept is referred to as synthetic lethality. Niraparib is an orally available, potent, highly selective PARP-1 and -2 inhibitor. We are studying the efficacy of Niraparib in pancreatic cancer patients that harbor DNA repair defects. Methods: This study is funded by a research grant from TESARO. Pre-screening of patients to find biomarker positive patients is funded by KU Cancer Center. This is a phase II open label single arm trial in metastatic pancreatic cancer patients with germline or somatic mutations, either already known, or tested after consent to pre-screening tumor tissue analysis in BRCA1/2, PALB2, ATM, NBN, ATR, BRIP1, IDH1/2, RAD51, RAD51B/C/D, RAD54L, CDK12, BARD1, FAM175A, BAP1, CHEK1/2, GEN1, MRE11A, XRCC2, SHFM1, FANCD2, FANCA, FANCC, FANCG, RPA1, ARID1A. Patients are being treated with Niraparib 300mg or 200mg by mouth daily for 28 days (1 cycle = 28 days) (200mg dose is for participants whose baseline weight is < 77 kg [169.756 lbs] or baseline platelet count is < 150,000 µL). The primary objective is to assess antitumor efficacy of niraparib using Objective Response Rate per RECIST 1.1. Secondary objectives include PFS, OS, DCR, DOR, and safety. Eligible patients received > 1 line of therapy, no prior PARP inhibitor(s), have measurable disease, and ECOG PS 0-1. Accrual target enrollment of 18 patients over a period of 24 months with a study duration of 30 months. Correlative studies include assessment of pharmacokinetics, circulating tumor cells and storing samples for future research. The trial is currently enrolling. Clinical trial information: NCT03553004.

Impaired TFEB-mediated lysosomal biogenesis promotes the development of pancreatitis in mice and is associated with human pancreatitis

Impaired macroautophagy/autophagy has been implicated in experimental and human pancreatitis. However, the transcriptional control governing the autophagy-lysosomal process in pancreatitis is largely unknown. We investigated the role and mechanisms of TFEB (transcription factor EB), a master regulator of lysosomal biogenesis, in the pathogenesis of experimental pancreatitis. We analyzed autophagic flux, TFEB nuclear translocation, lysosomal biogenesis, inflammation and fibrosis in GFP-LC3 transgenic mice, acinar cell-specific tfeb knockout (KO) and tfeb and tfe3 double-knockout (DKO) mice as well as human pancreatitis samples. We found that cerulein activated MTOR (mechanistic target of rapamycin kinase) and increased the levels of phosphorylated TFEB as well as pancreatic proteasome activities that led to rapid TFEB degradation. As a result, cerulein decreased the number of lysosomes resulting in insufficient autophagy in mouse pancreas. Pharmacological inhibition of MTOR or proteasome partially rescued cerulein-induced TFEB degradation and pancreatic damage. Furthermore, genetic deletion of tfeb specifically in mouse pancreatic acinar cells increased pancreatic edema, necrotic cell death, infiltration of inflammatory cells and fibrosis in pancreas after cerulein treatment. tfeb and tfe3 DKO mice also developed spontaneous pancreatitis with increased pancreatic trypsin activities, edema and infiltration of inflammatory cells. Finally, decreased TFEB nuclear staining was associated with human pancreatitis. In conclusion, our results indicate a critical role of impaired TFEB-mediated lysosomal biogenesis in promoting the pathogenesis of pancreatitis. Abbreviations: AC: acinar cell; AMY: amylase; ATP6V1A: ATPase, H+ transporting, lysosomal V1 subunit A; ATP6V1B2: ATPase, H+ transporting, lysosomal V1 subunit B2; ATP6V1D: ATPase, H+ transporting, lysosomal V1 subunit D; ATP6V1H: ATPase, H+ transporting, lysosomal V1 subunit H; AV: autophagic vacuole; CDE: choline-deficient, ethionine-supplemented; CLEAR: coordinated lysosomal expression and regulation; CQ: chloroquine; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; EM: electron microscopy; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; H & E: hematoxylin and eosin; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK1/ERK2: mitogen-activated protein kinase 1; MTORC1: mechanistic target of rapamycin kinase complex 1; ND: normal donor; NEU: neutrophil; PPARGC1A/PGC1α: peroxisome proliferator-activated receptor, gamma, coactivator 1 alpha; RIPA: radio-immunoprecipitation; RPS6: ribosomal protein S6; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TM: tamoxifen; WT: wild-type; ZG: zymogen granule.

PNPLA3 gene predicts clinical recovery after sustained virological response in decompensated hepatitis C cirrhosis

Background

Patients with decompensated hepatitis C virus (HCV) cirrhosis experience various outcomes after sustained virological response (SVR), ranging from clinical recovery to further deterioration. We hypothesised that the genetic risk for steatosis, namely the polymorphisms rs738409 of Patatin-like Phospholipase Domain-Containing 3 (PNPLA3), rs58542926 of Transmembrane-6-Superfamily-2 (TM6SF2), and rs641738 of Membrane-bound O-acyltransferase Domain-Containing 7 (MBOAT7), is predictive of recovery.

Methods

We prospectively enrolled 56 patients with Child-Pugh (CPT) B/C cirrhosis who underwent antiviral therapy. The primary outcome was change in CPT score at 12, 24, and 48 weeks after SVR. We used a linear mixed-effects model for analysis.

Results

Forty-five patients (PNPLA3: 21 CC, 19 CG, 5 GG) survived to the first endpoint without liver transplantation. The mean change in CPT score at 12, 24, and 48 weeks was −1.57 (SE=0.30), –1.76 (SE=0.32), and −2.0 (SE=0.36), respectively, among the patients with the PNPLA3 CC genotype and −0.50 (SE=0.20), –0.41 (SE=0.25), and −0.24 (SE=0.27), respectively, among the other 24 patients. After adjustment for baseline characteristics, the PNPLA3 CG/GG genotypes were associated with a 1.29 (SE=0.30, p<0.0001) point higher CPT score. Most of the difference came from differences in hepatic encephalopathy and bilirubin. The results for rs58542926 and rs641738 were not significant.

Conclusion

The PNPLA3 CG/GG genotypes could identify a subgroup of patients with decompensated HCV cirrhosis that had suboptimal clinical recovery despite SVR. An understanding of the genetic factors that influence clinical outcomes will help target patients for liver transplant based on individual genetic risk factors and provide insight leading to new therapeutic approaches.

Strain-engineering Mott-insulating La2CuO4

The transition temperature T_c of unconventional superconductivity is often tunable. For a monolayer of FeSe, for example, the sweet spot is uniquely bound to titanium-oxide substrates. By contrast for La_2-xSr_xCuO₄ thin films, such substrates are sub-optimal and the highest T_c is instead obtained using LaSrAlO₄. An outstanding challenge is thus to understand the optimal conditions for superconductivity in thin films: which microscopic parameters drive the change in T_c and how can we tune them? Here we demonstrate, by a combination of x-ray absorption and resonant inelastic x-ray scattering spectroscopy, how the Coulomb and magnetic-exchange interaction of La₂CuO₄ thin films can be enhanced by compressive strain. Our experiments and theoretical calculations establish that the substrate producing the largest T_c under doping also generates the largest nearest neighbour hopping integral, Coulomb and magnetic-exchange interaction. We hence suggest optimising the parent Mott state as a strategy for enhancing the superconducting transition temperature in cuprates.

Probing multi-spinon excitations outside of the two-spinon continuum in the antiferromagnetic spin chain cuprate Sr2CuO3

One-dimensional (1D) magnetic insulators have attracted significant interest as a platform for studying quasiparticle fractionalization, quantum criticality, and emergent phenomena. The spin-1/2 Heisenberg chain with antiferromagnetic nearest neighbour interactions is an important reference system; its elementary magnetic excitations are spin-1/2 quasiparticles called spinons that are created in even numbers. However, while the excitation continuum associated with two-spinon states is routinely observed, the study of four-spinon and higher multi-spinon states is an open area of research. Here we show that four-spinon excitations can be accessed directly in Sr2CuO3 using resonant inelastic x-ray scattering (RIXS) in a region of phase space clearly separated from the two-spinon continuum. Our finding is made possible by the fundamental differences in the correlation function probed by RIXS in comparison to other probes. This advance holds promise as a tool in the search for novel quantum states and quantum spin liquids.

Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates

We present a soft x-ray angle-resolved photoemission spectroscopy study of overdoped high-temperature superconductors. In-plane and out-of-plane components of the Fermi surface are mapped by varying the photoemission angle and the incident photon energy. No k_{z} dispersion is observed along the nodal direction, whereas a significant antinodal k_{z} dispersion is identified for La-based cuprates. Based on a tight-binding parametrization, we discuss the implications for the density of states near the van Hove singularity. Our results suggest that the large electronic specific heat found in overdoped La_{2-x}Sr_{x}CuO_{4} cannot be assigned to the van Hove singularity alone. We therefore propose quantum criticality induced by a collapsing pseudogap phase as a plausible explanation for observed enhancement of electronic specific heat.

Direct observation of orbital hybridisation in a cuprate superconductor

The minimal ingredients to explain the essential physics of layered copper-oxide (cuprates) materials remains heavily debated. Effective low-energy single-band models of the copper–oxygen orbitals are widely used because there exists no strong experimental evidence supporting multi-band structures. Here, we report angle-resolved photoelectron spectroscopy experiments on La-based cuprates that provide direct observation of a two-band structure. This electronic structure, qualitatively consistent with density functional theory, is parametrised by a two-orbital (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$d_{x^2 - y^2}$$\end{document}dx2-y2 and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$d_{z^2}$$\end{document}dz2) tight-binding model. We quantify the orbital hybridisation which provides an explanation for the Fermi surface topology and the proximity of the van-Hove singularity to the Fermi level. Our analysis leads to a unification of electronic hopping parameters for single-layer cuprates and we conclude that hybridisation, restraining d-wave pairing, is an important optimisation element for superconductivity.

The essential physics of cuprate superconductors is often described by single-band models. Here, Matt et al. report direct observation of a two-band electronic structure in La-based cuprates.

Protein arginine methyl transferase 1- and Jumonji C domain-containing protein 6-dependent arginine methylation regulate hepatocyte nuclear factor 4 alpha expression and hepatocyte proliferation in mice

Alcohol is a well-established risk factor for hepatocellular carcinoma (HCC), but the mechanisms by which it promotes liver cancer are not well understood. Several studies have shown that cellular protein arginine methylation is inhibited by alcohol. Arginine methylation is controlled by the reciprocal activity of protein arginine methyltransferases, primarily protein arginine methyl transferase 1 (PRMT1), and a demethylase Jumonji C domain-containing protein 6 (JMJD6). The aim of this study was to explore the role of arginine methylation changes in alcohol pathogenesis. We found that PRMT1 activity is inhibited in livers of mice fed with alcohol compared to pair-fed mice. Using hepatocyte-specific PRMT1 knockout mice, we identified that loss of PRMT1 results in enhanced hepatocyte proliferation and a 33% increase in liver size. This increased hepatocyte proliferation was associated with reduced expression of hepatocyte nuclear factor 4 alpha (Hnf4α), an important regulator of liver tumorigenesis. We found that PRMT1 regulates Hnf4α expression directly through arginine methylation at the (Hnf4α) promoter. In the absence of PRMT1, JMJD6 can demethylate the Hnf4α promoter and suppress its expression. We were able to restore Hnf4α expression and abolish the increase in hepatocyte proliferation by knockdown of JMJD6 in PRMT1 knockout mice. Knockdown of JMJD6 in alcohol-fed mice similarly increased Hnf4α expression. We then examined whether loss of arginine methylation might play a role in alcohol-associated liver cancers. We examined 25 human HCC specimens and found a strong correlation (R = 0.8; P < 0.01) between arginine methylation levels and Hnf4α expression in these specimens, suggesting that the above mechanism is relevant in patients.

CONCLUSION

Taken together, these data suggest that PRMT1 inhibition, such as induced by alcohol, may result in epigenetic changes leading to loss of Hnf4α. This effect may contribute to alcohol's ability to promote liver tumors. (Hepatology 2018;67:1109-1126).

Crossover from Collective to Incoherent Spin Excitations in Superconducting Cuprates Probed by Detuned Resonant Inelastic X-Ray Scattering

Spin excitations in the overdoped high temperature superconductors Tl_{2}Ba_{2}CuO_{6+δ} and (Bi,Pb)_{2}(Sr,La)_{2}CuO_{6+δ} were investigated by resonant inelastic x-ray scattering (RIXS) as functions of doping and detuning of the incoming photon energy above the Cu-L_{3} absorption peak. The RIXS spectra at optimal doping are dominated by a paramagnon feature with peak energy independent of photon energy, similar to prior results on underdoped cuprates. Beyond optimal doping, the RIXS data indicate a sharp crossover to a regime with a strong contribution from incoherent particle-hole excitations whose maximum shows a fluorescencelike shift upon detuning. The spectra of both compound families are closely similar, and their salient features are reproduced by exact-diagonalization calculations of the single-band Hubbard model on a finite cluster. The results are discussed in the light of recent transport experiments indicating a quantum phase transition near optimal doping.

Three-Dimensional Electronic Structure of the Type-II Weyl Semimetal WTe_{2}

By combining bulk sensitive soft-x-ray angular-resolved photoemission spectroscopy and first-principles calculations we explored the bulk electron states of WTe_{2}, a candidate type-II Weyl semimetal featuring a large nonsaturating magnetoresistance. Despite the layered geometry suggesting a two-dimensional electronic structure, we directly observe a three-dimensional electronic dispersion. We report a band dispersion in the reciprocal direction perpendicular to the layers, implying that electrons can also travel coherently when crossing from one layer to the other. The measured Fermi surface is characterized by two well-separated electron and hole pockets at either side of the Γ point, differently from previous more surface sensitive angle-resolved photoemission spectroscopy experiments that additionally found a pronounced quasiparticle weight at the zone center. Moreover, we observe a significant sensitivity of the bulk electronic structure of WTe_{2} around the Fermi level to electronic correlations and renormalizations due to self-energy effects, previously neglected in first-principles descriptions.

The evolution of a complex trait: cuticular hydrocarbons in ants evolve independent from phylogenetic constraints

Cuticular hydrocarbons (CHCs) are ubiquitous and highly diverse in insects, serving as communication signal and waterproofing agent. Despite their vital function, the causes, mechanisms and constraints on CHC diversification are still poorly understood. Here, we investigated phylogenetic constraints on the evolution of CHC profiles, using a global data set of the species-rich and chemically diverse ant genus Crematogaster. We decomposed CHC profiles into quantitative (relative abundances, chain length) and qualitative traits (presence/absence of CHC classes). A species-level phylogeny was estimated using newly generated and previously published sequences from five nuclear markers. Moreover, we reconstructed a phylogeny for the chemically diverse Crematogaster levior species group using cytochrome oxidase I. Phylogenetic signal was measured for these traits on genus and clade level and within the chemically diverse C. levior group. For most quantitative CHC traits, phylogenetic signal was low and did not differ from random expectation. This was true on the level of genus, clade and species group, indicating that CHC traits are evolutionary labile. In contrast, the presence or absence of alkenes and alkadienes was highly conserved within the C. levior group. Hence, the presence or absence of biosynthetic pathways may be phylogenetically constrained, especially at lower taxonomic levels. Our study shows that CHC composition can evolve rapidly, allowing insects to quickly adapt their chemical profiles to external selection pressures, whereas the presence of biosynthetic pathways appears more constrained. However, our results stress the importance to consider the taxonomic level when investigating phylogenetic constraints.

The presence of donor liver granuloma requiring further workup to rule out parasitic disease

A shortage of donor organs is a major limitation to liver transplantation. Expansion of donor pool criteria to include patients with schistosomiasis diagnosed on liver biopsy might allow the allocation of more transplant livers. Schistosomiasis is a chronic parasitic disease affecting millions in endemic areas including sub-Sahara Africa that might lead to the development of granulomas as a response to the parasite’s ova and might cause chronic liver disease and portal hypertension. Due to increased mobility globally, schistosomiasis may be encountered in non-endemic areas. Currently, the usage of donor livers with known Schistosomiasis is not universally defined.

Doping Dependence of Collective Spin and Orbital Excitations in the Spin-1 Quantum Antiferromagnet La_{2-x}Sr_{x}NiO_{4} Observed by X Rays

We report the first empirical demonstration that resonant inelastic x-ray scattering (RIXS) is sensitive to collective magnetic excitations in S=1 systems by probing the Ni L_{3} edge of La_{2-x}Sr_{x}NiO_{4} (x=0, 0.33, 0.45). The magnetic excitation peak is asymmetric, indicating the presence of single and multi-spin-flip excitations. As the hole doping level is increased, the zone boundary magnon energy is suppressed at a much larger rate than that in hole doped cuprates. Based on the analysis of the orbital and charge excitations observed by RIXS, we argue that this difference is related to the orbital character of the doped holes in these two families. This work establishes RIXS as a probe of fundamental magnetic interactions in nickelates opening the way towards studies of heterostructures and ultrafast pump-probe experiments.

Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7}

We use resonant elastic and inelastic x-ray scattering at the Ir-L_{3} edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} (0≤x≤0.065). With increasing doping x, the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x=0 to 0.05, followed by a transition to two-dimensional short range order between x=0.05 and 0.065. Because of the interactions between the J_{eff}=1/2 pseudospins and the emergent itinerant electrons, magnetic excitations undergo damping, anisotropic softening, and gap collapse, accompanied by weakly doping-dependent spin-orbit excitons. Therefore, we conclude that electron doping suppresses the magnetic anisotropy and interlayer couplings and drives (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the J_{eff}=1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.

Ultralow refractive index optical films with enhanced mechanical performance obtained by hybrid glancing angle deposition

Ultralow refractive index materials (n less than 1.38 at 550 nm) are of particular interest in the context of antireflective coatings, allowing one to enhance their overall optical performance. However, application of such materials is typically limited by their mechanical properties. In this study, we explore the characteristics of a new category of hybrid (organic/inorganic) SiOCH thin films prepared by glancing angle deposition (GLAD) using electron beam evaporation of SiO₂ in the presence of an organosilicon precursor. The resulting layers exhibited n as low as 1.2, showed high elastic rebound, and generally better mechanical properties than their inorganic counterparts. In addition, hybrid GLAD films were found to be highly hydrophobic. The performance of the films is discussed in terms of their hybridicity (organic/inorganic) ratio determined by infrared spectroscopic ellipsometry as well as the presence of anisotropy assessed by the nanostructure-based spectroscopic ellipsometry model. Finally, we demonstrate successful implementation of the ultralow-index material in a complete antireflective stack.

Electronic structure of (In,Mn)As quantum dots buried in GaAs investigated by soft-x-ray ARPES

Electronic structure of a molecular beam epitaxy-grown system of (In,Mn)As quantum dots (QDs) buried in GaAs is explored with soft-x-ray angle-resolved photoelectron spectroscopy (ARPES) using photon energies around 1 keV. This technique, ideally suited for buried systems, extends the momentum-resolving capabilities of conventional ARPES with enhanced probing depth as well as elemental and chemical state specificity achieved with resonant photoexcitation. The experimental results resolve the dispersive energy bands of the GaAs substrate buried in ∼2 nm below the surface, and the impurity states (ISs) derived from the substitutional Mn atoms in the (In,Mn)As QDs and oxidized Mn atoms distributed near the surface. An energy shift of the Mn ISs in the QDs compared to (In,Mn)As DMS is attributed to the band offset and proximity effect at the interface with the surrounding GaAs. The absence of any ISs in the vicinity of the VBM relates the electron transport in (In,Mn)As QDs to the prototype (In,Mn)As diluted magnetic semiconductor. The SX-ARPES results are supported by measurements of the shallow core levels under variation of probing depth through photon energy. X-ray absorption measurements identify significant diffusion of interstitial Mn atoms out of the QDs towards the surface, and the role of magnetic circular dichroism is to block the ferromagnetic response of the (In,Mn)As QDs. Possible routes are drawn to tune the growth procedure aiming at practical applications of the (In,Mn)As based systems.

Orbital Engineering in Nickelate Heterostructures Driven by Anisotropic Oxygen Hybridization rather than Orbital Energy Levels

Resonant inelastic x-ray scattering is used to investigate the electronic origin of orbital polarization in nickelate heterostructures taking LaTiO_{3}-LaNiO_{3}-3×(LaAlO_{3}), a system with exceptionally large polarization, as a model system. We find that heterostructuring generates only minor changes in the Ni 3d orbital energy levels, contradicting the often-invoked picture in which changes in orbital energy levels generate orbital polarization. Instead, O K-edge x-ray absorption spectroscopy demonstrates that orbital polarization is caused by an anisotropic reconstruction of the oxygen ligand hole states. This provides an explanation for the limited success of theoretical predictions based on tuning orbital energy levels and implies that future theories should focus on anisotropic hybridization as the most effective means to drive large changes in electronic structure and realize novel emergent phenomena.

Quenched Magnon excitations by oxygen sublattice reconstruction in (SrCuO2)n/(SrTiO3)2 superlattices

The recently discovered structural reconstruction in the cuprate superlattice (SrCuO2)n/(SrTiO3)2 has been investigated across the critical value of n = 5 using resonant inelastic x-ray scattering (RIXS). We find that at the critical value of n, the cuprate layer remains largely in the bulk-like two-dimensional structure with a minority of Cu plaquettes being reconstructed. The partial reconstruction leads to quenching of the magnons starting at the Γ-point due to the minority plaquettes acting as scattering points. Although comparable in relative abundance, the doped charge impurities in electron-doped cuprate superconductors do not show this quenching of magnetic excitations.

[When love becomes eternal: Two embedded rings, a case report]

Embedded ring injury is a rare condition often associated with mental illness or cognitive disorders. Clinical presentation varies from simple oedema to serious neurovascular deficits. We report the unusual case of a 69-year-old woman presenting with two embedded ring injuries. The rings had been in place for over 20 years, however she had no past medical history of psychiatric or neurological disorder. A non-invasive approach was decided to treat the patient by simply cutting the rings allowing to resolve the situation without further morbidity.

Polaronic metal state at the LaAlO3/SrTiO3 interface

Interplay of spin, charge, orbital and lattice degrees of freedom in oxide heterostructures results in a plethora of fascinating properties, which can be exploited in new generations of electronic devices with enhanced functionalities. The paradigm example is the interface between the two band insulators LaAlO3 and SrTiO3 that hosts a two-dimensional electron system. Apart from the mobile charge carriers, this system exhibits a range of intriguing properties such as field effect, superconductivity and ferromagnetism, whose fundamental origins are still debated. Here we use soft-X-ray angle-resolved photoelectron spectroscopy to penetrate through the LaAlO3 overlayer and access charge carriers at the buried interface. The experimental spectral function directly identifies the interface charge carriers as large polarons, emerging from coupling of charge and lattice degrees of freedom, and involving two phonons of different energy and thermal activity. This phenomenon fundamentally limits the carrier mobility and explains its puzzling drop at high temperatures.

Fermi states and anisotropy of Brillouin zone scattering in the decagonal Al-Ni-Co quasicrystal

Quasicrystals (QCs) are intermetallic alloys that have excellent long-range order but lack translational symmetry in at least one dimension. The valence band electronic structure near the Fermi energy EF in such materials is of special interest since it has a direct relation to their unusual physical properties. However, the Fermi surface (FS) topology as well as the mechanism of QC structure stabilization are still under debate. Here we report the first observation of the three-dimensional FS and valence band dispersions near EF in decagonal Al70Ni20Co10 (d-AlNiCo) QCs using soft X-ray angle-resolved photoemission spectroscopy. We show that the FS, formed by dispersive Al sp-states, has a multicomponent character due to a large contribution from high-order bands. Moreover, we discover that the magnitude of the gap at the FS related to the interaction with Brillouin zone boundary (Hume-Rothery gap) critically differs for the periodic and quasiperiodic directions.

Collective nature of spin excitations in superconducting cuprates probed by resonant inelastic X-ray scattering

We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa_{2}Cu_{3}O_{6+x} over a wide range of doping levels (0.1≤x≤1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from incoherent particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.

Rydberg-resolved resonant inelastic soft x-ray scattering: dynamics at core ionization thresholds

Resonant inelastic x-ray scattering spectra excited in the immediate vicinity of the core-level ionization thresholds of N2 have been recorded. Final states of well-resolved symmetry-selected Rydberg series converging to valence-level ionization thresholds with vibrational excitations are observed. The results are well described by a quasi-two-step model which assumes that the excited electron is unaffected by the radiative decay. This threshold dynamics simplifies the interpretation of resonant inelastic x-ray scattering spectra considerably and facilitates characterization of low-energy excited final states in molecular systems.

Snapshots of the fluctuating hydrogen bond network in liquid water on the sub-femtosecond timescale with vibrational resonant inelastic x-ray scattering

Liquid water molecules interact strongly with each other, forming a fluctuating hydrogen bond network and thereby giving rise to the anomalous phase diagram of liquid water. Consequently, symmetric and asymmetric water molecules have been found in the picosecond time average with IR and optical Raman spectroscopy. With subnatural linewidth resonant inelastic x-ray scattering (RIXS) at vibrational resolution, we take sub-femtosecond snapshots of the electronic and structural properties of water molecules in the hydrogen bond network. We derive a strong dominance of nonsymmetric molecules in liquid water in contrast to the gas phase on the sub-femtosecond timescale of RIXS and determine the fraction of highly asymmetrically distorted molecules.

Functional coupling of ATP-binding cassette transporter Abcb6 to cytochrome P450 expression and activity in liver

Although endogenous mechanisms that negatively regulate cytochrome P450 (P450) monooxygenases in response to physiological and pathophysiological signals are not well understood, they are thought to result from alterations in the level of endogenous metabolites, involved in maintaining homeostasis. Here we show that homeostatic changes in hepatic metabolite profile in Abcb6 (mitochondrial ATP-binding cassette transporter B6) deficiency results in suppression of a specific subset of hepatic P450 activity. Abcb6 null mice are more susceptible to pentobarbital-induced sleep and zoxazolamine-induced paralysis, secondary to decreased expression and activity of Cyp3a11 and Cyp2b10. The knock-out mice also show decrease in both basal and xeno-inducible expression and activity of a subset of hepatic P450s that appear to be related to changes in hepatic metabolite profile. These data, together with the observation that liver extracts from Abcb6-deficient mice suppress P450 expression in human primary hepatocytes, suggest that this mouse model may provide an opportunity to understand the physiological signals and the mechanisms involved in negative regulation of P450s.

Charge order and its connection with Fermi-liquid charge transport in a pristine high-T(c) cuprate

Electronic inhomogeneity appears to be an inherent characteristic of the enigmatic cuprate superconductors. Here we report the observation of charge-density-wave correlations in the model cuprate superconductor HgBa2CuO(4+δ) (T(c)=72 K) via bulk Cu L3-edge-resonant X-ray scattering. At the measured hole-doping level, both the short-range charge modulations and Fermi-liquid transport appear below the same temperature of about 200 K. Our result points to a unifying picture in which these two phenomena are preceded at the higher pseudogap temperature by q=0 magnetic order and the build-up of significant dynamic antiferromagnetic correlations. The magnitude of the charge modulation wave vector is consistent with the size of the electron pocket implied by quantum oscillation and Hall effect measurements for HgBa2CuO(4+δ) and with corresponding results for YBa2Cu3O(6+δ), which indicates that charge-density-wave correlations are universally responsible for the low-temperature quantum oscillation phenomenon.

Self-doping processes between planes and chains in the metal-to-superconductor transition of YBa2Cu3O6.9

The interplay between the quasi 1-dimensional CuO-chains and the 2-dimensional CuO2 planes of YBa(2)Cu(3)O(6+x) (YBCO) has been in focus for a long time. Although the CuO-chains are known to be important as charge reservoirs that enable superconductivity for a range of oxygen doping levels in YBCO, the understanding of the dynamics of its temperature-driven metal-superconductor transition (MST) remains a challenge. We present a combined study using x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) revealing how a reconstruction of the apical O(4)-derived interplanar orbitals during the MST of optimally doped YBCO leads to substantial hole-transfer from the chains into the planes, i.e. self-doping. Our ionic model calculations show that localized divalent charge-transfer configurations are expected to be abundant in the chains of YBCO. While these indeed appear in the RIXS spectra from YBCO in the normal, metallic, state, they are largely suppressed in the superconducting state and, instead, signatures of Cu trivalent charge-transfer configurations in the planes become enhanced. In the quest for understanding the fundamental mechanism for high-Tc-superconductivity (HTSC) in perovskite cuprate materials, the observation of such an interplanar self-doping process in YBCO opens a unique novel channel for studying the dynamics of HTSC.

Lack of detectable genetic differentiation between den populations of the Prairie Rattlesnake (Crotalusviridis) in a fragmented landscape

Numerous studies have reported genetic fragmentation of species whose habitat has been modified by roads and other anthropogenic features, but it is still not clear how most species respond to roads and whether genetic effects can be detected over a limited number of generations. We used road-crossing models and population genetic analysis (based on microsatellite loci) to make inferences about functional connectivity between populations of the Prairie Rattlesnake (Crotalus viridis (Rafinesque, 1818)) on opposite sides of the Trans-Canada Highway near Medicine Hat (Alberta, Canada). The road-crossing model predicted a high probability of mortality while crossing the Trans-Canada Highway. However, model-based genetic clustering methods (STRUCTURE and BAPS) did not detect structure; a nonmodel-based clustering method (DAPC) found structure, but most groups consisted of individuals captured throughout the study area. Estimates of effective population size were immeasurably large and power to detect genic differentiation was diminished if the effective size exceeded 500; this reduction in power was intensified when the number of loci was reduced (from eight to five to account for null alleles). Our results corroborate accounts of long-distance migration by this species and indicate that genetic fragmentation may not be easily detectable over this spatial and temporal scale.