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Pseudogene-Derived Long Noncoding RNAs GSTM3P1/Gstm2-ps1 Exacerbate Sepsis-Associated Acute Kidney Injury by Suppressing Their Parent Gene Translation.

Long noncoding RNAs are emerging as critical regulators of acute kidney injury (AKI). In this study, the pathologic role of pseudogene-derived long noncoding RNAs GSTM3P1 (human)/Gstm2-ps1 (mouse) in sepsis-associated AKI (SA-AKI) was investigated. Glutathione S-transferase mu 3, pseudogene 1 (GSTM3P1)/glutathione S-transferase mu 2, pseudogene 1 (Gstm2-ps1) were transiently up-regulated in kidney proximal tubular cells at the early stage of SA-AKI in mice treated with lipopolysaccharide (LPS) or cecal ligation and puncture, as well as in LPS-treated proximal tubular cells. Functionally, overexpression of GSTM3P1/Gstm2-ps1 exacerbated LPS-induced proximal tubular cell apoptosis and oxidative stress. In contrast, proximal tubule-specific Gstm2-ps1 knockout mice were significantly protected from LPS-induced AKI, as evidenced by improved renal function and reduced apoptosis, kidney injury markers, and reactive oxygen species. Similarly, these mice showed renal protective effects against cecal ligation and puncture-induced AKI. Mechanistically, overexpression of GSTM3P1/Gstm2-ps1 in proximal tubular cells markedly suppressed parent gene GSTM3/GSTM2 protein but not mRNA expression, indicating a translational repression. Restoration of GSTM3/GSTM2 rescued proximal tubular cells from LPS-induced apoptosis. Furthermore, an RNA pulldown assay revealed that Gstm2-ps1 binds to human antigen R (HuR), a known post-transcriptional regulator for mRNA stability and translation. Overexpression of HuR antagonized Gstm2-ps1-mediated repression of GSTM2, associated with increased cell survival after LPS injury. In conclusion, the early induction of GSTM3P1/Gstm2-ps1 in SA-AKI exacerbates kidney injury by a novel mechanism to sequester HuR and inhibit the translation of parent gene GSTM3/gstm2 for oxidative stress detoxification.

Animals

The proteomic origin of the genetic code.

INTRODUCTION: The origin and evolution of the genetic code is a central problem in molecular biology. Classical models have emphasized stereochemistry, frozen accidents, or adaptive optimization, often treating proteins as passive products of preexisting codes. More recent views instead portray the code as a dynamic, coevolving system shaped by reciprocal interactions among amino acids, RNA, and early catalysts. AREAS COVERED: Here, I review efforts of phylogeny reconstruction of the history of tRNA, protein structural domains, and dipeptide sequences in proteomes. These complementary approaches allow exploration of the entry of amino acids and codons into the code, and the transition from an operational RNA code in the tRNA acceptor arm to the canonical code in the anticodon loop. Evidence for ancestral synthetase enzymes with dual functions in aminoacylation and peptide-bond formation, as well as early bidirectional (sense-antisense) coding reflected in dipeptide-antidipeptide emergence is also discussed. EXPERT OPINION: The genetic code is best viewed as a proteome-driven, evolvable system in which early peptides actively shaped coding rules by stabilizing structure, expanding chemical diversity, and enhancing catalysis. This perspective connects origin-of-life studies with modern efforts of code expansion, translational engineering, and peptide-based therapeutics, highlighting the impact of the code's proteomic origin.

Genetic Code

Chromosome engineering to correct a complex rearrangement on Chromosome 8 reveals the effects of 8p syndrome on gene expression and neural differentiation.

Chromosomal rearrangements on the short arm of Chromosome 8 cause 8p syndrome, a rare developmental disorder characterized by neurodevelopmental delays, epilepsy, and cardiac abnormalities. Although significant progress has been made in managing the symptoms of 8p syndrome and other conditions caused by large-scale chromosomal aneuploidies, no therapeutic approach has yet been demonstrated to target the underlying disease-causing chromosome. Here, we establish a two-step approach to eliminate the abnormal copy of Chromosome 8 and restore euploidy in cells derived from an individual with a complex rearrangement of Chromosome 8p. Transcriptomic analysis revealed 361 differentially expressed genes between the proband and the euploid revertant, highlighting genes both within and outside the 8p region that may contribute to 8p syndrome pathology. Furthermore, we demonstrate that the proband exhibits a significant defect in neural differentiation that could be partially rescued by treatment with small-molecule inhibitors of cell death. Our work demonstrates the feasibility of using chromosome engineering to correct complex aneuploidies in vitro and establishes a platform to further dissect the pathophysiology of 8p syndrome and other conditions caused by chromosomal rearrangements.

Humans

RAS-GTP Inhibition Overcomes Acquired Resistance to KRASG12C Inhibitors Mediated by Oncogenic and Wild-Type RAS Activation in Non-Small Cell Lung Cancer.

UNLABELLED: Small-molecule KRASG12C(OFF) inhibitors that bind to the inactive GDP-bound state of KRAS have demonstrated efficacy in patients with KRASG12C-mutant tumors, yet responses tend to be transient because of emergence of on-treatment resistance. Recently, RAS(ON) G12C-selective inhibitors, which bind to the active GTP-bound state of RAS, were described, and elironrasib is undergoing evaluation in multiple clinical trials. In this study, we generated resistant cell lines and patient-derived xenograft models to KRASG12C(OFF) and RAS(ON) G12C-selective inhibitors and interrogated resistance mechanisms using a multiomics strategy consisting of phosphoproteomics, whole-exome sequencing, and RNA sequencing combined with functional testing using small-molecule and CRISPR screens and RAS(ON) inhibitors being evaluated in clinical trials. Two models reactivated RAS signaling, either via KRASG12C gene amplification or NRASG13R mutation, and were vulnerable to dual inhibition by RAS(ON) G12C-selective and RAS(ON) multiselective inhibitors, RMC-4998 and RMC-7977. Two models, which lacked any discernable genomic alteration, acquired resistance associated with increased receptor tyrosine kinase activity and downstream persistent RAS activity and were sensitive to RAS-GTP inhibition by RMC-7977. Finally, one model displayed epithelial-mesenchymal transition, loss of RAS dependence, and acquired reliance on cell-cycle kinases and proteins associated with DNA damage response. This work highlights KRASG12C-selective inhibitor resistant states that parallel and complement clinical findings and demonstrate that a large subset could be overcome with a RAS(ON) multi-selective inhibitor as a stand-alone agent or in combination with other therapies. SIGNIFICANCE: Multi-omic characterization of resistance mechanisms to KRASG12C-selective inhibitors in non-small cell lung cancer provides insights that could inform precision medicine-based therapeutic approaches for improving the treatment of KRASG12C mutant tumors. See related article by Stern et al., p. 485.

Humans

From Worms to Tumors: Conserved Strategies of Cellular Arrest and Survival Governing Dormancy.

The recurrence of metastatic lesions months to years after the treatment of primary cancers remains a major contributor to cancer-related mortality, highlighting the need to better understand the mechanisms that govern dormancy and dormancy reawakening. A major hurdle is the lack of adequate in vitro and in vivo models to dissect the complex cascades that trigger tumor cell dissemination, adoption of the dormant state, or tumor cell outgrowth in the new metastatic microenvironmental niche. However, many organisms use dormancy to survive stressful environments or periods of nutrient deprivation. Of these, the dauer state of the free-living nematode Caenorhabditis elegans has unparalleled characterization. In this study, we discuss the remarkable physiologic, signaling, genomic, and metabolic similarities between dormant cancer cells and C. elegans dauers, arguing for the use of dauers as a facile model to help dissect dormancy and reawakening pathways in cancer cells.

Animals

Reprogramming of TLR-Ferroptosis Signaling and Immunometabolic Pathways Overcomes Myeloid Suppression to Improve Checkpoint Blockade in Prostate Cancer.

UNLABELLED: The limited efficacy of immunotherapies in advanced prostate cancer stems from a tumor microenvironment (TME) in which myeloid-driven immune suppression, stromal remodeling, and metabolic barriers converge to limit antitumor immunity. In this study, we characterized the immunometabolic properties of an ultrasmall prostate-specific membrane antigen-targeting silica particle therapy as a first-in-class strategy to reprogram the Toll-like receptor (TLR)-ferroptosis axis in MYC-driven prostate cancer. As single agents, these particles suppressed lipid and steroid biosynthesis, disrupted lipid peroxidation control, and impaired nutrient flux, sensitizing tumors to ferroptosis. Coordinated redox remodeling, stromal reprogramming, and innate immune activation reversed myeloid suppression and promoted CD8+ T-cell infiltration. When combined with CSF-1R inhibition and immune checkpoint blockade, the particles suppressed tumor growth, extended survival beyond 100 days, and achieved up to 50% complete remission in MYC-overexpressing models. These findings position TLR-ferroptosis axis remodeling as a mechanistic blueprint for rational, particle-driven immunotherapies with broad translational potential in prostate cancer and other immunologically refractory malignancies. SIGNIFICANCE: Clinically validated, PSMA-targeted ultrasmall core-shell silica particles reprogram immunometabolic pathways via a TLR-ferroptosis axis, enabling tumor microenvironment remodeling and potentiating checkpoint blockade in prostate cancer, with translational implications for treatment-resistant disease.

Male

Breast Cancer Risk Stratification in Black Women: Current Status and Potential Solutions to Improve Accuracy.

Breast cancer risk stratification models identify individuals at increased risk, allowing earlier screening than for those at average risk and potentially improving health outcomes. Due to the increasing rates of breast cancer in individuals aged <40 years, especially among Black females, the American College of Radiology now recommends all females initiate breast cancer risk assessment by age 25 years. Several breast cancer risk prediction models are readily available, including the Gail Model, Breast Cancer Surveillance Consortium Risk Calculator, BOADICEA, and Tyrer-Cuzick Model. However, because these models were primarily developed using data from White women of European ancestry, they may underestimate risk in Black women. Indeed, current evidence suggests that these models underpredict breast cancer risk among Black women, particularly those of African ancestry. Although cancer risk prediction models typically incorporate personal characteristics, family history of cancer, and hormonal and lifestyle factors, inherited breast cancer genes can also increase risk for breast cancer. Beyond monogenic inherited breast cancer genes that increase breast cancer risk, emerging data suggest that single nucleotide polymorphisms identified through genome-wide association studies (GWAS) may be used to generate polygenic risk scores, which may further refine breast cancer risk. However, GWAS data are also primarily gathered from European ancestry females, further reducing the ability to accurately stratify breast cancer risk in non-European ancestry populations. Current data highlight the importance of ensuring representation from all populations in developing cancer risk prediction models, conducting genomics research, and designing effective implementation strategies to enhance the use of these models in routine clinical care. Although new analytic methods and models are being developed to improve breast cancer risk stratification across populations, it remains critical to assess the utility and calibration of existing and new models to ensure applicability across non-European ancestry populations.

Humans

A Prospective Validation of the Decipher Genomic Classifier in Men With Early Localized Prostate Cancer: The VANDAAM Study.

BACKGROUND: The emergence of genomic precision oncology has advanced personalized care for some patients with prostate cancer (PCa), while threatening to widen existing disparities due to the historically low recruitment of African American men (AAM), who have the highest disease burden. Here, we report the first prospective validation of a genomic classifier (GC) to predict rapid-onset biochemical recurrence (BCR) in AAM. METHODS: Between 2016 and 2021, this multicenter prospective validation study recruited 243 patients with low- or intermediate-risk PCa who received treatment for their disease. Patients were recruited on a 1:1 basis (AAM:White) and matched by CAPRA score. Patients who elected active surveillance were ineligible for participation. Decipher GC testing was ordered for all patients using their biopsy and/or radical prostatectomy (RP) tumor tissue. The primary outcome was to determine whether the GC could predict 2-year BCR rates-used as a surrogate for disease aggressiveness-following standard treatment. The secondary outcome evaluated the concordance between biopsy- and RP-derived GC risk scores for treatment recommendations. RESULTS: The final analytical cohort included 226 matched patients with genomic information, and 207 evaluable cases (104 AAM, 103 White) with both genomic and complete clinical outcome data. Overall, a high genomic-risk GC score was associated with a 5.25-fold increase in the odds of rapid-onset 2-year BCR compared with the low-risk group (odds ratio, 5.25 [95% CI, 1.27-21.66]; P=.021). In a subset of the surgical cohort (n=74), biopsy- and RP-derived GC scores exhibited a 77% concordance rate, defined as no reclassification in GC risk-based categories. CONCLUSIONS: This study represents the first prospective validation of GC performance in predicting early 2-year BCR in both AAM and White men. The findings provide strong evidence supporting the integration of the GC into clinical practice guidelines to improve risk stratification and management of AAM with early-stage PCa. CLINICALTRIALS: gov identifier: NCT02723734.

Aged

MIF as an oncogenic driver of low-heterogeneity melanomas.

Identifying targets involved in tumor evolution and immune escape is an active area of research in oncology. Macrophage migration inhibitory factor (MIF) is an upstream immunoregulatory cytokine that promotes transformed cell proliferation and survival, and generates a tumor-permissive immune landscape of immunosuppressive myeloid and T&#xa0;cells. Shvefel and colleagues have identified a key role for MIF in tumor progression in melanoma clones with low tumor heterogeneity. These findings provide important insights into the potential therapeutic utility of MIF antagonists and support ongoing research to utilize MIF pathway inhibitors for improved therapeutic outcomes.

Animals

Metabolism and gene expression models for the microbiome reveal how diet and metabolic dysbiosis impact disease.

The gut microbiome plays a critical role in human health, spurring extensive research using multi-omic technologies. Although these tools offer valuable insights, they often fall short in capturing the complexity of microbial interactions that associate with disease onset, progression, and treatment. Thus, integration of multi-omics datasets with metabolic models is needed to predict associations between microbial activity and disease. Here, we automated the reconstruction of 495 metabolic and gene expression models (ME-models), overcoming the main limitation preventing the wide use of this approach. We integrated them with multi-omics data from patients with inflammatory bowel disease (IBD), identifying taxa associated with variations in amino acids, short-chain fatty acids, and pH in the gut of IBD patients. In general, this approach provides testable hypotheses of the metabolic activity of the gut microbiota, and the automated pipeline opens the opportunity to study microbial interactions in other biologically relevant settings using ME-models.

Humans

Large language models improve annotation of prokaryotic viral proteins.

Viral genomes are poorly annotated in metagenomic samples, representing an obstacle to understanding viral diversity and function. Current annotation approaches rely on alignment-based sequence homology methods, which are limited by the paucity of characterized viral proteins and divergence among viral sequences. Here we show that protein language models can capture prokaryotic viral protein function, enabling new portions of viral sequence space to be assigned biologically meaningful labels. When applied to global ocean virome data, our classifier expanded the annotated fraction of viral protein families by 29%. Among previously unannotated sequences, we highlight the identification of an integrase defining a mobile element in marine picocyanobacteria and a capsid protein that anchors globally widespread viral elements. Furthermore, improved high-level functional annotation provides a means to characterize similarities in genomic organization among diverse viral sequences. Protein language models thus enhance remote homology detection of viral proteins, serving as a useful complement to existing approaches.

Viral Proteins

Mapping the stereotyped behaviour of freely moving fruit flies.

A frequent assumption in behavioural science is that most of an animal's activities can be described in terms of a small set of stereotyped motifs. Here, we introduce a method for mapping an animal's actions, relying only upon the underlying structure of postural movement data to organize and classify behaviours. Applying this method to the ground-based behaviour of the fruit fly, Drosophila melanogaster, we find that flies perform stereotyped actions roughly 50% of the time, discovering over 100 distinguishable, stereotyped behavioural states. These include multiple modes of locomotion and grooming. We use the resulting measurements as the basis for identifying subtle sex-specific behavioural differences and revealing the low-dimensional nature of animal motions.

Animals

Whole-genome sequencing-based pathogen characterization for streptococcal infection directly from positive blood culture samples.

Clinical laboratories are increasingly using diagnostic tests directly on positive blood cultures, which may lead to fewer attempts to recover bacterial isolates. Consequently, public health laboratories can benefit from assays that directly process blood culture samples without requiring submission of clinical isolates to determine additional pathogen features not identified by clinical tests, such as vaccine serotype and bacterial genomic relatedness, for surveillance and outbreak response purposes. In partnership with the Minnesota Active Bacterial Core surveillance (ABCs) site, we identified blood culture samples positive for ABCs streptococcal pathogens and characterized them by a direct whole-genome sequencing from blood culture (dWGS) assay. The dWGS results were compared with the results of a reference method (WGS of isolates from the same cultures) to evaluate concordance in pathogen features and genome assemblies. Of the 97 eligible blood culture samples, 83 (86%) passed dWGS quality control criteria and were subjected to a total of 655 dWGS-based tests, which yielded 651 (99.3%) evaluable results. The percent agreement with reference results was 100% (83/83) for M protein gene (emm)/capsular types and 100% (81/81) for multilocus sequencing types. For genotypic antimicrobial susceptibility testing prediction, the percent prediction agreement was 100% (487/487), false resistant prediction rate was 0% (0/417), and the false susceptible prediction rate was 0% (0/66). Assemblies of pathogen genomes from the same patient differed by 1.08 &#xb1; 1.68 (mean &#xb1; SD) sites per genome. The dWGS assay can extract high-quality, important streptococcal strain characteristics directly from positive blood culture samples to support evolving public health needs.IMPORTANCEWhole-genome sequencing (WGS) technologies have emerged as a transformative toolkit used by public health microbiology laboratories to detect and characterize pathogens. The surveillance of bacterial diseases often relies on clinical laboratories to submit pathogen isolates to regional or national public health laboratories, which have the capacity to routinely conduct WGS-based strain characterization. Clinical laboratories are increasingly using diagnostic tests directly on positive blood cultures, which may lead to fewer attempts to recover bacterial isolates. The study evaluated a direct whole-genome sequencing from blood culture (dWGS) assay that directly processes blood culture samples. The dWGS assay recovered high quality, important streptococcal strain characteristics, including vaccine serotypes and whole-genome assemblies, without requiring submission of clinical isolates. Thus, the dWGS assay represents a promising tool for addressing the evolving needs of public health laboratories in the metagenomics era.

Humans

Aging and DNA damage are associated with the development of endothelial cell clonal expansion.

Endothelial dysfunction is a hallmark of vascular aging and a key contributor to cardiovascular disease. Although senescence has been widely studied as a terminal endothelial cell fate, recent evidence suggests that clonal expansion, the proliferative expansion of genetically identical cells, may also occur in aged tissues. We sought to determine whether endothelial clonal expansion increases with age, specifically at the atheroprone regions of the aorta, and to evaluate whether DNA damage promotes endothelial cell clonal expansion. Tamoxifen-inducible, endothelial-specific Cdh5-CreERT2 male and female mice were used to quantify clonal expansion in endothelial cells (ECs) across the aortic region in both young (4 mo) and aged (24 mo) mice. We further examined the effect of DNA damage by administering systemic doxorubicin (DOXO) to assess clonal dynamics in different aortic regions. Aging significantly increased EC clone size and the percentage of clonal ECs in atheroprone regions, particularly the minor arch, whereas only clone size increased in nonatheroprone regions. Systemic DOXO administration increased clone size across the aortic region without altering clonal recruitment, indicating selective amplification of preexisting clones. These findings suggest that clonal expansion is promoted by both aging and DNA damage. Clonal expansion may represent an underrecognized mechanism contributing to endothelial homogeneity and vascular remodeling during aging and in response to sublethal genomic stress.NEW & NOTEWORTHY Aging reshapes the vascular endothelium in unexpected ways. Using lineage tracing in mice, we show that endothelial cells undergo age-dependent clonal expansion, particularly in atheroprone regions exposed to disturbed blood flow. This process is amplified by DNA damage and reflects the selective expansion of preexisting clones rather than increased recruitment. Endothelial clonal expansion may represent an underrecognized mechanism driving vascular remodeling during aging and genotoxic stress.

Animals

Loss of ovarian function and estrogen therapy remodel the brain's synaptic and metabolic proteome.

Menopause is linked to cognitive decline and reduced brain metabolism, whereas estrogen (E2) therapy has been shown to mitigate these effects. Understanding the molecular mechanisms by which ovarian hormones and E2 influence neuroprotection is essential for developing strategies to maintain brain health in women. In this study, we examined how the loss of ovarian hormones, with or without E2 treatment, affects the brain proteome and mitochondrial energy production in aged female C57BL/6J mice (36-40 wk). The mice underwent sham or ovariectomy (OVX) surgery and were fed a high-fat diet for 10 wk; 6 wk after surgery, OVX mice received either sesame oil or E2 treatment for 4 wk. Proteomic analysis of brain homogenates revealed 4,992 proteins regulated by E2, with pathway analysis showing increased signaling proteins related to synaptogenesis. OVX reduced proteins involved in synaptic function, branched-chain amino acid and ketone metabolism, the tricarboxylic acid cycle, and oxidative phosphorylation (Complexes I, IV, and V), whereas E2 restored protein expression within these pathways. Despite alterations in OxPhos proteins, basal and state 3 mitochondrial respiration remained unchanged, although notable impairments in Complex IV enzymatic activity were apparent in OVX, which were partially reversed by E2 treatment. Overall, these results indicate that E2 supports brain health by maintaining proteins crucial for synaptic integrity and metabolism, while partially offsetting the functional decline in mitochondrial bioenergetics associated with menopause.NEW & NOTEWORTHY The menopausal transition, marked by declining estrogen levels, alters cognition, neuroplasticity, and brain metabolism. Although hormone therapy benefits cognition, its molecular effects on the brain remain unclear. Using whole-brain proteomics in aged ovariectomized (OVX) mice with or without estrogen treatment, we found that OVX reduced proteins linked to synaptogenesis and mitochondrial metabolism. Estrogen reversed these declines, restoring pathways supporting neuronal signaling and energy balance, identifying estrogen-regulated proteins critical for maintaining brain health during menopause.

Animals

Reduced legacy precipitation decreases microbial community growth efficiency and alters soil organic carbon in a California grassland.

BACKGROUND: Changes in global patterns can leave a lasting legacy in semiarid grasslands by reshaping microbial growth dynamics and carbon cycling during the first wet-up in the autumn-a period known for intense microbial activity and significant carbon emissions. To study the lasting impacts of decreased winter rain, we implemented two precipitation regimes (100% vs. 50% mean annual precipitation) in California Mediterranean-climate grassland field plots. After the dry season, soils were rewetted in the laboratory with H218O and sampled at 0&#xa0;h, 3&#xa0;h, 24&#xa0;h, 48&#xa0;h, 72&#xa0;h, and 168&#xa0;h post rewet. We quantified CO2 efflux, measured microbial growth and mortality via quantitative 18O stable isotope probing and 16S rRNA gene amplicon sequencing, and characterized the soil organic carbon chemical composition, metagenomes, and metatranscriptomes. RESULTS: We found that reduced winter precipitation imposed a strong legacy effect on microbial turnover; despite maintaining similar respiration rates, microbial growth declined by&#x2009;~1 order of magnitude, yielding decreased community growth efficiency (CGE&#x2009;=&#x2009;new biomass growth/respiration), and microbial mortality declined by ~2 orders of magnitude. Soil organic carbon also shifted from lipid-like, amino-sugar-like, and protein-like compounds (indicative of microbial necromass) to more oxidized lignin-like and tannin-like compounds (indicative of decomposing plant-derived compounds). Meta-omics revealed distinct metabolic strategies linked to CGE. At high-CGE, microbes appeared to consume more energetically favorable N-rich necromass (released via high microbial turnover); this allowed for increased amino acids and peptidoglycan biosynthesis and greater aromatic compound degradation, fueling further energy production and growth efficiency. At low CGE, communities had elevated carbohydrate metabolism and lipid turnover, consistent with increased investment in plant detritus degradation and membrane repair and maintenance rather than growth. CONCLUSIONS: Together, our findings demonstrate that reduced winter rainfall decreases microbial turnover following rewetting without a concurrent reduction in CO2 emissions. This shift results in persistently lower CGE, which has the potential to increase soil carbon loss as CO2. If such conditions are maintained over multiple years, these changes could reshape soil organic carbon stocks and alter the balance of grassland ecosystems under future climate scenarios. While our data suggest that sustained reductions in CGE may drive SOC decline, the magnitude and persistence of these effects depend on long-term environmental dynamics and warrant further investigation. Video Abstract.

Soil Microbiology

Genome-resolved multi-omics provide new insights into microbial nitrogen utilization by the rumen microbiota.

BACKGROUND: Optimizing nitrogen (N) utilization in ruminant production systems holds both economic and environmental significance. However, traditional paradigms of N metabolism, derived primarily from well-studied model rumen bacteria, do not fully reflect the diverse and complex N metabolism in the rumen ecosystem. RESULTS: To address this gap, we utilized comparative genomics and genome-resolved multi-omics analyses using a curated set of microbial genomes to investigate N assimilation and regulation in rumen microbes. We discovered that well-established mechanisms of ammonia assimilation and regulation, such as the glutamine synthetase (GS)/glutamate synthase (GOGAT) pathways and their regulatory proteins, are absent in many of the predominant rumen microbes, which likely utilize alternative pathways for ammonia assimilation. These findings challenge the applicability of E. coli-based N regulation models to rumen bacteria in response to ammonia availability. We further linked polysaccharide utilization and ammonia assimilation across hundreds of rumen microbial species. Furthermore, we identified specific microbial species involved in ureolysis and denitrification, as well as phages carrying auxiliary metabolic genes involved in N assimilation. Using an animal trial involving 11 pairs of lamb twins in a crossover design, we demonstrated that dietary crude protein (CP) at 10% and 13% had minimal impact on rumen microbiome composition and expression of N assimilation genes. Instead, changes in concentrate levels altered N assimilation, notably increasing expression of amino acid biosynthesis pathways. CONCLUSION: These findings indicate a nuanced, species-specific microbial response to dietary interventions, highlighting the limitations of traditional N metabolism models applied to rumen microbes and the need for more granular studies of rumen microbial ecosystems.

Multiomics

Anoxia tolerant DNA replication is supported by ATR kinase in the annual killifish Austrofundulus limnaeus.

Hypoxia and anoxia suppress cell proliferation due to an increase in replication stress and activation of DNA damage checkpoints. Embryos of the annual killifish Austrofundulus limnaeus tolerate prolonged anoxia, indicating improved genomic stability under oxygen starvation. We investigated the cell cycle regulation of the anoxia tolerant killifish embryonic cell line PSU-AL-WS40NE during anoxia. Live-cell imaging confirms continued proliferation of WS40NE cells for the first 24&#x2005;h of anoxia with minimal cell death. Fluorescence imaging shows that cells accumulate in G1 after the first day in anoxia with a rapid entry into S phase upon reoxygenation. Pharmacological inhibition shows a reliance on ataxia telangiectasia and Rad3 related (ATR) signaling, suggesting that increased &#x3b3;H2AX levels are driven by replication stress instead of DNA damage. This conclusion is supported by a lack of induction of a G2 checkpoint, suggesting minimal DNA damage during anoxic exposure. Maintaining cellular proliferation during anoxia and accumulating cells in the G1 phase for extended anoxic exposure is likely one way that embryos of the killifish can survive prolonged anoxia, which provides insight into mechanisms that enable cells to proliferate under metabolic stress.

Animals