Equine Musculoskeletal Pathologies: Clinical Approaches and Therapeutical Perspectives-A Review.

Musculoskeletal injuries such as equine osteoarthritis, osteoarticular defects, tendonitis/desmitis, and muscular disorders are prevalent among sport horses, with a fair prognosis for returning to exercise or previous performance levels. The field of equine medicine has witnessed rapid and fruitful development, resulting in a diverse range of therapeutic options for musculoskeletal problems. Staying abreast of these advancements can be challenging, prompting the need for a comprehensive review of commonly used and recent treatments. The aim is to compile current therapeutic options for managing these injuries, spanning from simple to complex physiotherapy techniques, conservative treatments including steroidal and non-steroidal anti-inflammatory drugs, hyaluronic acid, polysulfated glycosaminoglycans, pentosan polysulfate, and polyacrylamides, to promising regenerative therapies such as hemoderivatives and stem cell-based therapies. Each therapeutic modality is scrutinized for its benefits, limitations, and potential synergistic actions to facilitate their most effective application for the intended healing/regeneration of the injured tissue/organ and subsequent patient recovery. While stem cell-based therapies have emerged as particularly promising for equine musculoskeletal injuries, a multidisciplinary approach is underscored throughout the discussion, emphasizing the importance of considering various therapeutic modalities in tandem.

A brain-enriched circular RNA controls excitatory neurotransmission and restricts sensitivity to aversive stimuli.

Circular RNAs (circRNAs) are a large class of noncoding RNAs. Despite the identification of thousands of circular transcripts, the biological significance of most of them remains unexplored, partly because of the lack of effective methods for generating loss-of-function animal models. In this study, we focused on circTulp4, an abundant circRNA derived from the Tulp4 gene that is enriched in the brain and synaptic compartments. By creating a circTulp4-deficient mouse model, in which we mutated the splice acceptor site responsible for generating circTulp4 without affecting the linear mRNA or protein levels, we were able to conduct a comprehensive phenotypic analysis. Our results demonstrate that circTulp4 is critical in regulating neuronal and brain physiology, modulating the strength of excitatory neurotransmission and sensitivity to aversive stimuli. This study provides evidence that circRNAs can regulate biologically relevant functions in neurons, with modulatory effects at multiple levels of the phenotype, establishing a proof of principle for the regulatory role of circRNAs in neural processes.

Balancing Act: Tubulin Glutamylation and Microtubule Dynamics in Toxoplasma gondii.

The success of the intracellular parasite Toxoplasma gondii in invading host cells relies on the apical complex, a specialized microtubule cytoskeleton structure associated with secretory organelles. The T. gondii genome encodes three isoforms of both α- and ß-tubulin, which undergo specific post-translational modifications (PTMs), altering the biochemical and biophysical proprieties of microtubules and modulating their interaction with associated proteins. Tubulin PTMs represent a powerful and evolutionarily conserved mechanism for generating tubulin diversity, forming a biochemical 'tubulin code' interpretable by microtubule-interacting factors. T. gondii exhibits various tubulin PTMs, including α-tubulin acetylation, α-tubulin detyrosination, Δ5α-tubulin, Δ2α-tubulin, α- and ß-tubulin polyglutamylation, and α- and ß-tubulin methylation. Tubulin glutamylation emerges as a key player in microtubule remodeling in Toxoplasma, regulating stability, dynamics, interaction with motor proteins, and severing enzymes. The balance of tubulin glutamylation is maintained through the coordinated action of polyglutamylases and deglutamylating enzymes. This work reviews and discusses current knowledge on T. gondii tubulin glutamylation. Through in silico identification of protein orthologs, we update the recognition of putative proteins related to glutamylation, contributing to a deeper understanding of its role in T. gondii biology.

Effectiveness and safety of lenvatinib in a series of advanced well-differentiated thyroid carcinomas from a single tertiary cancer center and literature review.

BACKGROUND: Treatment of advanced differentiated thyroid carcinoma (DTC) remains a challenge as 25-50% of patients with locally invasive or distant metastatic disease become refractory to radioiodine (RAI) therapy. Tyrosine kinase inhibitors (TKI) are increasingly used in this setting. The SELECT trial demonstrated that lenvatinib, a multikinase inhibitor, significantly improved progression free survival (PFS) compared to placebo. Our aim was to report the effectiveness and safety of lenvatinib in our series of patients with advanced DTC. METHODS: A total of 25 patients with advanced DTC followed at a single tertiary center from January of 2016 to January of 2022 were retrospectively reviewed. RESULTS: Patients were treated with a mean daily dose of lenvatinib of 16.9 mg for a mean of 9.1 months. Median estimated PFS was 31.3 months. One patient achieved complete response. The objective response rate (ORR) was 40% and the disease control rate was 84%. The mean change in summed longest diameter of target lesions from baseline to nadir was -36.9%. Lenvatinib prolonged the tumor volume doubling time in 86.7% patients. Interestingly, we found that patients treated with a lower dose of lenvatinib (<16.9 mg daily) had a significantly higher PFS and ORR than patients treated with higher dosages (>16.9 mg). Adverse events were frequently reported. CONCLUSIONS: Our results confirm the effectiveness of lenvatinib in the management of patients with advanced DTC and support the need to adjust the dosage of lenvatinib to patient´s performance status and comorbidities.

Repurposing Kraft black Liquor as Reductant for Enhanced Lithium-Ion Battery Leaching.

The economic advantages of H2SO4 make it the acid of choice for the hydrometallurgical treatment of waste lithium-ion batteries (LIBs). However, to facilitate the full dissolution of the higher valency metal oxides present in the cathode black mass, a suitable reducing agent is required. Herein, the application of industrial black liquor (BL) obtained from the Kraft pulping for papermaking is investigated as a renewable reducing agent for the enhanced leaching of transition metals from LIB powder with H2SO4. The addition of acidified BL to H2SO4 significantly improved the leaching efficiency for a range of LIB cathode chemistries, with the strongest effect observed for manganese-rich active material. Focusing on NMC111 (LiMnxCoyNizO2) material, a linear correlation between the BL concentration and the leaching yield of Mn was obtained, with the best overall leaching efficiencies being achieved for 2.0 mol L-1 H2SO4 and 50 vol % of BL at 353 K. A quasi-total degradation of oxygenated and aromatic groups from the BL during NMC111 dissolution was observed after leaching, suggesting that these chemical groups are essential for LIB reduction. Finally, the leached transition metals could be easily recovered by pH adjustment and oxalic acid addition, closing the resource loop and fostering resource efficiency.

Gut enterotype-dependent modulation of gut microbiota and their metabolism in response to xanthohumol supplementation in healthy adults.

Xanthohumol (XN), a polyphenol found in the hop plant (Humulus lupulus), has antioxidant, anti-inflammatory, prebiotic, and anti-hyperlipidemic activity. Preclinical evidence suggests the gut microbiome is essential in mediating these bioactivities; however, relatively little is known about XN's impact on human gut microbiota in vivo. We conducted a randomized, triple-blinded, placebo-controlled clinical trial (ClinicalTrials.gov NCT03735420) to determine safety and tolerability of XN in healthy adults. Thirty healthy participants were randomized to 24 mg/day XN or placebo for 8 weeks. As secondary outcomes, quantification of bacterial metabolites and 16S rRNA gene sequencing were utilized to explore the relationships between XN supplementation, gut microbiota, and biomarkers of gut health. Although XN did not significantly change gut microbiota composition, it did re-shape individual taxa in an enterotype-dependent manner. High levels of inter-individual variation in metabolic profiles and bioavailability of XN metabolites were observed. Moreover, reductions in microbiota-derived bile acid metabolism were observed, which were specific to Prevotella and Ruminococcus enterotypes. These results suggest interactions between XN and gut microbiota in healthy adults are highly inter-individualized and potentially indicate that XN elicits effects on gut health in an enterotype-dependent manner.

Lipid profile and reproductive performance of female offspring of SWISS mouse females supplemented with resveratrol or canjiqueira (Byrsonima cydoniifolia A Juss) during gestation.

This study aimed to resveratrol supplementation (at 5 or 10 mg/kg) and a hydroethanolic extract of canjiqueira fruits (150 mg/kg) on female SWISS mice. Total cholesterol, high-density lipoprotein (HDL), triglyceride levels, gestation rates, and embryonic implantation rates in their female Offspring was evaluated. In conclusion, the consumption of canjiqueira fruit extract altered the lipid profile of their female offspring, and did not impact their reproductive performance. Supplementing female SWISS mice with 10 mg/kg of resveratrol increased total cholesterol, triglycerides, and HDL levels, thereby enhancing the reproductive efficiency of their offspring.

Affinity- and activity-based probes synthesized from structurally diverse hops-derived xanthohumol flavonoids reveal highly varied protein profiling in Escherichia coli.

Xanthohumol, the principle prenylflavonoid found in hops (Humulus lupulus) and a reported anti-inflammatory agent, has great potential for pharmaceutical interventions related to inflammatory disorders in the gut. A suite of probes was prepared from xanthohumol and its structural isomer isoxanthohumol to enable profiling of both protein affinity binding and catalytic enzyme reactivity. The regiochemistry of the reactive group on the probes was altered to reveal how probe structure dictates protein labeling, and which probes best emulate the natural flavonoids. Affinity- and activity-based probes were applied to Escherichia coli, and protein labeling was measured by chemoproteomics. Structurally dependent activity-based probe protein labeling demonstrates how subtle alterations in flavonoid structure and probe reactive groups can result in considerably different protein interactions. This work lays the groundwork to expand upon unexplored cellular activities related to xanthohumol interactions, metabolism, and anti-inflammatory mechanisms.

1,4-Diaryl-1,2,3-triazole neolignan-celecoxib hybrids inhibit experimental arthritis induced by zymosan.

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes cartilage damage. Anti-inflammatories are widely used in the management of RA, but they can have side effects such as gastrointestinal and/or cardiovascular disorders. Studies published by our group showed that the synthesis of hybrid triazole analogs neolignan-celecoxib containing the substituent groups sulfonamide (L15) or carboxylic acid (L18) exhibited anti-inflammatory activity in an acute model of inflammation, inhibited expression of P-selectin related to platelet activation and did not induce gastric ulcer, minimizing the related side effects. In continuation, the present study evaluated the anti-inflammatory effects of these analogs in an experimental model of arthritis and on the functions of one of the important cells in this process, macrophages. Mechanical hyperalgesia, joint edema, leukocyte recruitment to the joint and damage to cartilage in experimental arthritis and cytotoxicity, spread of disease, phagocytic activity and nitric oxide (NO) and hydrogen peroxide production by macrophages were evaluated. Pre-treatment with L15 and L18 reduced mechanical hyperalgesia, joint edema and the influx of leukocytes into the joint cavity after different periods of the stimulus. The histological evaluation of the joint showed that L15 and L18 reduced cartilage damage and there was no formation of rheumatoid pannus. Furthermore, L15 and L18 were non-cytotoxic. The analogs inhibited the spreading, the production of NO and hydrogen peroxide. L15 decreased the phagocytosis. Therefore, L15 and L18 may be potential therapeutic prototypes to treat chronic inflammatory diseases such as RA.

Meeting report: the ALPHA project: a stakeholder meeting on lupus clinical trial outcome measures and the patient perspective.

Drug development in lupus has improved over the past 10 years but still lags behind that of other rheumatic disease areas. Assessment of prospective lupus therapies in clinical trials has proved challenging for reasons that are multifactorial including the heterogeneity of the disease, study design limitations and a lack of validated biomarkers which greatly impacts regulatory decision-making. Moreover, most composite outcome measures currently used in trials do not include patient-reported outcomes. Given these factors, the Addressing Lupus Pillars for Health Advancement Global Advisory Committee members who serve on the drug development team identified an opportunity to convene a meeting to facilitate information sharing on completed and existing outcome measure development efforts. This meeting report highlights information presented during the meeting as well as a discussion on how the lupus community may work together with regulatory agencies to simplify and standardise outcome measures to accelerate development of lupus therapeutics.

Organismal landscape of clock cells and circadian gene expression in Drosophila.

Background: Circadian rhythms time physiological and behavioral processes to 24-hour cycles. It is generally assumed that most cells contain self-sustained circadian clocks that drive circadian rhythms in gene expression that ultimately generating circadian rhythms in physiology. While those clocks supposedly act cell autonomously, current work suggests that in Drosophila some of them can be adjusted by the brain circadian pacemaker through neuropeptides, like the Pigment Dispersing Factor (PDF). Despite these findings and the ample knowledge of the molecular clockwork, it is still unknown how circadian gene expression in Drosophila is achieved across the body. Results: Here, we used single-cell and bulk RNAseq data to identify cells within the fly that express core-clock components. Surprisingly, we found that less than a third of the cell types in the fly express core-clock genes. Moreover, we identified Lamina wild field (Lawf) and Ponx-neuro positive (Poxn) neurons as putative new circadian neurons. In addition, we found several cell types that do not express core clock components but are highly enriched for cyclically expressed mRNAs. Strikingly, these cell types express the PDF receptor (Pdfr), suggesting that PDF drives rhythmic gene expression in many cell types in flies. Other cell types express both core circadian clock components and Pdfr, suggesting that in these cells, PDF regulates the phase of rhythmic gene expression. Conclusions: Together, our data suggest three different mechanisms generate cyclic daily gene expression in cells and tissues: canonical endogenous canonical molecular clock, PDF signaling-driven expression, or a combination of both.

Selective Separation of Vanillic Acid from Other Lignin-Derived Monomers Using Centrifugal Partition Chromatography: The Effect of pH.

In this work, centrifugal partition chromatography (CPC) assisted by a polyethylene glycol (PEG)/sodium polyacrylate (NaPA) aqueous biphasic system (ABS) was applied in the separation of five lignin-derived monomers (vanillin, vanillic acid, syringaldehyde, acetovanillone, and p-hydroxybenzaldehyde). The influence of the system pH (unbuffered, pH 5, and pH 12) and added electrolytes (inorganic salts or ionic liquids (ILs)) on the compound partition was initially evaluated. The obtained data revealed that ILs induced more adequate partition coefficients (K < 5) than inorganic salts (K > 5) to enable separation performance in CPC, while alkaline conditions (pH 12) demonstrated a positive impact on the partition of vanillic acid. CPC runs, with buffered ABS at pH 12, enabled a selective separation of vanillic acid from other lignin monomers. Under these conditions, a distinct interaction between the top (PEG-rich) and bottom (NaPA-rich) phases of the ABS with the double deprotonated form of vanillic acid is expected when compared to the remaining lignin monomers (single deprotonated). This is an impactful result that shows the pH to be a crucial factor in the separation of lignin monomer compounds by CPC, while only unbuffered systems have been previously studied in the literature. Finally, the recovery of vanillic acid up to 96% purity and further recycling of ABS phase-forming components were approached as a proof of concept through the combination of ultrafiltration and solid-phase extraction steps.

Xanthohumol improves cognition in farnesoid X receptor-deficient mice on a high-fat diet.

Xanthohumol (XN) improves cognition of wild-type rodents on a high-fat diet (HFD). Bile acids and ceramide levels in the liver and hippocampus might be linked to these effects. XN modulates activity of the nuclear farnesoid X receptor (FXR; also known as NR1H4), the primary receptor for bile acids. To determine the role of FXR in the liver and intestine in mediating the effects of XN on cognitive performance, mice with intestine- and liver-specific FXR ablation (FXRIntestine-/- and FXRLiver-/-, respectively) on an HFD or an HFD containing XN were cognitively tested. XN improved cognitive performance in a genotype- and sex-dependent manner, with improved task learning in females (specifically wild-type), reversal learning in males (specifically wild-type and FXRIntestine-/- mutant) and spatial learning (both sexes). XN increased hippocampal diacylglycerol and sphingomyelin levels in females but decreased them in males. XN increased the ratio of shorter-chain to longer-chain ceramides and hexaceramides. Higher diacylglycerol and lower longer-chain ceramide and hexaceramide levels were linked to improved cognitive performance. Thus, the beneficial sex-dependent cognitive effects of XN are linked to changes in hippocampal diacylglycerol and ceramide levels. This article has an associated First Person interview with the first author of the paper.

Establishing brown trout primary hepatocyte spheroids as a new alternative experimental model-Testing the effects of 5α-dihydrotestosterone on lipid pathways.

Three-dimensional (3D) fish liver cultures mimic the in vivo cellular microenvironment, which is ideal for ecotoxicological research. Despite that, the application of these cultures to evaluate toxic effects in fish is scarce. A 3D model of brown trout (Salmo trutta f. fario) primary hepatocyte spheroids was optimized in this study by using DMEM/F-12 with 15 mM of HEPES, 10 mL/L of an antibiotic and antimycotic solution and FBS 10% (v/v), at 18 °C with ∼100 rpm. The selection of optimal conditions was based on a multiparametric characterization of the spheroids, including biometry, viability, microanatomy and immunohistochemistry. Biometric and morphologic stabilization of spheroids was reached within 12-16 days of culture. To our knowledge, this study is the first to culture and characterize viable spheroids from brown trout primary hepatocytes for over 30 days. Further, the 3D model was tested to explore the androgenic influences on lipidic target genes after 96 h exposures to control, solvent control, 10 and 100 µM of 5α-dihydrotestosterone (DHT), a non-aromatizable androgen. Spheroids exposed to 100 µM of DHT had decreased sphericity. DHT at 100 µM also significantly down-regulated Acox1-3I, PPARγ and fatty acid synthesis targets (i.e., ACC), and significantly up-regulated Fabp1. Acsl1 was significantly up-regulated after exposure to both 10 and 100 µM of DHT. The results support that DHT modulates distinct lipidic pathways in brown trout and show that this 3D model is a new valuable tool for physiological and toxicological mechanistic studies.

ApoE isoform-dependent effects of xanthohumol on high fat diet-induced cognitive impairments and hippocampal metabolic pathways.

Consumption of a high fat diet (HFD) is linked to metabolic syndrome and cognitive impairments. This is exacerbated in age-related cognitive decline (ACD) and in individuals with a genetic risk for Alzheimer's disease (AD). Apolipoprotein E (apoE) is involved in cholesterol metabolism. In humans, there are three major isoforms, E2, E3, and E4. Compared to E3, E4 increases ACD and AD risk and vulnerability to the deleterious cognitive effects of a HFD. The plant compound Xanthohumol (XN) had beneficial effects on cognition and metabolism in C57BL/6J wild-type (WT) male mice put on a HFD at 9 weeks of age for 13 weeks. As the effects of XN in the context of a HFD in older WT, E3, and E4 female and male mice are not known, in the current study male and female WT, E3, and E4 mice were fed a HFD alone or a HFD containing 0.07% XN for 10 or 19 weeks, starting at 6 months of age, prior to the beginning of behavioral and cognitive testing. XN showed sex- and ApoE isoform-dependent effects on cognitive performance. XN-treated E4 and WT, but not E3, mice had higher glucose transporter protein levels in the hippocampus and cortex than HFD-treated mice. E3 and E4 mice had higher glucose transporter protein levels in the hippocampus and lower glucose transporter protein levels in the cortex than WT mice. In the standard experiment, regardless of XN treatment, E4 mice had nearly double as high ceramide and sphingomyelin levels than E3 mice and male mice had higher level of glycosylated ceramide than female mice. When the differential effects of HFD in E3 and E4 males were assessed, the arginine and proline metabolism pathway was affected. In the extended exposure experiment, in E3 males XN treatment affected the arginine and proline metabolism and the glycine, serine, and threonine metabolism. Myristic acid levels were decreased in XN-treated E3 males but not E3 females. These data support the therapeutic potential for XN to ameliorate HFD-induced cognitive impairments and highlight the importance of considering sex and ApoE isoform in determining who might most benefit from this dietary supplement.

E-Learning Impact on Veterinary Medical Student's Mental Health during the COVID-19 Pandemic.

Veterinary medical students are known to have significant levels of mental illness. The COVID-19 pandemic and the shift to online learning have brought increased psychological stress. We used a web-based survey to ask 415 veterinary medical students from Portugal about the impact of the pandemic and online learning on their anxiety levels. Results were analyzed using logistic regressions and Spearman's correlation. Results indicated that 15.4% had no symptoms of anxiety, 39.5% experienced mild anxiety, 21.4% had moderate anxiety, and 23.6% experienced severe anxiety. Having difficulty sleeping, the stress associated with confinement, and family conflicts were risk factors for anxiety, while being male was found to be protective. Most veterinary medical students (77%) were satisfied with online learning. The university's adaptation to online teaching and time spent participating in online classes were significantly associated with anxiety. Due to the known fragility of veterinary medical students' mental health, this group should be monitored and supported closely during life-disrupting events such as public health emergencies.

Impact of Endemic Besnoitiosis on the Performance of a Dairy Cattle Herd.

This study aimed to assess the effect of Besnoitia besnoiti infection on the reproductive and productive performance of a dairy cattle herd. A serological screening was performed by indirect fluorescent antibody test (IFAT) on every animal aged over one year (n = 262). Subsequently, 211 animals were clinically examined, with 96 of those being screened for detection of sclerocysts. The overall seroprevalence was 62.9% (CI95%: 56.1-69.5%). On clinical examination, 7.6% (16/211) of the animals presented chronic skin lesions, and 47.9% (46/96) had sclerocysts. Multivariate logistic regression showed that the time on herd represented a risk factor, and the odds of acquiring the infection increased 1.683× per additional year on herd, ranging from less than a year to 8 years. Seropositivity and the presence of sclerocysts revealed an association with a higher milk somatic cell count, which may have a considerable economic impact on dairy production. Regarding reproductive indicators, no negative impact could be associated with clinical besnoitiosis or positive serological results. In conclusion, our study highlights the need to thoroughly evaluate the economic impact of this emerging disease in dairy herd production to help with decision making at both herd and regional levels, particularly in endemic areas.

Impact of Deficit Irrigation on Grapevine cv. 'Touriga Nacional' during Three Seasons in Douro Region: An Agronomical and Metabolomics Approach.

The introduction of irrigation in vineyards of the Mediterranean basin is a matter of debate, in particular in those of the Douro Demarcated Region (DDR), due to the limited number of available studies. Here, we aimed to perform a robust analysis in three consecutive vintages (2018, 2019, and 2020) on the impact of deficit irrigation on the yield, berry quality traits, and metabolome of cv. 'Touriga Nacional'. Results showed that in the peaks of extreme drought, irrigation at 30% crop evapotranspiration (ETc) (R30) was able to prevent a decay of up to 0.4 MPa of leaf predawn water potential (ΨPd), but irrigation at 70% ETc (R70) did not translate into additional protection against drought stress. Following three seasons of irrigation, the yield was significantly improved in vines irrigated at R30, whereas irrigation at R70 positively affected the yield only in the 2020 season. Berry quality traits at harvest were not significantly changed by irrigation, except for Total Soluble Solids (TSS) in 2018. A UPLC-MS-based targeted metabolomic analysis identified eight classes of compounds, amino acids, phenolic acids, stilbenoid DP1, stilbenoid DP2, flavonols, flavan-3-ols, di-OH- and tri-OH anthocyanins, and showed that anthocyanins and phenolic acids did not change significantly with irrigation. The present study showed that deficit irrigation partially mitigated the severe summer water deficit conditions in the DDR but did not significantly change key metabolites.

SARS-CoV-2 Nsp14 mediates the effects of viral infection on the host cell transcriptome.

Viral infection involves complex set of events orchestrated by multiple viral proteins. To identify functions of SARS-CoV-2 proteins, we performed transcriptomic analyses of cells expressing individual viral proteins. Expression of Nsp14, a protein involved in viral RNA replication, provoked a dramatic remodeling of the transcriptome that strongly resembled that observed following SARS-CoV-2 infection. Moreover, Nsp14 expression altered the splicing of more than 1000 genes and resulted in a dramatic increase in the number of circRNAs, which are linked to innate immunity. These effects were independent of the Nsp14 exonuclease activity and required the N7-guanine-methyltransferase domain of the protein. Activation of the NFkB pathway and increased expression of CXCL8 occurred early upon Nsp14 expression. We identified IMPDH2, which catalyzes the rate-limiting step of guanine nucleotides biosynthesis, as a key mediator of these effects. Nsp14 expression caused an increase in GTP cellular levels, and the effect of Nsp14 was strongly decreased in the presence of IMPDH2 inhibitors. Together, our data demonstrate an unknown role for Nsp14 with implications for therapy.

Viruses are parasites, relying on the cells they infect to make more of themselves. In doing so they change how an infected cell turns its genes on and off, forcing it to build new virus particles and turning off the immune surveillance that would allow the body to intervene. This is how SARS-CoV-2, the virus that causes COVID, survives with a genome that carries instructions to make just 29 proteins. One of these proteins, known as Nsp14, is involved in both virus reproduction and immune escape. Previous work has shown that it interacts with IMPDH2, the cellular enzyme that controls the production of the building blocks of the genetic code. The impact of this interaction is not clear. To find out more, Zaffagni et al. introduced 26 of the SARS-CoV-2 proteins into human cells one at a time. Nsp14 had the most dramatic effect, dialing around 4,000 genes up or down and changing how the cell interprets over 1,000 genes. Despite being just one protein, it mimicked the genetic changes seen during real SARS-CoV-2 infection. Blocking IMPDH2 partially reversed the effects, which suggests that the interaction of Nsp14 with the enzyme might be responsible for the effects of SARS-CoV-2 on the genes of the cell. Understanding how viral proteins affect cells can explain what happens during infection. This could lead to the discovery of new treatments designed to counteract the effects of the virus. Further work could investigate whether interfering with Nsp14 helps cells to overcome infection.

SARS-CoV-2 Nsp14 mediates the effects of viral infection on the host cell transcriptome.

Viral infection involves complex set of events orchestrated by multiple viral proteins. To identify functions of SARS-CoV-2 proteins, we performed transcriptomic analyses of cells expressing individual viral proteins. Expression of Nsp14, a protein involved in viral RNA replication, provoked a dramatic remodeling of the transcriptome that strongly resembled that observed following SARS-CoV-2 infection. Moreover, Nsp14 expression altered the splicing of more than 1,000 genes and resulted in a dramatic increase in the number of circRNAs, which are linked to innate immunity. These effects were independent of the Nsp14 exonuclease activity and required the N7-guanine-methyltransferase domain of the protein. Activation of the NFkB pathway and increased expression of CXCL8 occurred early upon Nsp14 expression. We identified IMPDH2, which catalyzes the rate-limiting step of guanine nucleotides biosynthesis, as a key mediator of these effects. Nsp14 expression caused an increase in GTP cellular levels, and the effect of Nsp14 was strongly decreased in presence of IMPDH2 inhibitors. Together, our data demonstrate an unknown role for Nsp14 with implications for therapy.