PIKFYVE inhibition mitigates disease in models of diverse forms of ALS.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that results from many diverse genetic causes. Although therapeutics specifically targeting known causal mutations may rescue individual types of ALS, these approaches cannot treat most cases since they have unknown genetic etiology. Thus, there is a pressing need for therapeutic strategies that rescue multiple forms of ALS. Here, we show that pharmacological inhibition of PIKFYVE kinase activates an unconventional protein clearance mechanism involving exocytosis of aggregation-prone proteins. Reducing PIKFYVE activity ameliorates ALS pathology and extends survival of animal models and patient-derived motor neurons representing diverse forms of ALS including C9ORF72, TARDBP, FUS, and sporadic. These findings highlight a potential approach for mitigating ALS pathogenesis that does not require stimulating macroautophagy or the ubiquitin-proteosome system.

Single-neuron sequencing analysis of L1 retrotransposition and somatic mutation in the human brain.

A major unanswered question in neuroscience is whether there exists genomic variability between individual neurons of the brain, contributing to functional diversity or to an unexplained burden of neurological disease. To address this question, we developed a method to amplify genomes of single neurons from human brains. Because recent reports suggest frequent LINE-1 (L1) retrotransposition in human brains, we performed genome-wide L1 insertion profiling of 300 single neurons from cerebral cortex and caudate nucleus of three normal individuals, recovering >80% of germline insertions from single neurons. While we find somatic L1 insertions, we estimate <0.6 unique somatic insertions per neuron, and most neurons lack detectable somatic insertions, suggesting that L1 is not a major generator of neuronal diversity in cortex and caudate. We then genotyped single cortical cells to characterize the mosaicism of a somatic AKT3 mutation identified in a child with hemimegalencephaly. Single-neuron sequencing allows systematic assessment of genomic diversity in the human brain.

Novel Z-DNA binding domains in giant viruses.

Z-nucleic acid structures play vital roles in cellular processes and have implications in innate immunity due to their recognition by Zα domains containing proteins (Z-DNA/Z-RNA binding proteins, ZBPs). Although Zα domains have been identified in six proteins, including viral E3L, ORF112, and I73R, as well as, cellular ADAR1, ZBP1, and PKZ, their prevalence across living organisms remains largely unexplored. In this study, we introduce a computational approach to predict Zα domains, leading to the revelation of previously unidentified Zα domain-containing proteins in eukaryotic organisms, including non-metazoan species. Our findings encompass the discovery of new ZBPs in previously unexplored giant viruses, members of the Nucleocytoviricota phylum. Through experimental validation, we confirm the Zα functionality of select proteins, establishing their capability to induce the B-to-Z conversion. Additionally, we identify Zα-like domains within bacterial proteins. While these domains share certain features with Zα domains, they lack the ability to bind to Z-nucleic acids or facilitate the B-to-Z DNA conversion. Our findings significantly expand the ZBP family across a wide spectrum of organisms and raise intriguing questions about the evolutionary origins of Zα-containing proteins. Moreover, our study offers fresh perspectives on the functional significance of Zα domains in virus sensing and innate immunity and opens avenues for exploring hitherto undiscovered functions of ZBPs.

Z-RNA biology: a central role in the innate immune response?

Z-RNA is a higher-energy, left-handed conformation of RNA, whose function has remained elusive. A growing body of work alludes to regulatory roles for Z-RNA in the immune response. Here, we review how Z-RNA features present in cellular RNAs-especially containing retroelements-could be recognized by a family of winged helix proteins, with an impact on host defense. We also discuss how mutations to specific Z-contacting amino acids disrupt their ability to stabilize Z-RNA, resulting in functional losses. We end by highlighting knowledge gaps in the field, which, if addressed, would significantly advance this active area of research.

Zα Domain of ADAR1 Binds to an A-Form-like Nucleic Acid Duplex with Low Micromolar Affinity.

The left-handed Z-conformation of nucleic acids can be adopted by both DNA and RNA when bound by Zα domains found within a variety of viral and innate immune response proteins. While Z-form adoption is preferred by certain sequences, such as the commonly studied (CpG)n repeats, Zα has been reported to bind to a wide range of sequence contexts. Studying how Zα interacts with B-/A-form helices prior to their conversion to the Z-conformation is challenging as binding coincides with Z-form adoption. Here, we studied the binding of Zα fromHomo sapiens ADAR1 to a locked "A-type" version of the (CpG)3 construct (LNA (CpG)3) where the sugar pucker is locked into the C3'-endo/C2'-exo conformation, which prevents the duplex from adopting the alternating C2'/C3'-endo sugar puckers found in the Z-conformation. Using NMR and other biophysical techniques, we find that ZαADAR1 binds to the LNA (CpG)3 using a similar interface as for Z-form binding, with a dissociation constant (KD) of ∼4 µM. In contrast to Z-DNA/Z-RNA, where two ZαADAR1 bind to every 6 bp stretch, our data suggests that ZαADAR1 binds to multiple LNA molecules, indicating a completely different binding mode. Because ZαADAR1 binds relatively tightly to a non-Z-form model, its binding to B/A-form helices may need to be considered when experiments are carried out which attempt to identify the Z-form targets of Zα domains. The use of LNA constructs may be beneficial in experiments where negative controls for Z-form adoption are needed.

Z-Form Adoption of Nucleic Acid is a Multi-Step Process Which Proceeds through a Melted Intermediate.

The left-handed Z-conformation of nucleic acids can be adopted by both DNA and RNA when bound by Zα domains found within a variety of innate immune response proteins. Zα domains stabilize this higher-energy conformation by making specific interactions with the unique geometry of Z-DNA/Z-RNA. However, the mechanism by which a right-handed helix contorts to become left-handed in the presence of proteins, including the intermediate steps involved, is poorly understood. Through a combination of nuclear magnetic resonance (NMR) and other biophysical measurements, we have determined that in the absence of Zα, under low salt conditions at room temperature, d(CpG) and r(CpG) constructs show no observable evidence of transient Z-conformations greater than 0.5% on either the intermediate or slow NMR time scales. At higher temperatures, we observed a transient unfolded intermediate. The ease of melting a nucleic acid duplex correlates with Z-form adoption rates in the presence of Zα. The largest contributing factor to the activation energies of Z-form adoption as calculated by Arrhenius plots is the ease of flipping the sugar pucker, as required for Z-DNA and Z-RNA. Together, these data validate the previously proposed "zipper model" for Z-form adoption in the presence of Zα. Overall, Z-conformations are more likely to be adopted by double-stranded DNA and RNA regions flanked by less stable regions and by RNAs experiencing torsional/mechanical stress.

Genetic and pharmacological PARP inhibition reduces axonal degeneration in C. elegans models of ALS.

Axonal degeneration is observed in early stages of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). This degeneration generally precedes apoptosis and therefore may be a promising therapeutic target. An increasing number of genes have been identified to actively regulate axonal degeneration and regeneration; however, only a few potential therapeutic targets have been identified in the context of neurodegenerative diseases. Here we investigate DLK-1, a major axonal regeneration pathway and its contribution to axonal degeneration phenotypes in several Caenorhabditis elegans ALS models. From this pathway, we identified the poly (ADP-ribose) (PAR) polymerases (PARP) PARP-1 and PARP-2 as the most consistent modifiers of axonal degeneration in our models of ALS. Genetic and pharmacological inhibition of PARP-1 and PARP-2 reduces axonal degeneration and improves related motor phenotypes.

Expectations and outcomes of varying treatment strategies for CML presenting during pregnancy.

Diagnosing chronic myeloid leukaemia (CML) during pregnancy is rare. Tyrosine kinase inhibitors (TKIs) have traditionally been contraindicated owing to their teratogenicity. Management decisions should consider the risks to mother and foetus of uncontrolled disease and teratogenic medications. Further cases are required to build upon the paucity of current literature. We report 22 cases of CML diagnosed during pregnancy from 2002 to date. Twenty-one pregnancies resulted in healthy babies and one patient miscarried. Some patients remained untreated throughout pregnancy but the majority received one or both of interferon-α and leucapheresis. One patient was started on imatinib at Week 26, and one on hydroxycarbamide in the third trimester. We report haematological parameters during pregnancy to provide clinicians with realistic expectations of management. There were no fetal abnormalities related to treatment during pregnancy. Seventeen patients achieved at least major molecular response on first-line TKI. A diagnosis of CML during pregnancy can be managed without significant consequences for mother or child. Leucapheresis and interferon-α are generally safe throughout pregnancy. Despite having been avoided previously, there is growing evidence that certain TKIs may be used in particular circumstances during the later stages of pregnancy. Future work should aim to further elucidate this safety profile.

Early-career general practitioners' antibiotic prescribing for acute infections: a systematic review.

BACKGROUND: Antimicrobial resistance is a worldwide threat, exacerbated by inappropriate prescribing. Most antibiotic prescribing occurs in primary care. Early-career GPs are important for the future of antibiotic prescribing and curbing antimicrobial resistance. OBJECTIVES: To determine antibiotic prescribing patterns by early-career GPs for common acute infections. METHODS: A systematic literature search was conducted using PubMed, Embase and Scopus. Two authors independently screened abstracts and full texts for inclusion. Primary outcomes were antibiotic prescribing rates for common acute infections by GPs with experience of 10 years or less. Secondary outcomes were any associations between working experience and antibiotic prescribing. RESULTS: Of 1483 records retrieved, we identified 41 relevant studies. Early-career GPs were less likely to prescribe antibiotics compared with their more experienced colleagues (OR range 0.23-0.67). Their antibiotic prescribing rates for 'any respiratory condition' ranged from 14.6% to 52%, and for upper respiratory tract infections from 13.5% to 33%. Prescribing for acute bronchitis varied by country, from 15.9% in Sweden to 26% in the USA and 63%-73% in Australia. Condition-specific data for all other included acute infections, such as sinusitis and acute otitis media, were limited to the Australian context. CONCLUSIONS: Early-career GPs prescribe fewer antibiotics than later-career GPs. However, there are still significant improvements to be made for common acute conditions, as their prescribing is higher than recommended benchmarks. Addressing antimicrobial resistance requires an ongoing worldwide effort and early-career GPs should be the target for long-term change.

Laser Measurement of Anomalous Electron Diffusion in a Crossed-Field Plasma.

The anomalous diffusion of particles and energy in magnetized plasma systems is a widespread phenomenon that can adversely impact their operation and preclude predictive models. In this Letter, this diffusion is characterized noninvasively in a low-temperature, Hall-type plasma. Laser-induced fluorescence and incoherent Thomson scattering measurements are combined with a 1D generalized Ohm's law to infer the time-averaged inverse Hall parameter, a transport coefficient that governs cross-field diffusion. While the measured diffusion profile agrees with model-based estimates in magnitude, the measurements do not exhibit the steep "transport barrier" typically imposed in models. Instead, these results show that the electric field is primarily driven by a diamagnetic contribution due to the large peak electron temperature exceeding 75 eV. This finding motivates a reconsideration of nonclassical energy transport across field lines in low-temperature plasmas.

Structural and chemical properties of anion exchanged CsPb(Br(1-x)Clx)3heterostructured perovskite nanowires imaged by nanofocused x-rays.

Over the last years metal halide perovskites have demonstrated remarkable potential for integration in light emitting devices. Heterostructures allow for tunable bandgap depending on the local anion composition, crucial for optoelectronic devices, but local structural effects of anion exchange in single crystals is not fully understood. Here, we investigate how the anion exchange of CsPbBr3nanowires fully and locally exposed to HCl vapor affects the local crystal structure, using nanofocused x-rays. We study the nanoscale composition and crystal structure as function of HCl exposure time and demonstrate the correlation of anion exchange with changes in the lattice parameter. The local composition was measured by x-ray fluorescence and x-ray diffraction, with general agreement of both methods but with much less variation using latter. The heterostructured nanowires exhibit unintentional gradients in composition, both axially and radially. Ferroelastic domains are observed for all HCl exposure times, and the magnitude of the lattice tilt at the domain walls scales with the Cl concentration.

Chemical and genetic rescue of in vivo progranulin-deficient lysosomal and autophagic defects.

In 2006, GRN mutations were first linked to frontotemporal dementia (FTD), the leading cause of non-Alzheimer dementias. While much research has been dedicated to understanding the genetic causes of the disease, our understanding of the mechanistic impacts of GRN deficiency has only recently begun to take shape. With no known cure or treatment available for GRN-related FTD, there is a growing need to rapidly advance genetic and/or small-molecule therapeutics for this disease. This issue is complicated by the fact that, while lysosomal dysfunction seems to be a key driver of pathology, the mechanisms linking a loss of GRN to a pathogenic state remain unclear. In our attempt to address these key issues, we have turned to the nematode, Caenorhabditis elegans, to model, study, and find potential therapies for GRN-deficient FTD. First, we show that the loss of the nematode GRN ortholog, pgrn-1, results in several behavioral and molecular defects, including lysosomal dysfunction and defects in autophagic flux. Our investigations implicate the sphingolipid metabolic pathway in the regulation of many of the in vivo defects associated with pgrn-1 loss. Finally, we utilized these nematodes as an in vivo tool for high-throughput drug screening and identified two small molecules with potential therapeutic applications against GRN/pgrn-1 deficiency. These compounds reverse the biochemical, cellular, and functional phenotypes of GRN deficiency. Together, our results open avenues for mechanistic and therapeutic research into the outcomes of GRN-related neurodegeneration, both genetic and molecular.

Sustaining attention in affective contexts during adolescence: age-related differences and association with elevated symptoms of depression and anxiety.

Sustained attention, a key cognitive skill that improves during childhood and adolescence, tends to be worse in some emotional and behavioural disorders. Sustained attention is typically studied in non-affective task contexts; here, we used a novel task to index performance in affective versus neutral contexts across adolescence (N = 465; ages 11-18). We asked whether: (i) performance would be worse in negative versus neutral task contexts; (ii) performance would improve with age; (iii) affective interference would be greater in younger adolescents; (iv) adolescents at risk for depression and higher in anxiety would show overall worse performance; and (v) would show differential performance in negative contexts. Results indicated that participants performed more poorly in negative contexts and showed age-related performance improvements. Those at risk of depression performed more poorly than those at lower risk. However, there was no difference between groups as a result of affective context. For anxiety there was no difference in performance as a function of severity. However, those with higher anxiety showed less variance in their reaction times to negative stimuli than those with lower anxiety. One interpretation is that moderate levels of emotional arousal associated with anxiety make individuals less susceptible to the distracting effects of negative stimuli.

Association of HER2DX with pathological complete response and survival outcomes in HER2-positive breast cancer.

BACKGROUND: The HER2DX genomic test predicts pathological complete response (pCR) and survival outcome in early-stage HER2-positive (HER2+) breast cancer. Here, we evaluated the association of HER2DX scores with (i) pCR according to hormone receptor status and various treatment regimens, and (ii) survival outcome according to pCR status. MATERIALS AND METHODS: Seven neoadjuvant cohorts with HER2DX and clinical individual patient data were evaluated (DAPHNe, GOM-HGUGM-2018-05, CALGB-40601, ISPY-2, BiOnHER, NEOHER and PAMELA). All patients were treated with neoadjuvant trastuzumab (n = 765) in combination with pertuzumab (n = 328), lapatinib (n = 187) or without a second anti-HER2 drug (n = 250). Event-free survival (EFS) and overall survival (OS) outcomes were available in a combined series of 268 patients (i.e. NEOHER and PAMELA) with a pCR (n = 118) and without a pCR (n = 150). Cox models were adjusted to evaluate whether HER2DX can identify patients with low or high risk beyond pCR status. RESULTS: HER2DX pCR score was significantly associated with pCR in all patients [odds ratio (OR) per 10-unit increase = 1.59, 95% confidence interval 1.43-1.77; area under the ROC curve = 0.75], with or without dual HER2 blockade. A statistically significant increase in pCR rate due to dual HER2 blockade over trastuzumab-only was observed in HER2DX pCR-high tumors treated with chemotherapy (OR = 2.36 (1.09-5.42). A statistically significant increase in pCR rate due to multi-agent chemotherapy over a single taxane was observed in HER2DX pCR-medium tumors treated with dual HER2 blockade (OR = 3.11, 1.54-6.49). The pCR rates in HER2DX pCR-low tumors were ≤30.0% regardless of treatment administered. After adjusting by pCR status, patients identified as HER2DX low-risk had better EFS (P < 0.001) and OS (P = 0.006) compared with patients with HER2DX high-risk. CONCLUSIONS: HER2DX pCR score and risk score might help identify ideal candidates to receive neoadjuvant dual HER2 blockade in combination with a single taxane in early-stage HER2+ breast cancer.

Chromatin remodeller CHD7 is required for GABAergic neuron development by promoting PAQR3 expression.

Mutations in the chromatin remodeller-coding gene CHD7 cause CHARGE syndrome (CS). CS features include moderate to severe neurological and behavioural problems, clinically characterized by intellectual disability, attention-deficit/hyperactivity disorder and autism spectrum disorder. To investigate the poorly characterized neurobiological role of CHD7, we here generate a zebrafish chd7-/- model. chd7-/- mutants have less GABAergic neurons and exhibit a hyperactivity behavioural phenotype. The GABAergic neuron defect is at least in part due to downregulation of the CHD7 direct target gene paqr3b, and subsequent upregulation of MAPK/ERK signalling, which is also dysregulated in CHD7 mutant human cells. Through a phenotype-based screen in chd7-/- zebrafish and Caenorhabditis elegans, we show that the small molecule ephedrine restores normal levels of MAPK/ERK signalling and improves both GABAergic defects and behavioural anomalies. We conclude that chd7 promotes paqr3b expression and that this is required for normal GABAergic network development. This work provides insight into the neuropathogenesis associated with CHD7 deficiency and identifies a promising compound for further preclinical studies.

False-Positive and False-Negative Contrast-enhanced Mammograms: Pitfalls and Strategies to Improve Cancer Detection.

Contrast-enhanced mammography (CEM) is a relatively new breast imaging modality that uses intravenous contrast material to increase detection of breast cancer. CEM combines the structural information of conventional mammography with the functional information of tumor neovascularity. Initial studies have demonstrated that CEM and MRI perform with similar accuracies, with CEM having a slightly higher specificity (fewer false positives), although larger studies are needed. There are various reasons for false positives and false negatives at CEM. False positives at CEM can be caused by benign lesions with vascularity, including benign tumors, infection or inflammation, benign lesions in the skin, and imaging artifacts. False negatives at CEM can be attributed to incomplete or inadequate visualization of lesions, marked background parenchymal enhancement (BPE) obscuring cancer, lack of lesion contrast enhancement due to technical issues or less-vascular cancers, artifacts, and errors of lesion perception or characterization. When possible, real-time interpretation of CEM studies is ideal. If additional views are necessary, they may be obtained while contrast material is still in the breast parenchyma. Until recently, a limitation of CEM was the lack of CEM-guided biopsy capability. However, in 2020, the U.S. Food and Drug Administration cleared two devices to support CEM-guided biopsy using a stereotactic biopsy technique. The authors review various causes of false-positive and false-negative contrast-enhanced mammograms and discuss strategies to reduce these diagnostic errors to improve cancer detection while mitigating unnecessary additional imaging and procedures. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Outcomes of complex colorectal polyps managed by multi-disciplinary team strategies-a multi-centre observational study.

PURPOSE: Team management strategies for complex colorectal polyps are recommended by professional guidelines. Multi-disciplinary meetings are used across the UK with limited information regarding their impact. The aim of this multi-centre observational study was to assess procedures and outcomes of patients managed using these approaches. METHOD: This was a retrospective, observational study of patients managed by six UK sites. Information was collected regarding procedures and outcomes including length of stay, adverse events, readmissions and cancers. RESULTS: Two thousand one hundred ninety-two complex polyps in 2109 patients were analysed with increasing referrals annually. Most presented symptomatically and the mean polyp size was 32.1 mm. Primary interventions included endoscopic therapy (75.6%), conservative management (8.3%), colonic resection (8.1%), trans-anal surgery (6.8%) or combined procedures (1.1%). The number of primary colonic resections decreased over the study period without a reciprocal increase in secondary procedures or recurrence. Secondary procedures were required in 7.8%. The median length of stay for endoscopic procedures was 0 days with 77.5% completed as day cases. Median length of stay was 5 days for colonic resections. Overall adverse event and 30-day readmission rates were 9.0% and 3.3% respectively. Malignancy was identified in 8.8%. Benign polyp recurrence occurred in 13.1% with a median follow up of 30.4 months. Screening detected lesions were more likely to undergo bowel resection. Colonic resection was associated with longer stays, higher adverse events and more cancers on final histology. CONCLUSION: Multi-disciplinary team management of complex polyps is safe and effective. Standardisation of organisation and quality monitoring is needed to continue positive effects on outcomes and services.

C. elegans neurons jettison protein aggregates and mitochondria under neurotoxic stress.

The toxicity of misfolded proteins and mitochondrial dysfunction are pivotal factors that promote age-associated functional neuronal decline and neurodegenerative disease. Accordingly, neurons invest considerable cellular resources in chaperones, protein degradation, autophagy and mitophagy to maintain proteostasis and mitochondrial quality. Complicating the challenges of neuroprotection, misfolded human disease proteins and mitochondria can move into neighbouring cells via unknown mechanisms, which may promote pathological spread. Here we show that adult neurons from Caenorhabditis elegans extrude large (approximately 4 µm) membrane-surrounded vesicles called exophers that can contain protein aggregates and organelles. Inhibition of chaperone expression, autophagy or the proteasome, in addition to compromising mitochondrial quality, enhances the production of exophers. Proteotoxically stressed neurons that generate exophers subsequently function better than similarly stressed neurons that did not produce exophers. The extruded exopher transits through surrounding tissue in which some contents appear degraded, but some non-degradable materials can subsequently be found in more remote cells, suggesting secondary release. Our observations suggest that exopher-genesis is a potential response to rid cells of neurotoxic components when proteostasis and organelle function are challenged. We propose that exophers are components of a conserved mechanism that constitutes a fundamental, but formerly unrecognized, branch of neuronal proteostasis and mitochondrial quality control, which, when dysfunctional or diminished with age, might actively contribute to pathogenesis in human neurodegenerative disease and brain ageing.

Characteristics and Outcomes of Prehospital Tourniquet Use for Trauma in the United States.

INTRODUCTION: The use of the extremity tourniquet in military environments has reduced preventable deaths due to exsanguinating hemorrhage, leading to increased use in civilian settings. However, the outcomes of contemporary prehospital tourniquet use in civilian settings are not well-described nationally. The objective of this study was to describe the characteristics and outcomes following prehospital tourniquet use by emergency medical services (EMS) in the United States. METHODS: All trauma activations reported to the National EMS Information System 2019 (NEMSIS) were included. Patients who had ≥1 tourniquet applied were identified. Descriptive analyses were used to compare characteristics between tourniquet and no-tourniquet cohorts. Coarsened exact matching was performed to generate a k2k match (on age, sex, lowest-systolic blood pressure, initial patient acuity, provider's initial impression, injury mechanism, and presence of upper/lower extremity injuries) and used to compare outcomes. Trauma patients who may have potentially benefited from tourniquet application (extremity injury, shock index ≥1 and no documented tourniquet application) were identified. RESULTS: A total of 7,161 tourniquets were applied among 4,571,379 trauma activations (1.6/1000 activations). Patients in the tourniquet cohort were younger (40 ± 18 vs 52 ± 26 mean ± SD years), more hypotensive (16.1% vs. 2.5%) and had higher initial acuity (65.0% critical/emergent vs. 20.6%) [p < 0.01 for all]. A total of 7,074 patients in the tourniquet cohort were matched with 7,074 patients in the non-tourniquet cohort. Post-match analysis revealed that the patients in tourniquet cohort had a higher final acuity (80.8% vs. 75.0%, p < 0.01), lower scene-time (15.4 ± 13.6 vs. 17.0 ± 14.2 mean ± SD minutes, p < 0.01), and higher survival-to-hospital (83.6% vs. 75.1%, p < 0.01). A total of 141,471 trauma patients who may have potentially benefited from tourniquet application were identified. CONCLUSION: Prehospital tourniquet use by EMS in the United States is associated with lower scene-time and improved survivability to hospital. Results indicate that patients might benefit from wider tourniquet use in the civilian prehospital setting.

Structure and Formation of Z-DNA and Z-RNA.

Despite structural differences between the right-handed conformations of A-RNA and B-DNA, both nucleic acids adopt very similar, left-handed Z-conformations. In contrast to their structural similarities and sequence preferences, RNA and DNA exhibit differences in their ability to adopt the Z-conformation regarding their hydration shells, the chemical modifications that promote the Z-conformation, and the structure of junctions connecting them to right-handed segments. In this review, we highlight the structural and chemical properties of both Z-DNA and Z-RNA and delve into the potential factors that contribute to both their similarities and differences. While Z-DNA has been extensively studied, there is a gap of knowledge when it comes to Z-RNA. Where such information is lacking, we try and extend the principles of Z-DNA stability and formation to Z-RNA, considering the inherent differences of the nucleic acids.