Medulloblastoma Spatial Transcriptomics Reveals Tumor Microenvironment Heterogeneity with High-Density Progenitor Cell Regions Correlating with High-Risk Disease.

The tumor microenvironment (TME) of medulloblastoma (MB) influences progression and therapy response, presenting a promising target for therapeutic advances. Prior single-cell analyses have characterized the cellular components of the TME but lack spatial context. To address this, we performed spatial transcriptomic sequencing on sixteen pediatric MB samples obtained at diagnosis, including two matched diagnosis-relapse pairs. Our analyses revealed inter- and intra-tumoral heterogeneity within the TME, comprised of tumor-associated astrocytes (TAAs), macrophages (TAMs), stromal components, and distinct subpopulations of MB cells at different stages of neuronal differentiation and cell cycle progression. We identified dense regions of quiescent progenitor-like MB cells enriched in patients with high-risk (HR) features and an increase in TAAs, TAMs, and dysregulated vascular endothelium following relapse. Our study presents novel insights into the spatial architecture and cellular landscape of the medulloblastoma TME, highlighting spatial patterns linked to HR features and relapse, which may serve as potential therapeutic targets.

Core items to be included in a definition of moderate psoriatic arthritis: literature review and expert opinion.

Evidence-based treatment recommendations for psoriatic arthritis (PsA) suggest that treatment should be individualised but acknowledge the difficulty of correctly defining levels of activity (mild, moderate and severe). The aim of this study was to define the parameters or disease characteristics that should be included in a future definition of moderate PsA. Mixed. methods: (1) literature review to identify previous assessment tools used to classify patients into mild, moderate and severe forms, and (2) survey of rheumatologists, and experts in PsA, to obtain their opinion on the degree of validation and applicability of published definitions and tools, and on the parameters that should be included in a future definition of moderate PsA. We propose eight domains/items to be included in a definition of moderate PsA: number of active joints and inflamed entheses, physician global assessment (by visual analogue scale), dactylitis, body surface area (BSA) affected by psoriasis, psoriasis in special locations, and absence of hip involvement. The Disease Activity Index for Psoriatic Arthritis (DAPSA) score would be supported as part of this definition, as would the Psoriatic Arthritis Impact of Disease (PsAID) index. This study proposes a set of items/domains to be included in a definition of moderate PsA based on literature and expert opinion, which can be the starting point for further development and validation studies of the proposed items.

A retrospective study of deep learning generalization across two centers and multiple models of X-ray devices using COVID-19 chest-X rays.

Generalization of deep learning (DL) algorithms is critical for the secure implementation of computer-aided diagnosis systems in clinical practice. However, broad generalization remains to be a challenge in machine learning. This research aims to identify and study potential factors that can affect the internal validation and generalization of DL networks, namely the institution where the images come from, the image processing applied by the X-ray device, and the type of response function of the X-ray device. For these purposes, a pre-trained convolutional neural network (CNN) (VGG16) was trained three times for classifying COVID-19 and control chest radiographs with the same hyperparameters, but using different combinations of data acquired in two institutions by three different X-ray device manufacturers. Regarding internal validation, the addition of images from an external institution to the training set did not modify the algorithm's internal performance, however, the inclusion of images acquired by a device from a different manufacturer decreased the performance up to 8% (p < 0.05). In contrast, generalization across institutions and X-ray devices with the same type of response function was achieved. Nonetheless, generalization was not observed across devices with different types of response function. This factor was the key impediment to achieving broad generalization in our research, followed by the device's image-processing and the inter-institutional differences, which both reduced generalization performance to 18.9% (p < 0.05), and 9.8% (p < 0.05), respectively. Finally, clustering analysis with features extracted by the CNN was performed, revealing a substantial dependence of feature values extracted by the pre-trained CNN on the X-ray device which acquired the images.

Axonal and Glial PIEZO1 and PIEZO2 Immunoreactivity in Human Clitoral Krause's Corpuscles.

Krause's corpuscles are typical of cutaneous mucous epithelia, like the lip vermillion or the glans clitoridis, and are associated with rapidly adapting low-threshold mechanoreceptors involved in gentle touch or vibration. PIEZO1 and PIEZO2 are transmembrane mechano-gated proteins that form a part of the cationic ion channels required for mechanosensitivity in mammalian cells. They are involved in somatosensitivity, especially in the different qualities of touch, but also in pain and proprioception. In the present study, immunohistochemistry and immunofluorescence were used to analyze the occurrence and cellular location of PIEZO1 and PIEZO2 in human clitoral Krause's corpuscles. Both PIEZO1 and PIEZO2 were detected in Krause's corpuscles in both the axon and the terminal glial cells. The presence of PIEZOs in the terminal glial cells of Kraus's corpuscles is reported here for the first time. Based on the distribution of PIEZO1 and PIEZO2, it may be assumed they could be involved in mechanical stimuli, sexual behavior, and sexual pleasure.

Using Microfluidic Hepatic Spheroid Cultures to Assess Liver Toxicity of T-2 Mycotoxin.

The Fusarium fungi is found in cereals and feedstuffs and may produce mycotoxins, which are secondary metabolites, such as the T-2 toxin (T-2). In this work, we explored the hepatotoxicity of T-2 using microfluidic 3D hepatic cultures. The objectives were: (i) exploring the benefits of microfluidic 3D cultures compared to conventional 3D cultures available commercially (Aggrewell plates), (ii) establishing 3D co-cultures of hepatic cells (HepG2) and stellate cells (LX2) and assessing T-2 exposure in this model, (iii) characterizing the induction of metabolizing enzymes, and (iv) evaluating inflammatory markers upon T-2 exposure in microfluidic hepatic cultures. Our results demonstrated that, in comparison to commercial (large-volume) 3D cultures, spheroids formed faster and were more functional in microfluidic devices. The viability and hepatic function decreased with increasing T-2 concentrations in both monoculture and co-cultures. The RT-PCR analysis revealed that exposure to T-2 upregulates the expression of multiple Phase I and Phase II hepatic enzymes. In addition, several pro- and anti-inflammatory proteins were increased in co-cultures after exposure to T-2.

Alternative CNDOL Fockians for fast and accurate description of molecular exciton properties.

CNDOL is an a priori, approximate Fockian for molecular wave functions. In this study, we employ several modes of singly excited configuration interaction (CIS) to model molecular excitation properties by using four combinations of the one electron operator terms. Those options are compared to the experimental and theoretical data for a carefully selected set of molecules. The resulting excitons are represented by CIS wave functions that encompass all valence electrons in the system for each excited state energy. The Coulomb-exchange term associated to the calculated excitation energies is rationalized to evaluate theoretical exciton binding energies. This property is shown to be useful for discriminating the charge donation ability of molecular and supermolecular systems. Multielectronic 3D maps of exciton formal charges are showcased, demonstrating the applicability of these approximate wave functions for modeling properties of large molecules and clusters at nanoscales. This modeling proves useful in designing molecular photovoltaic devices. Our methodology holds potential applications in systematic evaluations of such systems and the development of fundamental artificial intelligence databases for predicting related properties.

Pediatric Chordoma: A Tale of Two Genomes.

Little is known regarding the genomic alterations in chordoma, with the exception of loss of SMARCB1, a core member of the SWI/SNF complex, in poorly differentiated chordomas. A TBXT duplication and rs2305089 polymorphism, located at 6q27, are known genetic susceptibility loci. A comprehensive genomic analysis of the nuclear and mitochondrial genomes in pediatric chordoma has not yet been reported. In this study, we performed whole exome and mitochondrial DNA (mtDNA) genome sequencing on 29 chordomas from 23 pediatric patients. Findings were compared with that from whole genome sequencing datasets of 80 adult skull base chordoma patients. In the pediatric chordoma cohort, 81% percent of the somatic mtDNA mutations were observed in NADH complex genes, which is significantly enriched compared to the rest of the mtDNA genes (p=0.001). In adult chordomas, mtDNA mutations were also enriched in the NADH complex genes (p<0.0001). Furthermore, a progressive increase in heteroplasmy of non-synonymous mtDNA mutations was noted in patients with multiple tumors (p=0.0007). In the nuclear genome, rare likely germline in-frame indels in ARID1B, a member of the SWI/SNF complex located at 6q25.3, were observed in five pediatric patients (22%) and four patients in the adult cohort (5%). The frequency of rare ARID1B indels in the pediatric cohort is significantly higher than that of the adult cohort (p=0.0236, Fisher's exact test), but they were both significantly higher than that in the ethnicity-matched populations (p<5.9e-07 and p<0.0001174, respectively). Implications: germline ARID1B indels and mtDNA aberrations appear important for chordoma genesis, especially in pediatric chordoma.

Genome-wide association analyses using multi-locus models on bananas (Musa spp.) reveal candidate genes related to morphology, fruit quality, and yield.

Bananas (Musa spp.) are an essential fruit worldwide and rank as the fourth most significant food crop for addressing malnutrition due to their rich nutrients and starch content. The potential of their genetic diversity remains untapped due to limited molecular breeding tools. Our study examined a phenotypically diverse group of 124 accessions from the Colombian Musaceae Collection (CMC) conserved in AGROSAVIA. We assessed 12 traits categorized into morphology, fruit quality, and yield, alongside sequence data. Our sequencing efforts provided valuable insights, with an average depth of about 7X per accession, resulting in 187,133 SNPs against Musa acuminata (A genome) and 220,451 against Musa balbisiana (B genome). Population structure analysis grouped samples into four and five clusters based on the reference genome. By using different association models, we identified marker-trait associations (MTAs). The mixed linear model (MLM) revealed four MTAs, while the BLINK and FarmCPU models identified 82 and 70 MTAs, respectively. We identified 38 and 40 candidate genes in linkage proximity to significant MTAs for the A-genome and B-genome, respectively. Our findings provide insights into the genetic underpinnings of morphology, fruit quality, and yield. Once validated, the SNP markers and candidate genes can potentially drive advancements in genomic-guided breeding strategies to enhance banana crop improvement.

Reduced precipitation can induce ecosystem regime shifts in lakes by increasing internal nutrient recycling.

Eutrophication is a main threat to continental aquatic ecosystems. Prevention and amelioration actions have been taken under the assumption of a stable climate, which needs reconsideration. Here, we show that reduced precipitation can bring a lake ecosystem to a more productive regime even with a decline in nutrient external load. By analyzing time series of several decades in the largest lake of the Iberian Peninsula, we found autocorrelated changes in the variance of state variables (i.e., chlorophyll and oxygen) indicative of a transient situation towards a new ecosystem regime. Indeed, exceptional planktonic diatom blooms have occurred during the last few years, and the sediment record shows a shift in phytoplankton composition and an increase in nutrient retention. Reduced precipitation almost doubled the water residence time in the lake, enhancing the relevance of internal processes. This study demonstrates that ecological quality targets for aquatic ecosystems must be tailored to the changing climatic conditions for appropriate stewardship.

A Dye Uptake Assay to Measure Large-Pore Channel Activity in Trypanosoma cruzi.

Large-pore channels allow the exchange of ions and molecules between the intra- and extracellular compartments. These channels are structures formed by several protein families with little or no evolutionary linkages that include connexins (Cxs), pannexins (Panxs), innexins (Inxs), CALHM1, and LRRC8 proteins. Recently, we have described the unnexins (Unxs) proteins expressed in Trypanosoma cruzi (T. cruzi) that also is like to form large-pore channels at the plasma membrane. In this chapter, we describe a dye uptake method for evaluating the unnexin-formed channel function in T. cruzi, as well as the methods for evaluating their participation in the transformation of trypomastigotes into amastigotes. These methods can facilitate understanding the role of large-pore channels in the parasite's biology.

Cone-Beam Computed Tomography for the Evaluation of Dental Pulp Chamber Volume: Implications for Clinics and Teaching.

The dental pulp chamber volume is a fundamental measurement in the field of endodontics, but also in forensic sciences, teaching and training, or tissue engineering. This study evaluates the precision of cone-beam computed tomography (CBCT) in comparison with computed micro-tomography (micro-CT) in evaluating the pulp chamber volume of the upper central incisors ex vivo. The intra-operator and inter-operator errors were evaluated, and the results for the two techniques were compared with those of a T-test for paired samples. The intra-operator and inter-operator errors were >0.05, indicating adequate reproducibility in each operator and no significant differences between their measurements. On the other hand, no significant differences between the two measurement techniques were found. The present results demonstrate that CBCT is a precise, feasible, and reproducible technique for the evaluation of the dental pulp chamber volume ex vivo. The results provided with this method are useful for different medical domains but also for the teaching and training of undergraduate and postgraduate students. Furthermore, the findings of this study carry significant clinical implications, as the accurate assessment of the pulp chamber volume is critical in the diagnosis and treatment of various endodontic conditions. The ability of CBCT to provide reliable 3D dental anatomy measurements can enhance the planning of endodontic treatments by allowing for a better understanding of the internal tooth morphology. Additionally, the precision and reproducibility of CBCT in assessing the pulp chamber volume can contribute to improved clinical outcomes and reduced complications during endodontic procedures. These findings further support the increasingly vital role of CBCT in modern clinical practice and underscore its value as an indispensable tool in the field of dentistry.

Oral infectivity through carnivorism in murine model of Trypanosoma cruzi infection.

Introduction: Oral transmission of T. cruzi is probably the most frequent transmission mechanism in wild animals. This observation led to the hypothesis that consuming raw or undercooked meat from animals infected with T. cruzi may be responsible for transmitting the infection. Therefore, the general objective of this study was to investigate host-pathogen interactions between the parasite and gastric mucosa and the role of meat consumption from infected animals in the oral transmission of T. cruzi. Methods: Cell infectivity assays were performed on AGS cells in the presence or absence of mucin, and the roles of pepsin and acidic pH were determined. Moreover, groups of five female Balb/c mice were fed with muscle tissue obtained from mice in the acute phase of infection by the clone H510 C8C3hvir of T. cruzi, and the infection of the fed mice was monitored by a parasitemia curve. Similarly, we assessed the infective capacity of T. cruzi trypomastigotes and amastigotes by infecting groups of five mice Balb/c females, which were infected orally using a nasogastric probe, and the infection was monitored by a parasitemia curve. Finally, different trypomastigote and amastigote inoculums were used to determine their infective capacities. Adhesion assays of T. cruzi proteins to AGS stomach cells were performed, and the adhered proteins were detected by western blotting using monoclonal or polyclonal antibodies and by LC-MS/MS and bioinformatics analysis. Results: Trypomastigote migration in the presence of mucin was reduced by approximately 30%, whereas in the presence of mucin and pepsin at pH 3.5, only a small proportion of parasites were able to migrate (∼6%). Similarly, the ability of TCTs to infect AGS cells in the presence of mucin is reduced by approximately 20%. In all cases, 60-100% of the animals were fed meat from mice infected in the acute phase or infected with trypomastigotes or amastigotes developed high parasitemia, and 80% died around day 40 post-infection. The adhesion assay showed that cruzipain is a molecule of trypomastigotes and amastigotes that binds to AGS cells. LC-MS/MS and bioinformatics analysis, also confirmed that transialidase, cysteine proteinases, and gp63 may be involved in TCTs attachment or invasion of human stomach cells because they can potentially interact with different proteins in the human stomach mucosa. In addition, several human gastric mucins have cysteine protease cleavage sites. Discussion: Then, under our experimental conditions, consuming meat from infected animals in the acute phase allows the T. cruzi infection. Similarly, trypomastigotes and amastigotes could infect mice when administered orally, whereas cysteinyl proteinases and trans-sialidase appear to be relevant molecules in this infective process.

Global Safety Assessment of Adverse Events of Special Interest Following 2 Years of Use and 772 Million Administered Doses of mRNA-1273.

Background: Large-scale use of mRNA COVID-19 vaccines during the pandemic was associated with enhanced safety monitoring to ensure accurate and timely review of safety. We reviewed the mRNA-1273 (original strain) safety profile following 2 years of use (>772 million administered doses), primarily focusing on predefined safety topics (ie, adverse events of special interest [AESIs]) proposed in advance of COVID-19 vaccine use. Methods: Cumulative mRNA-1273 safety data were included from spontaneous adverse event (AE) cases reported to Moderna's global safety database between 18 December 2020 and 17 December 2022. Reporting rates of AESIs were calculated per 1 million doses of mRNA-1273 administered. Observed-to-expected (OE) ratios were computed by comparing observed rates of AESIs with the background/expected rate for these events to evaluate potential associations with mRNA-1273. Results: There were 658 759 identified case reports associated with 2 517 669 AEs. Most AEs were nonserious (83.4%; 2 098 954/2 517 669). Overall 0.7% (17 751/2 517 669) were fatal. AESIs represented 13.7% of all AEs (344 921/2 517 669), with reporting rates for most AESIs below the expected background incidence. Exceptions included anaphylaxis (OE ratio 3 days after vaccination, 2.09; 95% CI, 1.93-2.25) and, among individuals aged 12 to 40 years, myocarditis (OE ratio 7 days after any dose, 3.89 [3.50-4.32]; among men after dose 2, 8.57 [6.88-10.68]) and pericarditis (OE ratio 7 days after vaccination, 3.47; 2.89-4.16). Conclusions: This safety analysis of mRNA-1273 identified evidence of increased risk for anaphylaxis, myocarditis, and pericarditis but not for other AESIs identified for enhanced monitoring ahead of COVID-19 vaccine use.

Exploring perceptions of extreme environments and extremophiles in Chilean schoolchildren: an ethnographic study.

Chile is unique because of its diverse extreme environment, ranging from arid climates in the north to polar climates in Patagonia. Microorganisms that live in these environments are called extremophiles, and these habitats experience intense ecosystem changes owing to climate warming. Most studies of extremophiles have focused on their biotechnological potential; however, no study has examined how students describe extremophiles. Therefore, we were interested in answering the following question: How do schoolchildren living in extreme environments describe their environments and extremophiles? We performed an ethnographic study and analyzed the results of 347 representative drawings of participants aged 12-16 years from three schools located in the extreme environments of Chile San Pedro de Atacama (hyper-arid, 2,400 m), Lonquimay (forest, 925 m), and Punta Arenas (sub-Antarctic, 34 m). The social representation approach was used to collect data, and systemic networks were used to organize and systematize the drawings. The study found that, despite differences between extreme environments, certain natural elements, such as trees and the sun, are consistently represented by schoolchildren. The analysis revealed that the urban and rural categories were the two main categories identified. The main systemic networks were rural-sun (21,1%) for hyper-arid areas, urban-tree (14,1%) for forest areas, and urban-furniture (23,4%) for sub-Antarctic areas. When the results were analyzed by sex, we found a statistically significant difference for the rural category in the 7th grade, where girls mentioned being more rural than boys. Students living in hyper-arid areas represented higher extremophile drawings, with 57 extremophiles versus 20 and 39 for students living in sub-Antarctic and forest areas, respectively. Bacteria were extremophiles that were more represented. The results provide evidence that natural variables and semantic features that allow an environment to be categorized as extreme are not represented by children when they are focused on and inspired by the environment in which they live, suggesting that school literacy processes impact representations of their environment because they replicate school textbooks and not necessarily their environment.

NAB2::STAT6 fusions and genome-wide DNA methylation profiling: Predictors of patient outcomes in meningeal solitary fibrous tumors.

Meningeal solitary fibrous tumors (SFT) are rare and have a high frequency of local recurrence and distant metastasis. In a cohort of 126 patients (57 female, 69 male; mean age at surgery 53.0 years) with pathologically confirmed meningeal SFTs with extended clinical follow-up (median 9.9 years; range 15 days-43 years), we performed extensive molecular characterization including genome-wide DNA methylation profiling (n = 80) and targeted TERT promoter mutation testing (n = 98). Associations were examined with NAB2::STAT6 fusion status (n = 101 cases; 51 = ex5-7::ex16-17, 26 = ex4::ex2-3; 12 = ex2-3::exANY/other and 12 = no fusion) and placed in the context of 2021 Central Nervous System (CNS) WHO grade. NAB2::STAT6 fusion breakpoints (fusion type) were significantly associated with metastasis-free survival (MFS) (p = 0.03) and, on multivariate analysis, disease-specific survival (DSS) when adjusting for CNS WHO grade (p = 0.03). DNA methylation profiling revealed three distinct clusters: Cluster 1 (n = 38), Cluster 2 (n = 22), and Cluster 3 (n = 20). Methylation clusters were significantly associated with fusion type (p < 0.001), with Cluster 2 harboring ex4::ex2-3 fusion in 16 (of 20; 80.0%), nearly all TERT promoter mutations (7 of 8; 87.5%), and predominantly an "SFT" histologic phenotype (15 of 22; 68.2%). Clusters 1 and 3 were less distinct, both dominated by tumors having ex5-7::ex16-17 fusion (respectively, 25 of 33; 75.8%, and 12 of 18; 66.7%) and with variable histological phenotypes. Methylation clusters were significantly associated with MFS (p = 0.027), but not overall survival (OS). In summary, NAB2::STAT6 fusion type was significantly associated with MFS and DSS, suggesting that tumors with an ex5::ex16-17 fusion may have inferior patient outcomes. Methylation clusters were significantly associated with fusion type, TERT promoter mutation status, histologic phenotype, and MFS.

Assessment of muscle endocrine function and inflammatory signalling in male school children following a physical activity programme.

BACKGROUND & AIMS: Regular and planned physical activity can diminish the risk of numerous illnesses. However, school children and teenagers often exercise intermittently and for brief periods, restricting potential benefits. Furthermore, previous studies mainly focused on body composition, without providing molecular mechanisms elucidating the role of physical activity in muscle tissue and inflammatory signalling. The objective of this study was to determine the effect of a vigorous physical activity intervention on endocrine muscle function and cytokine output in children. METHODS: 103 boys were divided into two groups: control (n = 51, did not perform additional physical activity) and exercise (n = 52, performed vigorous physical activity). Body composition measurements, endocrine muscle function and inflammatory signalling biomarkers were assessed at enrolment and after 6 months of intervention. RESULTS: No statistical significance was found for fractalkine, oncostatin, EGF, TNF-α and eotaxin. However, LIF, FBAP3, IL-6, FGF21 and IL-15 increased in the exercise group at the end of the protocol, though myostatin got decreased. In contrast, IFN-γ was increased in the exercise group at the beginning and end of the exercise protocol, IL-10 was also increased in this group, IL-1α decreased in the exercise group before and after the exercise protocol, and IP-10 and MCP-1 also decreased in the exercise group. CONCLUSION: It can be affirmed that a physical activity programme for boys was shown to produce changes in body composition (decreased fat mass, increased lean mass) and in markers of endocrine muscle function and cytokine release. It is possible that these changes, if sustained, could reduce the risk of chronic disease.

Lung Inflammatory Phenotype in Mice Deficient in Fibulin-2 and ADAMTS-12.

Interaction between extracellular matrix (ECM) components plays an important role in the regulation of cellular behavior and hence in tissue function. Consequently, characterization of new interactions within ECM opens the possibility of studying not only the functional but also the pathological consequences derived from those interactions. We have previously described the interaction between fibulin2 and ADAMTS-12 in vitro and the effects of that interaction using cellular models of cancer. Now, we generate a mouse deficient in both ECM components and evaluate functional consequences of their absence using different cancer and inflammation murine models. The main findings indicate that mice deficient in both fibulin2 and ADAMTS12 markedly increase the development of lung tumors following intraperitoneal urethane injections. Moreover, inflammatory phenotype is exacerbated in the lung after LPS treatment as can be inferred from the accumulation of active immune cells in lung parenchyma. Overall, our results suggest that protective effects in cancer or inflammation shown by fibulin2 and ADAMTS12 as interactive partners in vitro are also shown in a more realistic in vivo context.

Earliest directly dated rock art from Patagonia reveals socioecological resilience to mid-Holocene climate.

The timing for the evolution of the capacity to inscribe the landscape with rock art has global relevance. While this was an in-built capacity when Homo sapiens first colonized the Americas, the heterogeneous distribution of rock art shows that it was a facultative behavior arising under unknown socioecological conditions. Patagonia was the last region to be explored by humans. While its rock art is globally important, it remains largely undated by absolute methods. We report the earliest set of directly radiocarbon-dated rock art motifs from the archaeological site Cueva Huenul 1 (northwestern Patagonia, Argentina), starting at 8.2 thousand years before the present (ka B.P.), predating previous records by several millennia, and encompassing over 3 ka (~130 human generations). This mid-Holocene "rock art emergence" phase overlaps with extremely arid conditions and a human demographic stasis. We suggest that this diachronic rock art emerged as part of a resilient response to ecological stress by highly mobile and low-density populations.

Tropical tree ectomycorrhiza are distributed independently of soil nutrients.

Mycorrhizae, a form of plant-fungal symbioses, mediate vegetation impacts on ecosystem functioning. Climatic effects on decomposition and soil quality are suggested to drive mycorrhizal distributions, with arbuscular mycorrhizal plants prevailing in low-latitude/high-soil-quality areas and ectomycorrhizal (EcM) plants in high-latitude/low-soil-quality areas. However, these generalizations, based on coarse-resolution data, obscure finer-scale variations and result in high uncertainties in the predicted distributions of mycorrhizal types and their drivers. Using data from 31 lowland tropical forests, both at a coarse scale (mean-plot-level data) and fine scale (20 × 20 metres from a subset of 16 sites), we demonstrate that the distribution and abundance of EcM-associated trees are independent of soil quality. Resource exchange differences among mycorrhizal partners, stemming from diverse evolutionary origins of mycorrhizal fungi, may decouple soil fertility from the advantage provided by mycorrhizal associations. Additionally, distinct historical biogeographies and diversification patterns have led to differences in forest composition and nutrient-acquisition strategies across three major tropical regions. Notably, Africa and Asia's lowland tropical forests have abundant EcM trees, whereas they are relatively scarce in lowland neotropical forests. A greater understanding of the functional biology of mycorrhizal symbiosis is required, especially in the lowland tropics, to overcome biases from assuming similarity to temperate and boreal regions.