Biology subjects

Lopez, A.

Publications and source records attributed to Lopez, A..

At least 37 records · Page 2Linked to original sources

bioRxiv2025

The essential co-chaperone Sgt1 regulates client dwell time in the Hsp90 chaperone cycle

The Hsp90 machinery is the most complex chaperone system in the eukaryotic cell. It is characterized by numerous co-chaperones that modulate the function of Hsp90. In S. cerevisiae, most of these cofactors can be deleted without affecting viability. Of the three essential ones, only the function of Sgt1 remained enigmatic. Our in vivo and in vitro experiments define key structural elements and determine the essential function of Sgt1 in the chaperoning of client proteins. We show that yeast Sgt1 exhibits a unique binding mode to Hsp90. The simultaneous interaction of Sgt1 with Hsp90 and client proteins enhances client maturation efficiency. Specifically, Sgt1 stabilizes Hsp90-client complexes and prevents their dissociation by the co-chaperone Aha1. Together, our findings reveal a distinct regulatory mechanism of the Hsp90 function, highlighting Sgt1 as a critical modulator of chaperone cycle progression.

biochemistry↗

bioRxiv2025

Deep Mutational Scanning Reveals EGFR Mutations Conferring Resistance to the 4th-generation EGFR tyrosine kinase inhibitor BLU-945

IntroductionOsimertinib, a covalent third-generation EGFR tyrosine kinase inhibitor (TKI) is the first-line standard of care for EGFR L858R and ex19del lung adenocarcinoma; however, tumors frequently acquire resistance through second-site mutations. Fourth-generation inhibitors designed to overcome common second-site resistance liabilities are in clinical development. MethodsWe performed deep mutational scanning (DMS) of the EGFR kinase domain in the context of an EGFR L858R driver mutation by transducing Ba/F3 cells with a saturation library of [~]17,000 EGFR L858R kinase domain variants. Ba/F3 cells expressing the DMS library were exposed to either osimertinib or BLU-945 to select for escape mutations. ResultsL718X mutations were enriched across all conditions as well as mutations private to BLU-945 treated samples including K714R, K716T, L718V, T725M, K728E, K754E/N, N771S/T, T783I, Q791L/K, G863S, S895N, K929I, and M971L. In silico pairwise comparisons of resistance profiles between each single agent condition suggested that combination treatment with osimertinib and BLU-945 would effectively suppress orthogonal resistance mechanisms, apart from L718X. A secondary DMS screen with osimertinib and BLU-945 in combination exclusively enriched for L718X mutations. L718X mutations were present in two patients treated with BLU-945 at our institution. One patient with both EGFR L858R and L718Q mutations prior to treatment was noted to have early progression. A second patient with EGFR L858R, T790M, and C797S at the time of enrollment acquired an L718V mutation at progression. ConclusionsThis study underscores the utility of comprehensive resistance profiles of single compounds, which can be used to predict the emergence of clinical resistance mutations and to devise combination treatments designed to suppress clonal escape.

cancer biology↗

bioRxiv2025

Sex-specific effects of appetite suppressants and stereotypy in rats

This study investigated the sex-specific effects of commonly prescribed appetite suppressants on body weight and the manifestation of motor side effects, specifically stereotypy. Employing video recordings and DeepLabCut (DLC) for precise behavioral quantification, we analyzed stereotypy, defined as purposeless, repetitive motor behaviors, in male and female rats. Under control (saline) conditions, male rats exhibited a greater propensity for weight gain compared to females. However, in contrast, female rats demonstrated greater and more homogenous weight loss than males following the administration of diethylpropion and tesofensine. Phentermine and mazindol induced comparable weight loss in both sexes, whereas cathine elicited weight reduction exclusively in males. 5-HTP and d-amphetamine administration only prevented weight gain relative to controls. Analysis of motor side effects revealed that drugs primarily targeting dopamine pathways - specifically, phentermine, mazindol, diethylpropion, cathine, and d-amphetamine - induced pronounced stereotypies, particularly head-weaving, in both sexes. Interestingly, tesofensine elicited head-weaving behavior exclusively in female subjects, albeit to a lesser extent than that observed with other dopaminergic agents; conversely, tesofensine was most frequently associated with orolingual dyskinesia. Moreover, one of the most potent forms of stereotypy--backward locomotion, here referred to as "moonwalking"--was sporadically observed only following the administration of phentermine, diethylpropion, cathine, and mazindol, with diethylpropion inducing it most frequently. Male subjects treated with these same drugs exhibited an unexpected effect: spontaneous ejaculations, potentially attributable to the combined effects on dopamine and serotonin signaling in brain regions regulating sexual function. Network analysis and Markov transition matrices revealed distinct behavioral profiles associated with head-weaving, which emerged as the dominant attractor state, suggesting potential mechanistic differences among these drugs. Collectively, this study provides a valuable database characterizing the behavioral side effects of appetite suppressants.

neuroscience↗

bioRxiv2025

Single-cell transcriptional profiling reveals a novel RAB13+ endothelial subpopulation and profibrotic mesenchymal cells in the aged human bone marrow

The bone marrow (BM) microenvironment plays a crucial role in regulating hematopoiesis, yet the molecular changes associated with aging in humans remain poorly understood. Using single-cell RNA sequencing, we uncovered transcriptional shifts in BM endothelial cells (EC) and mesenchymal stem cells (MSC) during aging. Aged sinusoidal EC exhibited a prothrombotic phenotype with compromised mitochondrial and vascular function. Additionally, we identified a novel arterial EC subset, emerging in aged individuals, characterized by RAB13 expression and associated with transcriptional regulatory processes. MSC from aged subjects displayed impaired matrix remodeling and epithelial-mesenchymal transition, driven partly by a subpopulation of THY1+ profibrotic cells absent in younger individuals. Finally, immunofluorescent imaging and spatial transcriptomics confirmed the presence of these aging-associated cells in BM samples from aged individuals. In summary, this work provides a comprehensive view of the transcriptional landscape, cellular interactions, and spatial organization of aged EC and MSC, offering novel insights and potential targets that could be exploited for preventing age-associated changes in humans. TeaserAging reshapes the bone marrow with emergence of RAB13+ endothelial cells and profibrotic stromal cells altering tissue function.

molecular biology↗

bioRxiv2024

A complete approach for circRNA therapeutics from purification to lyophilized delivery using novel ionizable lipids

Circular RNA (circRNA) has gained significant attention as a potential therapeutic tool due to its remarkable stability and resistance to degradation by exonucleases. However, scalable and efficient methods for purification and delivery remain critical challenges that must be addressed. In this study, we developed and evaluated an optimized affinity chromatography method using Oligo(dT) columns for the purification of circRNA, achieving high yield and purity comparing with high-performance liquid chromatography. Additionally, we investigated the in vivo efficacy of circRNA-Oligo(dT) encapsulated in lipid nanoparticles (LNPs) formulated with emerging STAAR ionizable lipids, including CP-LC-0867 and CP-LC-0729. Our results showed that LNPs formulated with CP-LC-0867 consistently produced higher protein expression compared to SM-102, with sustained luciferase activity observed over a 14-day period. Furthermore, we assessed the lyophilization potential of LNP-circRNA-Oligo(dT) using CP-LC-0729 to extend shelf life and eliminate the need for ultra-low temperature storage. Remarkably, the lyophilized LNPs exhibited no significant differences in protein expression compared to their non-lyophilized counterparts, demonstrating that lyophilization is a viable strategy for extending the storage and transport of circRNA therapies. These findings underscore the potential of optimized new ionizable lipids, improved purification strategies, and lyophilization techniques to enhance the scalability, stability, and practical application of circRNA therapies. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=91 SRC="FIGDIR/small/620632v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@8bb7eeorg.highwire.dtl.DTLVardef@d8a1eeorg.highwire.dtl.DTLVardef@6f359forg.highwire.dtl.DTLVardef@1295d05_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

Multicomponent Thiolactone-Based Ionizable Lipid Screening Platform for an Efficient and Tunable mRNA Delivery to the Lungs

Ionizable lipids are an essential component of lipid nanoparticles (LNPs) for an efficient mRNA delivery. However, optimizing their chemical structures for high protein expression, efficient endosomal escape, and selective organ targeting remains challenging due to complex structure-activity relationships and multistep synthesis. In this study, we introduce a rapid, high-throughput platform for screening ionizable lipids using a two-step, scalable synthesis involving a one-pot 3-component click-like reaction. This method, herein known as the STAAR approach, standing for Sequential Thiolactone Amine Acrylate Reaction, allowed for the combinatorial synthesis and in vivo screening of 91 novel lipids, followed by a structure-activity study. This led to the development of CP-LC-0729, an ionizable lipid that significantly surpasses the benchmark in protein expression while showing no in vivo toxicity. Additionally, the STAAR lipid platform was further validated by incorporating a one-step strategy to yield a permanently cationic lipid which was tested following a fifth-lipid formulation strategy. The in vivo results showed a highly selective lung delivery with a 32-fold increase in protein expression, outperforming current endogenous targeting strategies. All these findings underscore the potential of lipid CP-LC-0729 and the STAAR lipid platform in advancing the efficiency and specificity of mRNA delivery systems, while also advancing the development of new ionizable lipids.

biochemistry↗

bioRxiv2024

A combinatorial approach to ALS therapies in the PrP.TDP43-315 model of ALS; complications and tribulations

Effective treatment for sporadic amyotrophic lateral sclerosis has been steadily advancing towards combinatorial therapies. For many years, riluzole was the only approved drug and it offered modest benefits. In 2017, edaravone was approved for ALS and became the first drug to be used in combination with riluzole. In the present study, we have attempted to build on the concepts of combinatorial therapy by testing novel drug combinations in a transgenic mouse model. Mice that express A315T mutant TDP43, using the mouse prion promoter, have been reported to develop many of the symptoms of ALS, including paralysis. Aberrant TDP43 function is a common feature in sporadic ALS, and thus TDP43 transgenic models may recapitulate disease processes that occur in humans with sporadic ALS. Although the PrP.TDP43-A315T model has been reported to develop abnormalities in gut motility that contribute to early mortality, recent studies indicated that gut motility issues could be mitigated by feeding mice with gel-based diets rather than the standard dry chow. In the present study, we have attempted to use the PrP.TDP43-A315T model to test whether we could identify a drug combination that synergized to extend life span in this model substantially. The drug combinations were built around the existing drug modalities, adding additional drugs that had indications of utility from the literature. To mitigate gut motility issues, we fed the mice gel-based diets with or without added drug combinations. Although the gel-based diets extended life expectancy in PrP.TDP43-A315T mice, most of the animals still developed gut motility abnormalities that may have contributed to early mortality. None of the drug combinations we tested extended life expectancy in this model substantially.

neuroscience↗

bioRxiv2024

The resilience of the oral microbiome and lability of the hair microbiome across host environments in wild and captive lemurs

Microbiome diversity and composition in mammals is affected by the hosts environment and has been linked to important immune and physiological host functions, yet most of these data come from the gut microbiome. Research on the oral and hair microbiome in nonhuman primates has been far less common, and information from wild primates is even rarer. These overlooked patterns of environmental effects on microbial communities across the body may have important implications for a range of host functions. Therefore, in this study we characterized the gut, oral, and hair microbiomes across nine different captive and wild lemur species: Eulemur collaris, Eulemur coronatus, Eulemur mongoz, Lemur catta, Microcebus griseorufus, Microcebus murinus, Propithecus coquereli, Propithecus verreauxi, and Varecia rubra. We explored how host environment affects the microbiome diversity of these three body regions using 16S rRNA sequencing and found significant differences in microbiome composition, diversity, and environmental influence across body regions. The oral microbiome was least diverse and most resilient to different environmental effects; conversely, the hair microbiome was both most diverse and most labile. Differentially abundant bacterial taxa across oral, gut, and hair microbiota may also reflect selective regimes unique to each body region. These results emphasize the importance of accounting for body region when conducting microbiome studies. ImportanceAn organisms microbiome plays important roles in a wide variety of the host animals physiological functions, yet how these microbial communities in body regions beyond the gut are affected by the hosts environment is not clearly understood. We therefore analyzed how the oral, gut, and hair microbiomes of nine lemur species (genera Eulemur, Lemur, Microcebus, Propithecus, and Varecia) varied across wild and captive environments. We found that host environment affected the microbiomes of each body region in distinct ways, with the oral microbiome appearing conserved and more resilient to environmental effects, particularly compared to the diverse and widely variable hair microbiome. To our knowledge, this study is the most comprehensive multi-body-region analysis of the lemur microbiome to date. Our results demonstrate that the environment does not have a universal effect on the microbiome across body regions, but is instead mediated by body-region specific factors.

ecology↗

bioRxiv2024

Transcriptional Characterization of the Stromal and Endothelial Bone Marrow Microenvironment during Progression from MGUS to Multiple Myeloma

The role of the non-immune bone marrow microenvironment (BME) in the transition from monoclonal gammopathy of undetermined significance (MGUS) into clinically active multiple myeloma (MM) remains incompletely defined. To address this, we transcriptionally profiled endothelial cells (EC), mesenchymal stem cells (MSC) and MM cells at single-cell resolution from two genetically engineered mouse models (BIc{gamma}1 and MIc{gamma}1) that recapitulate MGUS to MM progression. Our analysis revealed distinct transcriptional trajectories in EC and MSC, uncovering stage-specific BME-PC interactions shaping disease progression. EC acquired a stress phenotype during MGUS transitioning to angiogenesis in MM, while MSC exhibited early impaired differentiation capacity during MGUS that persisted in MM. Notably, an interferon (IFN)-associated MM signature was detected in EC and MSC from the BIc{gamma}1 model but was absent in the more aggressive MIc{gamma}1 model. Treatment with bortezomib, lenalidomide, and dexamethasone remodeled the BME by suppressing MM-IFN signaling, promoting an adaptive response in EC, and restoring osteogenic potential in MSC-- shifting the niche toward a less tumor-permissive state. Importantly, the MM-IFN signature was validated in patients across the MGUS-to-MM spectrum, supporting the translational relevance of our findings. Together, these data define novel dynamic and targetable alterations in the non-immune BME during myeloma progression. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/589777v5_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@1a0ef62org.highwire.dtl.DTLVardef@c44014org.highwire.dtl.DTLVardef@4b1df6org.highwire.dtl.DTLVardef@19c29a2_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

Environmental DNA as a complementary tool for biodiversity monitoring: A multi-technique and multi-trophic approach to investigate cetacean distribution and feeding ecology

The use of environmental DNA (eDNA) to assess the presence of biological communities has emerged as a promising monitoring tool in the marine conservation landscape. Moreover, advances in Next-Generation Sequencing techniques, such as DNA metabarcoding, enable multi-species detection in mixed samples, allowing the study of complex ecosystems such as oceanic ones. We aimed at using these molecular-based techniques to characterise cetacean communities, as well as potential prey in the northern coast of Mainland Portugal. During seasonal campaigns, we collected seawater samples, along with visual records of cetacean occurrence. The eDNA extracted from 64 environmental samples was sequenced in an Illumina platform, with universal primers targeting marine vertebrates. Five cetacean species were identified by molecular detection: common dolphin (Delphinus delphis), bottlenose dolphin (Tursiops truncatus), Rissos dolphin (Grampus griseus), harbour porpoise (Phocoena phocoena) and fin whale (Balaenoptera physalus). Overall, except for the fin whale (not sighted during the campaigns), this cetacean community composition was similar to that obtained through visual monitoring, and the complementary results suggest their presence in the region all year round. In addition, the positive molecular detections of B. physalus are of special relevance since there are no visual records reported in the area. The detection of multiple known preys of the identified dolphins indicates they use these coastal areas for feeding purposes. While this methodological approach remains in a development stage, the present work highlights the benefits of using eDNA to study marine communities, with specific applications for research on cetacean distribution and feeding ecology, ultimately serving as the baseline of a methodological approach for biodiversity monitoring and marine conservation.

ecology↗

bioRxiv2023

Electroadhesive hydrogel interface for prolonged mucosal theranostics

Establishing a robust and intimate mucosal interface that allows medical devices to remain within lumen-confined organs for extended periods has valuable applications, particularly for gastrointestinal (GI) theranostics. Here, we report the development of e-GLUE, an electroadhesive hydrogel interface for robust and prolonged mucosal retention following electrical activation. Notably, this novel mucosal adhesion mechanism can increase the adhesion energy of hydrogels on the mucosa by up to 30-fold and enable in vivo GI retention of e-GLUE devices for up to 30 days. Strong mucosal adhesion occurs within one minute of electrical activation, despite the presence of luminal fluid, mucus exposure, and organ motility, thereby ensuring compatibility with complex in vivo environments. In swine studies, we demonstrate the utility of e-GLUE for mucosal hemostasis, sustained local delivery of therapeutics, and intimate biosensing in the GI tract. This system can enable improved treatments for various health conditions, including gastrointestinal bleeding, inflammatory bowel disease, and diagnostic applications in the GI tract and beyond.

bioengineering↗

bioRxiv2023

Tesofensine, a novel antiobesity drug, silences GABAergic hypothalamic neurons

Obesity is a major global health epidemic that has adverse effects on both the people affected as well as the cost to society. Several anti-obesity drugs that target GLP-1 receptors have recently come to the market. Here we describe the effects of tesofensine, a novel anti-obesity drug that acts as a triple monoamine neurotransmitter reuptake inhibitor. We investigated its effects on weight loss and underlying neuronal mechanisms in mice and rats using various techniques. These include behavioral tasks, DeepLabCut videotaped analysis, electrophysiological ensemble recordings, optogenetic activation, and chemogenetic silencing of GABAergic neurons in the Lateral Hypothalamus (LH). We found that tesofensine induced greater weight loss in obese than lean rats, which was associated with changes in LH ensemble activity. In Vgat-ChR2 and Vgat-IRES-cre transgenic mice, we found for the first time that tesofensine inhibited a subset of LH GABAergic neurons, reducing their ability to promote feeding behavior, and chemogenetically silencing them enhanced tesofensines food-suppressing effects. Unlike phentermine, a dopaminergic appetite suppressant, tesofensine causes few, if any, head-weaving stereotypy at therapeutic doses. Most importantly, we found that tesofensine prolonged the weight loss induced by 5-HTP, a serotonin precursor, and blocked the body weight rebound that often occurs after weight loss. Behavioral studies on rats with the tastant sucrose indicated that tesofensines appetite suppressant effects are independent of taste aversion and do not directly affect the perception of sweetness or palatability of sucrose. In summary, our data provide new insights into the effects of tesofensine on weight loss and the underlying neuronal mechanisms, suggesting that tesofensine may be an effective treatment for obesity and that it may be a valuable adjunct to other appetite suppressants to prevent body weight rebound.

neuroscience↗

bioRxiv2023

A deep catalog of protein-coding variation in 985,830 individuals

Coding variants that have significant impact on function can provide insights into the biology of a gene but are typically rare in the population. Identifying and ascertaining the frequency of such rare variants requires very large sample sizes. Here, we present the largest catalog of human protein-coding variation to date, derived from exome sequencing of 985,830 individuals of diverse ancestry to serve as a rich resource for studying rare coding variants. Individuals of African, Admixed American, East Asian, Middle Eastern, and South Asian ancestry account for 20% of this Exome dataset. Our catalog of variants includes approximately 10.5 million missense (54% novel) and 1.1 million predicted loss-of-function (pLOF) variants (65% novel, 53% observed only once). We identified individuals with rare homozygous pLOF variants in 4,874 genes, and for 1,838 of these this work is the first to document at least one pLOF homozygote. Additional insights from the RGC-ME dataset include 1) improved estimates of selection against heterozygous loss-of-function and identification of 3,459 genes intolerant to loss-of-function, 83 of which were previously assessed as tolerant to loss-of-function and 1,241 that lack disease annotations; 2) identification of regions depleted of missense variation in 457 genes that are tolerant to loss-of-function; 3) functional interpretation for 10,708 variants of unknown or conflicting significance reported in ClinVar as cryptic splice sites using splicing score thresholds based on empirical variant deleteriousness scores derived from RGC-ME; and 4) an observation that approximately 3% of sequenced individuals carry a clinically actionable genetic variant in the ACMG SF 3.1 list of genes. We make this important resource of coding variation available to the public through a variant allele frequency browser. We anticipate that this report and the RGC-ME dataset will serve as a valuable reference for understanding rare coding variation and help advance precision medicine efforts.

genetics↗

bioRxiv2023

In vivo metabolomics identifies CD38 as an emergent vulnerability in LKB1-mutant lung cancer

LKB1/STK11 is a serine/threonine kinase that plays a major role in controlling cell metabolism, resulting in potential therapeutic vulnerabilities in LKB1-mutant cancers. Here, we identify the NAD+ degrading ectoenzyme, CD38, as a new target in LKB1-mutant NSCLC. Metabolic profiling of genetically engineered mouse models (GEMMs) revealed that LKB1 mutant lung cancers have a striking increase in ADP-ribose, a breakdown product of the critical redox co-factor, NAD+. Surprisingly, compared with other genetic subsets, murine and human LKB1-mutant NSCLC show marked overexpression of the NAD+-catabolizing ectoenzyme, CD38 on the surface of tumor cells. Loss of LKB1 or inactivation of Salt-Inducible Kinases (SIKs)--key downstream effectors of LKB1-- induces CD38 transcription induction via a CREB binding site in the CD38 promoter. Treatment with the FDA-approved anti-CD38 antibody, daratumumab, inhibited growth of LKB1-mutant NSCLC xenografts. Together, these results reveal CD38 as a promising therapeutic target in patients with LKB1 mutant lung cancer. SIGNIFICANCELoss-of-function mutations in the LKB1 tumor suppressor of lung adenocarcinoma patients and are associated with resistance to current treatments. Our study identified CD38 as a potential therapeutic target that is highly overexpressed in this specific subtype of cancer, associated with a shift in NAD homeostasis.

cancer biology↗

bioRxiv2023

MeC3HDZ1/MeCNA is a strong candidate for cassava storage root productivity improvement.

The storage root (SR) of cassava is the main staple food in sub-Saharan Africa, where it feeds over 500 million people. However, little is known about the genetic and molecular regulation underlying its development. Unraveling such regulation would pave the way for biotechnology approaches aimed at enhancing cassava productivity. Anatomical studies indicate that SR development relies on the massive accumulation of xylem parenchyma, a cell-type derived from the vascular cambium. The C3HDZ family of transcription factors regulate cambial cells proliferation and xylem differentiation in Arabidopsis and other species. We thus aimed at identifying C3HDZ proteins in cassava and determining whether any of them shows preferential activity in the SR cambium and/or xylem. Using phylogeny and synteny studies, we identified eight C3HDZ proteins in cassava, namely MeCH3DZ1-8. We observed that the expression of MeC3HDZ1 in SR cambium and xylem is higher than that of any other MeC3HDZ gene in any of the SR vascular tissues or any of the other vegetative organs. We established an in-silico pipeline which revealed the existence of a number of theoretical C3HDZ targets displaying significant preferential expression in the SR. Subsequent Y1H analyses proved that MeC3HDZ1 can bind canonical C3HDZ binding sites in the promoters of these targets. Transactivation assays demonstrated that MeC3HDZ1 can regulate the expression of genes downstream of promoters harboring such binding sites, thereby demonstrating that MeC3HDZ1 is a C3HDZ transcription factor which constitutes a strong candidate for future biotechnology strategies directed at increasing cassava productivity.

plant biology↗

bioRxiv2022

Evaluating restriction enzyme selection for genome reduction in conservation genomics

Conservation genomic studies in non-model organisms generally rely on genome reduction techniques based on restriction enzymes to identify population structure as well as candidate loci for local adaptation. These reduced libraries ensure a high density of SNP loci and high coverage for accurate genotyping. Despite the fraction of the genome that is sequenced is expected to be randomly located, the reduction of the genome might depend on the recognition site of the restriction enzyme used. Here, we evaluate the distribution and functional composition of loci obtained after Genotyping-by-sequencing (GBS) genome reduction with two widely used restriction enzymes (EcoT22I and ApeKI). To do so, we compared data from two endemic fish species (Symphodus ocellatus and Symphodus tinca, EcoT22I enzyme) and two ecosystem engineer sea urchins (Paracentrotus lividus and Arbacia lixula, ApeKI enzyme). In brief, we mapped the sequenced loci to the phylogenetically closest reference genome available (Labrus bergylta for fish and Strongylocentrotus purpuratus for sea urchins), classified them as exonic, intronic, and intergenic, and studied their functionality by using GO terms. We detected an enrichment towards exonic or intergenic regions depending on the restriction enzyme used, and we did not detect differences between total loci and candidate loci for adaptation. Despite most GO terms being shared between species, the analysis of their abundance showed differences between taxonomic groups, which may be attributed to differences of the targeted loci. Our results highlight the importance of restriction enzyme selection and the need for high-quality annotated genomes in conservation genomic studies.

genomics↗

bioRxiv2022

Systematic functional screening of chromatin factors identifies strong lineage and disease dependencies in normal and malignant haematopoiesis

Interactions between transcription factors (TF) and chromatin factors (CF) regulate gene expression programmes to determine cellular fate. However, unlike for TF, the exact role of CF in this process is poorly understood. Using haematopoiesis as a model system and utilising novel functional CRISPR screens ex vivo and in vivo, coupled with Perturb-Seq, CF binding and genome-wide chromatin accessibility in primary murine cells, we assess the role of 550 chromatin factors in lineage choice in normal haematopoiesis and the maintenance of acute myeloid leukaemia (AML). These studies demonstrate marked specificity for a large number of CFs in lineage determination, highlighting functional diversity within specific families of chromatin regulators, including MLL-H3K4-methyltransferases and different BAF-complexes, that regulate disparate lineage decisions across haematopoiesis. Conversely, we demonstrate that unrelated Repressive complexes function similarly to restrain excessive myeloid differentiation and protect lineage diversity. We identify interactions between CF and TF that, at least in part, explain the regulatory function of CF and link Brd9-loss to a premalignant state. Utilising similar experiments in a relevant murine AML model, we demonstrate opposing effects for CF in normal haematopoiesis and AML, where MLL-H3K4-methyltransferases, c-BAF-remodelers and Repressive complexes prevent differentiation and maintain leukaemic fitness. We show that this alteration relates to differential utilisation of TF by CF complexes between normal and malignant haematopoiesis, highlighting corrupted TF-CF interactions as potential novel avenues for therapeutic intervention in AML. Together, this study provides novel insights on the functional diversity of chromatin factors in governing cell-fate.

genomics↗

bioRxiv2022

Rapid estimation of cortical neuron activation thresholds by transcranial magnetic stimulation using convolutional neural networks

BackgroundTranscranial magnetic stimulation (TMS) can modulate neural activity by evoking action potentials in subpopulations of cortical neurons. The TMS-induced electric field (E-field) can be simulated in subject-specific head models derived from MR images, but the spatial distribution of the E-field alone does not predict the physiological response. Coupling E-field models to populations of biophysically realistic neuron models yields insights into the activation mechanisms of TMS, but the significant computational cost associated with these models limits their use and eventual translation to clinically relevant applications. ObjectiveThe objective was to develop computationally efficient estimators of the activation thresholds of multi-compartmental cortical neuron models in response to TMS-induced E-field distributions. MethodsMulti-scale models combining anatomically accurate finite element method (FEM) simulations of the TMS E-field with layer-specific representations of cortical neurons were used to generate a large dataset of activation thresholds. 3D convolutional neural networks (CNNs) were trained on these data to predict the activation threshold of specific model neurons given the local E-field distribution. Using training and test data from different head models, the CNN estimator was compared to an approach using the uniform E-field approximation to estimate thresholds in the non-uniform TMS-induced E-field. ResultsThe 3D CNNs were more accurate than the uniform E-field approach, with mean absolute percent error (MAPE) on the test dataset below 2.5% compared to 5.9 - 9.8% with the uniform E-field approach. Further, there was a strong correlation between the CNN predicted and actual thresholds for all cell types (R2 > 0.96) compared to the uniform E-field approach (R2 = 0.62 - 0.91). The CNNs estimate thresholds with a 2 - 4 orders of magnitude reduction in the computational cost of the multi-compartmental neuron models. Conclusion3D CNNs can estimate rapidly and accurately the TMS activation thresholds of biophysically realistic neuron models using sparse samples of the local E-field, enabling simulating responses of large neuron populations or parameter space exploration on a personal computer.

bioengineering↗