Biology subjects

Flores, C.

Publications and source records attributed to Flores, C..

At least 19 recordsLinked to original sources

bioRxiv2026

The Genome In A Bottle HG002 assembly-based variant benchmark set enables comprehensive benchmarking of small and structural variants.

High-accuracy, high-resolution benchmark data are fundamental to improving the accuracy and generalizability of sequencing technologies and associated algorithms. Most existing benchmarks for DNA sequencing rely on mapping to a single linear reference, omitting inaccessible and highly repetitive complex genomic regions. Here, we present the Genome in a Bottle (GIAB) Consortium's HG002 v5.0q benchmark set, a more comprehensive variant benchmark derived from a fully phased, highly curated, and accurate diploid assembly of HG002. Our approach leverages recent advances in long-read sequencing and assembly to provide confident small- and structural-variant calls across previously inaccessible regions, including segmental duplications, homopolymers, tandem repeats, and complex immune loci. The v5.0 benchmark significantly expands the callable genome relative to v4.2.1, adding x200 Mbp of sequence and increasing variant detection by 18 % for small variants and 3-fold for structural variants compared to previous benchmarks. The benchmark regions include more variants in repetitive regions, including 1.2 x segmental duplications, 1.8 x tandem repeats, and 2.0 x homopolymers, compared to v4.2.1. Separate and combined small- and structural-variant benchmarks are available for three versions of the human reference genome (GRCh37, GRCh38, and CHM13). We validate the reliability of this benchmark set by comparing multiple sequencing technologies and variant calling pipelines and curating differences. The v5.0q benchmark provides a critical resource for the development and validation of next-generation sequencing technologies and analysis methods.

genomics↗

bioRxiv2026

Competition against the intestinal microbiota selects for pathoadaptive traits in ESBL E. coli

The intestinal tract is a reservoir for Extended-Spectrum {beta}-Lactamase (ESBL)-producing Escherichia coli. Asymptomatic gut colonization by these pathobionts represents a major risk for extraintestinal infections. Despite clinical relevance, the genetic basis of gut colonization by ESBL E. coli remains poorly understood. Here, we determined how the microbiota shapes the fitness landscape of diverse ESBL E. coli strains, defining the functional requirements for intestinal colonization. In microbiota-depleted hosts, colonization relies mostly on metabolic functions. In contrast, in mice harbouring a microbiota, pathoadaptive functions associated with adhesion and biofilm formation are dominant determinants of E. coli fitness, together with accessory virulence functions. Consistent with these observations, experimental evolution in mice reveals convergent adaptation of ESBL E. coli to the presence of a complex microbiota through enhanced adhesion. These findings establish the microbiota as a major ecological driver of pathoadaptation in antibiotic-resistant pathobionts.

microbiology↗

bioRxiv2026

Enzyme-Constrained Metabolic Modeling of the Tripartite Synapse Links Astrocyte-Neuron Lactate Shuttle to Lipid Trafficking and Redox Homeostasis

Neuron-astrocyte metabolic coupling sustains synaptic function through coordinated substrate exchange, redox homeostasis, and lipid handling, yet the systems-level mechanism remains poorly understood. Here, we developed an enzyme-constrained, genome-scale metabolic model of the mouse tripartite synapse to test whether protein allocation can reproduce the astrocyte-neuron lactate shuttle (ANLS). Starting from the iMM1865 mouse metabolic model, we corrected mass and charge imbalances, expanded fatty acid and lipid pathways, and standardized annotations to obtain a high-quality, generic mouse model, improving the MEMOTE score from 46% to 83%. Cell type-specific astrocyte and neuron models were reconstructed using the integrative metabolic analysis tool (iMAT) with cell type-resolved mouse brain proteomics, and were further extended to represent the tripartite synapse. Enzyme-constrained resource allocation models (RAMs) were reconstructed for the astrocyte and neuron models using the GECKO 3.0 pipeline and integrated into a tripartite synapse community model via a modified SteadyCom framework. In the stoichiometry-only model, minimum lactate exchange remained at zero across the entire biomass envelope, indicating no coupling between astrocyte lactate secretion and neuronal uptake arising from the metabolic network itself. Imposing enzyme constraints caused growth-coupled lactate secretion above 90% of maximal growth, with corresponding neuronal lactate uptake, indicating that protein limitation partially drives astrocyte-neuron lactate coupling consistent with ANLS. Incorporation of reactive oxygen species (ROS) and lipid peroxidation pathways demonstrated that the brain-type fatty acid binding protein (FABP7) knockout redistributed flux away from astrocytic detoxification, increased neuronal ROS burden, and produced cell-type-specific suppression of lipid-associated reporter metabolites, including prostaglandin J2, hydroxymethylglutaryl-CoA (HMG-CoA), mevalonate, phosphoinositide/DAG intermediates, fatty-acyl-CoA pools, and ceramide-related sphingolipids. Model predictions, including lactate shuttling and lipid metabolic shifts in FABP7 knockout, align with published experimental studies, supporting the biological relevance of this framework. These findings indicate that ANLS emerges from enzyme limitation in the tripartite synapse model and that FABP7-mediated lipid trafficking is essential for lipid-redox homeostasis at the tripartite synapse. Author SummaryThe brain relies on metabolic cooperation between astrocytes and neurons. Astrocytes convert glucose into lactate, which neurons use for energy. This process is known as the astrocyte-neuron lactate shuttle (ANLS). It is still unclear whether this shuttle is just one possible metabolic pathway or is required due to resource limitations. To explore this, we created two detailed mathematical models of the tripartite synapse, where an astrocyte process extends to meet the synapse. The first model consisted only of the stoichiometry of the metabolic network, whereas the second reflected each cells limited ability to make proteins. When these protein limits were imposed, lactate secretion by astrocytes and uptake by the neurons became mandatory, providing a systems-level mathematics-driven demonstration of ANLS. We also examined the role of Fatty Acid Binding Protein 7 (FABP7), a protein primarily expressed in astrocytes that shuttles fatty acids within astrocyte cells. Modeling FABP7 knockout caused astrocytes to lose their ROS detoxification capacity, increased oxidative stress in neurons, and altered lipid metabolism across cell types. Key affected lipid pathways included prostaglandin signaling, HMG-CoA/ketone body metabolism, cholesterol/mevalonate metabolism, phosphoinositide/DAG signaling, fatty acyl-CoA metabolism, and ceramide-related sphingolipid metabolism. These results show how energy supply, lipid trafficking, and oxidative stress control are linked across cell types and provide a way to identify metabolic vulnerabilities in neurological diseases.

Systems Biology↗

bioRxiv2026

A basophil-specific GPCR mediates the immune response to helminth infection

Basophils are rare innate immune cells that contribute to type 2 immunity in allergy and parasitic helminth infection, yet the receptors governing their activation remain poorly defined. Here, we identify the G protein-coupled receptor (GPCR) Mrgpra6 as a basophil-specific gene that mediates the host response to helminth infection. Mrgpra6 expression is restricted to basophils in blood and lung and is uniformly expressed across the population. Knockout of Mrgpra6 impairs early innate immunity to invading helminths, resulting in increased larval burden, elevated mortality, and disrupted parasite progression within the host. Transcriptional profiling of FACS-sorted basophils during helminth infection reveals how Mrgpra6 shapes the basophil transcriptional landscape needed for effective host defense. Together, these findings identify Mrgpra6 as a functional regulator of basophil-mediated anti-helminth immunity.

immunology↗

bioRxiv2026

Monitoring intracellular antibiotic concentrations in real-time using allosteric biosensors

Antibiotic treatment can fail due to insufficient drug availability at the site of infection or limited accumulation within bacterial pathogens. However, it is poorly understood how antibiotics penetrate infected tissues and complex bacterial aggregates, limiting insights into the mechanisms of treatment failure. Here, we present genetically-encoded allosteric biosensors for two antibiotic classes, trimethoprim and tetracycline, which enable real-time monitoring of antibiotic concentrations inside bacterial cells. The biosensors consist of circularly permuted EGFP linked to the sensory domains DHFR or TetR. To extend this approach to low oxygen environments, we engineered an oxygen-independent trimethoprim biosensor by fusing DHFR to a circularly permuted version of the fluorogenic protein FAST. Using these biosensors, we monitored the antibiotic exposure dynamics of intracellular Salmonella enterica during macrophage infection at the single-cell level, and antibiotic penetration into anaerobic regions of Vibrio cholerae biofilms, as well as antibiotic availability in microoxic conditions in a human bladder tissue model infected with uropathogenic Escherichia coli. These fluorescent biosensors have the potential to be broadly applied for determining antibiotic distributions at infection sites with high spatial and temporal resolution.

microbiology↗

bioRxiv2026

Human exploitation of shellfish in the Atacama desert coast and environmental variability: a trans-Holocene perspective

The Humboldt upwelling ecosystem has been intensively harvested by people since the early Holocene. Understanding past and present human choices under climatic variability in these productive environments may hold key insights for its future sustainability by unraveling different adaptive pathways. To this end, we studied shellfish exploitation and climate patterns in the Taltal region of the Atacama desert coast (25{whitebullet}S) from the early Holocene until today using a compilation of archaeological, and modern benthic fisheries data together with direct ecological surveys. In addition we obtained satellite sea surface temperature (SST) and published{delta} 18O SST for the study region. The archaeological record and the modern rocky shore assemblage were dominated by herbivorous gastropods -Fissurella spp., Enoplochiton spp., Tegula spp.-and the carnivorous whelk Concholepas concholepas. Functional composition from the early Holocene to the present was remarkably stable. Using SST as a latent variable, we examined changes in functional composition across the Holocene and in a 16-year series of artisanal fisheries landings using bayesian ordination. The analysis identified functional groups characteristic of kelp ecosystems in association with cooler SST conditions during the Holocene and the present. Changes in functional composition during warm and cold periods of the Holocene broadly mirrored effects of interannual SST variability in the modern fisheries. The archaeological record suggests two cross-Holocene transitions social-ecological transitions. The generalized shoreline harvesting strategy that prevailed during the cold early Holocene shifted to a specialized maritime economy towards the warmer mid-Holocene. The maritime technological and cultural adaptions remained, but were part of more diversified lifestyles in the cooler and more variable late Holocene. The latter emerged at the same time as the modern El Nino climate pattern. Our insights from the direct analysis of human choices and SST variability highlight the role of flexibility and agency under a changing environment. The broad range of human decisions in the past, inform current regulatory frameworks for benthic artisanal fisheries. Marine resources and the livelihoods that depend on them are integrated into coupled coastal socioecological systems; their future sustainability hinges on fostering the different dimension of their adaptive capacity.

ecology↗

bioRxiv2025

A Physically-Realistic Simulator and Cosine-Based Decoder for MERFISH Spatial Transcriptomics

Imaging-based spatial transcriptomics technologies have opened new avenues for studying cellular organization and gene expression within intact tissues. However, the accuracy of downstream analyses depends critically on the decoding step that reconstructs barcodes from fluorescence patterns and maps them to gene identities. Despite a growing number of decoding methods, systematic benchmarking has been limited. Here, we introduce Serval, a modular framework for developing and benchmarking decoding methods across diverse spatial transcriptomics platforms. Serval separates key decoding stages into independently configurable modules, enabling flexible integration of alternative algorithms. Using this framework, we develop the Cosine decoder, a novel method that improves transcript recovery by optimizing cosine similarity to known barcodes. We evaluate Cosine and baseline methods on synthetic and real MERFISH datasets, showing that Cosine achieves higher transcript recovery and superior correlation with expression references compared to existing methods. Furthermore, we demonstrate that the Serval framework generalizes beyond MERFISH. By extending to the DART-FISH platform, we show that Cosine improves transcript recovery, clustering stability and supports more direct annotation of complex biological structures such as the human primary motor cortex. These results establish that modular decoding frameworks facilitate robust, platformagnostic benchmarking, ultimately supporting more accurate spatial transcriptomics analysis across diverse biological samples.

bioinformatics↗

bioRxiv2025

Reduced carbohydrate complexity alters gut microbial structure independent of total carbohydrate intake

Dietary habits have dramatically altered over recent decades, yet the impact of simplified carbohydrate intake on the gut microbiomes complexity and function remains poorly understood. This study investigates how the variety of dietary carbohydrates--not just their amount--shapes gut microbial diversity and resilience in C57BL/6 mice. Over eight weeks, mice consumed diets varying in carbohydrate complexity but matched for total carbohydrate content. Using 16S rRNA sequencing, we found that reduced carbohydrate diversity led to significant declines in microbial diversity and taxonomic redundancy among important bacterial groups, such as unclassified Lachnospiraceae, Ruminococcaceae, and Muribaculaceae, despite no immediate changes in host physiology. Concurrently, Akkermansia increased under low-complexity diets, suggesting a shift toward mucin degradation when complex polysaccharides are scarce. These changes indicate that loss of carbohydrate complexity narrows microbial niches, potentially disrupting metabolic interactions and functional stability of the gut ecosystem. Given the widespread adoption of processed, low-fiber diets in modern societies, these findings emphasize the importance of macronutrient complexity in maintaining gut microbial health. While short-term host effects were minimal, the microbial shifts observed could presage long-term consequences for gut resilience and disease susceptibility. This study underscores the need to consider carbohydrate diversity in dietary recommendations and microbial ecology research to safeguard gut health in the face of global dietary simplification.

microbiology↗

bioRxiv2025

Amphetamine in Adolescence Induces a Sex-Specific Mesolimbic Dopamine Phenotype in the Adult Prefrontal Cortex

Drugs of abuse in adolescence impact brain maturation and increase psychiatric risk, with differences in sensitivity between males and females. Amphetamine in adolescent male, but not female mice, causes dopamine axons intended to innervate the nucleus accumbens and to grow ectopically to the prefrontal cortex (PFC). This is mediated by drug-induced downregulation of the Netrin-1 receptor DCC. How off-target dopamine axons function in the adult PFC remains to be determined. Here we report that males and females show place preference for amphetamine in adolescence. However, only in males, amphetamine increases PFC dopamine transporter expression in adulthood: leading to aberrant baseline dopamine transients, faster dopamine release, and exaggerated responses to acute methylphenidate. Upregulation of DCC in adolescence, using CRISPRa, prevents all these changes. Mesolimbic dopamine axons rerouted to the PFC in adolescence retain anatomical and functional phenotypes of their intended target, rendering males enduringly vulnerable to the harmful effects of drugs of abuse.

neuroscience↗

bioRxiv2024

A robust benchmark for detecting low-frequency variants in the HG002 Genome In A Bottle NIST reference material.

Somatic mosaicism is an important cause of disease, but mosaic and somatic variants are often challenging to detect because they exist in only a fraction of cells. To address the need for benchmarking subclonal variants in normal cell populations, we developed a benchmark containing mosaic variants in the Genome in a Bottle Consortium (GIAB) HG002 reference material DNA from a large batch of a normal lymphoblastoid cell line. First, we used a somatic variant caller with high coverage (300x) Illumina whole genome sequencing data from the Ashkenazi Jewish trio to detect variants in HG002 not detected in at least 5% of cells from the combined parental data. These candidate mosaic variants were subsequently evaluated using >100x BGI, Element, and PacBio HiFi data. High confidence candidate SNVs with variant allele fractions above 5% were included in the HG002 draft mosaic variant benchmark, with 13/85 occurring in medically relevant gene regions. We also delineated a 2.45 Gbp subset of the previously defined germline autosomal benchmark regions for HG002 in which no additional mosaic variants >2% exist, enabling robust assessment of false positives. The variant allele fraction of some mosaic variants is different between batches of cells, so using data from the homogeneous batch of reference material DNA is critical for benchmarking these variants. External validation of this mosaic benchmark showed it can be used to reliably identify both false negatives and false positives for a variety of technologies and detection algorithms, demonstrating its utility for optimization and validation. By adding our characterization of mosaic variants in this widely-used cell line, we support extensive benchmarking efforts using it in simulation, spike-in, and mixture studies.

bioinformatics↗

bioRxiv2024

Molecular basis of one-step methyl anthranilate biosynthesis in grapes, sweet orange, and maize

Plants synthesize an array of volatile compounds, many of which serve ecological roles in attracting pollinators, deterring herbivores, and communicating with their surroundings. Methyl anthranilate is an anti-herbivory defensive volatile responsible for grape aroma that is emitted by several agriculturally relevant plants, including citrus, grapes, and maize. Unlike maize, which uses a one-step anthranilate methyltransferase, grapes have been thought to use a two-step pathway for methyl anthranilate biosynthesis. By mining available transcriptomics data, we identified two anthranilate methyltransferases in Vitis vinifera (wine grape), as well as one ortholog in Concord grape. Many angiosperms methylate the plant hormone salicylic acid to produce methyl salicylate, which acts as a plant-to-plant communication molecule. Because the Citrus sinensis (sweet orange) salicylic acid methyltransferase can methylate both anthranilate and salicylic acid, we used this enzyme to examine the molecular basis of anthranilate activity by introducing rational mutations, which identified several active site residues that increase activity with anthranilate. Reversing this approach, we introduced mutations that imparted activity with salicylic acid in the maize anthranilate methyltransferase, which uncovered different active site residues from those in the citrus enzyme. Sequence and phylogenetic analysis revealed that one of the Vitis anthranilate methyltransferases shares an ancestor with jasmonic acid methyltransferases, similar to the anthranilate methyltransferase from strawberry (Frageria sp.). Collectively, these data demonstrate the molecular mechanisms underpinning anthranilate activity across methyltransferases and identified one-step enzymes by which grapes synthesize methyl anthranilate. Significance StatementWhile the two-step pathway responsible for the biosynthesis of the grape aroma molecule, methyl anthranilate, has remained incomplete in Vitis spp., we identified two one-step anthranilate methyltransferases in wine and one in Concord grapes that can methylate the tryptophan pathway intermediate anthranilate. Tracing the molecular basis of anthranilate activity in the maize and sweet orange methyltransferases uncovered distinct active site amino acids that impart substrate specificity.

plant biology↗

bioRxiv2024

Benchmarking of bioinformatics tools for the hybrid de novo assembly of human whole-genome sequencing data

Accurate and complete de novo assembled genomes sustain variant identification and catalyze the discovery of new genomic features and biological functions. However, accurate and precise de novo assemblies of large and complex genomes remains a challenging task. Long-read sequencing data alone or in hybrid mode combined with more accurate short-read sequences facilitate the de novo assembly of genomes. A number of software exists for de novo genome assembly from long-read data although specific performance comparisons to assembly human genomes are lacking. Here we benchmarked 11 different pipelines including four long-read only assemblers and three hybrid assemblers, combined with four polishing schemes for de novo genome assembly of a human reference material sequenced with Oxford Nanopore Technologies and Illumina. In addition, the best performing choice was validated in a non-reference routine laboratory sample. Software performance was evaluated by assessing the quality of the assemblies with QUAST, BUSCO, and Merqury metrics, and the computational costs associated with each of the pipelines were also assessed. We found that Flye was superior to all other assemblers, especially when relying on Ratatosk error-corrected long-reads. Polishing improved the accuracy and continuity of the assemblies and the combination of two rounds of Racon and Pilon achieved the best results. The assembly of the non-reference sample showed comparable assembly metrics as those of the reference material. Based on the results, a complete optimal analysis pipeline for the assembly, polishing, and contig curation developed on Nextflow is provided to enable efficient parallelization and built-in dependency management to further advance in the generation of high-quality and chromosome-level human assemblies.

bioinformatics↗

bioRxiv2024

The CCR4/CCL17 axis drives intestinal acute Graft versus Host disease after allogeneic bone marrow transplantation

Acute-Graft-versus-Host disease (aGvHD) is a life-threatening complication after allogeneic stem-cell-transplantation. It is mediated by alloreactive T cells whose trafficking to aGvHD target organs is orchestrated by chemokines. We here asked whether CCL17 and its corresponding receptor CCR4 are involved in aGvHD development and severity. We applied an experimental mouse model of aGvHD in CCR4/CCL17 knockout mice and analyzed gut biopsies of GvHD patients. We show that the absence of CCR4 in transplanted T cells induced significantly less severe aGvHD. This was accompanied by reduced expression of Gata3. Mechanistically, only CD4+, but not CD8+CCR4-/- T cells protected from aGvHD. We next identified dendritic cells in the small intestine to produce CCL17, which selectively recruited CD4+ T cells. IL-4 production by intestinal CD4+ T cells promoted proliferation of CD8+ T cells. In line, we detected an upregulation of CCL17 and Gata3 in human aGvHD samples. Our results indicate that local CCL17 production in aGvHD target organs recruits T cells, reinforcing local tissue damage and immune cell recruitment. We identified the JAK1/2-inhibitor ruxolitinib to dampen CCL17-expression, thereby reducing GvHD severity. We here dissect a to date unknown role of the CCL17-CCR4 axis in aGvHD, which might help to develop novel therapeutic strategies.

immunology↗

bioRxiv2023

Modelling the demographic history of human North African genomes points to a recent soft split divergence between populations

BackgroundNorth African human populations present a complex demographic scenario. The presence of an autochthonous genetic component and population substructure, plus extensive gene flow from the Middle East, Europe, and sub-Saharan Africa, have shaped the genetic composition of its people through time. ResultsWe conducted a comprehensive analysis of 364 genomes to construct detailed demographic models for the North African region, encompassing its two primary ethnic groups, the Arab and Amazigh populations. This was achieved through the utilization of the Approximate Bayesian Computation with Deep Learning (ABC-DL) framework and a novel algorithm called Genetic Programming for Population Genetics (GP4PG). This innovative approach enabled us to effectively model intricate demographic scenarios, utilizing a subset of 16 whole-genomes at >30X coverage. The demographic model suggested by GP4PG exhibited a closer alignment with the observed data compared to the ABC-DL model. Both methods point to a back-to-Africa origin of North African individuals and a close relationship of North African with Eurasian populations. Results support different origins for Amazigh and Arab populations, with Amazigh populations originating back in Epipaleolithic times, as early as 22.3 Kya. GP4PG model supports Arabization as the main source of Middle Eastern ancestry in North Africa. The GP4PG model better explaining the observed data includes population substructure in surrounding populations (sub-Saharan Africa and Middle East) with continuous gene flow after the split between populations (migration decay). In contrast to what we observed in the ABC-DL, the best GP4PG model does not require pulses of admixture from surrounding populations into North Africa pointing to soft splits as drivers of divergence in North Africa. ConclusionsWe have built a demographic model on North Africa that points to a back-to-Africa expansion and a differential origin between Arab and Amazigh populations, emphasizing the complex demographic history at a population level.

genomics↗

bioRxiv2023

Small variant benchmark from a complete assembly of X and Y chromosomes

The sex chromosomes contain complex, important genes impacting medical phenotypes, but differ from the autosomes in their ploidy and large repetitive regions. To evaluate variant detection on chromosomes X and Y, we created an 111,725 variant benchmark for the Genome in a Bottle HG002 reference material. We show how complete assemblies can expand benchmarks to difficult regions, but highlight remaining challenges benchmarking complex gene conversions, copy number variable gene arrays, and human satellites.

genomics↗

bioRxiv2023

A human urothelial microtissue model reveals shared colonization and survival strategies between uropathogens and asymptomatic bacteria

Urinary tract infection is among the most common infections worldwide, and is typically studied in animals and cell lines with limited uropathogenic strains. Here, we assessed diverse bacterial pathogens and asymptomatic bacteria (ASB) in a human urothelial microtissue model including full stratification/differentiation and urine tolerance. Several uropathogens and ASB-like E. coli invaded intracellularly, suggesting invasion is a shared survival strategy, instead of a virulence hallmark. The E. coli adhesin FimH was required for intracellular community formation, but not for invasion. Other shared lifestyles included filamentation (Gram-negatives), chaining (Gram-positives) and hijacking of exfoliating cells, while biofilm-like aggregates formed mainly with Pseudomonas and Proteus. Urothelial cells expelled invasive bacteria in Rab-/LC3-decorated structures, while highly cytotoxic/invasive uropathogens, but not ASB, disrupted host barrier function and strongly induced exfoliation and cytokine production. Overall, this work highlights diverse species-/strain-specific infection strategies and corresponding host responses in a human urothelial microenvironment, providing insights at the tissue, cell and molecular level. One-Sentence SummaryA human urothelial model revealed shared colonization strategies between uropathogens and asymptomatic bacteria, and pathogen-specific innate immune responses

microbiology↗

bioRxiv2023

Developmental Characterization of Neuronal Migration Anomalies and Axon Proliferation in mTOR pathway-associated Malformations of Cortical Development

Drug-resistant epilepsy (DRE) is a prevalent problem in children that can lead to abnormal development and various psychiatric comorbidities. Malformations of cortical development (MCD) include focal cortical dysplasia, tuberous sclerosis complex and hemimegalencephaly, which are the most common pathologies among children who undergo surgical resection for treatment of DRE. These disorders share many histopathological features, including dyslamination of the cerebral cortex and enlarged neuronal somata. Recently, genetic mutations in the mammalian target of rapamycin (mTOR) signaling cascade have been shown to underpin most MCDs. Rodent models, including the RhebCA model, recapitulate histologic and physiologic aspects of human DRE. However, there have been few studies characterizing the developmental time point of the histological changes seen in MCDs. In this study, we use in utero electroporation to upregulate the Rheb protein (directly upstream of mTOR) in a focal area of the neocortex. We demonstrate that mTOR dysregulation leads to focal dyslamination and increased neuronal size that is histologically similar to MCD, which correlates to spontaneous recurrent seizures. We used immunohistochemistry to investigate neuronal lamination at several time points during development between E18 and P21 and show early differences in lamination that persisted through development. Furthermore, the increased axonal length associated with mTOR upregulation occurs early in development. Our study provides a time frame for the initial development of abnormal neuronal migration and cellular growth that occurs in MCDs, and our data supports that these anatomical changes may contribute to the formation of epileptic networks.

neuroscience↗

bioRxiv2023

The scheduling of adolescence with Netrin-1 and UNC5C

Dopamine axons are the only axons known to grow during adolescence. Here, using rodent models, we examined how two proteins, Netrin-1 and its receptor, UNC5C, guide dopamine axons towards the prefrontal cortex and shape behaviour. We demonstrate in mice (Mus musculus) that dopamine axons reach the cortex through a transient gradient of Netrin-1 expressing cells - disrupting this gradient reroutes axons away from their target. Using a seasonal model (Siberian hamsters; Phodopus sungorus) we find that mesocortical dopamine development can be regulated by a natural environmental cue (daylength) in a sexually dimorphic manner - delayed in males, but advanced in females. The timings of dopamine axon growth and UNC5C expression are always phase-locked. Adolescence is an ill-defined, transitional period; we pinpoint neurodevelopmental markers underlying this period.

neuroscience↗