bioRxiv Science⌕ Search

Biology subjects

Botas, J.

Publications and source records attributed to Botas, J..

17 recordsLinked to original sources

Vision-Based Genomic Model for Copy Number Variant Pathogenicity Prediction

Copy number variants (CNVs) are a major class of structural genomic alterations underlying rare disease, including neurodevelopmental delay and intellectual disability, yet predicting their pathogenicity remains challenging. Existing methods reduce CNVs to region-level numerical features, discarding the positional structure and cross-track patterns that expert clinical reviewers use to interpret genomic evidence. To address this, we introduce TO_SCPLOWESSERACTC_SCPLOW for CNV, a track-based spatial representation for CNV pathogenicity prediction, which represents each variant as a base-pair-resolution multi-track image and models spatial genomic patterns across annotation tracks while preserving positional structure and cross-track dependencies. Trained on a chromosome-level hold-out split of the ClinVar dataset, TO_SCPLOWESSERACTC_SCPLOW outperforms prior methods on held-out and curated noncoding benchmarks, improving AUROC by up to 0.10 over the state-of-the-art baseline. On the independent DECIPHER cohort, the model demonstrates generalizability by maintaining the highest AUROC and the highest F1 score across baselines. Furthermore, our model localizes pathogenic signals to clinically meaningful genomic subregions, providing track-annotated evidence that supports practical clinical interpretation.

bioinformatics↗

Co-option of ILF2/3 in primates restrains Alu hyper-editing to enable cell fate transitions

Understanding human specific mechanisms of cell fate control is essential for advancing developmental biology and regenerative medicine. Here, we identify the ILF2/3 complex as a critical regulator of primate cell fate transitions. Using genetically and epigenetically engineered gastruloids and adult stem cells, we show that ILF2/3 is required for gastrulation in primates but not mice, and for differentiation of adult progenitor cells. Mechanistically, ILF2/3 directly binds Alu elements in chromatin-associated RNAs and shields them from ADAR1-mediated adenosine-to-inosine (A-to-I) editing. Acute ILF2/3 degradation increases A-to-I editing at Alu elements, but not murine retrotransposons, leading to aberrant splicing and nonsense-mediated decay of transcripts encoding key chromatin regulators in primate cells. This in turn destabilizes the epigenetic landscape and blocks lineage commitment across all three germ layers. Re-expression of correctly spliced chromatin regulators rescues differentiation defects in ILF2/3-deficient cells, functionally linking Alu editing control to chromatin regulation and cell fate. These findings define an evolutionary mechanism that restrains retrotransposon-associated RNA editing to preserve proteome integrity and enable primate-specific developmental programs.

genetics↗

Modeling the effects of Huntington disease on age-related genes reveals CXXC4 as an epigenetic target to restore health and excitability of Drd1-expressing striatal neurons

Neurons adapt gene expression to counter aging, yet the mechanisms by which they harness age- related genes to resist neurodegenerative disease remain elusive. We found that transcriptionalaging inversion (TAGI) in the Drd1-expressing striatal neurons (Drd1 SNs) of Huntingtons disease (HD) knock-in (Hdh) mice exhibits discrete patterns against a TAG-like (TAGL) signature. Strikingly, TAGI dynamics may explain disease progression more accurately than TAGL. Moreover, in Drd1 SNs, genes affected by 3UTR accumulation during aging are predisposed to downregulation in aging and deregulation in Hdh mice. By integrating age-related 3UTR data and Hdh-mice data, we identified a CAG-repeat-dependent network of upregulated genes with compensatory potential. This network features (i) Atad-5, a P CNA unloader that modifies CAG expansion in human HD plasma samples, and (ii) CXXC4 (IDAX), an epigenetic regulator whose early-stage upregulation is lost as behavioral symptoms worsen in Hdh mice. Functionally, CXXC4 reduces the senescence marker p16INK4a and restores glutamate excitability in human HD iPS cell-derived SNs. Collectively, these findings suggest that Drd1 SN resilience capacity against HD relies on discrete age-related patterns and responses transiently activated in early disease stages. The reactivation of specific age-related genes such as CXXC4 may notably restore cortico-striatal function in HD.

neuroscience↗

MARRVEL-MCP enables natural language variant interpretation through autonomous workflow construction

AO_SCPLOWBSTRACTC_SCPLOWRare disease variant interpretation requires navigating multiple genomic databases with strict input formats and synthesizing heterogeneous evidence, creating barriers for non-experts and cognitive burdens even for specialists. MARRVEL exemplifies this challenge by requiring precise queries (e.g., HGVS notation) and returning complex, difficult-to-synthesize outputs. To address this input-output asymmetry, we developed MARRVEL-MCP, a natural language interface enabling large language models (LLMs) to perform end-to-end variant interpretation via structured tool access. This work demonstrates the impact of context engineering--the deliberate design of domain-aware tool environments and information scaffolding--in reshaping the role of model scale in genomics. MARRVEL-MCP equips LLMs with 39 tools spanning gene and variant utilities, pathogenicity databases, phenotype resources, expression atlases, ortholog data, and literature APIs. Without hard-coded pipelines, LLMs autonomously infer workflows, performing named-entity recognition, identifier normalization, and multi-database synthesis from narrative queries. Using 45 expert-curated questions, lightweight models (3B-20B parameters) with MARRVEL-MCP matched or outperformed larger models lacking tool access. A 20B-parameter model (gpt-oss-20b) achieved a 95% pass rate versus 33% without MARRVEL-MCP, approaching state-of-the-art proprietary performance. Although accuracy remains below the 100% required for autonomous diagnosis and token usage is considerable, these results show that well-designed context can compensate for limited model capacity. These findings establish context engineering as a core principle for biomedical AI, enabling efficient, scalable integration of LLMs with curated genomic resources. MARRVEL-MCP is available at https://github.com/hyunhwan-bcm/MARRVEL_MCP/.

bioinformatics↗

Revealing the nervous system requirements of Alzheimer disease risk genes in Drosophila

Most Alzheimers disease (AD) susceptibility genes have poorly understood roles in the central nervous system (CNS). To address this gap, we systematically characterized 100 conserved candidate AD risk genes using a cross-species strategy in the fruit fly, Drosophila melanogaster. Genes were prioritized based primarily on human functional genomic evidence. We generated custom, loss-of-function alleles for each of the conserved fly orthologs. Most of the genes (80%) are expressed in the adult brain, including 24 neuron- and 13 glia-specific expression patterns. Overall, we identify 50 candidate AD risk gene homologs with requirements for CNS structure or function, including 18 whose loss of function causes neurodegeneration (e.g., Snx6/SNX32 and ClC-a/CLCN1), 35 required for neurophysiology (e.g., Arr1/ARRB2, stai/STMN4), and 8 with diminished CNS resilience following a thermal or mechanical stress (e.g., cindr/CD2AP, Amph/BIN1). In a parallel screen, we found 28 AD risk gene homologs (e.g, Ets98B/SPI1, Yod1/YOD1) that modify the neurotoxicity of either amyloid-{beta} peptide or tau protein, which aggregate to form AD pathology. To translate our findings back to human AD, we developed and deployed oligogenic risk scores based on gene clusters with shared nervous system phenotypes in flies, pinpointing functional pathways that differentially drive AD risk. Our results--available online via the Alzheimers Locus Integrative Cross-species Explorer (alice.nrihub.org)--reveal novel nervous system requirements for dozens of AD risk genes and may enable dissection of causal heterogeneity in AD.

genetics↗

Progressive Remodeling of Global Protein Interaction Networks in a Mouse Model of Tauopathy

Neurodegenerative disease is marked not just by loss of proteins or cells, but by dynamic rewiring of macromolecular interaction networks that precede and drive pathology. Here, we present the first temporally resolved, systems-scale map of multi-protein complex remodeling in a tauopathy model, integrating co-fractionation mass spectrometry, quantitative phosphoproteomics, and machine learning to decode phosphorylation-dependent shifts in protein interactomes across disease progression. This interactomic atlas identifies functionally validated assemblies--including MAPT-Dpysl2 and Cyfip1-actin complexes--that modulate early disease phenotypes in vivo. By revealing how phosphorylation tunes macromolecular complex architecture and function, this work reframes tauopathy as a disease of dynamic network instability, and establishes a generalizable framework for early detection and mechanistic dissection of neurodegeneration.

neuroscience↗

Lemur: A Single-Cell Foundation Model with Fine-Tuning-Free Hierarchical Cell-Type Generation for Drosophila melanogaster

Single-cell genomics has revolutionized our understanding of cellular heterogeneity, but automating its analysis remains an open challenge. Cell-type annotation represents a critical bottleneck, particularly as datasets grow in size and complexity. While foundation models have shown promise in addressing this challenge, existing approaches require extensive fine-tuning for effective cell-type annotation. Here, we present Lemur (Large Expression Model for Understanding scRNA-seq), a single-cell foundation model specifically designed for Drosophila melanogaster. Lemur achieves fine-tuning-free cell-type annotation through comprehensive pre-training on an integrated whole-organism atlas with a unified cell-type annotation schema. To leverage this unified schema, we developed a dedicated hierarchical cell-type decoder architecture. This approach enables Lemur to generate consistent cell-type predictions across multiple levels of granularity without requiring additional training on new datasets. The model demonstrates strong performance across diverse tissue types, experimental conditions, and sequencing technologies. It also achieves batch-effect correction without explicitly training for this task. This automated analysis capability positions Lemur as an effective tool for the fly research community. Beyond its immediate applications, Lemur establishes a framework for accelerating biological discovery. It enables rapid iteration between computational predictions and experimental validation in the highly controlled Drosophila melanogaster system, with potential implications for translational research in human biology, particularly in aging and neurodegenerative disease studies.

bioinformatics↗

Systems genetic dissection of Alzheimer's disease brain gene expression networks

In Alzheimers disease (AD), changes in the brain transcriptome are hypothesized to mediate the impact of neuropathology on cognition. Gene expression profiling from postmortem brain tissue is a promising approach to identify causal pathways; however, there are challenges to definitively resolve the upstream pathologic triggers along with the downstream consequences for AD clinical manifestations. We have functionally dissected 30 AD-associated gene coexpression modules using a cross-species strategy in fruit fly (Drosophila melanogaster) models. Integrating longitudinal RNA-sequencing and behavioral phenotyping, we interrogated the unique and shared transcriptional responses to amyloid beta (A{beta}) plaques, tau neurofibrillary tangles, and/or aging, along with potential links to progressive neuronal dysfunction. Our results highlight hundreds of conserved, differentially expressed genes mapping to human AD regulatory networks. To confirm causal modules and pinpoint AD network drivers, we performed systematic in vivo genetic manipulations of 357 conserved, prioritized targets, identifying 141 modifiers of A{beta}- and/or tau-induced neurodegeneration. We discover an up-regulated network that is significantly enriched for both AD risk variants and markers of immunity / inflammation, and which promotes A{beta} and tau-mediated neurodegeneration based on fly genetic manipulations in neurons. By contrast, a synaptic regulatory network is strongly downregulated in human brains with AD and is enriched for loss-of-function suppressors of A{beta}/tau in Drosophila. Additional experiments suggest that this human brain transcriptional module may respond to and modulate A{beta}-induced glutamatergic hyperactivation injury. In sum, our cross-species, systems genetic approach establishes a putative causal chain linking AD pathology, large-scale gene expression perturbations, and ultimately, neurodegeneration.

systems biology↗

Genetic analysis of the X-linked Adrenoleukodystrophy ABCD1 gene in Drosophila uncovers a role in Peroxisomal dynamics

X-linked adrenoleukodystrophy (X-ALD) is a progressive neurodegenerative disorder caused by a loss-of-function (LOF) mutation in the ATP-binding cassette subfamily D member 1 (ABCD1) gene, leading to the accumulation of very long-chain fatty acids (VLCFAs). This disorder exhibits striking heterogeneity; some male patients develop an early childhood neuroinflammatory demyelination disorder, while other patients, including adult males and most affected female carriers, experience a chronic progressive myelopathy. Adrenocortical failure is observed in almost all male patients, with age of onset varying sometimes being the first diagnostic finding. The gene underlying this spectrum of disease encodes an ATP-binding cassette (ABC) transporter that localizes to peroxisomes and facilitates VLCFA transport. X-ALD is considered a single peroxisomal component defect and does not play a direct role in peroxisome assembly. Drosophila models of other peroxisomal genes have provided mechanistic insight into some of the neurodegenerative mechanisms with reduced lifespan, retinal degeneration, and VLCFA accumulation. Here, we perform a genetic analysis of the fly ABCD1 ortholog Abcd1 (CG2316). Knockdown or deficiency of Abcd1 leads to VLCFA accumulation, salivary gland defects, locomotor impairment and retinal lipid abnormalities. Interestingly, there is also evidence of reduced peroxisomal numbers. Flies overexpressing the human cDNA for ABCD1 display a wing crumpling phenotype characteristic of the pex2 loss-of-function. Surprisingly, overexpression of human ABCD1 appears to inhibit or overwhelm peroxisomal biogenesis to levels similar to null mutations in fly pex2, pex16 and pex3. Drosophila Abcd1 is therefore implicated in peroxisomal number, and overexpression of the human ABCD1 gene acts a potent inhibitor of peroxisomal biogenesis in flies.

genetics↗

Multi-epitope immunocapture of huntingtin reveals striatum-selective molecular signatures

Huntingtons disease (HD) is a debilitating neurodegenerative disorder affecting an individuals cognitive and motor abilities. HD is caused by mutation in the huntingtin gene producing a toxic polyglutamine-expanded protein (mHTT) and leading to degeneration in the striatum and cortex. Yet, the molecular signatures that underlie tissue-specific vulnerabilities remain unclear. Here, we investigate this aspect by leveraging multi-epitope protein interaction assays, subcellular fractionation, thermal proteome profiling, and genetic modifier assays. Use of human cell, mouse, and fly models afforded capture of distinct subcellular pools of epitope-enriched and tissue-dependent interactions linked to dysregulated cellular pathways and disease relevance. We established an HTT association with nearly all subunits of the transcriptional regulatory Mediator complex (20/26), with preferential enrichment of MED15 in the tail domain. Using HD and KO models, we find HTT modulates the subcellular localization and assembly of Mediator. We demonstrated striatal enriched and functional interactions with regulators of calcium homeostasis and chromatin remodeling, whose disease relevance was supported by HD fly genetic modifiers assays. Altogether, we offer insights into tissue- and localization-dependent (m)HTT functions and pathobiology.

neuroscience↗

MeCP2 Interacts with the Super Elongation Complex to Regulate Transcription

Loss-of-function mutations in methyl-CpG binding protein 2 (MECP2) cause Rett syndrome, a postnatal neurodevelopmental disorder that occurs in [~]1/10,000 live female births. MeCP2 binds to methylated cytosines across genomic DNA and recruits various partners to regulate gene expression. MeCP2 has been shown to repress transcription in vitro and interacts with co-repressors such as the Sin3A and NCoR complexes. Based on these observations, MeCP2 has been largely considered as a repressor of transcription. However, a mouse model of RTT displays many down-regulated genes, and those same genes are up-regulated in a MECP2 duplication mouse model. Furthermore, TCF20, which has been associated with transcriptional activation, have recently been identified as a protein interactor of MeCP2. These data broaden the potential functions of MeCP2 as a regulator of gene expression. Yet, the molecular mechanisms underlying MeCP2-dependent gene regulation remain largely unknown. Here, using a human MECP2 gain-of-function Drosophila model, we screened for genetic modifiers of MECP2-induced phenotypes. Our approach identified several subunits of the Drosophila super elongation complex, a P-TEFb containing RNA polymerase II (RNA pol II) elongation factor required for the release of promoter-proximally paused RNA pol II, as genetic interactors of MECP2. We discovered that MeCP2 physically interacts with the SEC in human cells and in the mouse brain. Furthermore, we found that MeCP2 directly binds AFF4, the scaffold of the SEC, via the transcriptional repression domain. Finally, loss of MeCP2 in the mouse cortex caused reduced binding of AFF4 specifically on a subset of genes involved in the regulation of synaptic function, which also displayed the strongest decrease in RNA pol II binding in the genebody. Taken together, our study reveals a previously unrecognized mechanism through which MeCP2 regulates transcription, providing a new dimension to its regulatory role in gene expression.

molecular biology↗

SPA-STOCSY: An Automated Tool for Identification of Annotated and Non-Annotated Metabolites in High-Throughput NMR Spectra

Nuclear Magnetic Resonance (NMR) spectroscopy is widely used to analyze metabolites in biological samples, but the analysis can be cumbersome and inaccurate. Here, we present a powerful automated tool, SPA-STOCSY (Spatial Clustering Algorithm - Statistical Total Correlation Spectroscopy), which overcomes the challenges by identifying metabolites in each sample with high accuracy. As a data-driven method, SPA-STOCSY estimates all parameters from the input dataset, first investigating the covariance pattern and then calculating the optimal threshold with which to cluster data points belonging to the same structural unit, i.e. metabolite. The generated clusters are then automatically linked to a compound library to identify candidates. To assess SPA-STOCSYs efficiency and accuracy, we applied it to synthesized and real NMR data obtained from Drosophila melanogaster brains and human embryonic stem cells. In the synthesized spectra, SPA outperforms Statistical Recoupling of Variables, an existing method for clustering spectral peaks, by capturing a higher percentage of the signal regions and the close-to-zero noise regions. In the real spectra, SPA-STOCSY performs comparably to operator-based Chenomx analysis but avoids operator bias and performs the analyses in less than seven minutes of total computation time. Overall, SPA-STOCSY is a fast, accurate, and unbiased tool for untargeted analysis of metabolites in the NMR spectra. As such, it might accelerate the utilization of NMR for scientific discoveries, medical diagnostics, and patient-specific decision making.

bioinformatics↗

Tau polarizes an aging transcriptional signature to excitatory neurons and glia

Aging is a major risk factor for Alzheimers disease (AD), and cell-type vulnerability underlies its characteristic clinical manifestations. We have performed longitudinal, single-cell RNA-sequencing in Drosophila with pan-neuronal expression of human tau, which forms AD neurofibrillary tangle pathology. Whereas tau- and aging-induced gene expression strongly overlap (93%), they differ in the affected cell types. In contrast to the broad impact of aging, tau-triggered changes are strongly polarized to excitatory neurons and glia. Further, tau can either activate or suppress innate immune gene expression signatures in a cell type-specific manner. Integration of cellular abundance and gene expression pinpoints Nuclear Factor Kappa B signaling as a potential marker for neuronal vulnerability. We also highlight the conservation of cell type-specific transcriptional patterns between Drosophila and human postmortem brain tissue. Overall, our results create a resource for dissection of dynamic, age-dependent gene expression changes at cellular resolution in a genetically tractable model of tauopathy.

genomics↗

Functional screening of lysosomal storage disorder genes identifies modifiers of alpha-synuclein mediated neurodegeneration

Heterozygous variants in the glucocerebrosidase (GBA) gene are common and potent risk factors for Parkinsons disease (PD). GBA also causes the autosomal recessive lysosomal storage disorder (LSD), Gaucher disease, and emerging evidence from human genetics implicates many other LSD genes in PD susceptibility. We have systemically tested 88 conserved fly homologs of 38 human LSD genes for requirements in the aging adult Drosophila brain and for potential genetic interactions with neurodegeneration caused by -synuclein (Syn), which forms Lewy body pathology in PD. Our screen identifies 15 genetic enhancers of Syn-induced progressive locomotor dysfunction, following knockdown of fly homologs of GBA and other LSD genes with independent support as PD susceptibility factors from human genetics (SCARB2, SMPD1, CTSD, GNPTAB, SLC17A5). For several genes, results from multiple alleles support dose-sensitivity and context-dependent pleiotropy in the presence or absence of Syn. Homologs of 2 genes causing cholesterol storage disorders, Npc1a / NPC1 and Lip4 / LIPA, were independently confirmed as loss-of-function enhancers of Syn-induced brain structural degeneration. The enzymes encoded by several modifier genes are upregulated in Syn transgenic flies, based on unbiased proteomics, revealing a possible compensatory response. Overall, our results reinforce the important role of lysosomal genes in brain health and PD pathogenesis, and implicate several metabolic pathways, including cholesterol homeostasis, in Syn-mediated neurodegeneration.

genetics↗

Functional and evolutionary significance of unknown genes from uncultivated taxa

Most microbes on our planet remain uncultured and poorly studied. Recent efforts to catalog their genetic diversity have revealed that a significant fraction of the observed microbial genes are functional and evolutionary untraceable, lacking homologs in reference databases. Despite their potential biological value, these apparently unrelated orphan genes from uncultivated taxa have been routinely discarded in metagenomics surveys. Here, we analyzed a global multi-habitat dataset covering 151,697 medium and high-quality metagenome assembled genomes (MAGs), 5,969 single-amplified genomes (SAGs), and 19,642 reference genomes, and identified 413,335 highly curated novel protein families under strong purifying selection out of previously considered orphan genes. These new protein families, representing a three-fold increase over the total number of prokaryotic orthologous groups described to date, spread out across the prokaryote phylogeny, can span multiple habitats, and are notably overrepresented in recently discovered taxa. By genomic context analysis, we pinpointed thousands of unknown protein families to phylogenetically conserved operons linked to energy production, xenobiotic metabolism and microbial resistance. Most remarkably, we found 980 previously neglected protein families that can accurately distinguish entire uncultivated phyla, classes, and orders, likely representing synapomorphic traits that fostered their divergence. The systematic curation and evolutionary analysis of the unique genetic repertoire of uncultivated taxa opens new avenues for understanding the biology and ecological roles of poorly explored lineages at a global scale.

microbiology↗

Modulating glial genes involved in synaptic function mitigates pathogenesis and behavioral deficits in a Drosophila model of Huntington's Disease

Most research on neurodegenerative diseases has focused on neurons, yet glia help form and maintain the synapses whose loss is so prominent in these conditions. To investigate the contributions of glia to Huntingtons disease (HD), we studied transcriptomic changes in HD human, HD mice, and Drosophila expressing human mutant Huntingtin (mHTT) in either glia, neurons or both. A large portion of conserved genes are concordantly dysregulated across the three species; we tested these genes in a high-throughput behavioral assay and found that downregulation of genes involved in synapse assembly mitigated pathogenesis and behavioral deficits. To our surprise, mitigating glial pathogenesis by dNRXN3 knockdown was sufficient to improve the phenotype of flies expressing mHTT in neurons, suggesting that mHTTs toxic effects in glia ramify throughout the brain. This supports a model in which dampening synaptic function is protective because it attenuates the excitotoxicity that characterizes HD.

systems biology↗

Spinocerebellar Ataxia Type 1 protein Ataxin-1 is signalled to DNA damage by Ataxia Telangiectasia Mutated kinase

Spinocerebellar Ataxia Type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by a polyglutamine expansion in the ataxin-1 protein. Recent genetic correlational studies have implicated DNA damage repair pathways in modifying the age at onset of disease symptoms in SCA1 and Huntingtons Disease, another polyglutamine expansion disease. We demonstrate that both endogenous and transfected ataxin-1 localizes to sites of DNA damage, which is impaired by polyglutamine expansion. This response is dependent on ataxia telangiectasia mutated (ATM) kinase activity. Further, we characterize an ATM phosphorylation motif within ataxin-1 at serine 188. We show reduction of the Drosophila ATM homolog levels in a ATXN1[82Q] Drosophila model through shRNA or genetic cross ameliorates motor symptoms. These findings offer a possible explanation as to why DNA repair was implicated in SCA1 pathogenesis by past studies. The similarities between the ataxin-1 and the huntingtin responses to DNA damage provide further support for a shared pathogenic mechanism for polyglutamine expansion diseases.

cell biology↗