Biology subjects

Montgomery, A.

Publications and source records attributed to Montgomery, A..

11 recordsLinked to original sources

bioRxiv2026

CX3CR1 And MHCII Define Distinct Synovial Macrophage Populations With Conserved Inflammatory Response Across Mouse Models Of Rheumatoid Arthritis.

Macrophages in the synovial lining are critical for the maintenance of healthy tissue while also contributing to the pathogenesis of rheumatoid arthritis (RA). However, the field currently lacks a unifying characterization of synovial macrophage heterogeneity across steady-state and inflammation. Here, we defined 4 transcriptionally distinct populations of synovial macrophages CX3CR1+MHCII- (lining); CX3CR1-MHCII- (interstitial/sublining); CX3CR1-MHCII+ (monocyte-derived); and CX3CR1+MHCII+ (infiltrating). The MHCII-populations are long-lived and derived from embryonic precursors regardless of localization while the MHCII+ populations differentiate from bone marrow (BM) progenitors dependent on CCR2. We identified conserved activation pathways between acute and chronic mouse models of inflammatory arthritis as well as novel arthritis-associated subpopulations. During peak inflammation, the influx of BM-derived cells was associated with upregulation of monocyte-related genes with concurrent down-regulation of tissue-resident genes. Our results provide a unifying schema for describing synovial macrophages across conditions and pave the way for future studies in modulating transcriptional activity in rheumatoid arthritis.

immunology↗

bioRxiv2025

Tracking active heterotrophic microbial communities in the Guaymas Basin deep biosphere with BONCAT-FACS

The marine deep biosphere harbors microbial communities that drive organic matter transformations and biogeochemical cycles. Previous work on these communities has focused either on genomic characterization or metabolic activity measurements. However, to understand microbial ecophysiology in the deep biosphere taxonomic identity and metabolic function must be connected on both single-cell and ecosystem scales. In this work, we optimized a bioorthogonal non-canonical amino acid tagging fluorescence-activated cell sorting (BONCAT-FACS) workflow for low-biomass deep-biosphere sediments obtained during International Ocean Discovery Program Expedition 385 (IODP 385). BONCAT-FACS with 16S rRNA gene amplicon sequencing as well as metagenomics of sediment communities was applied to characterize translationally active communities in hydrothermally altered subsurface sediments of the Guaymas Basin. Our results revealed a heterotrophic microbial population throughout all sediments examined, with taxa translationally active down to our deepest sampling point, 154 meters below the seafloor. Based on 16S rRNA gene identities, the translationally active microbial community was dominated by heterotrophic members of the Gammaproteobacteria, Bacilli, Deinococci, and Alphaproteobacteria. These taxa are likely key contributors to cycling the large quantities of hydrothermally altered organic matter in Guaymas Basin sediments. To further elucidate the metabolic capacity of active taxa, we mapped 16S rRNA gene amplicons to metagenome assembled genomes (MAGs) previously obtained from IODP 385. These MAGs contained genes associated with C1 metabolism, carbohydrate degradation, and fermentation, indicating that active taxa leverage these metabolisms for energy conservation. Our results demonstrate that BONCAT-FACS provides high-throughput and single-cell insights into the metabolic activity of microbes in the low-biomass marine subsurface.

microbiology↗

bioRxiv2025

Histone methyltransferase PRDM9 promotes survival of drug-tolerant persister cells in glioblastoma

Chemotherapy often kills a large fraction of cancer cells but leaves behind a small population of drug- tolerant persister cells. These persister cells survive drug treatments through reversible, non-genetic mechanisms and cause tumour recurrence upon cessation of therapy. Here, we report a drug tolerance mechanism regulated by the germ-cell-specific H3K4 methyltransferase PRDM9. Through histone proteomic, transcriptomic, lipidomic, and ChIP-sequencing studies combined with CRISPR knockout and phenotypic drug screen, we identified that chemotherapy-induced PRDM9 upregulation promotes metabolic rewiring in glioblastoma stem cells, leading to chemotherapy tolerance. Mechanistically, PRDM9-dependent H3K4me3 at cholesterol biosynthesis genes enhances cholesterol biosynthesis, which persister cells rely on to maintain homeostasis under chemotherapy- induced oxidative stress and lipid peroxidation. PRDM9 inhibition, combined with chemotherapy, resulted in strong anti-cancer efficacy in preclinical glioblastoma models, significantly enhancing the magnitude and duration of the antitumor response by eliminating persisters. These findings demonstrate a previously unknown role of PRDM9 in promoting metabolic reprogramming that enables the survival of drug-tolerant persister cells.

cancer biology↗

bioRxiv2024

Methane production from hydrocarbons by consortia dominated by ANME archaea

Understanding microbial production and consumption of methane, a potent greenhouse gas in the atmosphere, is critical for bridging knowledge gaps in global carbon cycling. In anoxic environments, methane is known to be produced through hydrogenotrophic, acetoclastic or methylotrophic mechanisms. Methane production from hydrocarbons may also be important, especially in hydrocarbon-rich environments, like the Gulf of California, but the mechanism of this hydrocarbonoclastic methanogenesis remains unclear. The activity of consortia of anaerobic methane oxidizing (ANME) archaea and bacteria limits the release of methane to the atmosphere by consuming methane in anoxic environments globally. Here we used isotopic-labeling to track the conversion of hydrocarbons (hexadecane and naphthalene) to methane in enrichments from hydrothermally impacted, hydrocarbon-rich sediments from the Gulf of California. Methane was produced directly from hexadecane and naphthalene, in both the presence and absence of sulfate. We reconstructed metagenomic assembled-genomes (MAGs) from these experiments which revealed a mixture of bacteria dominated by Desulfobacteriota and Bacteroidota, and archaea dominated by Aeinigmarchaeota, Thermoplasmatota, and ANME group 2c. The ANME-2c were the only MAGs that encoded methyl coenzyme M reductases (McrA) and complete Wood-Ljungdahl pathways (WLP). This suggests that ANME-2c archaea may be involved in the production of methane along the seafloor, and that our understanding of the roles of these globally important microbes is not yet fully appreciated.

microbiology↗

bioRxiv2024

Ribosomal DNA arrays are the most H-DNA rich element in the human genome

Repetitive DNA sequences can form non-canonical structures such as H-DNA which is an intramolecular triplex DNA structure. The new Telomere-to-Telomere (T2T) genome assembly for the human genome has eliminated gaps, enabling the examination of highly repetitive regions including centromeric and pericentromeric repeats and ribosomal DNA arrays. This gapless assembly allows for the examination of the distribution of H-DNA sequences in parts of the human genome that were not previously annotated. We find that H-DNA appears once every 30,000 bps in the human genome. Its distribution is highly inhomogeneous with H-DNA motif hotspots being detectable in acrocentric chromosomes. Ribosomal DNA arrays in acrocentric chromosomes are the genomic element with the highest H-DNA enrichment, with 13.22% of total H-DNA motifs being found in ribosomal DNA arrays, representing a 42.65-fold enrichment over what would be expected by chance. Across the acrocentric chromosomes we report that 55.87% of all H-DNA motifs found in these chromosomes are in rDNA array loci. The H-DNA motifs are primarily found in the intergenic spacer regions of the ribosomal DNA arrays, generating repeated clusters. We also discover that binding sites for PRDM9, a protein that regulates the formation of double-strand breaks and determines the meiotic recombination hotspots in humans and most mammals, are over 5-fold enriched for H-DNA motifs. Finally, we provide evidence that our findings are consistent in other non-human great ape genomes. We conclude that ribosomal DNA arrays are the most enriched genomic loci for H-DNA sequences in human and other great ape genomes.

genomics↗

bioRxiv2024

Quadrupia: Derivation of G-quadruplexes for organismal genomes across the tree of life

G-quadruplex DNA structures exhibit a profound influence on essential biological processes, including transcription, replication, telomere maintenance, and genomic stability. These structures have demonstrably shaped organismal evolution. However, a comprehensive, organism-wide G-quadruplex map encompassing the diversity of life has remained elusive. Here, we introduce Quadrupia, the most extensive and well-characterized G-quadruplex database to date, facilitating the exploration of G-quadruplex structures across the evolutionary spectrum. Quadrupia has identified G-quadruplex sequences in 108,449 reference genomes, with a total of 140,181,277 G-quadruplexes. The database also hosts a collection of 319,784 G-quadruplex clusters of 20 or more members, annotated by taxonomic distributions, multiple sequence alignments, profile Hidden Markov Models and cross-references to G-quadruplex 3D structures. Examination of G-quadruplexes across functional genomic elements in different taxa indicates preferential orientation and positioning, with significant differences between individual taxonomic groups. For example, we find that G-quadruplexes in bacteria with a single replication origin display profound preference for the leading orientation. Finally, we experimentally validate the most frequently observed G-quadruplexes using CD-spectroscopy, UV melting, and fluorescent-based approaches. Quadrupia is publicly available through https://www.pavlopoulos-lab.org/quadrupia.

genomics↗

bioRxiv2023

Nucleic Quasi-Primes: Identification of the Shortest Unique Oligonucleotide Sequences in a Species

Despite the exponential increase in sequencing information driven by massively parallel DNA sequencing technologies, universal and succinct genomic fingerprints for each organism are still missing. Identifying the shortest species-specific nucleic sequences offers insights into species evolution and holds potential practical applications in agriculture, wildlife conservation, and healthcare. We propose a new method for sequence analysis termed nucleic "quasi-primes", the shortest occurring sequences in each of 45,785 organismal reference genomes, present in one genome and absent from every other examined genome. In the human genome, we find that the genomic loci of nucleic quasi-primes are most enriched for genes associated with brain development and cognitive function. In a single-cell case study focusing on the human primary motor cortex, nucleic quasi-prime genes account for a significantly larger proportion of the variation based on average gene expression. Non-neuronal cell-types, including astrocytes, endothelial cells, microglia perivascular-macrophages, oligodendrocytes, and vascular and leptomeningeal cells, exhibited significant activation of quasi-prime containing gene associations related to cancer, while simultaneously suppressing quasi-prime containing genes were associated with cognitive, mental, and developmental disorders. We also show that human disease-causing variants, eQTLs, mQTLs and sQTLs are 4.43-fold, 4.34-fold, 4.29-fold and 4.21-fold enriched at human quasi-prime loci, respectively. These findings indicate that nucleic quasi-primes are genomic loci linked to the evolution of species-specific traits and in humans they provide insights in the development of cognitive traits and human diseases, including neurodevelopmental disorders.

genomics↗

bioRxiv2023

kmerDB: A Database Encompassing the Set of Genomic and Proteomic Sequence Information for Each Species

The rapid decline in sequencing cost has enabled the generation of reference genomes and proteomes for a growing number of organisms. However, at the present time, there is no established repository that provides information about organism-specific genomic and proteomic sequences of certain lengths, also known as kmers, that are either present or absent in each genome or proteome. In this article, we present kmerDB, a database accessible through an interactive web interface that provides kmer based information from genomic and proteomic sequences in a systematic way. kmerDB currently contains 202,340,859,107 base pairs and 19,304,903,356 amino acids, spanning 45,785 and 22,386 reference genomes and proteomes, respectively, as well as 14,658,776 and 149,264,442 genomic and proteomic species-specific sequences, termed quasi-primes. Additionally, we provide access to 5,186,757 nucleic and 214,904,089 peptide sequences that are absent from every genome and proteome, termed primes. kmerDB features a user-friendly interface offering various search options and filters for easy parsing and searching. The service is available at: www.kmerdb.com.

genomics↗

bioRxiv2023

The determinants of the rarity of nucleic and peptide short sequences in nature

The prevalence of nucleic and peptide short sequences across organismal genomes and proteomes has not been thoroughly investigated. Here we examined 45,785 reference genomes and 21,871 reference proteomes, spanning archaea, bacteria, viruses and eukaryotes to calculate the rarity of short sequences in them. To capture this, we developed a metric of the rarity of each sequence in nature, the Anti-Kardashian index. We find that the frequency of certain dipeptides in rare oligopeptide sequences is hundreds of times lower than expected, which is not the case for any dinucleotides. We also generate predictive regression models that infer the rarity of nucleic and proteomic sequences in nature. For six-mer peptide kmers the R2 performance of the regression models based on amino acid and dipeptide content is 0.816, whereas models based on physicochemical features achieve an R2 of 0.788. For twelve-mer nucleic kmers the R2 performance of our models based on mono and dinucleotides is 0.481. Our results indicate that the mono and dinucleotide composition of nucleic sequences and the amino acids, dipeptides and physicochemical properties of peptide sequences can explain a significant proportion of the variance in their frequencies between organisms in nature.

genomics↗

bioRxiv2022

KAP is the neuronal organelle adaptor for Kinesin-2 KIF3AB and KIF3AC

Kinesin-driven organelle transport is crucial for neuron development and maintenance, yet the mechanisms by which kinesins specifically bind their organelle cargoes remain undefined. In contrast to other transport kinesins, the neuronal function and specific organelle adaptors of heterodimeric Kinesin-2 family members KIF3AB and KIF3AC remain unknown. We developed a novel microscopy-based assay to define protein-protein interactions in intact neurons. The experiments found that KIF3AB and KIF3AC both bind KAP. These interactions are mediated by the distal C-terminal tail regions and not the coiled-coil domain. We used live-cell imaging in cultured hippocampal neurons to define the localization and trafficking parameters of KIF3AB and KIF3AC organelle populations. We discovered that KIF3AB/KAP and KIF3AC/KAP bind the same organelle populations and defined their transport parameters in axons and dendrites. The results also show that [~]12% of KIF3 organelles contain the RNA binding protein, adenomatous polyposis coli. These data point towards a model in which KIF3AB and KIF3AC use KAP as their neuronal organelle adaptor and that these kinesins mediate transport of a range of organelles.

neuroscience↗

bioRxiv2020

Macrophages drive the inflammatory phase in experimental osteoarthritis

Macrophages fulfill critical functions in maintaining tissue homeostasis in steady-state, as well as in inflammation and immune response. Inflammation is not considered a major driver of osteoarthritis (OA), but macrophages have been implicated in its pathogenesis. Here, we use two mouse models of experiment OA - collagenase-induced osteoarthritis (CIOA) and destabilization of the medial meniscus (DMM) - to quantify the immune cell infiltration into the knee joint during the early stages of disease. We find that the peak of inflammation occurs at day 3 in CIOA and is characterized by a transitory increase in neutrophils and monocytes and a longer-lived expansion of synovial macrophages. Macrophage sub-populations are disproportionally expanded with CX3CR1+ cells accounting for a larger proportion of the macrophage compartment. Transcriptional profiling demonstrates that synovial macrophages up-regulate inflammatory genes coinciding with peak inflammation and down-regulate genes associated with homeostasis and tissue-residence. Female mice exhibit a similar expansion of macrophages post-CIOA indicating that the inflammatory phase is not sex-specific. Finally, we find day 7 post-DMM is also characterized by increases in neutrophil, monocyte, and macrophage sub-population numbers. These results support a role for macrophages in early stages of OA through driving the inflammatory phase. Further investigation may elucidate potential targets for the prevention or attenuation of OA-associated cartilage damage.

immunology↗