Biology subjects

Zhang, Q.

Publications and source records attributed to Zhang, Q..

At least 253 records · Page 14Linked to original sources

bioRxiv2025

Detection of Diffuse to Focal Myocardial Fibrosis by Cardiovascular Magnetic Resonance Against Histology in Mini-Swine

BackgroundMyocardial fibrosis predicts adverse outcomes in myocardial infarction (MI) and other cardiovascular conditions. Cardiovascular magnetic resonance (CMR) can non-invasively detect focal and diffuse myocardial fibrosis, but comprehensive validation against histology remains scarce. AimsTo assess the comparative diagnostic performance of CMR methods in detecting myocardial fibrosis, using a mini-swine model and histology as gold standard. MethodsEighteen mini-swine (16 MI; 2 healthy) underwent CMR cine, LGE, T1- and ECV-mapping. Two commonly-used T1-mapping methods - MOLLI 5(3)3 and ShMOLLI 5(1)1(1)1 - were included. Pathological sections were categorized as infarcted, peri-infarct, remote and healthy myocardium based on triphenyl tetrazolium chloride staining. Fibrotic burden was quantified by collagen volume fraction (CVF) into severe (CVF[≥]30%), moderate (CVF=10-25%), and mild (CVF=3-14%). The relationships between LGE, T1, ECV and CVF, and diagnostic performance using area-under-the-curve (AUC), were analyzed. ResultsFor detecting severe fibrosis, LGE, T1 and ECV all had excellent diagnostic performance (AUC: LGE=0.93, ECVShMOLLI=0.96, T1ShMOLLI=0.91, T1MOLLI=0.93, ECVMOLLI=0.88). ECVShMOLLI showed significantly better discriminatory accuracy than ECVMOLLI in detecting severe fibrosis and MI (both p<0.05), with the highest correlation to CVF (ECVShMOLLI r=0.86, ECVMOLLI r=0.82, T1ShMOLLI r=0.77, T1MOLLI r=0.77, semi-quantitative LGE r=0.75). Only T1ShMOLLI and ECVShMOLLI, but not LGE or T1MOLLI/ECVMOLLI, differentiated remote myocardium with mild fibrosis (CVF=8.23%) from healthy myocardium (CVF=2.01%). ConclusionsCMR can detect severe to mild myocardial fibrosis as validated against histology. For low-grade fibrosis, T1-mapping significantly outperformed LGE. Choice of CMR methodologies matters for myocardial fibrosis detection, which has importance for clinical trial design.

pathology↗

bioRxiv2025

Tunable porosity in a hydrogel with extreme vibration damping properties

We have developed hydrogel systems with tunable porosity through dialysis casting by varying alginate and poloxamer compositions from 0% to 10%. These gels feature diverse porosity topologies, yielding loss factors between 16% and 29% in the 50 Hz to 300 Hz frequency range. The dynamic modulus shows a remarkable increase of over an order of magnitude, reaching approximately 3 MPa compared to the static modulus. Vibration transmissibility tests and dynamic mechanical analysis reveal that the poroelastic and pneumatic-like effects from the tunable porous structures contribute significantly to this damping effect. Furthermore, these hydrogels are biosourced and biodegradable, providing a sustainable alternative to conventional fossil-based damping materials.

bioengineering↗

bioRxiv2025

Spacer Extension Reconciles Specificity and Activity in High-Fidelity Cas9 Genome Editing

AbstractEngineering high-fidelity CRISPR enzymes often leads to reduced cleavage activity, creating a significant hurdle in balancing nuclease specificity and efficiency for clinical applications. Here, we demonstrate that extending the spacer to 21 or 22 nucleotides restores the impaired cleavage activity of SuperFi-Cas9, an engineered high-fidelity Cas9 variant with seven mutations at the PAM-distal region. Structural and mutational analyses reveal that the spacer extension strengthens additional interactions at the PAM-distal end, stabilizing the nuclease- sgRNA-DNA complex, which appears to be disturbed due to the seven mutations. This approach not only provides a high-fidelity Cas9 with uncompromised efficiency but also introduces a novel strategy to enhance CRISPR complex stability. Our findings offer a promising avenue for precise and efficient genome editing, crucial for advancing CRISPR technologies toward clinical translation.

genomics↗

bioRxiv2025

Investigation of Bile Salt Hydrolase Activity in Human Gut Bacteria Reveals Production of Conjugated Secondary Bile Acids

Through biochemical transformation of host-derived bile acids (BAs), gut bacteria mediate host-microbe crosstalk and sit at the interface of nutrition, the microbiome, and disease. BAs play a crucial role in human health by facilitating the absorption of dietary lipophilic nutrients, interacting with hormone receptors to regulate host physiology, and shaping gut microbiota composition through antimicrobial activity. Bile acid deconjugation by bacterial bile salt hydrolase (BSH) has long been recognized as the first necessary BA modification required before further transformations can occur. Here, we show that BSH activity is common among human gut bacterial isolates spanning seven major phyla. We observed variation in both the extent and the specificity of deconjugation of BAs among the tested taxa. Unexpectedly, we discovered that certain strains were capable of directly dehydrogenating conjugated BAs via hydroxysteroid dehydrogenases (HSD) to produce conjugated secondary BAs. These results challenge the prevailing notion that deconjugation is a prerequisite for further BA modifications and lay a foundation for new hypotheses regarding how bacteria act individually or in concert to diversify the BA pool and influence host physiology.

microbiology↗

bioRxiv2025

Combinatorial phosphorylation on CTD of RNA polymerase II selectively controls transcription and export of protein-coding mRNAs

C-terminal domain (CTD) of RNA polymerase II is crucial for recruiting transcription regulators via specific post-translational modifications (PTM), especially phosphorylation. The hypothesis of combination of PTMs, or CTD code, that can allow precise and dynamic recruitment of transcription machinery is highly attractive, yet the experimental evidence to support this hypothesis has been scarce. Here, despite lacking specific antibodies for combinatorial CTD phosphorylation, we developed an innovative approach that detects double phosphorylation patterns on the CTD in a whole-genomic fashion by leveraging the antibody masking effect with selectively removing the flanking interference. Using this method, we detected pT4pS5 double phosphosites occurring exclusively during the transcription of protein-coding genes. Furthermore, we showed that pT4pS5 marks recruit the Transcription and Export complex (TREX), which specifically facilitates mRNA processing and nucleocytoplasmic export of protein-coding mRNAs. The recruitment of TREX by pT4pS5 phosphosites is particularly important for the processing of lengthy neurogenesis-related genes. Our results provide experimental support for the notion that CTD coding system can function combinatorially and in a gene-specific manner, which encodes an exact information about the transcription of specific gene clusters. This method can be broadly applied to map all combinatorial PTM patterns on RNA polymerase II, paving the way for a deeper understanding of gene-specific transcription regulation at the molecular level.

molecular biology↗

bioRxiv2025

Melatonin attenuates kidney injury by alleviating lysosomal damage in diabetic kidney disease

Proteinuria-induced damage to renal tubular epithelial cells is one of the main causes of diabetic kidney disease (DKD), and the clearance of overloaded albumin by lysosomes is crucial for maintaining the homeostasis of renal tubular epithelial cells. Therefore, lysosomal damage is closely related to the pathogenesis of DKD, but effective prevention and treatment measures are still lacking. Melatonin (MLT) is secreted by the pineal gland and can not only regulate circadian rhythms but also maintain lysosomal homeostasis. In this study, we demonstrate the presence of significant lysosomal damage in renal tubules of DKD patients, which causes autophagy impairment and a concomitant oxidative stress imbalance; however, MLT can upregulate transcription factor EB (TFEB) to improve lysosomal damage and restore the biosynthesis in this organelle. Mechanistically, MLT may protect lysosomes via the upregulation of TFEB and the miR-205-5p-LRP-1 pathway in renal tubules, thus improving autophagy dysfunction and oxidative imbalance in DKD.

pathology↗

bioRxiv2025

Cycling Molecular Assemblies for Selective Cancer Cell Golgi Disruption

The Golgi apparatus is a critical organelle responsible for intracellular trafficking and signaling, orchestrating essential processes such as protein and lipid sorting1-5. Dysregulation of its function has been implicated in various pathologies, including obesity, diabetes, and cancer, highlighting its importance as a potential therapeutic target. Despite this, the development of tools to selectively target the Golgi in specific cell types remain a significant unmet challenge in imaging and drug discovery. Golgi-specific enzyme activities, such as those mediated by protein acyltransferases and thioesterases6, offer an untapped opportunity to develop subcellularly localized therapeutics. Current approaches predominantly rely on direct protein binding but lack the necessary cell selectivity7, underscoring the unmet need for innovative strategies to selectively disrupt Golgi function in cancer cells. Here, we report the development of cycling molecular assemblies (CyMA), a novel class of small peptide derivatives (e.g., dipeptides), which exploit the unique enzymatic environment of the Golgi to establish futile cycles of reversible S-acylation. These assemblies selectively accumulate in cancer cell Golgi, interfering with protein S-acylation cycles and disrupting organelle homeostasis. CyMA impair key Golgi functions, including protein trafficking, glycosylation, and secretion, while demonstrating selective sparing hepatocytes and immune cells such as M1 macrophages. This selective activity represents a paradigm shift, utilizing an enzyme switch and leveraging intracellular environment rather than direct protein binding. Unlike conventional approaches, CyMA reduce tumor growth, drug resistance, and metastasis by pleiotropically disrupting Golgi related functions. By demonstrating the potential of futile cycles as a therapeutic strategy8, this study introduces a generalizable method for targeting organelle-specific enzyme activities. These findings not only underscore the therapeutic potential of CyMA in cancer but also pave the way for future applications in other Golgi-associated diseases.

biochemistry↗

bioRxiv2024

Molecular mechanisms of dynamics-mediated effects of pathogenic missense mutations on Menin protein function

Understanding how disease-causing missense mutations (DCMMs) affect protein function is fundamental. The traditional structure-function paradigm for proteins has evolved into a structure-dynamics-function model, as dynamics is increasingly recognized as a key regulator of protein function. Consequently, it is essential to incorporate dynamics into the once heavily emphasized structure-function framework to explain the effects of DCMMs. Although research in this area is emerging, evidence supporting a definitive role of dynamics in mediating DCMM effects on protein function remains limited. In this study, we used Menin--a mutation-prone scaffold protein involved in various pathologies--as a model system to explore how DCMMs affect Menins function. By performing molecular dynamics (MD) simulations on 24 clinically confirmed DCMMs, we showed that DCMMs do not necessarily destabilize protein stability. Instead, they induce similar dynamic changes in the protein. The consequences of DCMMs on Menins function were further assessed through umbrella sampling of the Menin-JunD protein protein interaction (PPI). We found that DCMMs attenuate this interaction and disrupt a highly conserved JunD dissociation pathway in wild-type (WT) Menin. The underlying mechanism was revealed through allosteric analysis, which showed that, despite being located far from the JunD binding site, DCMMs uniformly disturbed the coupling between residue E179 and the binding pocket. Additionally, forced maintenance of E197-pocket coupling restored the impaired Menin-JunD PPI in DCMMs. Together, these data demonstrate that DCMMs alter Menins function through dynamics, with allostery playing a crucial role. This study further supports the incorporation of dynamics into the traditional "structure-function" diagram to better explain the effects of DCMMs.

biophysics↗

bioRxiv2024

Phages-bacteria interactions underlying the dynamics of polyhydroxyalkanoates-producing mixed microbial cultures via meta-omics study

The dynamics of the structure of polyhydroxyalkanoates-producing mixed microbial cultures (PHA-MMCs) during enrichment and maintenance is an unsolved problem. The effect of phages has been proposed as a cause of dynamic changes in community structure, but evidence is lacking. To address this question, we enriched five PHA-MMCs and sampled temporally to study the interactions between phage and prokaryotic members by combining metagenomics and metatranscriptomics. 963 metagenome-assemble genomes and 4294 phage operational taxonomic units were assembled from bulk metagenomic data. There were complex interactions between the phages in Casadabanvirus and Unclassified Hendrixvirinae and the dominant species in Azomonas, Paracoccus, Thauera and Breundimonas. The dynamic change of the structure of phage and prokaryotic communities were remarkably consistent. Further structural equation modeling analysis showed that phage communities could significantly affect the activity and community structure of prokaryotic microorganisms. In addition, seven key auxiliary metabolic genes (phaC, fadJ, acs, ackA, phbB, acdAB and fadD) in the PHA synthesis pathway were identified from phage sequences. Importantly, these auxiliary metabolic genes were expressed at the transcriptional level, indicating that they were in an active functional state. This meta-analysis provides the first catalog of phages in PHA-MMCs and the auxiliary metabolic genes they carry, as well as how they play a role in the dynamic changes of prokaryotic communities. This study provides a reference for subsequent studies on understanding and regulating the microbial community structure of artificial open microbial systems. ImportanceThe synthesis of biodegradable plastic PHA from organic waste through mixed microbial cultures (MMCs), with extremely low cost, has the potential for expanded production. However, there is a gap of understanding of the dynamics of dominant species in MMCs to better control community structure. Our results demonstrate for the first time the impact of phages on the structure of prokaryotic communities in the MMCs. There are complex interactions between the PHA producers (Azomonas, Paracoccus, Thauera) and phages (Casadabanvirus and Unclassified Hendrixvirinae). Phage communities can negatively regulate the activity and structure of prokaryotic communities. In addition, the auxiliary metabolic genes in the PHA synthesis pathways carried by phages may promote the PHA synthesis ability of prokaryotic members. This study highlights the impact of phages on prokaryotic community structure, suggesting that phages have the potential to become a tool for better controlling the microbial community structure of PHA-MMCs.

microbiology↗

bioRxiv2024

Phosphorylation of α-synuclein fibrils at S129 changes DNAJB1 binding as probed by solid-state NMR

Amyloid fibrils composed of the protein -synuclein (aSyn) are implicated in the pathogenesis of synucleinopathies. These pathological fibrils, characterized by their rigid amyloid cores, also feature flexible intrinsically disordered regions (IDRs) that interact with various cellular components. Due to their solvent exposure and flexibility, the N- and C-termini, IDRs of aSyn fibrils, have been used as targets for immunotherapies and serve as binding sites for many chaperones. Chaperones are known to play a vital role in preventing and reversing amyloid formation in neurodegenerative diseases, but how they recognize misfolded proteins is often poorly understood. DNAJB1 is a co-chaperone that is part of a larger complex formed with Hsp70 and Apg2, which collectively disaggregate amyloid fibrils such as those formed by aSyn, tau, or huntingtin. Although the entire chaperone and co-chaperone complex are required for aggregate disassembly, DNAJB1 directly recognizes these amyloid fibrils. More specifically, DNAJB1 preferentially binds to the C-terminus of wild-type aSyn. However, over 90% of aSyn fibrils in Lewy bodies are phosphorylated at S129. Here, we determine the effect of S129 phosphorylation on DNAJB1-aSyn fibril binding using biochemical assays and solid-state NMR. We show that DNAJB1 preferentially binds aSyn pS129 fibrils and that the aSyn binding site of pS129 and wild-type fibrils is different. These results suggest that pS129 might influence chaperone-mediated degradation efficiency.

biophysics↗

bioRxiv2024

Deciphering the thiolactonization mechanism in thiolactomycin biosynthesis

Thiolactomycin (1), which features a unique{gamma} -thiolactone ring, is a promising antibiotic candidate that specifically targets bacterial type II fatty acid synthase. Despite extensive studies on its pharmacological activities, modes of action, and chemical synthesis, the enzymatic processes responsible for forming the activity-determining{gamma} -thiolactone ring have remained largely unknown. Here, we resolve this problem by revealing that the condensation and heterocyclization (Cy) domain of the nonribosomal peptide synthetase (NRPS) TlnC (TlnCCy), along with the cytochrome P450 enzyme TlnA, cooperatively enable the{gamma} -thiolactone assembly. TlnCCy mediates an unusual sulfurtransfer reaction to sulfurate the polyketide intermediate, generating a thiocarboxylate intermediate. Subsequently, TlnA acts as a{gamma} -thiolactone synthase, converting the linear thiocarboxylate intermediate into 1 via a distal radical-based cyclization mechanism. These findings not only expand the functional and catalytic repertoires of NRPS Cy domains and P450 enzymes, but also highlight a special enzymatic strategy for{gamma} -thiolactone biosynthesis in nature. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/629141v2_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@7e0ad2org.highwire.dtl.DTLVardef@f86b80org.highwire.dtl.DTLVardef@159d136org.highwire.dtl.DTLVardef@1b633ff_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

Unlocking the genomic repertoire of a cultivated megaphage

Megaphages are bacteriophages (i.e., phages) with exceptionally large genomes that are ecosystem cosmopolitans, infect various bacterial hosts, and have been discovered across various metagenomic datasets globally. To date, almost all megaphages have evaded cultivation, with only phage G being in active culture for over 50 years. We examined with multiomics this five decades long cultivated history from nine different laboratories with five different lab variants to the modern era. In this work, we resolved the five complete phage G genomes, the particle proteome, de novo methylome, and used artificial intelligence (AI) to annotate the genome of phage G. Phage G is one of the largest phages with a size of >0.6 {micro}m, about half the width of the host cell, and a 499 kbp, non-permuted, linear genome that has, uniquely among known phages, two pairs of ends. Its closest known relative is Moose phage W30-1 which was metagenomically assembled without cultivation from a moose rumen sample. Phage G has >650 protein-coding open reading frames (ORFs), with >65% being hypothetical proteins with no known function, with the rest of the genome geared towards nucleic acid replication (e.g., helicases, polymerases, endonucleases) and are structural in nature (e.g., capsid, tail, portal, terminase). The genome encodes a 35 kbp stretch with 66 ORFs without any known functional homology, a cryptic genomic region that is roughly the size of phage lambda. Phage G has an expansive repertoire of auxiliary metabolic genes (AMGs) acquired from its bacterial host, including a phoH,ftsZ,UvsX/RecA-like, gyrA, gyrB,and DHFR. Furthermore, AMGs discovered in phage G could manipulate host sporulation (sspD, RsfA, spoK) and antiviral escape genes (e.g., anti-CBass nuclease and Anti-Pycsar protein). Phage proteomics found >15% of the protein ORFs were present in either the wild-type or mutant variants of phage G, including genes involved in replication (e.g.,UvsX/RecA-like), host sporulation, as well as structural genes (e.g., capsid, tail, portal). The methylome of phage G was localized to the cryptic region with limited functional homology, with supervised machine learning (i.e., HMMs) was unable to resolve this region, but was resolved with protein structural AI. This cryptic region was a hot spot for methylation at 32%, where many of the functions of the ORF are still unknown. Our study represents a doorway into the complexity of the genomic repertoire of the only cultivated megaphage, highlighting five decades of continuous cultivation for the first time.

microbiology↗

bioRxiv2024

Binding items to contexts through conjunctive neural representations with the Method of Loci

Schematic prior knowledge can provide a powerful scaffold for episodic memories, yet the neural mechanisms underlying this scaffolding process are still poorly understood. A crucial step of the scaffolding process is the way in which details of a new episode are connected to an existing schema, forming a robust memory representation that can be easily accessed in the future. A unique testbed for studying this binding process is a mnemonic technique called the Method of Loci (MoL), in which people meaningfully connect items to be remembered with a well-learned list of imagined loci. We collected fMRI data from participants in 3 longitudinal sessions while they were enrolled in a month-long MoL training course, all of whom showed dramatic improvements in their ability to remember lists of 20 or 40 words. We obtained neural patterns when the loci and objects are presented by themselves, when they are combined into an integrated representation at encoding, and when the integrated representation was subsequently retrieved, as well as verbal descriptions from the participants about the way they associated each item to each locus. We found that in default mode network regions, including medial prefrontal cortex (mPFC), the combined representations of loci and items are highly conjunctive: the unified locus-item representation was substantially different from a linear combination of the isolated locus and item representation, reflecting the addition of new integrative details specific to each combined pair. The conjunctive component of the representation reflected the particular creative details generated by individual participants and increased over time as participants gained expertise in MoL. Our findings reveal a critical role for the default mode network in creating meaningful connections between new information and well-learned schematic contexts.

neuroscience↗

bioRxiv2024

Deficiency of DDI2 suppresses liver cancer progression byworsening cell survival conditions

The levels of reactive oxygen species (ROS) and the extent of ensuing DNA damage significantly influence cancer initiation and progression. Of crucial importance, the aspartate protease DDI2 has been proposed to play a pivotal role in monitoring intracellular ROS levels (to trigger oxidative eustress or distress), as well as in the oxidative DNA damage repair, through redox homeostasis-determining factor Nrf1 (encoded by NFE2L1). However, the specific role of DDI2 in the multi-step process resulting in the development and progression of liver cancer remains elusive to date. In the present study, we employed the CRISPR/Cas9 gene editing system to create two nuanced lines of DDI2 knockout (i.e., DDI2-/- and DDI2insG/-) from liver cancer cells. Subsequent experiments indicate that the knockout of DDI2 leads to increased ROS levels in hepatoma cells by downregulating two major antioxidant transcription factors Nrf1 and Nrf2 (encoded by NFE2L2), exacerbating endogenous DNA damages caused by ROS and not-yet-identified factors, thereby inhibiting cell proliferation and promoting apoptosis, and ultimately hindering in vivo malignant growth of xenograft tumor cells. Conversely, the restoration of DDI2 expression reverses the accumulation of ROS and associated DNA damage caused by DDI2 knockout, eliminating the subsequent inhibitory effects of DDI2 deficiency on both in vitro and in vivo growth of liver cancer cells. Collectively, these findings demonstrate that DDI2 deficiency impedes liver tumor growth by disrupting its survival environment, suggesting that DDI2 may serve as a novel therapeutic target for anti-cancer strategies aimed at modulating ROS or DNA damage processes.

cancer biology↗

bioRxiv2024

Enantioselective photoenzymatic C(sp3)-H functionalization via single-electron oxidation of carbanions

Established strategies for enantioselective hydroalkylation for C(sp3)-C(sp3) bond formation usually require pre-functionalized substrates as radical precursors in both transition-metal and photoenzymatic catalysis. Based on a sequential proton transfer/electron transfer (PT/ET) strategy, here we show a cooperative photoenzymatic system consisting of a flavin-dependent ene-reductase (ER) and an organophotoredox catalyst fluorescein (FI) to achieve atom-economic enantiodivergent hydroalkylation of electron-deficient C(sp3)-H with olefins. Mechanistic studies revealed a pathway for radical intermediate formation via excited-state FI*-induced single-electron oxidation of carbanions under alkaline conditions. The overall catalytic efficiency is enhanced by the electron transfer (ET) between FMNox and FI-*, while the stereoselectivity is controlled by ERs through enantioselective hydrogen atom transfer (HAT). We anticipate that this mode of photoenzymatic catalysis will inspire new pathways for generating free radical intermediates and foster innovative strategies for achieving photoenzymatic new-to-nature reactions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/627421v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@11b6c1eorg.highwire.dtl.DTLVardef@1575346org.highwire.dtl.DTLVardef@1c24a2org.highwire.dtl.DTLVardef@1a93c0d_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

Optimization of metagenomic detection method for human breast milk microbiome

This study aims to optimize the metagenomic detection methodology of the human breast milk microbiome and analyze its composition. Twenty-two milk samples were collected from the left and right sides of lactating women during re-examinations at the Haidian Maternal and Child Health Hospital, Beijing. Microbial cell wall disruption parameters were optimized, and a nucleic acid extraction method was developed to construct a microbial DNA/RNA library. Metagenomic next-generation sequencing (mNGS) sequencing was performed, and microbial composition was analyzed using the k- mer Lowest Common Ancestor (LCA) method with a self-generated database constructed via Kraken2 software. Data showed Q20 > 95% and Q30 > 90%, with an average total data volume of 5,567 {+/-} 376.6 Mb and non-human sequence data of 445.1 {+/-} 63.75 Mb, significantly enhancing sequencing efficiency. The microbiome included 21 phyla, 234 genera, and 487 species, with Firmicutes and Proteobacteria as dominant phyla. Predominant genera included Staphylococcus and Streptococcus, and major species were Staphylococcus aureus, Streptococcus bradystis, and Staphylococcus epidermidis. Species levels exhibited significant variations among different individuals. Microbial profiles of left- and right-sided milk samples were consistent at the phylum, genus, and species levels. In addition to common bacteria, diverse viral, eukaryotic, and archaeal sequences were detected. This study refined metagenomic detection methods for human breast milk microbiota. Specific flora colonization occurred in healthy breast milk, with the left and right sides exhibiting both correlations and distinct flora environments. ImportanceBreast milk is a vital source of nutrition and immunity for infants, with its microbial composition playing a critical role in shaping the neonatal gut microbiome and supporting early development. However, technical challenges in detecting microorganisms in milks complex, lipid-rich environment have limited understanding of the diversity and function of these microbial communities. This study developed an optimized metagenomic sequencing method to analyze the microbial communities in breast milk from healthy mothers, identifying a wide array of bacteria, viruses, eukaryotes, and archaea. Key bacterial genera such as Staphylococcus and Streptococcus were predominant, with specific flora exhibiting inter-individual variability. Additionally, the study revealed distinct yet correlated microbial environments in the milk from the left and right breasts. These findings advance the understanding of breast milk microbiota and provide a foundation for exploring its implications for maternal and infant health.

microbiology↗

bioRxiv2024

Insights into Intestinal Barrier Disruption During Long-Term Gut Chlamydia Colonization in Mice: A Single-Cell Transcriptomic Approach

Chlamydia trachomatis, an intracellular pathogen, stands as the most prevalent sexually transmitted bacterial infection among women globally. Traditionally recognized as a genital pathogen, recent research indicates that the gastrointestinal tract may also act as a reservoir for its long-term colonization. However, the mechanisms underlying Chlamydias ability to persist in the gut remain poorly understood. This gap in knowledge limits our ability to develop effective treatments for persistent Chlamydia infections. In this study we utilized single-cell RNA sequencing to analyze the gene expression profiles and cellular heterogeneity of mouse colonic tissues during Chlamydia long-term infection. This approach provided detailed insights into the transcriptional changes and cellular interactions involved in the persistence of Chlamydia in the gut. Our results revealed significant alterations in the gene expression profiles of various intestinal cell populations, with distinct molecular pathways contributing to Chlamydia persistence. Notably, we observed a reduction in the expression of markers associated with epithelial tight junctions, indicating a potential breakdown of the intestinal epithelial barrier. This impairment may facilitate the penetration of Chlamydia into deeper tissues and contribute to the initiation of infection. We also found dysregulation of the transcriptional networks in goblet cells and an imbalance in communication between immune and epithelial cells. These disruptions were linked to the pathogens ability to establish persistent colonization and infection. IMPORTANCEFew studies have explored Chlamydia persistence in the gastrointestinal tract. In this study, we use single-cell RNA sequencing to identify the molecular and cellular mechanisms driving the pathogens long-term colonization. Our findings provide crucial insights into how Chlamydia overcomes the hosts immune defenses and epithelial barriers to establish chronic infection in the gut. Notably, we identify disruption of epithelial tight junctions and an imbalance in immune-cell interactions, offering new avenues for therapeutic interventions aimed at restoring mucosal integrity and preventing persistent infection.

microbiology↗

bioRxiv2024

Renovating the Barnes maze for mouse models of Dementia with STARR FIELD: A 4-day protocol that probes learning rate, retention and cognitive flexibility.

Land-based spatial mazes are a low-stress method to evaluate learning in rodent models of dementia. By using innate exploratory and hiding behavior, the Barnes maze requires fewer trials, allowing examination of early learning rate and retention, as well as executive and motivational features that can be characteristic of non-amnestic dementias. However, unwanted odor cues may disrupt interpretation of acquisition rate during typical learning trials. We designed and tested our Barnes FIELD protocol (Find the Invisible Exit to Locate the Domicile) to improve reproducibility, allow evaluation of learning trials, and limit experimenter influence. The protocol uses 3D-printed escape shuttles and docking tunnels, allowing mice to exit the maze to the home cage. We show evidence that our shuttles mitigate the possibility of undesired cues. We demonstrate the feasibility of our protocol across several models of cognitive impairment and aging, and develop an additional stage, the STARR (Spatial Training And Rapid Reversal) maze, to better challenge behavioral flexibility. By examining commonly used outcome measures we identify important considerations for interpretation. These insights are used to evaluate several models of cognitive change, including deficits in an Alzheimers disease mouse model, and behavioral flexibility in a model of brainstem dysfunction. This work provides comprehensive instructions to build, perform, and analyze a robust spatial maze that expands the range of behavioral and motivational outcomes that can be identified and screened. Our findings will aid interpretation of traditional protocols, enhance rigor and reproducibility, and provide an updated method to screen for cognitive changes in mice.

neuroscience↗