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Wan, D.

Publications and source records attributed to Wan, D..

15 recordsLinked to original sources

A Refined Developmental Transcriptomic Landscape Reveals Four Coordinated Programs in Chlamydia trachomatis

The developmental cycle of Chlamydia trachomatis requires coordinated transitions between infectious elementary bodies (EBs) and replicative reticulate bodies (RBs), yet the temporal organization of the underlying transcriptional programs remains incompletely resolved. We performed high-coverage RNA sequencing from 0 to 32 h post-infection (hpi), with closely spaced early sampling, and used unsupervised clustering of temporal expression profiles to identify four coordinated programs: immediate-early host adaptation and developmental program, RB formation and maintenance, RB proliferation and secondary differentiation, and EB formation and invasion. The immediate-early program peaked at 1 hpi and contained a strong representation of inclusion-membrane and intracellular-trafficking genes, together with the developmental regulator gene euo. The RB formation and maintenance program peaked at approximately 3 hpi and sustained expression throughout much of the cycle, encompassing genes that support transcription, translation, and core metabolism. The RB proliferation and secondary differentiation program combined DNA replication and cell-division genes with alternative sigma factors, partner-switching components, and type III secretion apparatus genes, consistent with developmental preparation during proliferation. The EB formation and invasion program contained genes associated with structural maturation, host-cell interaction, and infectious competence. These findings distinguish transient host-adaptation expression from sustained early biosynthetic expression, separate RB establishment from population expansion, and differentiate regulatory preparation for the RB-to-EB transition from later EB maturation. Together, the four programs define partially overlapping transcriptional priorities that provide a framework for investigating how gene expression coordinates chlamydial growth, differentiation, and preparation for the next infection cycle.

microbiology↗

A Generalized Spatial Progress Code for Navigation in the Medial Prefrontal Cortex

Goal-directed navigation requires an internal estimate of progress toward a desired outcome, yet how the brain constructs and represents such a signal remains unclear. Here, we designed a multi-route navigation paradigm with geometrically distinct paths and imaged medial prefrontal cortex (mPFC) activity as mice performed goal-directed route choice behavior. We found that a substantial fraction of mPFC neurons fired at consistent positions along a normalized start-to-goal axis, independent of path geometry, running direction, and task context. At the ensemble level, mPFC activity reliably decoded spatial progress but carried minimal information about path identity. This progress code emerged with task familiarity and required input from the hippocampal CA1. Inactivation of either mPFC or CA1[->]mPFC projection did not disrupt learned path preference but impaired navigational fluency in trained mice. These findings reveal a hippocampal-prefrontal mechanism for representing abstract, context-generalized spatial progress within a goal-directed navigational episode, supporting fluent navigation across variable routes.

neuroscience↗

Comparative Transcriptomics Reveals Genes Commonly Induced by Distinct Stressors in Chlamydia

Chlamydia trachomatis is a leading cause of urogenital infections that can result in serious long-term complications. This obligate intracellular bacterium undergoes a biphasic developmental cycle alternating between the infectious elementary body and the replicative reticulate body and can enter a persistent state in response to adverse environmental conditions. Although transcriptomic reprogramming is central to chlamydial stress adaptation and persistence, how responses differ across biologically distinct stressors remains incompletely defined. Here, we performed a comparative reanalysis of five published, high-quality C. trachomatis RNA-Seq datasets generated under prolonged interferon-{gamma} treatment, tryptophan starvation, iron starvation, penicillin exposure, or acute heat shock. Global transcriptomic analyses reveal extensive stress-specific reprogramming and a clear separation between the transcriptome induced by heat shock and those induced by chronic stresses. Transcriptomic overlap observed among chronic stress conditions is substantially reduced when the heat shock transcriptome is included, indicating that shared transcriptional features are stressor-dependent. Unexpectedly, tryptophan starvation and iron starvation exhibit particularly close transcriptomic similarity, consistent with regulatory cross-talk mediated by the iron-dependent transcriptional repressor YtgR. In contrast, interferon-{gamma} induces a distinct but partially overlapping transcriptome, likely reflecting activation of additional host-mediated antimicrobial mechanisms beyond tryptophan deprivation. Together, these findings demonstrate that adaptation to different biological stressors in C. trachomatis is driven by distinct transcriptomic reprogramming, while consistently involving a subset of functions that may represent points of vulnerability for disrupting chlamydial persistence.

microbiology↗

A lineage-specific heat-induced feedback loop controls HrcA to promote chlamydial fitness under stress

Bacterial stress responses rely on transcriptional regulation by sigma factors and repressors. In Chlamydia, which lacks a dedicated heat shock sigma factor, repressor HrcA limits chaperone gene expression under non-stressed conditions. While HrcA function may be enhanced by the chaperone GroESL in a positive feedback loop, here we identify a heat-induced negative feedback loop mediated by HagF, a protein unique to Chlamydiota and conserved across Chlamydia species. We show that HrcA represses hagF, but heat shock induces hagF expression, leading to HagF accumulation and binding to HrcA. Structural modeling and pulldown assays indicate that HagF blocks HrcA dimerization, impairing DNA binding. This relieves repression of the hrcA-grpE-dnaK operon and promotes secondary differentiation in the developmental cycle, enabling infectious elementary bodies to form under heat stress. Our findings reveal dual feedback regulation that tunes chaperone gene expression and illustrate how transcriptional repression can be modulated in a minimal-genome pathogen.

microbiology↗

Histone Chaperone HIRA facilitates transcription elongation to regulate insulin sensitivity and obesity-associated adipose expansion

Adipose tissue is essential for maintaining glucose and lipid homeostasis in mammals. However, epigenomic mechanisms underlying adipose tissue function remain largely unclear. Here, we identify the histone chaperon HIRA as a novel epigenomic regulator of adipose tissue function. Adipose tissue-specific knockout of Hira in mice impairs insulin sensitivity and restrains adipose tissue expansion during high-fat diet-induced obesity. Mechanistically, HIRA is required for the expression of Adipoq, encoding the adipokine adiponectin, and lipid metabolism genes in adipose tissue. Genomic mapping reveals that HIRA binds to promoters and enhancers of Adipoq and lipid metabolism genes in adipocytes. Acute HIRA depletion using the dTAG system, followed by nascent RNA-Seq and ChIP-Seq, demonstrates that while HIRA is largely dispensable for enhancer activation and coactivator binding, it promotes transcription of target genes by facilitating RNA polymerase II pause release and subsequent elongation likely independently of H3.3 deposition. Our findings uncover a novel mechanism by which HIRA regulates transcription and establish HIRAs critical role in insulin sensitivity and lipid metabolism, providing a potential therapeutic target for obesity and insulin resistance. Significance StatementDysregulated adipose tissue function leads to metabolic disorders including obesity and insulin resistance, yet the epigenomic mechanisms that maintain its normal function are incompletely understood. This study identifies the histone chaperone HIRA as a critical regulator of insulin sensitivity and obesity-associated adipose expansion. We show that HIRA directly controls adiponectin and lipid metabolism gene expression in adipocytes by promoting RNA polymerase II pause release, rather than transcription initiation or enhancer activation, and likely in a manner independent of H3.3 deposition. These findings uncover a novel mechanism of HIRA in regulating gene expression and highlight its critical role in insulin sensitivity and lipid metabolism in adipocytes.

physiology↗

Chlamydia plasmid-encoded protein Pgp2 is a replication initiator with a unique beta-hairpin necessary for iteron-binding and plasmid replication

The virulence plasmid of the obligate intracellular bacterium Chlamydia encodes eight proteins. Among these, Pgp3 is crucial for pathogenicity, and Pgp4 functions as a transcriptional regulator of both plasmid and chromosomal genes. The remaining proteins, Pgp1, Pgp5, Pgp6, Pgp7, and Pgp8, are predicted to play various roles in plasmid replication or maintenance based on their amino acid sequences. However, the function of Pgp2 remains unknown, even though it is required for transformation. In this study, we utilized AlphaFold to predict the 3-dimensional (3-D) structure of C. trachomatis Pgp2. Despite a lack of apparent sequence homology, the AlphaFold structure exhibited high similarity to experimentally determined structures of several plasmid replication initiators. Notably, Pgp2 features a unique {beta}-hairpin motif near the DNA-binding domain, absent in other plasmid replication initiators with overall 3-D structures similar to Pgp2. This {beta}-hairpin motif was also present in AlphaFold models of Pgp2s across all 13 Chlamydia species. To assess its significance, we engineered a plasmid lacking the 11 amino acids constituting the {beta}-hairpin motif in C. trachomatis Pgp2. Although this deletion did not alter the overall structure of Pgp2, the mutated plasmid failed to transform plasmid-free C. trachomatis. These findings reveal that Pgp2 is a plasmid replication initiator, with the {beta}-hairpin motif playing a critical role in binding to its cognate iteron sequences in the replication origin of the chlamydial plasmid.

microbiology↗

Analyzing RNA-Seq Data from Chlamydia with Super Broad Transcriptomic Activation: Challenges, Solutions, and Implications for Other Systems

MotivationRNA sequencing (RNA-Seq) offers profound insights into the complex transcriptomes of diverse biological systems. However, standard differential expression analysis pipelines based on DESeq2 and edgeR encounter challenges when applied to the immediate early transcriptomes of Chlamydia spp., obligate intracellular bacteria. These challenges arise from their reliance on assumptions that do not hold in scenarios characterized by extensive transcriptomic activation and limited repression. Standard analyses using unique chlamydial RNA-Seq reads alone identify nearly 300 upregulated and about 300 downregulated genes, significantly deviating from actual RNA-Seq read trends. ResultsBy incorporating both chlamydial and host reads or adjusting for total sequencing depth, the revised normalization methods each detected over 700 upregulated genes and 30 or fewer downregulated genes, closely aligned with observed RNA-Seq data. Further validation through qRT-PCR analysis confirmed the effectiveness of these adjusted approaches in capturing the true extent of transcriptomic activation during the immediate early phase of chlamydial infection. While the strategies employed are developed in the context of Chlamydia, the principles of flexible and context-aware normalization may inform adjustments in other systems with unbalanced gene expression dynamics, such as bacterial spore germination. Availability and implementationThe code for reproducing the presented bioinformatic analysis is available at https://zenodo.org/records/11201379.

bioinformatics↗

Glucocorticoids rapidly modulate CaV1.2-mediated calcium signals through Kv2.1 channel clusters in hippocampal neurons

The precise regulation of Ca2+ signals plays a crucial role in the physiological functions of neurons. Here, we investigated the rapid effect of glucocorticoids on Ca2+ signals in hippocampal neurons. In cultured hippocampal neurons, glucocorticoids inhibited the spontaneous somatic Ca2+ spikes generated by Kv2.1-organized Ca2+ microdomains. Furthermore, glucocorticoids rapidly reduced the cell surface expressions of Kv2.1 and CaV1.2 channels in hippocampal neurons. In HEK293 cells transfected with Kv2.1 alone, glucocorticoids significantly reduced the surface expression of Kv2.1 with little effect on K+ currents. Glucocorticoids inhibited CaV1.2 currents but had no effect on the cell surface expression of CaV1.2 in HEK293 cells transfected with CaV1.2 alone. Notably, in the presence of wild-type Kv2.1, glucocorticoids caused a decrease in the surface expression of CaV1.2 channels in HEK293 cells. However, this effect was not observed in the presence of non-clustering Kv2.1S586A mutant channels. Live cell imaging showed that glucocorticoids rapidly decreased Kv2.1 clusters on the plasma membrane. Correspondingly, western blot results indicated a significant increase in the cytoplasmic level of Kv2.1, suggesting the endocytosis of Kv2.1 clusters. Glucocorticoids rapidly decreased the intracellular cAMP concentration and the phosphorylation level of PKA in hippocampal neurons. The PKA inhibitor H89 mimicked the effect of glucocorticoids on Kv2.1, while the PKA agonist forskolin abrogated the effect. In conclusion, glucocorticoids rapidly regulate CaV1.2-mediated Ca2+ signals in hippocampal neurons by promoting the endocytosis of Kv2.1 channel clusters through reducing PKA activity. Significance StatementThe rapid non-genomic effect of glucocorticoids on the central nervous system is not fully understood. CaV1.2-mediated Ca2+ signaling microdomains control somatic Ca2+ signals and regulate excitation-transcription coupling in hippocampal neurons. Here, we demonstrate that glucocorticoids rapidly inhibit CaV1.2-mediated somatic Ca2+ spikes in hippocampal neurons. Glucocorticoids reduce the surface expression of Kv2.1 clusters but do not affect the surface expression of non-clustering Kv2.1. Moreover, glucocorticoids induce the endocytosis of CaV1.2 channels through wild-type Kv2.1. However, glucocorticoids cannot induce the endocytosis of CaV1.2 channels through Kv2.1S586A mutant channels, which cannot form clusters. This study sheds light on the intricate interplay between glucocorticoids, Kv2.1 channels, and CaV1.2 channels, unraveling a dual mechanism that influences both overall Ca2+ signaling and the intricate organization of neural microdomains.

neuroscience↗

Requirement of GrgA for Chlamydia infectious progeny production, optimal growth, and efficient plasmid maintenance

Chlamydia, an obligate intracellular bacterial pathogen, has a unique developmental cycle involving the differentiation of invading elementary bodies (EBs) to noninfectious reticulate bodies (RBs), replication of RBs, and redifferentiation of RBs into progeny EBs. Progression of this cycle is regulated by three sigma factors, which direct the RNA polymerase to their respective target gene promoters. We hypothesized that the Chlamydia-specific transcriptional regulator GrgA, previously shown to activate {sigma}66 and {sigma}28, plays an essential role in chlamydial development and growth. To test this hypothesis, we applied a novel genetic tool known as dependence on plasmid-mediated expression (DOPE) to create Chlamydia trachomatis with conditional GrgA-deficiency. We show that GrgA-deficient C. trachomatis RBs have a growth rate that is approximately half of the normal rate and fail to transition into progeny EBs. In addition, GrgA-deficient C. trachomatis fail to maintain its virulence plasmid. Results of RNA-seq analysis indicate that GrgA promotes RB growth by optimizing tRNA synthesis and expression of nutrient-acquisition genes, while it enables RB-to-EB conversion by facilitating the expression of a histone and outer membrane proteins required for EB morphogenesis. GrgA also regulates numerous other late genes required for host cell exit and subsequent EB invasion into host cells. Importantly, GrgA stimulates the expression of {sigma}54, the third and last sigma factor, and its activator AtoC, and thereby indirectly upregulating the expression of {sigma}54-dependent genes. In conclusion, our work demonstrates that GrgA is a master transcriptional regulator in Chlamydia and plays multiple essential roles in chlamydial pathogenicity. IMPORTANCEHallmarks of the developmental cycle of the obligate intracellular pathogenic bacterium Chlamydia are the primary differentiation of the infectious elementary body (EB) into the proliferative reticulate body (RB) and the secondary differentiation of RBs back into EBs. The mechanisms regulating these transitions remain unclear. In this report, we developed an effective novel strategy termed DOPE that allows for the knockdown of essential genes in Chlamydia. We demonstrate that GrgA, a Chlamydia-specific transcription factor, is essential for the secondary differentiation and optimal growth of RBs. We also show that GrgA, a chromosome-encoded regulatory protein, controls the maintenance of the chlamydial virulence plasmid. Transcriptomic analysis further indicates that GrgA functions as a critical regulator of all three sigma factors that recognize different promoter sets at developmental stages. The DOPE strategy outlined here should provide a valuable tool for future studies examining chlamydial growth, development, and pathogenicity.

microbiology↗

Genome-scale mRNA transcriptomic insights into the mature growth dynamic of Cigar tobacco leaves

The harvest time is a key factor for cigar leaves with high quality, which varies greatly depending on the environment. Here, we performed a genome-scale mRNA transcriptomic analysis on the cigar cultivar CX-26 (Nicotiana tabacum L.) to evaluate the relationship between gene expression and growth state. The leaves were harvested with 67 (T1), 71(T2) and 75 (T3)-day growth. A total of 80,502 genes were detected in the CX-26 leaves, of which 64,611 genes were annotated on the reference genome. Principal component analysis showed that T1 and T2 leaves had a high overlapping pattern, while T3 leaves were distinct. Indeed, T1 and T2 leaves had fewer differential expressing genes (DEGs), while T3 leaves had 26,456 DGEs from T2 leaves, supporting the distinct growth of T3 leaves. GO annotations mainly enriched the photosynthesis-related metabolic process, catalytic activity and binding biological processes. KEEG analysis identified the key pathways including photosynthesisantenna proteins, plant hormone/MAPK signaling pathway and plant-pathogen interaction. The maturity regulation and defense response-associated hormones abscisic acid and jasmonate acid were higher in the T3 leaves than that in T1 and T2 leaves confirming the KEEG analysis. Furthermore, several photosynthesis-related enzymes and a transcription factor were highlighted in the gene regulatory network, which might regulate the dynamics of carbohydrate metabolism, lipid metabolism and energy metabolism. In summary, our study provides insight into the growth state of CX-26 cigar leaves.

plant biology↗

PROTAC-mediated selective degradation of cytosolic soluble epoxide hydrolase enhances ER-stress reduction

Soluble epoxide hydrolase (sEH) is a bifunctional enzyme responsible for lipid metabolism and is a promising drug target. Here, we report the first-in-class PROTACs small molecule degraders of sEH. Our optimized PROTAC selectively targets the degradation of cytosolic but not peroxisomal sEH, resulting in exquisite spatiotemporal control. Remarkably, our sEH PROTAC molecule has higher potency in cellular assays compared to the parent sEH inhibitor as measured by significantly reduced ER stress. Interestingly, our mechanistic data indicate that our PROTAC directs degradation of cytosolic sEH via the lysosome, not through the proteasome. The molecules presented here are useful chemical probes to study the biology of sEH with the potential for therapeutic development. Broadly, our results represent a proof-of-concept for the superior cellular potency of sEH degradation over sEH enzymatic inhibition, as well as subcellular compartment-selective modulation of a protein by PROTACs. HighlightsO_LIFirst-in-class soluble epoxide hydrolase (sEH) small-molecule degraders. C_LIO_LISelective degradation of cytosolic but not peroxisomal sEH. C_LIO_LISignificant and stable reduction in sEH protein levels, leading to enhanced cellular efficacy in ER stress reduction relative to the parent inhibitor. C_LI

biochemistry↗

Epoxy fatty acid dysregulation and neuroinflammation in Alzheimer's disease is resolved by a soluble epoxide hydrolase inhibitor

Neuroinflammation has been increasingly recognized to play critical roles in Alzheimers disease (AD). The epoxy fatty acids (EpFAs) are derivatives of the arachidonic acid metabolism with anti-inflammatory activities. However, their efficacy is limited due to the rapid hydrolysis by the soluble epoxide hydrolase (sEH). We found that sEH is predominantly expressed in astrocytes where its levels are significantly elevated in postmortem human AD brains and in {beta}-amyloid mouse models, and the latter is correlated with drastic reductions of brain EpFA levels. Using a highly potent and specific small molecule sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), we report here that TPPU treatment potently protected against LPS-induced inflammation in vitro and in vivo. Long-term administration of TPPU to the 5xFAD mouse model via drinking water reversed microglia and astrocyte reactivity and immune pathway dysregulation, and this is associated with reduced {beta}-amyloid pathology and improved synaptic integrity and cognitive function. Importantly, TPPU treatment reinstated and positively correlated EpFA levels in the 5xFAD mouse brain, demonstrating its brain penetration and target engagement. These findings support TPPU as a novel therapeutic target for the treatment of AD and related disorders. One Sentence SummaryWe show that soluble epoxide hydrolase is upregulated in AD patients and mouse models, and that inhibition of this lipid metabolic pathway using an orally bioavailable small molecule inhibitor is effective in restoring brain epoxy fatty acids, ameliorating AD neuropathology and improving synaptic and cognitive function.

neuroscience↗

Computational target fishing by mining transcriptional data using a novel Siamese spectral-based graph convolutional network

Computational target fishing aims to investigate the mechanism of action or the side effects of bioactive small molecules. Unfortunately, conventional ligand-based computational methods only explore a confined chemical space, and structure-based methods are limited by the availability of crystal structures. Moreover, these methods cannot describe cellular context-dependent effects and are thus not useful for exploring the targets of drugs in specific cells. To address these challenges, we propose a novel Siamese spectral-based graph convolutional network (SSGCN) model for inferring the protein targets of chemical compounds from gene transcriptional profiles. Although the gene signature of a compound perturbation only provides indirect clues of the interacting targets, the SSGCN model was successfully trained to learn from known compound-target pairs by uncovering the hidden correlations between compound perturbation profiles and gene knockdown profiles. Using a benchmark set, the model achieved impressive target inference results compared with previous methods such as Connectivity Map and ProTINA. More importantly, the powerful generalization ability of the model observed with the external LINCS phase II dataset suggests that the model is an efficient target fishing or repositioning tool for bioactive compounds.

bioinformatics↗

Transmission dynamics of 2019 novel coronavirus (2019-nCoV)

RationaleSeveral studies have estimated basic production number of novel coronavirus pneumonia (NCP). However, the time-varying transmission dynamics of NCP during the outbreak remain unclear. ObjectivesWe aimed to estimate the basic and time-varying transmission dynamics of NCP across China, and compared them with SARS. MethodsData on NCP cases by February 7, 2020 were collected from epidemiological investigations or official websites. Data on severe acute respiratory syndrome (SARS) cases in Guangdong Province, Beijing and Hong Kong during 2002-2003 were also obtained. We estimated the doubling time, basic reproduction number (R0) and time-varying reproduction number (Rt) of NCP and SARS. Measurements and main resultsAs of February 7, 2020, 34,598 NCP cases were identified in China, and daily confirmed cases decreased after February 4. The doubling time of NCP nationwide was 2.4 days which was shorter than that of SARS in Guangdong (14.3 days), Hong Kong (5.7 days) and Beijing (12.4 days). The R0 of NCP cases nationwide and in Wuhan were 4.5 and 4.4 respectively, which were higher than R0 of SARS in Guangdong (R0=2.3), Hongkong (R0=2.3), and Beijing (R0=2.6). The Rt for NCP continuously decreased especially after January 16 nationwide and in Wuhan. The R0 for secondary NCP cases in Guangdong was 0.6, and the Rt values were less than 1 during the epidemic. ConclusionsNCP may have a higher transmissibility than SARS, and the efforts of containing the outbreak are effective. However, the efforts are needed to persist in for reducing time-varying reproduction number below one. At a Glance CommentaryO_ST_ABSScientific Knowledge on the SubjectC_ST_ABSSince December 29, 2019, pneumonia infection with 2019-nCoV, now named as Novel Coronavirus Pneumonia (NCP), occurred in Wuhan, Hubei Province, China. The disease has rapidly spread from Wuhan to other areas. As a novel virus, the time-varying transmission dynamics of NCP remain unclear, and it is also important to compare it with SARS. What This Study Adds to the FieldWe compared the transmission dynamics of NCP with SARS, and found that NCP has a higher transmissibility than SARS. Time-varying production number indicates that rigorous control measures taken by governments are effective across China, and persistent efforts are needed to be taken for reducing instantaneous reproduction number below one.

systems biology↗

Fecal microbiota as a non-invasive biomarker to predict the tissue iron accumulation in intestine epithelial cells and liver

Iron is an essential trace mineral for the growth, systemic metabolism, and immune response. Imbalance of tissue iron absorption and storage leads to various diseases. The excessive iron accumulation is associated with inflammation and cancer while iron deficiency leads to growth retardation. Studies investigated in Kenyan infants and school children suggests that both low and high iron intake result in dysbiosis of gut microbiota. This would lead to the disruption of microbial diversity, an increase of pathogen abundance and the induction of intestinal inflammation. Despite this progress, in-depth studies investigating the relationship between iron availability and gut microbiota is not completely explored. In the current study, we established a murine model to study the connection between iron and microbiota by feeding mice with either iron-deprived or -fortified diet. To identify key microbiota related to iron levels, we combined the 16S rRNA amplicon sequencing with the innovated bioinformatic algorithms, such as RDA, co-occurrence, and machine learning to identify key microbiota. Manipulation of iron levels in the diet leads to systemic iron dysregulation and dysbiosis of gut microbiota. The bioinformatic algorithms used here detect five key bacteria that correlate with systemic iron levels. Leveraging on these key microbiotas, we also established a prediction model which could precisely distinguish the individual under either iron-deprived or iron-fortified physiological condition to further prove the link between microbiota and systemic iron homeostasis. This innovated and non-invasive approach could be potentially used for the early diagnosis and therapy of iron-dysregulation related diseases, e.g. anemia, inflammatory disease, fibrosis, and cancers.

microbiology↗