Biology subjects

Chai, C.

Publications and source records attributed to Chai, C..

At least 19 recordsLinked to original sources

bioRxiv2026

Single-nucleus chromatin accessibility time course of excisional wound repair in rat skin

We present a time-series single-nucleus ATAC-seq dataset from full-thickness excisional wounds in Sprague-Dawley rats. Samples were taken from unwounded skin (normal control) and at 1, 2, 5, 10, and 19 days post-wounding, spanning the inflammatory, proliferative, and remodeling phases of skin repair. We extracted nuclei with a two-step tissue dissociation protocol and prepared libraries using the DNBelab C Series Single-Nucleus ATAC Kit, then sequenced on the MGI DNBSEQ-T1 platform. After stringent quality filtering, 37,555 nuclei passed quality control; the resulting chromatin accessibility profiles cover 23 cell types: fibroblast subpopulations, keratinocytes, vascular endothelial cells, immune cells, and skin appendage cell types. This genome-wide chromatin accessibility dataset is a resource for studying regulatory dynamics during excisional wound repair and for comparing results with other wound healing systems.

bioinformatics↗

bioRxiv2026

Generating a Collection of Single-Gene Deletions in the eps Operon in Bacillus subtilis Strain NCIB 3610

In the environment, bacteria mainly exist in multicellular, surface-adhered communities called biofilms. One key feature of the biofilms is a self-produced extracellular matrix that embeds cells within a structured community and contributes to their adhesion, organization, and retention. The matrix of most characterized biofilms contains three primary components: polysaccharides, protein, and extracellular DNA (eDNA). Upon biofilm induction, Bacillus subtilis produces and secretes a polysaccharide known as exopolysaccharide (EPS). The 15 genes of the epsA-O operon encode proteins that coordinate the assembly, export, and polymerization of EPS oligosaccharide (glycan) subunits. While much progress has been made to elucidate the chemical structure of EPS, further work is needed to determine the contributions of some eps genes to EPS biosynthesis experimentally. Here, we generated a collection of marker-less, in-frame deletions targeting each eps gene in the epsA-O operon in B. subtilis strain NCIB 3610 using the Cre system. Biofilm phenotypes of resulting mutants were used to assess each gene's importance to biofilm development. Impact The epsA-O single-gene deletion collection was designed to enable systematic assessment of the contribution of each eps gene to EPS production and biofilm-associated phenotypes. When combined with current knowledge of EPS structure, this collection will help clarify the roles of individual genes in EPS biosynthesis. This approach can also be easily adapted for the systematic analyses of other large, complex operons in diverse bacterial species.

microbiology↗

bioRxiv2026

Hypothalamic Cell Type Evolution across Vertebrates

The hypothalamus regulates vital functions and is highly conserved among vertebrates occupying diverse niches, but little is known about the evolution of its cell types. Using comparative single-cell transcriptomics across major vertebrate classes, we identified deeply conserved and clade-specific cell types. While homologous cell types express conserved transcription factors and neuropeptides, their regulatory linkages are often rewired across evolution. The paraventricular nucleus largely retains its neuropeptide expression and responds to dehydration with fine cellular resolution from amphibians to mammals, whereas lamina terminalis neurons are specific to terrestrial vertebrates and exhibit gene expression divergence in cell types activated by dehydration and heat. We propose that a conserved set of keystone cell types sustain essential functions across vertebrates, while flexible gene regulatory programs alongside numerous clade-specific cell types offer evolutionary fluidity.

evolutionary biology↗

bioRxiv2026

Within-Subject Optogenetic Model Reveals Spatiotemporal Cortical Reorganization in Artificial Vision

Visual prostheses can elicit simple percepts such as letter forms through dynamically patterned stimulation, yet naturalistic dynamic vision remains out of reach despite hardware fully capable of high-resolution temporal control. This persistent gap suggests the bottleneck lies in how artificial input is represented by the cortex itself. A fundamental question remains unresolved: when artificial vision bypasses natural retinal encoding, what is lost in cortical representation? We address this question in this paper using a retinal optogenetic mouse model that isolates the consequence of bypassing retinal encoding while preserving downstream pathways. Using within-subject V1 cortex electrophysiology and CNN-based decoding under identical dynamic stimuli, we reveal dissociable, dimension-specific gaps. Temporally, artificial vision bypassed the frequency-dependent compression imposed by natural vision, extending stimulus-locked entrainment bandwidth. Spatially, direction-selective representations underwent systematic remapping, with disrupted phase organization and reduced encoding regularity. These findings show that bypassing natural retinal encoding reorganizes cortical representation along dissociable spatiotemporal dimensions, establishing a within-subject framework that renders such structural divergences easy to locate and quantifiable.

bioengineering↗

bioRxiv2025

Explosive cytotoxicity of 'ruptoblasts' bridges hormonal surveillance and immune defense

Current understanding of cytotoxic immunity is shaped by hematopoietic-derived cells - T cells, natural killer cells, and neutrophils. Here, we identify ruptoblasts, a previously unknown cytotoxic glandular cell type in regenerative planarian flatworms. Ruptoblasts undergo an explosive cell death, ruptosis, triggered by activin, a multifunctional hormone that also acts as an inflammatory cytokine. Excessive activin - induced through protein injection, genetic chimerism, or bacterial infection - initiates ruptosis, discharging potent diffusible cytotoxic agents capable of eliminating any nearby cells, bacteria, and even mammalian cells within minutes. Ruptoblast ablation suppresses inflammation but compromises bacterial clearance, highlighting their broad-spectrum immune functions. Mechanistically distinct from known cytotoxic mechanisms, the explosive nature of ruptosis relies on intracellular calcium and dynamic cytoskeletal reorganization. Ruptoblast-like cells appear conserved in diverse basal bilaterians, implying an ancient evolutionary origin. These findings unveil a widespread strategy coupling hormonal regulation with immune defense and expand the landscape of evolutionary immune innovations.

immunology↗

bioRxiv2024

Flexible use of conserved motif vocabularies constrains genome access in cell type evolution

Cell types evolve into a hierarchy with related types grouped into families. How cell type diversification is constrained by the stable separation between families over vast evolutionary times remains unknown. Here, integrating single-nucleus multiomic sequencing and deep learning, we show that hundreds of sequence features (motifs) divide into distinct sets associated with accessible genomes of specific cell type families. This division is conserved across highly divergent, early-branching animals including flatworms and cnidarians. While specific interactions between motifs delineate cell type relationships within families, surprisingly, these interactions are not conserved between species. Consistently, while deep learning models trained on one species can predict accessibility of other species sequences, their predictions frequently rely on distinct, but synonymous, motif combinations. We propose that long-term stability of cell type families is maintained through genome access specified by conserved motif sets, or vocabularies, whereas cell types diversify through flexible use of motifs within each set.

evolutionary biology↗

bioRxiv2024

Regeneration in the absence of canonical neoblasts in an early branching flatworm

The remarkable regenerative abilities of flatworms are closely linked to neoblasts - adult pluripotent stem cells that are the only division-competent cell type outside of the reproductive system. Although the presence of neoblast-like cells and whole-body regeneration in other animals has led to the idea that these features may represent the ancestral metazoan state, the evolutionary origin of both remains unclear. Here we show that the catenulid Stenostomum brevipharyngium, a member of the earliest-branching flatworm lineage, lacks conventional neoblasts despite being capable of whole-body regeneration and asexual reproduction. Using a combination of single-nuclei transcriptomics, in situ gene expression analysis, and functional experiments, we find that cell divisions are not restricted to a single cell type and are associated with multiple fully differentiated somatic tissues. Furthermore, the cohort of germline multipotency genes, which are considered canonical neoblast markers, are not expressed in dividing cells, but in the germline instead, and we experimentally show that they are neither necessary for proliferation nor regeneration. Overall, our results challenge the notion that canonical neoblasts are necessary for flatworm regeneration and open up the possibility that neoblast-like cells may have evolved convergently in different animals, independent of their regenerative capacity.

zoology↗

bioRxiv2024

A genetic and microscopy toolkit for live imaging of whole-body regeneration in Macrostomum lignano

Live imaging of regenerative processes can reveal how animals restore their bodies after injury through a cascade of dynamic cellular events. Here, we present a comprehensive toolkit for live imaging of whole-body regeneration in the flatworm Macrostomum lignano, including a high throughput cloning pipeline, targeted cellular ablation, and advanced microscopy solutions. Using tissue-specific reporter expression, we examine how various structures regenerate. Enabled by a custom, low-cost luminescence/fluorescence microscope, we overcome intense stress-induced autofluorescence to demonstrate the first application of genetic cellular ablation in flatworms to reveal the limited regenerative capacity of neurons and their essential role during wound-healing. Finally, we build a novel open-source tracking microscope to continuously image moving animals throughout the week-long process of regeneration, quantifying kinetics of wound healing, nerve cord repair, body regeneration, growth, and behavioral recovery. Our findings suggest that nerve cord reconnection operates independently from primary body axis re-establishment and other downstream regenerative processes.

bioengineering↗

bioRxiv2023

Ultrafast and long-range coordination of wound responses is essential for whole-body regeneration

Injury induces systemic, global responses whose functions remain elusive. In addition, mechanisms that rapidly synchronize wound responses through long distances across the organismal scale are mostly unknown. Using planarians, which have extreme regenerative ability, we report that injury induces Erk activity to travel in a wave-like manner at an unexpected speed ([~]1 mm/h), 10-100 times faster than those measured in other multicellular tissues. This ultrafast signal propagation requires longitudinal body-wall muscles, elongated cells forming dense parallel tracks running the length of the organism. Combining experiments and computational models, we show that the morphological properties of muscles allow them to minimize the number of slow intercellular signaling steps and act as bidirectional superhighways for propagating wound signals and instructing responses in other cell types. Inhibiting Erk propagation prevents cells distant to the wound from responding and blocks regeneration, which can be rescued by a second injury to distal tissues within a narrow time window after the first injury. These results suggest that rapid responses in uninjured tissues far from wounds are essential for regeneration. Our findings provide a mechanism for long-range signal propagation in large and complex tissues to coordinate cellular responses across diverse cell types, and highlights the function of feedback between spatially separated tissues during whole-body regeneration.

developmental biology↗

bioRxiv2023

Adaptive robustness through incoherent signaling mechanisms in a regenerative brain

Animal behavior emerges from collective dynamics of interconnected neurons, making it vulnerable to connectome damage. Paradoxically, many organisms maintain significant behavioral output after large-scale neural injury. Molecular underpinnings of this extreme robustness remain largely unknown. Here, we develop a quantitative behavioral analysis pipeline to measure previously uncharacterized long-lasting latent memory states in planarian flatworms during whole-brain regeneration. By combining >20,000 animal trials with neural population dynamic modeling, we show that long-range volumetric peptidergic signals allow the planarian to rapidly reestablish latent states and restore coarse behavior after large structural perturbations to the nervous system, while small-molecule neuromodulators gradually refine the precision. The different time and length scales of neuropeptide and small-molecule transmission generate incoherent patterns of neural activity which competitively regulate behavior and memory. Controlling behavior through opposing communication mechanisms creates a more robust system than either alone and may serve as a generic approach to construct robust neural networks.

neuroscience↗

bioRxiv2022

Expansion Spatial Transcriptomics

Capture array-based spatial transcriptomics methods have been widely used to resolve gene expression in diverse tissue contexts, however, their spatial resolution is limited by array density. We present Expansion Spatial Transcriptomics (Ex-ST) to overcome this limitation by clearing and expanding tissue prior to capturing the entire transcriptome. This approach allows us to achieve near cellular resolution and higher capture efficiency of lowly-expressed genes, which we demonstrate using mouse brain samples.

genomics↗

bioRxiv2021

Heterologous reporter expression in the planarian Schmidtea mediterranea through somatic mRNA transfection

Planarians have long been studied for their regenerative abilities. Moving forward, tools for ectopic expression of non-native proteins will be of substantial value. Using a luminescent reporter to overcome the strong autofluorescence background of planarian tissues, we demonstrate heterologous protein expression in planarian cells and live animals. Our approach is based on the introduction of mRNA through several nanotechnological and chemical transfection methods. We improve reporter expression by altering untranslated region (UTR) sequences and codon bias, facilitating measurement of expression kinetics both in isolated cells and in whole planarians using luminescence imaging. We also examine protein expression as a function of variations in the UTRs of delivered mRNA, demonstrating a framework to investigate gene regulation at the post-transcriptional level. Together, these advances expand the toolbox for the mechanistic analysis of planarian biology and establish a strong foundation for the development and expansion of transgenic techniques in this unique model system. MotivationThe study of planarians has contributed to advances in our understanding of regeneration, stem cell dynamics, and many other fundamental biological processes. However, the persistent challenge of expressing transgenes in planarians has led to the speculation that they may be resistant to transfection. In this work, we develop methods to express exogenous mRNAs in both isolated planarian cells and whole animals by optimizing delivery techniques, genetic constructs, and detection methods. These methods allow us to study transfection kinetics and post-transcriptional regulation of gene expression in a quantitative manner. Beyond planarian research, this work should also provide a broadly applicable strategy to develop similar tools for animals that are also challenging to modify genetically.

bioengineering↗

bioRxiv2020

Squid: Simplifying Quantitative Imaging Platform Development and Deployment

With rapid developments in microscopy methods, highly versatile, robust and affordable implementations are needed to enable rapid and wide adoption by the biological sciences community. Here we report Squid, a quantitative imaging platform with a full suite of hardware and software components and configurations for deploying facility-grade widefield microscopes with advanced features like flat field fluorescence excitation, patterned illumination and tracking microscopy, at a fraction of the cost of commercial solutions. The open and modular nature (both in hardware and in software) lowers the barrier for deployment, and importantly, simplifies development, making the system highly configurable and experiments that can run on the system easily programmable. Developed with the goal of helping translate the rapid advances in the field of microscopy and microscopy-enabled methods, including those powered by deep learning, we envision Squid will simplify roll-out of microscopy-based applications - including at point of care and in low resource settings, make adoption of new or otherwise advanced techniques easier, and significantly increase the available microscope-hours to labs.

bioengineering↗

bioRxiv2020

mTOR S-nitrosylation inhibits autophagy and lysosomal proteolysis

Mammalian Target of Rapamycin (mTOR) is a master regulator of autophagy and lysosomes, and its downstream kinase-dependent pathways have been extensively characterized. Here, we report an unexpected kinase-independent regulation of autophagy and lysosomes by S-nitrosylation at Cys423 position of mTOR that resulted in suppression of VPS34 and PIKfyve-dependent phosphoinositide synthesis. Physiologically, S-nitrosylation of mTOR reduced basal lysosomal proteolysis via nitric oxide synthase (NOS)-mediated synthesis of NO from lysosomal arginine precursor, a marker of cellular nutrition status. Significantly, we found increased lysosomal NOS-mTOR complexes in APP-PS1 Alzheimers disease (AD) murine model, and increased mTOR S-nitrosylation in AD patient-derived fibroblasts. Lastly, we demonstrated that pharmacological inhibition of NOS or overexpression of mTORCys423Ala mutant reversed lysosomal and autophagic dysfunction in AD patient-derived fibroblasts, suggesting novel therapeutic strategies for autophagosome-lysosomal activation.

cell biology↗

bioRxiv2020

Integrated profiling of single cell epigenomic and transcriptomic landscape of Parkinson's disease mouse brain

Parkinsons disease (PD) is a neurodegenerative disease leading to the impairment of execution of movement. PD pathogenesis has been largely investigated, but either restricted in bulk level or at certain cell types, which failed to capture cellular heterogeneity and intrinsic interplays among distinct cell types. To overcome this, we applied single-nucleus RNA-seq and single cell ATAC-seq on cerebellum, midbrain and striatum of PD mouse and matched control. With 74,493 cells in total, we comprehensively depicted the dysfunctions under PD pathology covering proteostasis, neuroinflammation, calcium homeostasis and extracellular neurotransmitter homeostasis. Besides, by multi-omics approach, we identified putative biomarkers for early stage of PD, based on the relationships between transcriptomic and epigenetic profiles. We located certain cell types that primarily contribute to PD early pathology, narrowing the gap between genotypes and phenotypes. Taken together, our study provides a valuable resource to dissect the molecular mechanism of PD pathogenesis at single cell level, which could facilitate the development of novel methods regarding diagnosis, monitoring and practical therapies against PD at early stage.

cell biology↗

bioRxiv2020

Single cell atlas of trisomy 21 cerebral cortex

Down syndrome (DS) is one of the most common human birth defects caused by trisomy 21 (T21), leading to a variety of cognitive impairments. The cellular composition of human brain has been explored using single cell RNA sequencing in both physiological and pathological conditions. However, the cellular heterogeneity of human brain with chromosome aneuploidy is largely unknown. Here, we profiled the transcriptome of 36046 cells in cerebral cortex of T21 human fetus, covering frontal lobe, parietal lobe, occipital lobe and temporal lobe. Intriguingly, we detected several genes positively associated with neurons maturation was dysregulated in T21 frontal cortex (HIC2, POU2F2, ZGLP1 and FOXK1). To share, explore and utilized the data resources of T21 cerebral cortex, we developed a comprehensive platform named T21atlas, composing of two functional modules (T21cluster and T21talk). Overall, our study provides, as far as we know, the first single cell atlas for T21 cerebral cortex, which could promote our understanding of the molecular mechanism of DS at an unprecedented resolution and could potentially facilitate the development of novel clinical therapeutics against T21.

neuroscience↗

bioRxiv2019

Towards Practical and Robust DNA-based Data Archiving by Codec System Named ‘Yin-Yang’

DNA is a promising data storage medium due to its remarkable durability and space-efficient storage. Early bit-to-base transcoding schemes have primarily pursued information density, at the expense however of introducing biocompatibility challenges or at the risk of decoding failure. Here, we propose a robust transcoding algorithm named the "Yin-Yang Codec" (YYC), using two rules to encode two binary bits into one nucleotide, to generate DNA sequences highly compatible with synthesis and sequencing technologies. We encoded two representative file formats and stored them in vitro as 200-nt oligo pools and in vivo as an ~54-kb DNA fragment in yeast cells. Sequencing results show that YYC exhibits high robustness and reliability for a wide variety of data types, with an average recovery rate of 99.94% at 104 molecule copies and an achieved recovery rate of 87.53% at 100 copies. In addition, the in vivo storage demonstration achieved for the first time an experimentally measured physical information density of 198.8 EB per gram of DNA (44% of the theoretical maximum for DNA).

synthetic biology↗

bioRxiv2019

The small noncoding RNA sr8384 determines solvent synthesis and cell growth in industrial solventogenic clostridia

Small noncoding RNAs (sncRNAs) are crucial regulatory molecules in organisms and are well known not only for their roles in the control of diverse essential biological processes but also for their value in genetic modification. However, to date, in gram-positive anaerobic solventogenic clostridia (which are a group of important industrial bacteria with exceptional substrate and product diversity), sncRNAs remain minimally explored, leading to a lack of detailed understanding regarding these important molecules and their use as targets for genetic improvement. Here, we performed large-scale phenotypic screens of a transposon-mediated mutant library of Clostridium acetobutylicum, a typical solventogenic clostridial species, and discovered a novel sncRNA (sr8384) that functions as a determinant positive regulator of growth and solvent synthesis. Comparative transcriptomic data combined with genetic and biochemical analyses revealed that sr8384 acts as a pleiotropic regulator and controls multiple targets that are associated with crucial biological processes, through direct or indirect interactions. Notably, modulation of the expression level of either sr8384 or its core target genes significantly increased the growth rate, solvent titer and productivity of the cells, indicating the importance of sr8384-mediated regulatory network in C. acetobutylicum. Furthermore, a homolog of sr8384 was discovered and proven to be functional in another important Clostridium species, C. beijerinckii, suggesting the potential broad role of this sncRNA in clostridia. Our work showcases a previously unknown potent and complex role of sncRNAs in clostridia, providing new opportunities for understanding and engineering these anaerobes, including pathogenic Clostridium species.\n\nIMPORTANCEThe discovery of sncRNAs as new resources for functional studies and strain modifications are promising strategies in microorganisms. However, these crucial regulatory molecules have hardly been explored in industrially important solventogenic clostridia. Here, we identified sr8384 as a novel determinant sncRNA controlling cellular performance of solventogenic Clostridium acetobutylicum and performed detailed functional analysis, which is the most in-depth study of sncRNAs in clostridia to date. We reveal the pleiotropic function of sr8384 and its multiple direct and indirect crucial targets, which represents a valuable source for understanding and optimizing this anaerobe. Of note, manipulation of these targets leads to improved cell growth and solvent synthesis. Our findings provide a new perspective for future studies on regulatory sncRNAs in clostridia.

microbiology↗