Biology subjects

Dai, Q.

Publications and source records attributed to Dai, Q..

At least 55 records · Page 3Linked to original sources

bioRxiv2022

Real-time denoising of fluorescence time-lapse imaging enables high-sensitivity observations of biological dynamics beyond the shot-noise limit

A fundamental challenge in fluorescence microscopy is the inherent photon shot noise caused by the inevitable stochasticity of photon detection. Noise increases measurement uncertainty, degrades image quality, and limits imaging resolution, speed, and sensitivity. To achieve high-sensitivity imaging beyond the shot-noise limit, we provide DeepCAD-RT, a versatile self-supervised method for effective noise suppression of fluorescence time-lapse imaging. We made comprehensive optimizations to reduce its data dependency, processing time, and memory consumption, finally allowing real-time processing on a two-photon microscope. High imaging signal-to-noise ratio (SNR) can be acquired with 10-fold fewer fluorescence photons. Meanwhile, the self-supervised superiority makes it a practical tool in fluorescence microscopy where ground-truth images for training are hard to obtain. We demonstrated the utility of DeepCAD-RT in extensive experiments, including in vivo calcium imaging of various model organisms (mouse, zebrafish larva, fruit fly), 3D migration of neutrophils after acute brain injury, and 3D dynamics of cortical ATP (adenosine 5-triphosphate) release. DeepCAD-RT will facilitate the morphological and functional interrogation of biological dynamics with minimal photon budget.

biophysics↗

bioRxiv2022

Spinning Disk Multifocal Microscopy for Dynamic Arbitrarily Shaped Surface Imaging at Centimetre Scale and Micrometre Resolution

The large-scale fluorescence microscopy has enabled the observation of dynamic physiological activities at the single cellular level across the mouse cortex, such as distributed neuronal population representations. However, video-rate high-resolution microscopy at sophisticated biological surfaces in nature keeps a challenging task for the tradeoff between the speed, resolution, and field of view. Here we propose Spinning Disk Multifocal Microscopy (SDiM) for arbitrarily shaped surfaces, which enables imaging at centimeter field-of-view, micrometer resolution and up to 30 frames per second across the depth range of 450 {micro}m. We apply this technique in various microscopic systems, including customized macroscopic systems and the Real-time Ultra-large-Scale imaging at High resolution macroscopy (RUSH), in both the reflective mode and the fluorescence mode, and in the study of cortex-wide single-neuron imaging and immune cell tracking. SDiM provides an opportunity for studying the cortex-wide multi-scale cellular interactions in biological tissues.

bioengineering↗

bioRxiv2022

Rapid deep widefield neuron finder driven by virtual calcium imaging data

Widefield microscope provides optical access to multi-millimeter fields of view and thousands of neurons in mammalian brains at video rate. However, calcium imaging at cellular resolution has been mostly contaminated by tissue scattering and background signals, making neuronal activities extraction challenging and time-consuming. Here we present a deep widefield neuron finder (DeepWonder), which is fueled by simulated calcium recordings but effectively works on experimental data with an order of magnitude faster speed and improved inference accuracy than traditional approaches. The efficient DeepWonder accomplished fifty-fold signal-to-background ratio enhancement in processing terabytes-scale cortex-wide recording, with over 14000 neurons extracted in 17 hours in workstation-grade computing resources compared to nearly week-long processing time with previous methods. DeepWonder circumvented the numerous computational resources and could serve as a guideline to massive data processing in widefield neuronal imaging.

bioengineering↗

bioRxiv2021

The METTL5-TRMT112 N6-methyladenosine methyltransferase complex regulates metabolism and development via translation

Ribosomal RNAs (rRNAs) have long been known to carry modifications, including numerous sites of 2O-methylation and pseudouridylation, as well as N6-methyladenosine (m6A), and N6,6-dimethyladenosine. While the functions of many of these modifications are unclear, some are highly conserved and occur in regions of the ribosome critical for mRNA decoding. Both 28S rRNA and 18S rRNA carry m6A, and while ZCCHC4 has been identified as the methyltransferase responsible for the 28S rRNA m6A site, the methyltransferase responsible for the 18S rRNA m6A site has remained uncharacterized until recently. Here, we show that the METTL5-TRMT112 complex is the methyltransferase responsible for installing m6A at position 1832 of human 18S rRNA. TRMT112 is required for the metabolic stability of METTL5, and human METTL5 mutations associated with microcephaly and intellectual disability disrupt this interaction. Loss of METTL5 in human cancer lines alters the translation of transcripts associated with mitochondrial biogenesis and function. Mettl5 knockout mice display reduced body size and evidence of metabolic defects. This m6A site is located on the 3 end of 18S rRNA, which may become surface-exposed under some circumstances and thus may play a regulatory role in translation of specific transcripts. While recent work has focused heavily on m6A modifications in mRNA and its roles in mRNA processing and translation, deorphanizing putative methyltransferase enzymes is revealing previously unappreciated regulatory roles for m6A in noncoding RNAs.

biochemistry↗

bioRxiv2021

On the robustness of inference of association with the gut microbiota in stool, swab and mucosal tissue samples

The gut microbiota plays an important role in human health and disease. Stool, swab and mucosal tissue samples have been used in individual studies to survey the microbial community but the consequences of using these different sample types are not completely understood. We previously reported differences in microbial community composition with 16S rRNA amplicon sequencing between stool, swab and mucosal tissue samples. Here, we extended the previous study to a larger cohort and performed shotgun metagenome sequencing of 1,397 stool, swab and mucosal tissue samples from 240 participants. Consistent with previous results, taxonomic composition of stool and swab samples was distinct, but still more similar to each other than mucosal tissue samples, which had a substantially different community composition, characterized by a high relative abundance of the mucus metabolizers Bacteroides and Subdoligranulum, as well as bacteria with higher tolerance for oxidative stress such as Escherichia. As has been previously reported, functional profiles were more uniform across sample types than taxonomic profiles with differences between stool and swab samples smaller, but mucosal tissue samples remained distinct from the other two types. When the taxonomic and functional profiles of different sample types were used for inference in association with host phenotypes of age, sex, body mass index (BMI), antibiotics or non-steroidal anti-inflammatory drugs (NSAIDs) use, hypothesis testing using either stool or swab gave broadly similar results, but inference performed on mucosal tissue samples gave results that were generally less consistent with either stool or swab. Our study represents an important resource for the experimental design of studies aimed to understand microbiota perturbations specific to defined micro niches within the human intestinal tract.

microbiology↗

bioRxiv2020

Computational optical sectioning by phase-space imaging with an incoherent multiscale scattering model

Optical sectioning is essential for fluorescence imaging in thick tissue to extract in-focus information from noisy background. Traditional methods achieve optical sectioning by rejecting the out-of-focus photons at a cost of photon efficiency, resulting in a tradeoff between sectioning capability and detection parallelization. Here, we show phase-space imaging with an incoherent multiscale scattering model can achieve computational optical sectioning with ~20 dB improvement for signal-to-background ratio in scattering medium, while maximizing the detection parallelization by imaging the entire volume simultaneously. We validated the superior performance by imaging various biological dynamics in Drosophila embryos, zebrafish larvae, and mice.

cell biology↗

bioRxiv2020

Reinforcing neuron extraction and spike inference in calcium imaging using deep self-supervised learning

Calcium imaging is inherently susceptible to detection noise especially when imaging with high frame rate or under low excitation dosage. We developed DeepCAD, a self-supervised learning method for spatiotemporal enhancement of calcium imaging without requiring any high signal-to-noise ratio (SNR) observations. Using this method, detection noise can be effectively suppressed and the imaging SNR can be improved more than tenfold, which massively improves the accuracy of neuron extraction and spike inference and facilitate the functional analysis of neural circuits.

neuroscience↗

bioRxiv2020

A polymer gel index-matched to water enables diverse applications in fluorescence microscopy

We demonstrate diffraction-limited and super-resolution imaging through thick layers (tens-hundreds of microns) of BIO-133, a biocompatible, UV-curable, commercially available polymer with a refractive index (RI) matched to water. We show that cells can be directly grown on BIO-133 substrates without the need for surface passivation and use this capability to perform extended time-lapse volumetric imaging of cellular dynamics 1) at isotropic resolution using dual-view light-sheet microscopy, and 2) at super-resolution using instant structured illumination microscopy. BIO-133 also enables immobilization of 1) Drosophila tissue, allowing us to track membrane puncta in pioneer neurons, and 2) Caenorhabditis elegans, which allows us to image and inspect fine neural structure and to track pan-neuronal calcium activity over hundreds of volumes. Finally, BIO-133 is compatible with other microfluidic materials, enabling optical and chemical perturbation of immobilized samples, as we demonstrate by performing drug and optogenetic stimulation on cells and C. elegans.

bioengineering↗

bioRxiv2020

Tethering-facilitated DNA 'opening' and complementary roles of β-hairpin motifs in the Rad4/XPC DNA damage sensor protein

XPC/Rad4 initiates eukaryotic nucleotide excision repair on structurally diverse helix-destabilizing/distorting DNA lesions by selectively opening these sites while rapidly diffusing along undamaged DNA. Previous structural studies showed that Rad4, when tethered to DNA, could also open undamaged DNA, suggesting a kinetic gating mechanism whereby lesion discrimination relied on efficient opening versus diffusion. However, solution studies in support of such a mechanism were lacking and how opening is brought about remained unclear. Here, we present crystal structures and fluorescence-based conformational analyses on tethered complexes, showing that Rad4 can indeed open undamaged DNA in solution and that such opening can largely occur without one or the other of the {beta}-hairpin motifs in the BHD2 or BHD3 domains. Notably, the Rad4-bound open DNA adopts multiple conformations in solution notwithstanding the DNAs original structure or the {beta}-hairpins. Molecular dynamics simulations reveal compensatory roles of the {beta}-hairpins, which may render robustness in dealing with and opening diverse lesions. Our study showcases how fluorescence-based studies can be used to obtain information complementary to ensemble structural studies. The tethering-facilitated DNA opening of undamaged sites and the dynamic nature of open DNA may shed light on how the protein functions within and beyond NER in cells.

biochemistry↗

bioRxiv2020

Characterizing tissue composition through combined analysis of single-cell morphologies and transcriptional states

Advances in spatial transcriptomics technologies enable optical profiling of morphological and transcriptional modalities from the same cells within tissues. Here, we present multi-modal structured embedding (MUSE), an approach to deeply characterize tissue heterogeneity through analysis of combined image and transcriptional single-cell measurements. We demonstrate that MUSE can discover cellular subpopulations missed by either modality as well as compensate for modality-specific noise. MUSE identified biologically meaningful cellular subpopulations and stereotyped spatial patterning within heterogeneous mouse cortex brain tissues, profiled by seqFISH+ or STARmap technologies. MUSE provides a framework for combining multi-modal single-cell data to reveal deeper insights into the states, functions and organization of cells in complex biological tissues.

bioinformatics↗

bioRxiv2020

Comparison of SARS-CoV-2 infections among 3 species of non-human primates

COVID-19, caused by SARS-CoV-2 infection, has recently been announced as a pandemic all over the world. Plenty of diagnostic, preventive and therapeutic knowledges have been enriched from clinical studies since December 2019. However, animal models, particularly non-human primate models, are urgently needed for critical questions that could not be answered in clinical patients, evaluations of anti-viral drugs and vaccines. In this study, two families of non-human primates, Old world monkeys (12 Macaca mulatta, 6 Macaca fascicularis) and New world monkeys (6 Callithrix jacchus), were experimentally inoculated with SARS-CoV-2. Clinical signs were recorded. Samples were collected for analysis of viral shedding, viremia and histopathological examination. Increased body temperature was observed in 100% (12/12) M. mulatta, 33.3% (2/6) M. fascicularis and none (0/6) of C. jacchus post inoculation of SARS-CoV-2. All of M. mulatta and M. fascicularis showed chest radiographic abnormality. Viral genomes were detected in nasal swabs, throat swabs, anal swabs and blood from all 3 species of monkeys. Viral shedding from upper respiratory samples reached the peak between day 6 and day 8 post inoculation. From necropsied M. mulatta and M. fascicularis, the tissues showing virus positive were mainly lung, weasand, bronchus and spleen. No viral genome was seen in any of tissues from 2 necropsied C. jacchus. Severe gross lesions and histopathological changes were observed in lung, heart and stomach of SARS-CoV-2 infected animals. In summary, we have established a NHP model for COVID-19, which could be used to evaluate drugs and vaccines, and investigate viral pathogenesis. M. mulatta is the most susceptible to SARS-CoV-2 infection, followed by M. fascicularis and C. jacchus. One Sentence SummaryM. mulatta is the most susceptible to SARS-CoV-2 infection as compared to M. fascicularis and C. jacchus.

microbiology↗

bioRxiv2020

G2S3: a gene graph-based imputation method for single-cell RNA sequencing data

Single-cell RNA sequencing provides an opportunity to study gene expression at single-cell resolution. However, prevalent dropout events result in high data sparsity and noise that may obscure downstream analyses. We propose a novel method, G2S3, that imputes dropouts by borrowing information from adjacent genes in a sparse gene graph learned from gene expression profiles across cells. We applied G2S3 and other existing methods to seven single-cell datasets to compare their performance. Our results demonstrated that G2S3 is superior in recovering true expression levels, identifying cell subtypes, improving differential expression analyses, and recovering gene regulatory relationships, especially for mildly expressed genes.

bioinformatics↗

bioRxiv2020

Exposure to Mites Sensitizes Intestinal Stem Cell Maintenance, Splenic Marginal Zone B Cell Homeostasis, And Heart Development to Notch Dosage and Cooperativity.

Cooperative DNA binding is a key feature of transcriptional regulation. Here we examined the role of cooperativity in Notch signaling by CRISPR-mediated engineering of mice in which neither Notch1 nor Notch2 can homo- or heterodimerize, essential for cooperative binding to sequence paired sites (SPS) located near many Notch-regulated genes. While most known Notch-dependent phenotypes were unaffected in Notch1/2 dimer-deficient mice, a subset of tissues proved highly sensitive to loss of cooperativity. These phenotypes include heart development, compromising viability in combination with low gene dose, and the gut, developing ulcerative colitis in response to 1% DSS. The most striking phenotypes - gender imbalance and splenic marginal zone B cell lymphoma - emerged in combination with dose reduction or when challenged by chronic fur mite infestation. This study highlights the role of the environment in malignancy and colitis, and is consistent with Notch-dependent anti-parasite immune responses being compromised in the dimer deficient animals. HighlightsO_LINotch dimerization has an in vivo role in contributing to intestinal homeostasis C_LIO_LILoss of cooperativity can manifest as Notch gain or loss of function phenotypes C_LIO_LIMite infestation exacerbates all phenotypes, triggers MZB hyperproliferation in mutant animals C_LIO_LIMite-infested mutant mice develop SMZL with age C_LI

developmental biology↗

bioRxiv2020

Continual inactivation of stem cell functional identity genes stabilizes progenitor commitment

Expansion of the pool of stem cells that indirectly generate differentiated cells through intermediate progenitors drives vertebrate brain evolution. Due to a lack of lineage information, mechanistic investigation of the competency of stem cells to generate intermediate progenitors remains impossible. Fly larval brain neuroblasts provide excellent in vivo models for investigating the regulation of stem cell functionality during neurogenesis. Type II neuroblasts undergo indirect neurogenesis by dividing asymmetrically to generate a neuroblast and a progeny that commits to an intermediate progenitor (INP) identity. We identified Tailless (Tll) as the master regulator that maintains type II neuroblast functional identity, including the competency to generate INPs. Successive inactivation during INP commitment inhibits tll activation by Notch, preventing INPs from reacquiring neuroblast functionality. We propose that the continual inactivation of neural stem cell functional identity genes by histone deacetylation allows intermediate progenitors to stably commit to generating diverse differentiated cells during indirect neurogenesis.

developmental biology↗

bioRxiv2020

Fast and accurate assembly of Nanopore reads via progressive error correction and adaptive read selection

Although long Nanopore reads are advantageous in de novo genome assembly, applying Nanopore reads in genomic studies is still hindered by their complex errors. Here, we developed NECAT, an error correction and de novo assembly tool designed to overcome complex errors in Nanopore reads. We proposed an adaptive read selection and two-step progressive method to quickly correct Nanopore reads to high accuracy. We introduced a two-stage assembler to utilize the full length of Nanopore reads. NECAT achieves superior performance in both error correction and de novo assembly of Nanopore reads. NECAT requires only 7,225 CPU hours to assemble a 35X coverage human genome and achieves a 2.28-fold improvement in NG50. Furthermore, our assembly of the human WERI cell line showed an NG50 of 29 Mbp. The high-quality assembly of Nanopore reads can significantly reduce false positives in structure variation detection.

bioinformatics↗

bioRxiv2020

Deoxyribozyme-based Method for Site-specific Absolute Quantification of N6-methyladenosine Modification Fraction

N6-methyladenosine (m6A) is the most prevalent modified base in eukaryotic messenger RNA (mRNA) and long noncoding RNA (lncRNA). Although candidate sites for m6A modification are identified at the transcriptomic level, site-specific quantification methods for m6A modifications are still limited. Herein, we present a facile method implementing deoxyribozyme that preferentially cleaves the unmodified RNA. We leverage reverse transcription and real-time quantitative PCR along with key control experiments to quantify the absolute methylation fraction of specific m6A sites. We validate the accuracy of the method using synthetic RNA with controlled methylation fraction and apply our method on several endogenous sites that were previously identified in sequencing-based studies. This method provides a time and cost-effective approach for absolute quantification of the m6A fraction at specific loci, expanding the current toolkit for studying RNA modifications.

biochemistry↗

bioRxiv2020

Impact of DNA sequences in the DNA duplex opening by the Rad4/XPC nucleotide excision repair complex

Rad4/XPC is a key DNA damage sensor for nucleotide excision repair (NER) in eukaryotes. Rad4/XPC recognizes diverse bulky lesions by flipping out two lesion-containing nucleotide pairs and inserting a {beta}-hairpin from the BHD3 domain ({beta}-hairpin3) into the DNA duplex. We have previously observed that Rad4 can form the same open structure when covalently tethered to a normal DNA sequence containing consecutive C/Gs (CCC/GGG) and that a similar open-like structure can be formed even when the {beta}-hairpin3 is lacking. Here, we report a crystal structure of the {Delta}{beta}-hairpin3 mutant tethered to a sequence containing alternating C/Gs (CGC/GCG). In contrast to the previous structures, Rad4 bound to CGC/GCG in a 180{degrees}-reversed manner, capping the end of the duplex without flipping out the nucleotides. MD simulations showed that CGC/GCG was inherently less openable than CCC/GGG and that Rad4 failed to engage with its minor groove, a hallmark of productive binding towards opening. These results reveal that DNA sequences significantly influence the thermodynamic barrier for DNA opening by Rad4, which may render certain DNA structures/sequences resistant to opening despite a long residence time of Rad4. The reverse- mode may indicate unproductive binding for NER whereas the DNA end-binding may hint at Rad4/XPCs functions beyond NER.

biochemistry↗

bioRxiv2019

Explaining the genetic causality for complex diseases via deep association kernel learning

The genetic effect explains the causality from genetic mutation to the development of complex diseases. Existing genome-wide association study (GWAS) approaches are always built under a linear assumption, restricting their generalization in dissecting complicated causality such as the recessive genetic effect. Therefore, a sophisticated and general GWAS model that can work with different types of genetic effects is highly desired. Here, we introduce a Deep Association Kernel learning (DAK) model to enable automatic causal genotype encoding for GWAS at pathway level. DAK can detect both common and rare variants with complicated genetic effects that existing approaches fail. When applied to real-world GWAS data, our approach discovered potential casual pathways that could be explained by alternative biological studies.

bioinformatics↗