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Dai, Q.

Publications and source records attributed to Dai, Q..

63 records · Page 4Linked to original sources

Unsupervised content-preserving transformation for optical microscopy

The development of deep learning and the open access to a substantial collection of imaging data provide a potential solution to computational image transformation, which is gradually changing the landscape of optical imaging and biomedical research. However, current implementations of deep learning usually operate in a supervised manner and the reliance on a laborious and error-prone data annotation procedure remains a barrier towards more general applicability. Here, we propose an unsupervised image transformation to facilitate the utilization of deep learning for optical microscopy, even in some cases where supervised models cannot apply. By introducing a saliency constraint, the unsupervised model, dubbed as Unsupervised content-preserving Transformation for Optical Microscopy (UTOM), can learn the mapping between two image domains without requiring paired training data and avoid the distortion of the image content. UTOM shows promising performances in a wide range of biomedical image transformation tasks, including in silico histological staining, fluorescence image restoration, and virtual fluorescence labeling. Quantitative evaluations elucidate that UTOM achieves stable and high-fidelity image transformations across different imaging conditions and modalities. We anticipate that our framework will encourage a paradigm shift in training neural networks and enable more applications of artificial intelligence in biomedical imaging.

bioinformatics↗

3D observation of large-scale subcellular dynamics in vivo at the millisecond scale

Observing large-scale three-dimensional (3D) subcellular dynamics in vivo at high spatiotemporal resolution has long been a pursuit for biology. However, both the signal-to-noise ratio and resolution degradation in multicellular organisms pose great challenges. Here, we propose a method, termed Digital Adaptive Optics Scanning Lightfield Mutual Iterative Tomography (DAOSLIMIT), featuring both 3D incoherent synthetic aperture and tiled wavefront correction in post-processing. We achieve aberration-free fluorescence imaging in vivo over a 150 x 150 x 16 m3 field-of-view with the spatiotemporal resolution up to 250 nm laterally and 320 nm axially at 100 Hz, corresponding to a huge data throughput of over 15 Giga-voxels per second. Various fast subcellular processes are observed, including mitochondrial dynamics in cultured neurons, membrane dynamics in zebrafish embryos, and calcium propagation in cardiac cells, human cerebral organoids, and Drosophila larval neurons, enabling simultaneous in vivo studies of morphological and functional dynamics in 3D.

cell biology↗

Fast, Accurate Polarization and Polarity Imaging withPolarized Structured Illumination

The orientation and wobbling behavior of the fluorescent dipoles are of great significance in revealing the structure and state of cells. Due to the poor optical sectioning capability of wide-field microscopy, the polarization modulation signals are susceptible to the neighboring fluorophores. The missing cone of wide field optical transfer function induces vast out-of-focus background, resulting in biased polarization orientation and decrease polarization factor. Here, we apply polarized structured illumination to achieve polarization modulation imaging with optical sectioning, and simultaneously measure the lipid polarity with two-color ratiometric imaging. Our results demonstrate a significant increase in measurement accuracy of not only the dipole orientations but also the wobbling behavior of the ensemble dipole. Compared to the conventional confocal polarization imaging, our method obtains an order-of-magnitude faster imaging speed, capturing the fast dynamics of subcellular structures in live cells.

biophysics↗

Imaging chromatin interactions at sub-kilobase resolution Via Tn5-FISH

There is increasing interest in understanding how the three-dimensional organization of the genome is regulated. Different strategies have been employed to identify chromatin interactions genome wide. However, due to the current limitations in resolving genomic contacts, visualization and validation of these genomic loci with sub-kilobase resolution remain the bottleneck for many years. Here, we describe Tn5 transposase-based Fluorescence in situ Hybridization (Tn5-FISH), a Polymerase Chain Reaction (PCR)-based, cost-effective imaging method, which achieved the co-localization of genomic loci with sub-kilobase resolution, to fine dissect genome architecture at sub-kilobase resolution and to verify chromatin interactions detected by Chromatin Configuration Capture (3C)-derivative methods. Especially, Tn5-FISH is very useful to verify short-range chromatin interactions inside of contact domain and Topologically Associated Domain (TAD). It also offers one powerful molecular diagnosis tool for clinical detection of cytogenetic changes in cancers.

cell biology↗

BEN-solo factors partition active chromatin to ensure proper gene activation in Drosophila

The Drosophila genome encodes three BEN-solo proteins including Insensitive (Insv), Elba1 and Elba2 that possess activities in both transcriptional repression and chromatin insulation. These proteins all have a DNA binding BEN domain. A fourth protein Elba3 bridges Elba1 and Elba2 to form a heterotrimeric complex ELBA. Here we report comprehensive investigation on the in vivo functions of these proteins in Drosophila embryos. We generate ChIP-seq data of all these factors from all cognate and non-cognate mutants to assess common and distinct binding locations of Insv and ELBA, and genetic interdependencies. Notably, while most Elba1 and Elba2 binding requires the full ELBA complex, the adapter protein Elba3 can associate with chromatin and repress gene expression independently of Elba1 and Elba2. We also employ high-resolution ChIP-nexus mapping to show that Insv binds to DNA in a symmetric configuration while the ELBA complex binds asymmetrically in vivo. We observe that motifs of known insulator proteins are enriched in ELBA and Insv ChIP peaks and demonstrate that ELBA collaborates with other insulator factors to regulate developmental patterning in embryos. To differentiate the insulator function of ELBA and Insv from their repressor activity, we determined real-time transcription change in mutant embryos using precision nuclear run-on sequencing. ELBA factor mutants dampen expression differences between pairs of ELBA-bound neighboring genes. Finally, transgenic reporters confirm insulation activity of ELBA- and Insv-bound sites. Altogether, these findings define ELBA and Insv as general insulator proteins in Drosophila and demonstrate the functional importance of insulators in partitioning transcription units.

developmental biology↗

PRDM16 establishes lineage-specific transcriptional program to promote temporal progression of neural progenitors in the mouse neocortex

Radial glia (RG) in the neocortex sequentially generate distinct subtypes of projection neurons, accounting for the diversity and complex assembly of cortical neural circuits. Mechanisms that drive the rapid and precise temporal progression of RG are beginning to be elucidated. Here we reveal that the RG-specific transcriptional regulator PRDM16 promotes the transition of early to late phases of neurogenesis in the mouse neocortex. Prdm16 mutant RG delays the timely progression of RG, leading to defective cortical laminar organization. We show that PRDM16 regulates expression of neuronal specification genes and a subset of genes that are dynamically expressed between mid-and late-neurogenesis. Our genomic analysis suggests that PRDM16 suppresses target gene expression through maintaining chromatin accessibility of permissive enhancers. Altogether, our results demonstrate a critical role of PRDM16 in establishing stage-specific gene expression program of RG during cortical neurogenesis. These findings also support a model where progenitor cells are primed with daughter cell gene expression program for rapid cell differentiation.

developmental biology↗

JNK-IN-8, a c-Jun N-terminal kinase inhibitor, improves functional recovery through suppressing neuroinflammation in ischemic stroke

c-Jun N-terminal kinase (JNK), a mitogen activated protein kinase, is activated in ischemia brain injury and plays an important role in cerebral ischemic injury. Emerging studies demonstrated that JNK-IN-8 (a specific JNK inhibitor) regulates traumatic brain injury through controlling neuronal apoptosis and inflammation. However, the role of JNK-IN-8 in ischemic stroke and the underlying mechanisms of JNK-IN-8 involving neuroprotection remain poorly understood. In the present study, male rats were subjected to tMCAO (transient middle cerebral artery occlusion) followed by treatment with JNK-IN-8, and then the modified improved neurological function score (mNSS), the Foot-fault test and the level of inflammatory cytokines (IL-1{beta}, IL-6 and TNF-) were assessed. We found that JNK-IN-8-treated rats with MCAO exerted a significant improvement in spatial learning as measured by the improved mNSS, and showed sensorimotor functional recovery as measured by the Foot-fault test. JNK-IN-8 also exerted anti-inflammatory effects as indicated by decreased activation of microglia and the decreased expresson of IL-6, IL-1{beta} and TNF-. Furthermore, JNK-IN-8 suppressed the activation of JNK and subsequent activation of NF-{kappa}B signaling as indicated by the decreased level of phosphorylated JNK (p-JNK) and p65. These data suggest that JNK-IN-8 suppressed neuroinflammation and improved neurological function by inhibiting JNK/NF-{kappa}B pathway after ischemic brain injury, thus offering a new target for prevention of ischemic brain injury.

cancer biology↗

Massive single-cell RNA-seq analysis and imputation via deep learning

Recent advances in large-scale single cell RNA-seq enable fine-grained characterization of phenotypically distinct cellular states within heterogeneous tissues. We present scScope, a scalable deep-learning based approach that can accurately and rapidly identify cell-type composition from millions of noisy single-cell gene-expression profiles.

bioinformatics↗

Biogenesis of a young, 22-nt microRNA in Phaseoleae species by precursor-programmed uridylation

Phased, secondary siRNAs (phasiRNAs) represent a class of small RNAs in plants generated via distinct biogenesis pathways, predominantly dependent on the activity of 22 nt miRNAs. Most 22 nt miRNAs are processed by DCL1 from miRNA precursors containing an asymmetric bulge, yielding a 22/21 nt miRNA/miRNA* duplex. Here we show that miR1510, a soybean miRNA capable of triggering phasiRNA production from numerous NB-LRRs, previously described as 21 nt in its mature form, primarily accumulates as a 22 nt isoform via monouridylation. We demonstrate that in Arabidopsis, this uridylation is performed by HESO1. Biochemical experiments showed that the 3 terminus of miR1510 is only partially 2-O-methylated, because of the terminal mispairing in the miR1510/miR1510* duplex that inhibits HEN1 activity in soybean. miR1510 emerged in the Phaseoleae ~41 to 42 MYA with a conserved precursor structure yielding a 22 nt monouridylated form, yet a variant in mung bean is processed directly in a 22 nt mature form. This analysis of miR1510 yields two observations: (1) plants can utilize post-processing modification to generate abundant 22 nt miRNA isoforms to more efficiently regulate target mRNA abundances; (2) comparative analysis demonstrates an example of selective optimization of precursor processing of a young plant miRNA.

plant biology↗