Biology subjects

Yan, T.

Publications and source records attributed to Yan, T..

44 records · Page 3Linked to original sources

bioRxiv2022

Dimerization of iLID Optogenetic Proteins Observed Using 3D Single-Molecule Tracking in Live Bacterial Cells

3D single molecule tracking microscopy has enabled measurements of protein diffusion in living cells, offering information about protein dynamics and cellular environments. For example, different diffusive states can be resolved and assigned to protein complexes of different size and composition. However, substantial statistical power and biological validation, often through genetic deletion of binding partners, are required to support diffusive state assignments. When investigating cellular processes, transient perturbation to protein spatial distributions is preferable to permanent genetic deletion of an essential protein. In this context, optogenetic dimerization systems can be used to manipulate protein spatial distributions which could offer a means to deplete specific diffusive states observed in single molecule tracking experiments. Here, we evaluate the performance of the iLID optogenetic system in living E. coli cells using diffraction-limited microscopy and 3D single-molecule tracking. We observed a robust optogenetic response in protein spatial distributions after 488 nm laser activation. Surprisingly, 3D single-molecule tracking results indicate activation of the optogenetic response when illuminating with high intensity light with wavelengths at which there is minimal photon absorbance by the LOV2 domain. The pre-activation can be minimized through the use of iLID system mutants, and titration of protein expression levels. SIGNIFICANCE STATEMENTWe describe the combination of 3D single-molecule tracking microscopy and optogenetic manipulation of protein spatial distributions in living cells. Such a combination is impactful, because optogenetic systems enable sample perturbation in real time using light, which provides more flexibility than gene deletion and gene editing approaches that result in permanent changes to the specimen. We specifically investigate the performance of the iLID optogenetic system in a knocksideways experiment, in which cytosolic prey proteins (SspB) are sequestered to the membrane by interacting with membrane-anchored bait proteins (iLID). We quantified the magnitude of the optogenetic effect using both diffraction-limited imaging and 3D single-molecule tracking microscopy. We found, surprisingly, that the iLID optogenetic response is activated substantially by high intensity light at wavelengths for which there is negligible photon absorption by the iLID protein. Quantification of this alternative activation mechanism is a necessary component before optogenetic tools, such as iLIDs, are employed in single-molecule knocksideways experiment that are designed to provide new biological insights.

biophysics↗

bioRxiv2022

Human pancreatic islet microRNAs implicated in diabetes and related traits by large-scale genetic analysis

Genetic studies have identified [≥]240 loci associated with risk of type 2 diabetes (T2D), yet most of these loci lie in non-coding regions, masking the underlying molecular mechanisms. Recent studies investigating mRNA expression in human pancreatic islets have yielded important insights into the molecular drivers of normal islet function and T2D pathophysiology. However, similar studies investigating microRNA (miRNA) expression remain limited. Here, we present data from 63 individuals, representing the largest sequencing-based analysis of miRNA expression in human islets to date. We characterize the genetic regulation of miRNA expression by decomposing the expression of highly heritable miRNAs into cis- and trans-acting genetic components and mapping cis-acting loci associated with miRNA expression (miRNA-eQTLs). We find (i) 81 heritable miRNAs, primarily regulated by trans-acting genetic effects, and (ii) 5 miRNA-eQTLs. We also use several different strategies to identify T2D-associated miRNAs. First, we colocalize miRNA-eQTLs with genetic loci associated with T2D and multiple glycemic traits, identifying one miRNA, miR-1908, that shares genetic signals for blood glucose and glycated hemoglobin (HbA1c). Next, we intersect miRNA seed regions and predicted target sites with credible set SNPs associated with T2D and glycemic traits and find 32 miRNAs that may have altered binding and function due to disrupted seed regions. Finally, we perform differential expression analysis and identify 13 miRNAs associated with T2D status--including miR-187-3p, miR-21-5p, miR-668, and miR-199b-5p--and 4 miRNAs associated with a polygenic score for HbA1c levels--miR-216a, miR-25, miR-30a-3p, and miR-30a-5p.

genetics↗

bioRxiv2021

Episodic memory in aspects of brain information transfer by resting-state network topology

Studies suggest that resting-state functional connectivity conveys cognitive information; also, activity flow mediates cognitive information transfer. However, the exact mechanism of interregional interactions underlying episodic memory remains unclear. We performed a combined analysis of task-evoked activity and resting-state functional connectivity by activity flow mapping to estimate the information transfer mechanism of episodic memory. We found that the cognitive control and attentional networks were the most recruited structures in information transfers during both encoding and retrieval processes; these networks were correlated with task-evoked activation. Differences in information transfer intensity between encoding and retrieval mainly existed in the visual, somatomotor and hippocampal systems. Furthermore, information transfer showed high predictive power for episodic memory ability and mediated relationships between task-evoked activation and memory performance. Additional analysis indicated that structural connectivity had a transportive role in information transfer. Finally, our study presented the information transfer mechanism of episodic memory from multiple neural perspectives.

neuroscience↗

bioRxiv2019

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↗

bioRxiv2019

Ginsenoside Rg1 defenses PC-12 cells against hydrogen peroxide-caused damage via up-regulation of miR-216a-5p

BackgroundSpinal cord injury (SCI) is a destructive trauma accompanying with local injury, half of which cause chronic paralysis. Ginsenoside Rg1 exerts anti-apoptosis and anti-autophagy properties. Therefore, our goal was to study the protective mechanism of Rg1 in attenuating cell injury.\n\nMethodsMiR-216a-5p inhibitor was transfected into PC-12 cells, then cells were pre-treated by Rg1 and treated with 300 M hydrogen peroxide (H2O2) for 24 h. CCK-8 and apoptosis experiments were done to test cell activity and apoptosis respectively. Expression of miR-216a-5p and cell damage relative factors was tested via qRT-PCR and western blot experiments, respectively.\n\nResultsH2O2 induced cell activity suppression, apoptosis and autophagy well at the concentration of 300 M, leading cell injury. Rg1 could attenuate cell injury induced by H2O2 at the working concentration of 200 M that it elevated cell activity, attenuated apoptosis and autophagy and activated PI3K/AKT and AMPK signal pathways. Further, miR-216a-5p was up-regulated by Rg1. Rg1 played its role in relieving cell injury by positively regulating miR-216a-5p.\n\nConclusionOur study demonstrated that Rg1 attenuated H2O2-caused cell injury through positively regulated miR-216a-5p.

biochemistry↗

bioRxiv2019

Selection of appropriate reference genes for quantitative real-time PCR in Clerodendrum trichotomum

AbstrsctClerodendrum trichotomum, an important medicinal plant, has excellent salt tolerance and beautiful ornamental character. However, reliable reference genes for quantitative real-time PCR data (qRT-PCR) in C. trichotomum have not been investigated. Using our previous transcriptome data, 17 reference genes were selected in different tissues (leaves, flowers, fruits, stems, and roots) and under various abiotic stresses (salt, drought, flood, and heat) for C. trichotomum, using four different reference gene analysis software types: GeNorm, NormFinder, BestKeeper and ReFinder. The results identified RPL, ACT and HSP70 as the three most suitable reference genes for tissues. Genes ACT and AP-2 were most stably expressed under drought stress; MDH and UBCE2 were stable under flooding stress; RPL and UBCE2 were most stable under salt stress; and MDH and EF-1A were most appropriate under heat stress. For abiotic treatments, RPL, MDH and AP-2 were the most stable reference genes; and AP-2, RPL and ACT were stably expressed in all examined samples. The expression profile of the genes for Na+/H+ Exchanger1 (ClNHX1) and laccase (ClLAC) were selected to validate the stability of the determined reference genes. Our study provided reliable normalization for gene expression analysis and ensured more accurate data for further molecular mechanism research in C. trichotomum.

molecular biology↗

bioRxiv2018

Computational Correction of Spatially-Variant Optical Aberrations in 3D Single Molecule Localization Microscopy

3D single-molecule localization microscopy relies on fitting the shape of point-spread-functions (PSFs) recorded on a wide-field detector. However, optical aberrations distort those shapes, which compromise the accuracy and precision of single-molecule localization microscopy. Here we employ a computational phase retrieval based on a vectorial PSF model to quantify the spatially-variance of optical aberrations in a two-channel ultrawide-field single-molecule localization microscope. The use of a spatially-variant PSF model enables accurate and precise emitter localization in x, y- and z-directions throughout the entire field-of-view.\n\nOCIS Codes(100.6640) Superresolution; (180.2520) Fluorescence microscopy; (180.6900) Three-dimensional microscopy; (100.5070) Phase retrieval; (150.1135) Algorithms; (220.1010) Aberrations (global).

biophysics↗

bioRxiv2018

Resolving Cytosolic Diffusive States in Bacteria by Single-Molecule Tracking

The trajectory of a single protein in the cytosol of a living cell contains information about its molecular interactions in its native environment. However, it has remained challenging to accurately resolve and characterize the diffusive states that can manifest in the cytosol using analytical approaches based on simplifying assumptions. Here, we show that multiple intracellular diffusive states can be successfully resolved if sufficient single-molecule trajectory information is available to generate well-sampled distributions of experimental measurements and if experimental biases are taken into account during data analysis. To address the inherent experimental biases in camera-based and MINFLUX-based single-molecule tracking, we use an empirical data analysis framework based on Monte Carlo simulations of confined Brownian motion. This framework is general and adaptable to arbitrary cell geometries and data acquisition parameters employed in 2D or 3D single-molecule tracking. We show that, in addition to determining the diffusion coefficients and populations of prevalent diffusive states, the timescales of diffusive state switching can be determined by stepwise increasing the time window of averaging over subsequent single-molecule displacements. Time-averaged diffusion (TAD) analysis of single-molecule tracking data may thus provide quantitative insights into binding and unbinding reactions among rapidly diffusing molecules that are integral for cellular functions.

biophysics↗