Biology subjects

Ye, X.

Publications and source records attributed to Ye, X..

6 recordsLinked to original sources

bioRxiv2018

Targeting RyR2 with a phosphorylation site-specific nanobody Reverses Dysfunction of Failing Cardiomyocytes in Rat

Chronic PKA phosphorylation of RyR2 has been shown to increased diastolic SR Ca2+ leak and lead to cardiac dysfunction. Since the change of phosphorylation level of RyR2 is a biomarker of failing heart, we attempted to verify the hypothesis that intracellular gene delivery of a RyR2 targeting phosphorylation site-specific nanobody could preserve contractility of failing myocardium. In present study, we acquired the RyR2-specific nanobodies from a phage display library which are variable domains of camellidae heavy chain-only antibodies (VHH). One of the monoclonal nanobodies, AR185, inhibiting RyR2 phosphorylation in an in vitro assay was then chosen for further investigation. We investigated the potential of adeno-associated virus (AAV)-9-mediated cardiac expression of AR185 against post-ischemic heart failure. Adeno-associated virus gene delivery elevated the intracellular expression AR185 protein in the ischemic heart failure model of rats, and this treatment normalized the systolic and diastolic dysfunction of the failing myocardium in vivo and in vitro by reversing myocardial Ca2+ handling. Furthermore, AR185 gene transfer to failing cardiomyocytes reduced the frequency of sarcoplasmic reticulum (SR) calcium leak, thereby restoring the attenuated intracellular calcium transients and SR calcium load. Moreover, AR185 gene transfer inhibited PKA phosphorylation of RyR2 in failing cardiomyocytes. Our results provided strong pre-clinical experimental evidence of the cardiac expression of RyR2 nanobody with AAV9 vectors as a promising therapeutic strategy for ischemic heart failure.

pathology↗

bioRxiv2018

Ultrafast clustering of single-cell flow cytometry data using FlowGrid

Flow cytometry is a popular technology for quantitative single-cell profiling of cell surface markers. It enables expression measurement of tens of cell surface protein markers in millions of single cells. It is a powerful tool for discovering cell sub-populations and quantifying cell population heterogeneity. Traditionally, scientists use manual gating to identify cell types, but the process is subjective and is not effective for large multidimensional data. Many clustering algorithms have been developed to analyse these data but most of them are not scalable to very large data sets with more than ten million cells.\n\nHere, we present a new clustering algorithm that combines the advantages of density-based clustering algorithm DBSCAN with the scalability of grid-based clustering. This new clustering algorithm is implemented in python as an open source package, FlowGrid. FlowGrid is memory efficient and scales linearly with respect to the number of cells. We have evaluated the performance of FlowGrid against other state-of-the-art clustering programs and found that FlowGrid produces similar clustering results but with substantially less time. For example, FlowGrid is able to complete a clustering task on a data set of 23.6 million cells in less than 12 seconds, while other algorithms take more than 500 seconds or get into error.\n\nFlowGrid is an ultrafast clustering algorithm for large single-cell flow cy-tometry data. The source code is available at https://github.com/VCCRI/FlowGrid.

bioinformatics↗

bioRxiv2018

RepB C-terminus mutation of an ori pRi vector affects plasmid copy number in Agrobacterium and transgene copy number in plants

A native repABC replication origin, ori pRi, was previously reported as a single copy plasmid in Agrobacterium tumefaciens and can improve the production of transgenic plants with a single copy insertion of transgenes when it is used in binary vectors for Agrobacterium-mediated transformation. A high copy ori pRi variant plasmid, pTF::Ri, which does not improve the frequency of single copy transgenic plants, has been reported in the literature. Sequencing the high copy pTF::Ri repABC operon revealed the presence of two mutations: one silent mutation and one missense mutation that changes a tyrosine to a histidine (Y299H) in a highly conserved area of the C-terminus of the RepB protein (RepBY299H). Reproducing these mutations in the wild-type oriRi binary vector showed that Agrobacterium cells with the RepBY299H mutation grow faster on both solidified and in liquid medium, and have higher plasmid copy number as determined by ddPCR. In order to investigate the impact of the RepBY299H mutation on transformation and quality plant production, the RepBY299H mutated ori pRi binary vector was compared with the original wild-type ori pRi binary vector and a multi-copy oriV binary vector in canola transformation. Molecular analyses of the canola transgenic plants demonstrated that the multi-copy ori pRi with the RepBY299H mutation in Agrobacterium cells lost the advantage of generating high frequency single copy, backbone-free transgenic plants compared to using the single copy wild-type ori pRi binary vector.

molecular biology↗

bioRxiv2017

Embryonic lethality in mice lacking Trim59 due to impaired gastrulation development

TRIM family members have been implicated in a variety of biological processes such as differentiation and development. We here found that Trim59 plays a critical role in early embryo development from blastocyst stage to gastrula. There existed delayed development and empty yolk sacs from embryonic day (E) 8.5 in Trim59 -/- embryos. No viable Trim59 -/- embryos were observed beyond E9.5. Trim59 deficiency affected primary germ layer formation at the beginning of gastrulation. In Trim59 -/- embryos at E6.5 and E7.5, the expression of primary germ layer formation associated genes including Brachyury, lefty2, Cer1, Otx2, Wnt3 and BMP4 was reduced. Homozygous mutant embryonic epiblast was contracted and the mesoderm was absent. Trim59 could interact with actin and myosin associated proteins. Trim59 deficiency disturbed F-actin polymerization during inner cell mass differentiation. Trim59 mediated polymerization of F-actin was via WASH K63-linked ubiquitination. Thus, Trim59 may be a critical regulator for early embryo development from blastocyst stage to gastrula through modulating F-actin assembly.

developmental biology↗

bioRxiv2017

Molecular chaperones maximize the native state yield per unit time by driving substrates out of equilibrium

Molecular chaperones have evolved to facilitate folding of proteins and RNA in vivo where spontaneous self-assembly is sometimes prohibited. Folding of Tetrahymena ribozyme, assisted by the RNA chaperone CYT-19, surprisingly shows that at physiological Mg2+ ion concentrations, increasing the chaperone concentration reduces the yield of native ribozymes. In contrast, the more extensively investigated protein chaperone GroEL works in exactly the opposite manner--the yield of native substrate increases with the increase in chaperone concentration. Thus, the puzzling observation on the assisted-ribozyme folding seems to contradict the expectation that a molecular chaperone acts as an efficient annealing machine. We suggest a resolution to this apparently paradoxical behavior by developing a minimal stochastic model that captures the essence of the Iterative Annealing Mechanism (IAM), providing a unified description of chaperone mediated-folding of proteins and RNA. Our theory provides a general relation involving the kinetic rates of the system, which quantitatively predicts how the yield of native state depends on chaperone concentration. By carefully analyzing a host of experimental data on Tetrahymena (and its mutants) as well as the protein Rubisco and Malate Dehydrogenase, we show that although the absolute yield of native states decreases in the ribozyme, the rate of native state production increases in both the cases. By utilizing energy from ATP hydrolysis, both CYT-19 and GroEL drive their substrate concentrations far out of equilibrium, in an endeavor to maximize the native yield in a short time. Our findings are consistent with the general expectation that proteins or RNA need to be folded by the cellular machinery on biologically relevant timescales, even if the final yield is lower than what equilibrium thermodynamics would dictate. Besides establishing the IAM as the basis for functions of RNA and protein chaperones, our work shows that cellular copy numbers have been adjusted to optimize the rate of native state production of the folded states of RNA and proteins under physiological conditions.\n\nSignificance statementMolecular chaperones have evolved to assist the folding of proteins and RNA, thus avoiding the deleterious consequences of misfolding. Thus, it is expected that increasing chaperone concentration should lead to an enhancement in native yield. While this has been observed in GroEL-mediated protein folding, experiments on Tetrahymena ribozyme folding assisted by CYT-19, surprisingly show the opposite trend. Here, we reconcile these divergent experimental observations by developing a unified stochastic model of chaperone assisted protein and RNA folding. We show that chaperones drive their substrates out of equilibrium, and in the process maximize the rate of native substrate production rather than the absolute yield or the folding rate. In vivo the number of chaperones is regulated to optimize their functions.

biophysics↗

bioRxiv2016

Chimeras Link to Tandem Repeats and Transposable Elements in Tetraploid Hybrid Fish

The formation of the allotetraploid hybrid lineage (4nAT) encompasses both distant hybridization and polyploidization processes. The allotetraploid offspring have two sets of sub-genomes inherited from both parental species and therefore it is important to explore its genetic structure. Herein, we construct a bacterial artificial chromosome library of allotetraploids, and then sequence and analyze the full-length sequences of 19 bacterial artificial chromosomes. Sixty-eight DNA chimeras are identified, which are divided into four models according to the distribution of the genomic DNA derived from the parents. Among the 68 genetic chimeras, 44 (64.71%) are linked to tandem repeats (TRs) and 23 (33.82%) are linked to transposable elements (TEs). The chimeras linked to TRs are related to slipped-strand mispairing and double-strand break repair while the chimeras linked to TEs are benefit from the intervention of recombinases. In addition, TRs and TEs are linked not only with the recombinations, but also with the insertions/deletions of DNA segments. We conclude that DNA chimeras accompanied by TRs and TEs coordinate a balance between the sub-genomes derived from the parents which reduces the genomic shock effects and favors the evolutionary and adaptive capacity of the allotetraploidization. It is the first report on the relationship between formation of the DNA chimeras and TRs and TEs in the polyploid animals.

genetics↗