Biology subjects

Dong, L.

Publications and source records attributed to Dong, L..

119 records · Page 7Linked to original sources

bioRxiv2019

Infection risk and extensive parental care govern the molecular evolution of Toll-like receptors in birds.

The arms race between pathogens and the immune system of their hosts is a critical evolutionary force that affects the ecology and life history of organisms. An increased infection risk selects for adaptations in immune genes that encode receptors involved in pathogen recognition and the initiation of innate immune responses, including Toll-like receptor (TLR) genes. Although recent studies assessed the evolution of major histocompatibility complex (MHC) genes, the ecological and evolutionary processes that drive the evolution of immune genes across major phylogenetic lineages remain unstudied. Moreover, trade-offs between immune responses and other energy-demanding vital functions may limit the resource allocation into costly immune functions, and therefore affect the evolution of immune genes. Here we assess the evolutionary patterns of six TLR genes across 121 bird species, covering 95% of extant orders that represent diverse ecologies and life histories. Selection analyses revealed that all six TLR genes show strong signs of purifying selection, while few sites underwent episodic positive selection. Comparative phylogenetic analyses showed that the intensity of positive selection of TLR genes is associated with long-distance migration, extensive parental care (i.e., altricality and prolonged parent-offspring association), and a large body size (a proxy of increased longevity). Together, these results suggest that the evolution of immune genes is characterized by episodic positive selection, and is shaped by an increased inflection risk and extensive parental care that buffers the costs of immune functions.

evolutionary biology↗

bioRxiv2019

Profiling of chromatin accessibility across Aspergillus species and identification of transcription factor binding sites in the Aspergillus genome using filamentous fungi ATAC-seq

To identify cis-regulatory elements (CREs) and motifs of TF binding is an important step in understanding the regulatory functions of TF binding and gene expression. The lack of experimentally determined and computationally inferred data means that the genome-wide CREs and TF binding sites (TFBs) in filamentous fungi remain unknown. ATAC-seq is a technique that provides a high-resolution measurement of chromatin accessibility to Tn5 transposase integration. In filamentous fungi, the existence of cell walls and the difficulty in purifying nuclei have prevented the routine application of this technique. Herein, we modified the ATAC-seq protocol in filamentous fungi to identify and map open chromatin and TF-binding sites on a genome-scale. We applied the assay for ATAC-seq among different Aspergillus species, during different culture conditions, and among TF-deficient strains to delineate open chromatin regions and TFBs across each genome. The syntenic orthologues regions and differential changes regions of chromatin accessibility were responsible for functional conservative regulatory elements and differential gene expression in the Aspergillus genome respectively. Importantly, 17 and 15 novel transcription factor binding motifs that were enriched in the genomic footprints identified from ATAC-seq data of A. niger, were verified in vivo by our artificial synthetic minimal promoter system, respectively. Furthermore, we first confirmed the strand-specific patterns of Tn5 transposase around the binding sites of known TFs by comparing ATAC-seq data of TF-deficient strains with the data from a wild-type strain.

genomics↗

bioRxiv2019

Specific gyrA gene mutations correlate with high prevalence of discordant levofloxacin resistance in Mycobacterium tuberculosis isolates from Beijing, China

Although molecular diagnostics are highly sensitive in the diagnosis of fluroquinolone (FQ)-resistant tuberculosis (TB), the discordant results with the sequential phenotypic drug susceptibility testing (DST) invariably occur. To investigate the prevalence and the cause of discordant results between molecular and phenotypic DST for levofloxacin (LFX), the cases who were determined to be LFX-susceptible using the phenotypic DST but LFX-resistant using the MeltPro assay were retrospectively reviewed in Beijing, China. We measured LFX minimal inhibitory concentrations (MICs) using Middlebrook 7H9 broth. Sanger sequencing was used to determine genotypic characteristics of discordant isolates. Between January and December 2018, 126 (22.1%) out of 571 smear-positive TB patients were identified as LFX-resistant TB by MeltPro assay. Among the 126 LFX-resistant TB, there were 34 isolates identified as LFX-susceptible TB by phenotypical DST. This result demonstrated a discordance prevalence of 27.0%. LFX MICs were majorly centered around the critical concentration, and 7 (21.2%) and 13 (39.4%) had MICs of 2.0 mg/l and 4.0 mg/l, respectively. The most prevalent mutations conferring discordant LFX resistance were the amino acid substitutions of Ser to Leu in 90 codon (13, 39.4%) and Asp to Ala in 94 codon of gyrA (11, 33.3mg/l belonged to Ala90Val and Asp94Ala group. In conclusion, our data demonstrate that more than one quarter of LFX-resistant isolates by molecular method are susceptible to LFX using the phenotypic DST. The high prevalence of discordant LFX resistance is majorly due to the isolates with specific mutations within gyrA gene conferring proximity of MICs to the critical concentration.

microbiology↗

bioRxiv2019

Approach for Semi-Automated Measurement of Fiber Diameter in Murine and Canine Skeletal Muscle

Currently available software tools for automated segmentation and analysis of muscle cross-section images often perform poorly in cases of weak or non-uniform staining conditions. To address these issues, our group has developed the MyoSAT (Myofiber Segmentation and Analysis Tool) image-processing pipeline.\n\nMyoSAT combines several unconventional approaches including advanced background leveling, Perona-Malik anisotropic diffusion filtering, and Stegers line detection algorithm to aid in pre-processing and enhancement of the muscle image. Final segmentation is based upon marker-based watershed segmentation.\n\nValidation tests using collagen V labeled murine and canine muscle tissue demonstrate that MyoSAT can determine mean muscle fiber diameter with an average accuracy of ~97%. The software has been tested to work on full muscle cross-sections and works well even under non-optimal staining conditions.\n\nThe MyoSAT software tool has been implemented as a macro for the freely available ImageJ software platform. This new segmentation tool allows scientists to efficiently analyze large muscle cross-sections for use in research studies and diagnostics.

neuroscience↗

bioRxiv2018

PARIS, an optogenetic method for functionally mapping gap junctions

Cell-cell communication via gap junctions regulates a wide range of physiological processes by enabling the direct intercellular electrical and chemical coupling. However, the in vivo distribution and function of gap junctions remain poorly understood, partly due to the lack of non-invasive tools with both cell-type specificity and high spatiotemporal resolution. Here we developed PARIS (pairing actuators and receivers to optically isolate gap junctions), a new fully genetically encoded tool for measuring the cell-specific gap junctional coupling (GJC). PARIS successfully enabled monitoring of GJC in several cultured cell lines under physiologically relevant conditions and in distinct genetically defined neurons in Drosophila brain, with ~10-sec temporal resolution and sub-cellular spatial resolution. These results demonstrate that PARIS is a robust, highly sensitive tool for mapping functional gap junctions and study their regulation in both health and disease.

neuroscience↗

bioRxiv2018

Composition and consistence of the bacterial microbiome in upper, middle and lower esophagus before and after Lugol’s iodine staining

Esophageal bacteria, as the integral composition of human ecosystem, have been reported to be associated with esophageal lesions. However, few studies focus on microbial compositions in different esophageal segments, especially after Lugols iodine staining (LIS) in the endoscopic examination for the screening of esophageal cancer. To investigate the composition of the bacterial microbiome in upper, middle and lower esophagus and if LIS would affect the detection of bacteria, 141 fasting samples including the upper, middle and lower esophagus from 27 participants were collected by brushing the mucosal surface of the esophagus before (Eso) and after (Lug) LIS. Bacterial V3-V4 region of 16S rRNA gene was amplified and sequenced by Illuminas sequencing platform and analyzed using LEfSe system to identify specific microbiota. The top six abundant bacterial phyla taxa among three locations from both Eso and Lug groups were Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Fusobacteria and TM7. In terms of genera, the bacterium in three locations from two groups was all characterized by a highest relative abundance of Streptococcus. Bacteria diversity and the relative abundance between Eso and Lug were comparable (P > 0.05). Bacteria diversity was consistent in different esophageal locations for an individual, but it was significantly distinguishing in different subjects (P < 0.05). In Conclusion, the bacterial microbiome in healthy esophagus are highly diverse and consistent even among three physiological stenosis at all clades. Lugols iodine staining would not change local microenvironment in term of microbial composition. These finding provide an essential baseline for future studies investigating local and systemic bacterial microbiome and esophageal diseases.

epidemiology↗

bioRxiv2018

Genome-wide scan and fine-mapping of rare nonsynonymous associations implicates intracellular lipolysis genes in fat distribution and cardio-metabolic risk

Difficulties in identifying causal variants and genes underlying genetic associations have limited the translational potential of genetic studies of body fat distribution, an important, partly-heritable risk factor for cardio-metabolic disease. Rare variant associations facilitate fine-mapping of causal alleles, but their contribution to fat distribution is understudied. We performed a genome-wide scan of rare nonsynonymous variants for body mass index-adjusted waist-to-hip-ratio (BMI-adjusted WHR; a widely-used measure of fat distribution) in 450,562 European ancestry individuals, followed by systematic Bayesian fine-mapping at six genome-wide (p<5x10-08; main-analysis) and two subthreshold signals (significant at a Bonferroni-corrected p<1.3x10-06). We found strong statistical evidence of causal association for nonsynonymous alleles in CALCRL (p.L87P, pconditional=5.9x10-12; posterior-probability of association [PPA]=52%), PLIN1 (p.L90P, pconditional=5.5x10-13; PPA>99%), PDE3B (p.R783X, pconditional=6.2x10-15; PPA>99%), ACVR1C (p.I195T; pconditional=5.4x10-12; PPA>99%), and FGF1 (p.G21E, pconditional=1.6x10-07; PPA=98%). Alleles at the four likely-causal main-analysis genes affected fat distribution primarily via larger hip-rather than smaller waist-circumference and six of nine conditionally-independent WHR-lowering index-variants were associated with protection from cardiovascular or metabolic disease. All four genes are expressed in adipose tissue and have been linked with the regulation of intracellular lipolysis, which controls fat retention in mature cells. Targeted follow-up analyses of key intracellular-lipolysis genes revealed associations for a variant in the initiator of intracellular lipolysis PNPLA2 (p.N252K) with higher BMI-adjusted-WHR and higher cardio-metabolic risk. This study provides human genetic evidence of a link between intracellular lipolysis, fat-distribution and its cardio-metabolic complications in the general population.

genetics↗

bioRxiv2018

The first set of universal nuclear protein-coding loci markers for avian phylogenetic and population genetic studies

Multiple nuclear markers provide genetic polymorphism data for molecular systematics and population genetic studies. They are especially required for the coalescent-based analyses that can be used to accurately estimate species trees and infer population demographic histories. However, in avian evolutionary studies, these powerful coalescent-based methods are hindered by the lack of a sufficient number of markers. In this study, we designed PCR primers to amplify 136 nuclear protein-coding loci (NPCLs) by scanning the published Red Junglefowl (Gallus gallus) and Zebra Finch (Taeniopygia guttata) genomes. To test their utility, we amplified these loci in 41 bird species representing 23 Aves orders. The sixty-three best-performing NPCLs, based on high PCR success rates, were selected which had various mutation rates and were evenly distributed across 17 avian autosomal chromosomes and the Z chromosome. To test phylogenetic resolving power of these markers, we conducted a Neoavian phylogenies analysis using 63 concatenated NPCL markers derived from 48 whole genomes of birds. The resulting phylogenetic topology, to a large extent, is congruence with results resolved by previous whole genome data. To test the level of intraspecific polymorphism in these makers, we examined the genetic diversity in four populations of the Kentish Plover (Charadrius alexandrinus) at 17 of NPCL markers chosen at random. Our results showed that these NPCL markers exhibited a level of polymorphism comparable with mitochondrial loci. Therefore, this set of pan-avian nuclear protein-coding loci has great potential to facilitate studies in avian phylogenetics and population genetics.

evolutionary biology↗

bioRxiv2017

In the absence of apoptosis, myeloid cells arrest when deprived of growth factor, but remain viable without ATG5-dependent autophagy or uptake of glucose or glutamine.

Withdrawal of the growth factor interleukin 3 from IL3-dependent myeloid cells causes them to undergo Bax/Bak1-dependent apoptosis, whereas factor-deprived Bax-/-Bak1-/- cells remain viable, but arrest and shrink. It was reported that withdrawal of IL3 from Bax-/-Bak1-/- cells caused decreased expression of the glucose transporter Glut1, leading to reduced glucose uptake, so that arrested cells required Atg5-dependent autophagy for long-term survival. In other cell types, a decrease in Glut1 is mediated by the thioredoxin-interacting protein Txnip, which is induced in IL3-dependent myeloid cells when growth factor is removed. We mutated Atg5 and Txnip by CRISPR/Cas9 and found that Atg5-dependent autophagy was not necessary for the long-term viability of cycling or arrested Bax-/-Bak1-/- cells, and that Txnip was not required for the decrease in Glut1 expression in response to IL3 withdrawal. Surprisingly, Atg5-deficient Bax/Bak1 double mutant cells survived for several weeks in medium supplemented with 10% fetal bovine serum (FBS), without high concentrations of added glucose or glutamine. When serum was withdrawn, the provision of an equivalent amount of glucose present in 10% FBS (~0.5 mM) was sufficient to support cell survival for more than a week, in the presence or absence of IL3. Thus, Bax-/-Bak1-/- myeloid cells deprived of growth factor consume extracellular glucose to maintain long-term viability, without a requirement for Atg5-dependent autophagy.

cell biology↗

bioRxiv2017

Contextual Tumor Suppressor Function Of T Cell Death-Associated Gene 8 (TDAG8) In Hematological Malignancies

Key points1. TDAG8 (GPR65) gene expression is down-regulated in hematological malignancies.\n\n2. Restoration of TDAG8 gene expression in blood cancer cells suppresses tumor growth and metastasis.\n\nAbstractExtracellular acidosis is a condition found within the tumor microenvironment due to inadequate blood perfusion, hypoxia, and altered tumor cell metabolism. Acidosis has pleiotropic effects on malignant progression; therefore it is essential to understand how acidosis exerts its diverse effects. In this study a bioinformatics analysis revealed the expression of the proton sensing G-protein-coupled receptor TDAG8 is significantly reduced in human blood cancers in comparison to normal blood cells. To understand how TDAG8 functions in hematological malignancies, TDAG8 expression was restored in U937 acute myeloid leukemia cells and other blood cancer cells. It was discovered that severe acidosis, pH 6.4, inhibited U937 cell proliferation while mild acidosis, pH 6.9, stimulated cell proliferation. However, restoring TDAG8 gene expression modulated the U937 cell response to mild extracellular acidosis and physiological pH by reducing cell proliferation. Tumor xenograft experiments further revealed that restoring TDAG8 expression in U937 and Ramos cancer cells reduced tumor growth. It was also shown U937 cells with restored TDAG8 expression attached less to Matrigel, migrated slower toward a chemoattractant, and metastasized less in severe combined immunodeficient mice. These effects correlated with a reduction in c-myc oncogene expression. The mechanistic investigation indicated that G13/RhoA signaling arbitrated the TDAG8-mediated c-myc oncogene repression in response to acidosis. Overall, this study provides compelling data to support the concept that TDAG8 functions as a contextual tumor suppressor in hematological malignancies and sensitizes blood cancer cells to acidotic stress.

cancer biology↗

bioRxiv2017

Inoculation Of Biocontrol Bacteria Alleviated Panax ginseng Replanting Problem

Replanting problem is a common and serious issue hindering the continuous cultivation of Panax plants. Changes in soil microbial community driven by plant species of different ages and developmental stages are speculated to cause this problem. Inoculation of microbial antagonists is proposed to alleviate replanting issues efficiently.\n\nHigh-throughput sequencing revealed that bacterial diversity evidently decreased, and fungal diversity markedly increased in soils of adult ginseng plants in the root growth stage. Relatively few beneficial microbe agents, such as Luteolibacter, Cytophagaceae, Luteibacter, Sphingomonas, Sphingomonadaceae, and Zygomycota, were observed. On the contrary, the relative abundance of harmful microorganism agents, namely, Brevundimonas, Enterobacteriaceae, Pandoraea, Cantharellales, Dendryphion, Fusarium, and Chytridiomycota, increased with pant age. Furthermore, Bacillus subtilis 50-1 was isolated and served as microbial antagonists against pathogenic Fusarium oxysporum of ginseng root-rot, and its biocontrol efficacy was 67.8% using a dual culture assay. The ginseng death rate and relative abundance of Fusarium decreased by 63.3% and 46.1%, respectively, after inoculation with 50-1 in replanting soils. Data revealed that changes in the diversity and composition of rhizospheric microbial communities driven by ginseng of different ages and developmental stages could cause microecological degradation. Biocontrol using microbial antagonists was an effective method for alleviating the replanting problem.\n\nHighlightChanges in rhizospheric microbial communities driven by ginseng plants 13 of different ages and developmental stages could cause microecological degradation. 14 Biocontrol using microbial antagonists effectively alleviated the replanting problem.

microbiology↗