Biology subjects

Mei, H.

Publications and source records attributed to Mei, H..

46 records · Page 3Linked to original sources

bioRxiv2019

Doublecotin-like kinase 1 increases chemoresistance of colorectal cancer cells through the anti-apoptosis pathway

Colorectal cancer (CRC) is the third most common cancer diagnosed and the second leading cause of cancer-related deaths in the United States. About 50% of CRC patients relapsed after surgical resection and ultimately died of metastatic disease. Cancer stem cells (CSCs) are believed to be the primary reason for the recurrence of CRC. Specific stem cell marker, doublecortin-like kinase 1 (DCLK1) plays critical roles in initiating tumorigenesis, facilitating tumor progression, and promoting metastasis of CRC. It is up-regulated in CRC and up-regulation of DCLK1 indicates poor prognosis. Whether DCLK1 is correlated with enhanced chemoresistance of CRC cells is unclear. Our research aims to reveal association of DCLK1 with chemoresistance of CRC cells and the underlying molecular mechanisms. In order to achieve our goal, we established stable DCLK1 over-expression cells (DCLK1+) using the HCT116 cells (WT). DCLK1+ and WT cells were treated with 5-Fluorouracil (5-Fu) at different doses for 24 or 48 hours. MTT assay was used to evaluate cell viability and IC50 of 5-Fu was determined. Quantitative real time PCR was applied to determine gene expression of caspase-3 (casp-3), caspase-4 (casp-4), and caspase-10 (casp-10). Cleaved casp-3 expression was investigated using Western blot and immunofluorescence. Our results demonstrated that IC50 of 5-Fu for the DCLK1+ cells was significantly higher than that of the WT cells for both 24 and 48-hour treatment (P=0.002 and 0.048 respectively), indicating increased chemoresistance of the DCLK1+ cells. Gene expression of casp-3, casp-4, and casp-10 were significantly inhibited in the DCLK1+ cells after 5-Fu treatment compared to the WT cells (P=7.616e-08, 1.575e-05 and 5.307e-08, respectively). Cleaved casp-3 amount and casp-3 positive cells were significantly decreased in the DCLK1+ cells after 5-Fu treatment compared to the WT cells (P=0.015). In conclusion, our results demonstrated that DCLK1 overexpression enhanced the chemoresistance of CRC cells to 5-Fu treatment by suppressing gene expression of key caspases in the apoptosis pathway and activation of apoptosis pathway. DCLK1 can be an intriguing therapeutic target for the effective treatment of CRC patients.

cancer biology↗

bioRxiv2019

Functional dissection of Alzheimer’s disease brain gene expression signatures in humans and mouse models

Human brain transcriptomes can highlight biological pathways associated with Alzheimers disease (AD); however, challenges remain to link expression changes with causal triggers. We have examined 30 AD-associated, gene coexpression modules from human brains for overlap with 251 differentially-expressed gene sets from mouse brain RNA-sequencing experiments, including from models of AD and other neurodegenerative disorders. Human-mouse overlaps highlight responses to amyloid versus neurofibrillary tangle pathology and further reveal age- and sex-dependent expression signatures for AD progression. Human coexpression modules enriched for neuronal and/or microglial genes overlap broadly with signatures from mouse models of AD, Huntingtons disease, Amyotrophic Lateral Sclerosis, and also aging. Several human AD coexpression modules, including those implicated in the unfolded protein response and oxidative phosphorylation, were not activated in AD models, but instead were detected following other, unexpected mouse genetic manipulations. Our results comprise a powerful, cross-species resource and pinpoint experimental models for diverse features of AD pathophysiology from human brain transcriptomes.

systems biology↗

bioRxiv2019

The respiratory virome and exacerbations in patients with chronic obstructive pulmonary disease

IntroductionExacerbations are major contributors to morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD), and respiratory bacterial and viral infections are an important trigger for the occurrence of such exacerbations. However, using conventional diagnostic techniques, a causative agent is not always found. Metagenomic next-generation sequencing (mNGS) allows analysis of the complete virome, but has not yet been applied in COPD exacerbations.\n\nObjectivesTo study the respiratory virome in nasopharyngeal samples during COPD exacerbations using mNGS.\n\nStudy design88 nasopharyngeal swabs from 63 patients from the Bergen COPD Exacerbation Study (2006-2010) were analysed by mNGS and in-house qPCR for respiratory viruses. Both DNA and RNA were sequenced simultaneously using an lllumina library preparation protocol with in-house adaptations.\n\nResultsBy mNGS, 23/88 samples tested positive. Sensitivity and specificity were both 96% for diagnostic targets (23/24 and 1067/1120, respectively). Viral pathogens only detected by mNGS were herpes simplex virus type 1 and coronavirus OC43. A positive correlation was found between Cq value and mNGS viral species reads (p=0.008). Patients with viral pathogens had lower percentages of bacteriophages (p<0.000). No correlation was found between viral reads (species and genus level) and clinical markers.\n\nConclusionsThe mNGS protocol used was highly sensitive and specific for semi-quantitative detection of respiratory viruses. Excellent negative predictive value implicates the power of mNGS to exclude any infectious cause in one test, with consequences for clinical decision making. Reduced abundance of bacteriophages in COPD patients with viral pathogens implicates skewing of the virome, and speculatively the bacterial population, during infection.

microbiology↗

bioRxiv2018

METAGENOMIC SEQUENCING FOR COMBINED DETECTION OF RNA AND DNA VIRUSES IN RESPIRATORY SAMPLES FROM PAEDIATRIC PATIENTS

IntroductionViruses are the main cause of respiratory tract infections. Metagenomic next-generation sequencing (mNGS) enables the unbiased detection of all potential pathogens in a clinical sample, including variants and even unknown pathogens. To apply mNGS in viral diagnostics, there is a need for sensitive and simultaneous detection of RNA and DNA viruses. In this study, the performance of an in-house mNGS protocol for routine diagnostics of viral respiratory infections, with single tube DNA and RNA sample-pre-treatment and potential for automated pan-pathogen detection was studied.\n\nMaterials and MethodsThe sequencing protocol and bioinformatics analysis was designed and optimized including the optimal concentration of the spike-in internal controls equine arteritis virus (EAV) and phocine-herpes virus-1 (PhHV-1).The whole genome of PhHV-1 was sequenced and added to the NCBI database. Subsequently, the protocol was retrospectively validated using a selection of 25 respiratory samples with in total 29 positive and 346 negative PCR results, previously sent to the lab for routine diagnostics.\n\nResultsThe results demonstrated that our protocol using Illumina Nextseq 500 sequencing with 10 million reads showed high repeatability. The NCBI RefSeq database as opposed to the NCBI nucleotide database led to enhanced specificity of virus classification. A correlation was established between read counts and PCR cycle threshold value, demonstrating the semi-quantitative nature of viral detection by mNGS. The results as obtained by mNGS appeared condordant with PCR based diagnostics in 25 out of the 29 (86%) respiratory viruses positive by PCR and in 315 of 346 (91%) PCR-negative results. Viral pathogens only detected by mNGS, not present in the routine diagnostic workflow were influenza C, KI polyomavirus, and cytomegalovirus.\n\nConclusionsSensitivity and analytical specificity of this mNGS protocol was comparable with PCR and higher when considering off-PCR target viral pathogens. All potential viral pathogens were detected in one single test, while it simultaneously obtained detailed information on detected viruses.

microbiology↗

bioRxiv2018

A high resolution view of adaptive events

Coadaptation between bacterial hosts and plasmids often involves a small number of highly reproducible mutations. Yet little is known about the underlying complex dynamics that leads to such a single \"correct\" solution. Observing mutations in fine detail along the adaptation trajectory is necessary for understanding this phenomenon. We studied coadaptation between E. coli and a common artificial plasmid, pBR322, in a continuous turbidostat culture. To obtain a high resolution picture of early adaptive events, we used a highly sensitive duplex sequencing strategy to directly observe and track mutations with frequencies undetectable with conventional methods. The observed highly reproducible trajectories are governed by clonal interference and show rapid increases in the frequencies of beneficial mutations controlling plasmid replication followed by a profound diversity crash corresponding to the emergence of chromosomal variants. To the best of our knowledge our study represents the first comprehensive assessment of adaptive processes at a very fine level of resolution. Our work highlights the hidden complexity of coadaptation, and provides an experimental and theoretical foundation for future studies.

evolutionary biology↗

bioRxiv2018

LRRK2 kinase inhibitors induce a reversible effect in the lungs of non-human primates with no measurable pulmonary deficits

Putative gain-of-function mutations in leucine-rich repeat kinase 2 (LRRK2), resulting in increased kinase activity and cellular toxicity, are a leading genetic cause of Parkinsons disease (PD). Hence, there is strong interest in developing LRRK2 kinase inhibitors as a disease-modifying therapy. Published reports that repeat dosing with two LRRK2 kinase inhibitors (GNE-7915 and GNE-0877) induce histopathological changes in the lung of non-human primates Fuji et al. 2015 (1) raised concerns about potential safety liability of LRRK2 kinase inhibitors. In the present study, we sought to determine whether previously observed effects in the lung: (a) represent on-target pharmacology, but with the potential for margin of safety, (b) are reversible upon drug withdrawal, and (c) are associated with pulmonary function deficits. To this end, we evaluated the histopathological effects, toxicokinetics and target inhibition of three structurally diverse LRRK2 kinase inhibitors, GNE-7915 (30 mg/kg, BID, as a positive control), MLi-2 (15 and 50 mg/kg, QD) and PFE-360 (3 and 6 mg/kg, QD) following 2 weeks of dosing in non-human primates. Subsets of animals dosed with GNE-7915 or MLi-2 were evaluated after 2-week dose-free periods. All three LRRK2 kinase inhibitors induced mild cytoplasmic vacuolation of type II pneumocytes, as reported previously, confirming an on-target effect of these compounds. Interestingly, despite lower doses of both PFE-360 and MLi-2 producing nearly complete inhibition of LRRK2 kinase activity in the brain as assessed by levels of pS935-LRRK2, histopathological changes in lung were absent in animals treated with low-dose PFE-360 and observed only sporadically in the low-dose MLi-2 group. The lung effect was fully reversible at 2 weeks post-dosing of GNE-7915. In a second study of identical dosing with MLi-2 and GNE-7915, no deficits were observed in a battery of translational pulmonary functional tests. In aggregate, these results do not preclude the development of LRRK2 kinase inhibitors for clinical investigation in Parkinsons disease.

pharmacology and toxicology↗

bioRxiv2018

Understanding trivial challenges of microbial genomics: An assembly example

The perceived \"simplicity\" of bacterial genomics (these genomes are small and easy to assemble) feeds the decentralized state of the field where computational analysis standards have been slow to evolve. This situation has a historical explanation. In cases of human, mouse, fly, worm and other model organisms there have been large sustained multinational genome sequencing efforts and analysis consortia such as the 1,000 genomes, ENCODE, modENCODE, GTEx and others. These resulted in development and proliferation of common tools, workflows, and data standards. This is not the case in microbiology. After the development of highly parallel sequencing methodologies in mid-2000s bacterial genomes no longer required initiatives of such scale. The flipside of this is the extreme heterogeneity of approaches to many well established microbial genomic analysis problems such as genome assembly. While competition amongst different methods is good, we argue that the quality of data analyses will improve if cutting edge tools are more accessible and microbiologists become more computationally savvy. Here we use genome assembly as an example to highlight current challenges and to provide a possible solution.

microbiology↗

bioRxiv2018

Identification of rare de novo epigenetic variations in congenital disorders

Certain human traits such as neurodevelopmental disorders (NDs) and congenital anomalies (CAs) are believed to be primarily genetic in origin. With recent dramatic advances in genomic technologies, genome-wide surveys of cohorts of patients with ND/CAs for point mutations and structural variations have greatly advanced our understanding of their genetic etiologies1,2. However, even after whole genome sequencing (WGS), a substantial fraction of such disorders remain unexplained3. In contrast, the possibility that constitutive epigenetic variations (epivariations) might underlie such traits has not been well explored. We hypothesized that some cases of ND/CA are caused by aberrations of DNA methylation that lead to a dysregulation of normal genome function. By comparing DNA methylation profiles from 489 individuals with ND/CAs against 1,534 population controls, we identified epivariations as a frequent occurrence in the human genome. De novo epivariations were significantly enriched in cases when compared to controls. RNAseq data from population studies showed that epivariations often have an impact on gene expression comparable to loss-of-function mutations. Additionally, we detected and replicated an enrichment of rare sequence mutations overlapping CTCF binding sites close to epivariations. Thus, some epivariations occur secondary to cis-linked mutations in regulatory regions, providing a rationale for interpreting non-coding genetic variation. We propose that epivariations likely represent the causative genomic defect in 5-10% of patients with unexplained ND/CAs. This constitutes a yield comparable to CNV microarrays, and as such has significant diagnostic relevance.

genomics↗

bioRxiv2017

Transcriptional dysregulation study reveals a core network involving the genesis for Alzheimer’s disease

BackgroundThe pathogenesis of Alzheimers disease is associated with dysregulation at different levels from transcriptome to cellular functioning. Such complexity necessitates investigations of disease etiology to be carried out considering multiple aspects of the disease and the use of independent strategies. The established works more emphasized on the structural organization of gene regulatory network while neglecting the internal regulation changes.\n\nMethodsApplying a strategy different from popularly used co-expression network analysis, this study investigated the transcriptional dysregulations during the transition from normal to disease states.\n\nResults97 genes were predicted as dysregulated genes, which were also associated with clinical outcomes of Alzheimers disease. Both the co-expression and differential co-expression analysis suggested these genes to be interconnected as a core network and that their regulations were strengthened during the transition to disease states. Functional studies suggested the dysregulated genes to be associated with aging and synaptic function. Further, we checked the evolutionary conservation of the gene co-expression and found that human and mouse brain might have divergent transcriptional co-regulation even when they had conserved gene expression profiles.\n\nConclusionOverall, our study reveals a profile of transcriptional dysregulation in the genesis of Alzheimers disease by forming a core network with altered regulation; the core network is associated with Alzheimers diseases by affecting the aging and synaptic functions related genes; the gene regulation in brain may not be conservative between human and mouse.

systems biology↗

bioRxiv2017

Genome-wide identification of directed gene networks using large-scale population genomics data

Identification of causal drivers behind regulatory gene networks is crucial in understanding gene function. We developed a method for the large-scale inference of gene-gene interactions in observational population genomics data that are both directed (using local genetic instruments as causal anchors, akin to Mendelian Randomization) and specific (by controlling for linkage disequilibrium and pleiotropy). The analysis of genotype and whole-blood RNA-sequencing data from 3,072 individuals identified 49 genes as drivers of downstream transcriptional changes (P < 7 x 10-10), among which transcription factors were overrepresented (P = 3.3 x 10-7). Our analysis suggests new gene functions and targets including for SENP7 (zinc-finger genes involved in retroviral repression) and BCL2A1 (novel target genes possibly involved in auditory dysfunction). Our work highlights the utility of population genomics data in deriving directed gene expression networks. A resource of trans-effects for all 6,600 genes with a genetic instrument can be explored individually using a web-based browser.

genomics↗