Biology subjects

Lee, D.

Publications and source records attributed to Lee, D..

At least 307 records · Page 17Linked to original sources

bioRxiv2018

Disruption of IRE1α through its Kinase Domain Attenuates Multiple Myeloma

Multiple myeloma (MM) arises from malignant immunoglobulin-secreting plasma cells and remains an incurable, often lethal disease despite recent therapeutic advances. The unfolded-protein response sensor IRE1 supports protein secretion by deploying a kinase-endoribonuclease module to activate the transcription factor XBP1s. MM cells may coopt the IRE1-XBP1s pathway; however, the validity of IRE1 as a potential MM therapeutic target is controversial. Here we show that genetic disruption of IRE1 or XBP1s, or pharmacologic IRE1 kinase inhibition, attenuated subcutaneous or orthometastatic growth of MM tumors in mice, and augmented efficacy of two well-established frontline antimyeloma agents, bortezomib or lenalidomide. Mechanistically, IRE1 perturbation inhibited expression of key components of the ER-associated degradation machinery, as well as cytokines and chemokines known to promote MM growth. Selective IRE1 kinase inhibition reduced viability of CD138+ plasma cells while sparing CD138- cells from bone marrow of newly diagnosed MM patients or patients whose disease relapsed after 1 - 4 lines of treatment in both US- and EU-based cohorts. IRE1 inhibition preserved survival and glucose-induced insulin secretion by pancreatic microislets. Together, these results establish a strong therapeutic rationale for targeting IRE1 with kinase-based small-molecule inhibitors in MM.\n\nSignificance statementMultiple myeloma (MM) is a lethal malignancy of plasma cells. MM cells have an expanded endoplasmic reticulum (ER) that is constantly under stress due to immunoglobulin hyperproduction. The ER-resident sensor IRE1 mitigates ER stress by expanding the ERs protein-folding capacity while supporting proteasomal degradation of misfolded ER proteins. IRE1 elaborates these functions by deploying its cytoplasmic kinase-RNase module to activate the transcription factor XBP1s. The validity of IRE1 as a potential therapeutic target in MM has been questioned. Using genetic and pharmacologic disruption in vitro and in vivo, we demonstrate that the IRE1-XBP1s pathway plays a critical role in MM growth. We further show that IRE1s kinase domain is an effective and safe potential small-molecule target for MM therapy.

cancer biology↗

bioRxiv2018

Novel allelic variant of Lpa1 gene associated with a significant reduction in seed phytic acid content in rice (Oryza sativa L.)

In plants, myo-inositol-1,2,3,4,5,6-hexakisphosphate (InsP6), also known as phytic acid (PA), is a major component of organic phosphorus (P), and accounts for up to 85% of the total P in seeds. In rice (Oryza sativa L.), PA mainly accumulates in rice bran, and chelates mineral cations, resulting in mineral deficiencies among brown rice consumers. Therefore, considerable efforts have been focused on the development of low PA (LPA) rice cultivars. In this study, we performed genetic and molecular analyses of OsLpa1, a major PA biosynthesis gene, in Sanggol, a low PA mutant variety developed via chemical mutagenesis of Ilpum rice cultivar. Genetic segregation and sequencing analyses revealed that a recessive allele, lpa1-3, at the OsLpa1 locus (Os02g0819400) was responsible for a significant reduction in seed PA content in Sanggol. The lpa1-3 gene harboured a point mutation (C623T) in the fourth exon of the predicted coding region, resulting in threonine (Thr) to isoleucine (Ile) amino acid substitution at position 208 (Thr208Ile). Three-dimensional analysis of Lpa1 protein structure indicated that myo-inositol 3-monophosphate [Ins(3)P1] kinase binds to the active site of Lpa1, with ATP as a cofactor for catalysis. Furthermore, the presence of Thr208 in the loop adjacent to the entry site of the binding pocket suggests that Thr208Ile substitution is involved in regulating enzyme activity via phosphorylation. Therefore, we propose that Thr208Ile substitution in lpa1-3 reduces Lpa1 enzyme activity in Sanggol, resulting in reduced PA biosynthesis.

plant biology↗

bioRxiv2018

RADAR: annotation and prioritization of variants in the post-transcriptional regulome of RNA-binding proteins

RNA-binding proteins (RBPs) play key roles in post-transcriptional regulation and disease. Their binding sites cover more of the genome than coding exons; nevertheless, most noncoding variant-prioritization methods only focus on transcriptional regulation. Here, we integrate the portfolio of ENCODE-RBP experiments to develop RADAR, a variant-scoring framework. RADAR uses conservation, RNA structure, network centrality, and motifs to provide an overall impact score. Then it further incorporates tissue-specific inputs to highlight disease-specific variants. Our results demonstrate RADAR can successfully pinpoint variants, both somatic and germline, associated with RBP-function dysregulation, that cannot be found by most current prioritization methods, for example variants affecting splicing.

genomics↗

bioRxiv2018

Alteration of Vascular Endothelial Cadherin in Alzheimer’s Disease Patient and Mouse Model

Alzheimers disease (AD) is characterized by amyloid plaques and pathologic cerebrovascular remodeling. Cerebrovascular abnormalities may contribute to the pathology of AD, but the molecular mechanisms are not fully understood. In this study, we evaluated blood-brain barrier (BBB) disruption and the role of VE-cadherin in the progression of amyloid pathology. Here, we determined that levels of VE-cadherin are decreased in brain vessels of AD patients and mouse model of AD. In vitro experiments showed that the disappearance of VE-cadherin by beta-amyloid at the endothelial cell surface was due to cleavage of VE-cadherin. VE-cadherin cleavage was inhibited by a {gamma}-secretase and ADAM10 inhibitor. The disappearance of VE-cadherin in brain vessels was also seen in amyloid precursor protein transgenic mice. In the postmortem brain of individuals with AD, furthermore, levels of VE-cadherin were significantly reduced in vessels. Dementia patients showed a distinct blood biochemical profile characterized by high soluble VE-cadherin (sVEC). There was a strong association between plasma sVEC (adjusted odds ratio = 3.41, P < 0.001) and dementia. These results suggest that measurements of plasma VE-cadherin could have the potential for predicting the risk of progressive AD.

neuroscience↗

bioRxiv2018

A post-transcriptional program of chemoresistance by AU-rich elements/TTP in cancer quiescence

BackgroundQuiescence (G0) is a transient, cell cycle-arrested state. By entering G0, cancer cells survive unfavorable conditions such as chemotherapy and cause relapse. While G0 cells have been studied at the transcriptome level, how post-transcriptional regulation contributes to their chemoresistance remains unknown.\n\nResultsWe induced chemoresistant and quiescent (G0) leukemic cells by serum-starvation or chemotherapy treatment. To study post-transcriptional regulation in G0 leukemic cells, we systematically analyzed their transcriptome, translatome, and proteome. We find that our resistant G0 cells recapitulate gene expression profiles of in vivo chemoresistant leukemic and G0 models. In G0 cells, canonical translation initiation is inhibited; yet we find that inflammatory genes are highly translated, indicating alternative post-transcriptional regulation. Importantly, AU-rich elements (AREs) are significantly enriched in the up-regulated G0 translatome and transcriptome. Mechanistically, we find the stress-responsive p38 MAPK-MK2 signaling pathway stabilizes ARE mRNAs by phosphorylation and inactivation of mRNA decay factor, tristetraprolin (TTP) in G0. This permits expression of ARE-bearing TNF and DUSP1 that promote chemoresistance. Conversely, inhibition of TTP phophorylation by p38 MAPK inhibitors and non-phosphorylatable TTP mutant decreases ARE mRNAs and sensitizes leukemic cells to chemotherapy. Furthermore, co-inhibiting p38 MAPK and TNF--prior to or along with chemotherapy--substantially reduced chemoresistance in primary leukemic cells ex vivo and in vivo.\n\nConclusionsThese studies uncover post-transcriptional regulation underlying chemoresistance in leukemia. Our data reveal the p38 MAPK-MK2-TTP axis as a key regulator of expression of ARE bearing mRNAs that promote chemoresistance. By disrupting this pathway, we developed an effective combination therapy against chemosurvival.

cancer biology↗

bioRxiv2018

JEPEGMIX2-P: Novel pathway transcriptomic method greatly increases detection of molecular pathways in cosmopolitan cohorts

Genetic signal detection in genome-wide association studies (GWAS) is enhanced by pooling small signals from multiple Single Nucleotide Polymorphism (SNP), e.g. across genes and pathways. Because genes are believed to influence traits via gene expression, it is of interest to combine information from expression Quantitative Trait Loci (eQTLs) in a gene or genes in the same pathway. Such methods, widely referred as transcriptomic wide association analysis (TWAS), already exist for gene analysis. Due to the possibility of eliminating most of the confounding effect of linkage disequilibrium (LD) from TWAS gene statistics, pathway TWAS methods would be very useful in uncovering the true molecular bases of psychiatric disorders. However, such methods are not yet available for arbitrarily large pathways/gene sets. This is possibly due to it quadratic (in the number of SNPs) computational burden for computing LD across large regions. To overcome this obstacle, we propose JEPEGMIX2-P, a novel TWAS pathway method that i) has a linear computational burden, ii) uses a large and diverse reference panel (33K subjects), iii) is competitive (adjusts for background enrichment in gene TWAS statistics) and iv) is applicable as-is to ethnically mixed cohorts. To underline its potential for increasing the power to uncover genetic signals over the state-of-the-art and commonly used non-transcriptomics methods, e.g. MAGMA, we applied JEPEGMIX2-P to summary statistics of most large meta-analyses from Psychiatric Genetics Consortium (PGC). While our work is just the very first step toward clinical translation of psychiatric disorders, PGC anorexia results suggest a possible avenue for treatment.

bioinformatics↗

bioRxiv2018

C. elegans Mediator 15 permits low temperature-induced longevity via regulation of lipid and protein homeostasis

Low temperatures slow aging and extend lifespan in many organisms, including Caenorhabditis elegans. However, the metabolic and homeostatic aspects of low temperature-induced longevity remain poorly understood. Here, we show that changes in lipid composition regulated by MDT-15/Mediator 15, transcriptional co-regulator, is essential for low temperature-induced longevity and proteostasis in C. elegans. We find that inhibition of mdt-15 prevents animals from living long at low temperatures. We show that MDT-15 up-regulates fat-7, a fatty acid desaturase, at low temperatures, which increases the ratio of unsaturated to saturated fatty acids. We further demonstrate that maintaining this increased fatty acid ratio is essential for protein homeostasis and longevity at low temperatures. Thus, the homeostasis of lipid composition by MDT-15 appears to be a limiting factor for C. elegans proteostasis and longevity at low temperatures. Our findings highlight the crucial roles of fat regulation in maintaining normal organismal physiology under different environmental conditions.

developmental biology↗

bioRxiv2018

Mitogen-Activated Protein Kinase-Dependent Fiber-Type Regulation in Skeletal Muscle

Mitogen-activated protein kinases (MAPK) are conserved protein kinases that regulate a diverse array of cellular activities. Stress or mitogenic signals activate three primary branches of the greater MAPK cascade, each of which consists of a phosphorylation-dependent array of successively acting kinases. The extracellular signal-regulated kinase 1/2 (ERK1/2) branch is regulated by growth factory signaling at the cell membrane, leading to phosphorylation of the dual-specificity kinase MEK1, which is dedicated to ERK1/2 phosphorylation. Previous studies have established a link between MAPK activation and endurance exercise, but whether a single MAPK is responsible for establishing muscle metabolic fate is unclear. Using mouse genetics we observed that muscle-specific expression of a constitutively active MEK1 promotes greater ERK1/2 signaling that mediates fiber-type switching in mouse skeletal muscle to a slow, oxidative phenotype with type I myosin heavy chain expression. Induced expression of the activated MEK1 mutant using either a MyoD-Cre or myosin light chain-Cre strategy equally increased the number of type I fibers in skeletal muscle with significantly reduced size compared to controls. Moreover, activation of MEK1 in mature myofibers of an adult mouse using a transgene containing a tamoxifen inducible MerCreMer cDNA under the control of a skeletal -actin promoter produced a similar phenotype of switching towards a slow-oxidative program. Physiologic assessment of mice with greater skeletal muscle slow-oxidative fibers showed enhanced metabolic activity and oxygen consumption with greater fatigue resistance of individual muscles. In summary, these results show that sustained MEK1-ERK1/2 activity in skeletal muscle produces a fast-to-slow fiber-type switch, suggesting that modulation of this signaling pathway may represent a therapeutic approach to enhance the long-term metabolic effectiveness of muscle in vivo.

developmental biology↗

bioRxiv2018

microRNA-dependent regulation of biomechanical genes establishes tissue stiffness homeostasis

The mechanical properties of tissues, which are determined primarily by their extracellular matrix (ECM), are largely stable over time despite continual turnover of ECM constituents 1,2. These observations imply active homeostasis, where cells sense and adjust rates of matrix synthesis, assembly and degradation to keep matrix and tissue properties within the optimal range. However, the regulatory pathways that mediate this process are essentially unknown3. Genome-wide analyses of endothelial cells revealed abundant microRNA-mediated regulation of cytoskeletal, adhesive and extracellular matrix (CAM) mRNAs. High-throughput assays showed co-transcriptional regulation of microRNA and CAM genes on stiff substrates, which buffers CAM expression. Disruption of global or individual microRNA-dependent suppression of CAM genes induced hyper-adhesive, hyper-contractile phenotypes in multiple systems in vitro, and increased tissue stiffness in the zebrafish fin-fold during homeostasis and regeneration in vivo. Thus, a network of microRNAs and CAM mRNAs mediate tissue mechanical homeostasis.

cell biology↗

bioRxiv2018

Transient effect of mossy fiber stimulation on spatial firing of CA3 neurons

Strong hippocampal mossy fiber synapses are thought to function as detonators, imposing teaching signals onto CA3 neurons during new memory formation. For an empirical test of this long-standing view, we examined effects of stimulating mossy fibers on spatial firing of CA3 neurons in freely-moving mice. We found that optogenetic stimulation of mossy fibers can alter CA3 spatial firing, but their effects are only transient. Spatially restricted mossy fiber stimulation, either congruent or incongruent with CA3 place fields, was more likely to suppress than enhance CA3 neuronal activity. Also, changes in spatial firing induced by optogenetic stimulation reverted immediately upon stimulation termination, leaving CA3 place fields unaltered. Our results do not support the traditional view that mossy fibers impose teaching signals onto CA3 network, and show robustness of established CA3 spatial representations.

neuroscience↗

bioRxiv2018

Prospective control of movement in the basal ganglia

Neural systems control purposeful movements both within an animals body (e.g., pumping blood) and in the environment (e.g., reaching). This is vital for all animals. The movement control functions of globus pallidus (GP), subthalamic nucleus (STN) and zona incerta (ZI) were analyzed in monkeys reaching for seen targets. Temporal profiles of their hand movements and the synchronized pattern of neuropower (rate of flow of electrochemical energy) through the basal ganglia were analyzed in terms of general tau theory of movement control (Lee et al., 2009), using the variable rho (=1/tau). The results suggest: (i) the neuroinformation for controlling movement is the relative-rate-of-change, rho, of neuropower in the nervous system; (ii) GP is involved in creating prescriptive rhos of neuropower to guide movements; (iii) STN is involved in registering perceptual rhos of neuropower to monitor the movement; (iv) ZI is involved in combining the prescriptive and perceptual rhos of neuropower to generate performatory rhos of neuropower to activate the muscles to produce the movement. Possible implications for Parkinsons disease are discussed.

neuroscience↗

bioRxiv2018

MST1R/RON and EGFR in a complex with syndecans sustain carcinoma S-phase progression by preventing p38MAPK activation

Syndecan-4 (Sdc4) organizes a complex of receptors consisting of its homologue, Sdc2, the receptor tyrosine kinases EGFR and MST1R/RON, and the laminin-binding 3{beta}1 and 6{beta}4 integrins that depends on a docking site within its extracellular domain. A peptide mimetic of the extracellular docking site, synstatin-EGFR (SSTNEGFR), disrupts the receptor complex and prevents the invasion of non-transformed or carcinoma cells that relies on active EGFR. However, the peptide also prevents DNA replication that relies on active MST1R/RON and c-Abl kinase within the complex, resulting in rapid S-phase arrest of head & neck (HN) and breast carcinoma cells. SSTNEGFR does not affect DNA replication in non-transformed oral or breast epithelial cells, but it does block their EGF-dependent invasion. Although EGFR is required as a component of the complex, its kinase activity is not required to sustain S-phase progression in the carcinoma cells, perhaps explaining why many HN and breast carcinomas that overexpress EGFR are nonetheless refractory to EGFR inhibitors. The syndecan-organized receptor complex (Sdc:RTK:ITG complex) appears to suppress stress signals that would otherwise disrupt the replisome engaged in DNA synthesis. SSTNEGFR-treatment of carcinoma cells, or normal oral epithelial cells expressing stress-inducing HPV oncogenes, causes rapid activation of the p38 stress MAPK leading to loss of PCNA from the chromatin and cessation of DNA synthesis. This arrest is independent of the common DNA damage response (DDR) known to activate an S-phase checkpoint, revealing a novel arrest mechanism and a novel receptor complex that is activated on tumor cells to suppress stress-induced proliferation arrest.

cancer biology↗

bioRxiv2018

Aged blood inhibits hippocampal neurogenesis and activates microglia through VCAM1 at the blood-brain barrier

An aged circulatory environment can promote brain dysfunction and we hypothesized that the blood-brain barrier (BBB) mediates at least some of these effects. We observe brain endothelial cells (BECs) in the aged mouse hippocampus express an inflammatory transcriptional profile with focal upregulation of Vascular Cell Adhesion Molecule 1 (VCAM1), a protein that facilitates vascular-immune cell interactions. Concomitantly, the shed, soluble form of VCAM1 is prominently increased in the aged circulation of humans and mice, and aged plasma is sufficient to increase VCAM1 expression in cultured BECs and young mouse hippocampi. Systemic anti-VCAM1 antibody or genetic ablation of VCAM1 in BECs counteracts the detrimental effects of aged plasma on young brains and reverses aging aspects in old mouse brains. Thus, VCAM1 is a negative regulator of adult neurogenesis and inducer of microglial reactivity, establishing VCAM1 and the luminal side of the BBB as possible targets to treat age-related neurodegeneration.

neuroscience↗

bioRxiv2017

Discovery and characterization of coding and non-coding driver mutations in more than 2,500 whole cancer genomes

Discovery of cancer drivers has traditionally focused on the identification of protein-coding genes. Here we present a comprehensive analysis of putative cancer driver mutations in both protein-coding and non-coding genomic regions across >2,500 whole cancer genomes from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium. We developed a statistically rigorous strategy for combining significance levels from multiple driver discovery methods and demonstrate that the integrated results overcome limitations of individual methods. We combined this strategy with careful filtering and applied it to protein-coding genes, promoters, untranslated regions (UTRs), distal enhancers and non-coding RNAs. These analyses redefine the landscape of non-coding driver mutations in cancer genomes, confirming a few previously reported elements and raising doubts about others, while identifying novel candidate elements across 27 cancer types. Novel recurrent events were found in the promoters or 5UTRs of TP53, RFTN1, RNF34, and MTG2, in the 3UTRs of NFKBIZ and TOB1, and in the non-coding RNA RMRP. We provide evidence that the previously reported non-coding RNAs NEAT1 and MALAT1 may be subject to a localized mutational process. Perhaps the most striking finding is the relative paucity of point mutations driving cancer in non-coding genes and regulatory elements. Though we have limited power to discover infrequent non-coding drivers in individual cohorts, combined analysis of promoters of known cancer genes show little excess of mutations beyond TERT.

genomics↗

bioRxiv2017

Zika virus infection preferentially counterbalances human peripheral monocyte and/or NK-cell activity

Zika virus (ZIKV) has re-emerged in the population and caused unprecedented global outbreaks. Here, the transcriptomic consequences of ZIKV infection were studied systematically firstly in human peripheral blood CD14+ monocytes and monocyte-derived macrophages with high density RNA-sequencing. Analyses of the ZIKV genome revealed that the virus underwent genetic diversification and differential mRNA abundance was found in host cells during infection. Notably, there was a significant change in the cellular response with crosstalk between monocytes and natural killer (NK) cells as one of the highly identified pathway. Immune-phenotyping of peripheral blood from ZIKV-infected patients further confirmed the activation of NK cells during acute infection. ZIKV infection in peripheral blood cells isolated from healthy donors led to the induction of IFN{gamma} and CD107a -- two key markers of NK-cell function. Depletion of CD14+ monocytes from peripheral blood resulted in a reduction of these markers and reduced priming of NK cells during infection. This was complemented by the immunoproteomic changes observed. Mechanistically, ZIKV infection preferentially counterbalances monocyte and/or NK-cell activity, with implications for targeted cytokine immunotherapies.

immunology↗

bioRxiv2017

Multi-platform discovery of haplotype-resolved structural variation in human genomes

The incomplete identification of structural variants (SVs) from whole-genome sequencing data limits studies of human genetic diversity and disease association. Here, we apply a suite of long-read, short-read, and strand-specific sequencing technologies, optical mapping, and variant discovery algorithms to comprehensively analyze three human parent-child trios to define the full spectrum of human genetic variation in a haplotype-resolved manner. We identify 818,054 indel variants (<50 bp) and 27,622 SVs ([≥]50 bp) per human genome. We also discover 156 inversions per genome--most of which previously escaped detection. Fifty-eight of the inversions we discovered intersect with the critical regions of recurrent microdeletion and microduplication syndromes. Taken together, our SV callsets represent a sevenfold increase in SV detection compared to most standard high-throughput sequencing studies, including those from the 1000 Genomes Project. The method and the dataset serve as a gold standard for the scientific community and we make specific recommendations for maximizing structural variation sensitivity for future large-scale genome sequencing studies.

genomics↗

bioRxiv2017

Gene neighbourhood integrity disrupted by CTCF loss in vivo

The mammalian genome is coiled, compacted and compartmentalized into complex non-random three-dimensional chromatin loops in the nucleus1-3. At the core of chromatin loop formation is CCCTC-binding factor (CTCF), also described as a \"weaver of the genome\"45. Anchored by CTCF, chromatin loops are proposed to form through a loop extrusion process6, organising themselves into gene neighbourhoods2 that harbour insulated enhancer-promoter domains, restricting enhancer activities to genes within loops, and insulating genes from promiscuous interactions outside of loops2,7-9. Studies targeting CTCF binding site deletions at gene neighbourhood boundaries result in localised gene expression dysregulation8,10-12, and global CTCF depletion recently showed CTCF to be crucial for higher hierarchical chromatin organisation of topologically associating domains (TADs)13. However, the role for CTCF in maintaining sub-TAD CTCF gene neighbourhoods and how gene transcription is affected by CTCF loss remains unclear. In particular, how CTCF gene neighbourhoods govern genome-wide enhancer-promoter interactions require clarification. Here, we took an in vivo approach to assess the global dissolution of CTCF anchored structures in mouse cardiomyocyte-specific Ctcf-knockout (Ctcf-KO), and uncovered large-scale ectopic de novo Enhancer-Promoter (E-P) interactions. In vivo cardiomyocyte-specific Ctcf-KO leads to a heart failure phenotype14, but our analysis integrates genome-wide transcription dysregulation with aberrant E-P interactions in context of CTCF-loop structures, identifying how genes engage their E-P interactions, requiring CTCF looping for their maintenance. Our study points to a mammalian genome that possesses a strong propensity towards spontaneous E-P interactions in vivo, resulting in a diseased transcriptional state, manifest as organ failure. This work solidifies the role of CTCF as the central player for specifying global E-P connections.

genomics↗

bioRxiv2017

Spectrin is a mechanoresponsive protein shaping the architecture of intercellular invasion

Spectrin is a membrane skeletal protein best known for its structural role in maintaining cell shape and protecting cells from mechanical damage1-3. Here, we report that spectrin dynamically accumulates and dissolves at the fusogenic synapse, where an attacking fusion partner mechanically invades its receiving partner with actin-propelled protrusions to promote cell-cell fusion4-7. Using genetics, cell biology, biophysics and mathematical modeling, we demonstrate that unlike myosin II that responds to dilation deformation, spectrin exhibits a mechanosensitive accumulation in response to shear deformation, which is highly elevated at the fusogenic synapse. The accumulated spectrin forms an uneven network, which functions as a \"sieve\" to constrict the invasive fingerlike protrusions, thus putting the fusogenic synapse under high mechanical tension to promote cell membrane fusion. Taken together, our study has revealed a previously unrecognized function of spectrin as a dynamic mechanoresponsive protein that shapes the architecture of intercellular invasion. These findings have general implications for understanding spectrin function in other dynamic cellular processes beyond cell-cell fusion.

cell biology↗