Biology subjects

Thompson, M.

Publications and source records attributed to Thompson, M..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

Deep indel mutagenesis reveals the regulatory and modulatory architecture of alternative exon splicing

Altered splicing is a frequent mechanism by which genetic variants cause disease and antisense oligonucleotides (AONs) that target pre-mRNA splicing have been approved as therapeutics for multiple pathologies including patient-customized treatments for rare diseases. However, the regulatory architecture of human exons remains poorly understood and AON discovery is currently slow and expensive, limiting the wider adoption of the approach. Here we show that that systematic deletion scans -which can be made experimentally at very low cost - provide an efficient strategy to chart the regulatory landscape of human exons and to rapidly identify effective splicing-modulating oligonucleotides in a fully quantitative manner. Our results suggest a mechanism for the evolutionary origins of unusually short microexons and the repression of transmembrane domain-encoding exons, and reveal a checkerboard architecture of sequential enhancers and silencers in a model alternative exon. Accurate prediction of the effects of deletions using deep learning provides a resource, DANGO, that maps the splicing regulatory landscape of all human exons and predicts effective splicing-altering antisense oligonucleotides genome-wide.

genetics↗

bioRxiv2023

BayesAge: A Maximum Likelihood Algorithm To Predict Epigenetic Age

DNA methylation is a reaction that results in the formation of 5-methylcytosine when a methyl group is added to the cytosines C5 position. As organisms age, DNA methylation patterns change in a reproducible fashion. This phenomenon has established DNA methylation as a valuable biomarker in aging studies. Epigenetic clocks based on weighted combinations of methylation sites have been developed to accurately predict the age of an individual from their methylome. However, many epigenetic clocks, particularly those that utilize penalized regression, model the changes in methylation linearly with age. Moreover, these models, which use methylation levels as features, are not robust to missing data and do not account the count-based nature of bisulfite sequence data. Additionally, the models are generally not interpretable. To overcome these challenges, we present BayesAge, an extension of the previously developed scAge approach that was developed for the analysis of single cell DNA methylation datasets. BayesAge utilizes maximum likelihood estimation (MLE) to infer ages, models count data using binomial distributions, and uses LOWESS smoothing to capture the non-linear dynamics between methylation and age. Our approach is designed for use with bulk bisulfite sequencing datasets. BayesAge outperforms scAge in several respects. Specifically, BayesAges age residuals are not age associated, thus providing a less biased representation of epigenetic age variation across populations. Moreover, BayesAge enables the estimation of error bounds on age inference and, when run on down-sampled data, its coefficient of determination between predicted and actual ages surpasses both scAge and penalized regression.

bioinformatics↗

bioRxiv2023

Genetically refactored Agrobacterium-mediated transformation

Members of Agrobacterium are costly plant pathogens while also essential tools for plant transformation. Though Agrobacterium-mediated transformation (AMT) has been heavily studied, its polygenic nature and its complex transcriptional regulation make identifying the genetic basis of transformational efficiency difficult through traditional genetic and bioinformatic approaches. Here we use a bottom-up synthetic approach to systematically refactor the tumor-inducing plasmid, wherein the majority of AMT machine components are encoded, into a minimal set of genes capable of plant and fungal transformation that is both controllable and orthogonal to its environment. We demonstrate that engineered vectors can be transferred to new heterologous bacteria, enabling them to transform plants. Our reductionist approach demonstrates how bottom-up engineering can be used to dissect and elucidate the genetic underpinnings of complex biological traits, and may lead to the development of strains of bacteria more capable of transforming recalcitrant plant species of societal importance.

microbiology↗

bioRxiv2023

The pGinger family of expression plasmids

The pGinger suite of expression plasmids comprises 43 plasmids that will enable precise constitutive and inducible gene expression in a wide range of gram-negative bacterial species. Constitutive vectors are composed of 16 synthetic constitutive promoters upstream of RFP, with a broad host range BBR1 origin and a kanamycin resistance marker. The family also has seven inducible systems (Jungle Express, Psal/NahR, Pm/XylS, Prha/RhaS, LacO1/LacI, LacUV5/LacI, and Ptet/TetR) controlling RFP expression on BBR1/kanamycin plasmid backbones. For four of these inducible systems (Jungle Express, Psal/NahR, LacO1/LacI, and Ptet/TetR), we created variants that utilize the RK2 origin and spectinomycin or gentamicin selection. Relevant RFP expression and growth data have been collected in the model bacterium Escherichia coli as well as Pseudomonas putida. All pGinger vectors are available via the Joint BioEnergy Institute (JBEI) Public Registry.

synthetic biology↗

bioRxiv2022

Induction of Autophagy Prevents Mutant SOD1G93A Related Neurotoxicity in Experimental Models of Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder resulting from the progressive loss of both upper and lower motor neurons in the cerebral cortex, brainstem, and spinal cord. Currently, there are only two drugs, Riluzole (Rilutek) and Edaravone (Radicava), approved by FDA for ALS treatment. These two drugs are very expensive with only a few months of life extension. So far, there is no cure for ALS. Aberrant protein aggregation in motor neurons is an intracellular hallmark of ALS. The disturbance in protein homeostasis may contribute to the onset and progression of ALS. Autophagy plays an important role in degrading misfolded proteins, thereby preventing their aggregation. Pharmacological manipulation of autophagy has been proposed as a new therapeutic approach for treating ALS. IADB, a novel indole alkaloid derivative, has been reported to exert mitochondrial protection and cardioprotection through its autophagy-modulating potential. Our present study attempted to examine whether IADB has therapeutic potential in SOD1G93A-associated experimental models of ALS. We found that IADB could promote the clearance of SOD1G93A aggregates and reduce the overproduction of mitochondrial reactive oxygen species (mtROS) in motor neuron-like NSC-34 cells transfected with SOD1G93A. We further examined the IADB in a SOD1-G93A mouse model of ALS. Administration of IADB started at the age of 55 days until the end stage of the disease. IADB treatment significantly increased LC3-II levels and decreased human SOD1 levels and p62 expression in the spinal cords of SOD1G93A mice, suggesting that IADB treatment could induce autophagy activation and promote clearance of mutant SOD1 aggregates in this mouse model of ALS. Moreover, IADB treatment could alleviate the activation of microglia and astrocytes and reduce mitochondrial oxidative damage in the spinal cord of SOD1G93A mice. Finally, we demonstrated that IADB treatment could improve motor performance and delay the onset and progression of the disease in a mouse model of ALS. The neuroprotective effects of IADB may mainly originate from its autophagy-promoting property.

neuroscience↗

bioRxiv2022

Early precision of radial patterning of the mouse cochlea is achieved by a linear BMP signaling gradient and is further refined by SOX2

Positional information encoded in signaling molecules is essential for early patterning in the prosensory domain of the developing cochlea. The cochlea contains an exquisite repeating pattern of sensory hair cells and supporting cells. This requires precision in the morphogen signals that set the initial radial compartment boundaries, but this has not been investigated. To measure gradient formation and morphogenetic precision in developing cochlea, we developed a quantitative image analysis procedure measuring SOX2 and pSMAD1/5/9 profiles in mouse embryos at embryonic day (E)12.5, E13.5, and E14.5. Intriguingly, we found that the pSMAD1/5/9 profile forms a linear gradient in the medial [~]75% of the PSD during E12.5 and E13.5. This is a surprising activity readout for a diffusive BMP4 ligand secreted from a tightly constrained lateral region1,2 since morphogens typically form exponential or power-law gradient shapes. This is meaningful for gradient interpretation because while linear profiles offer the theoretically highest information content and distributed precision for patterning, a linear morphogen gradient has not yet been observed. In addition to the information-optimized linear profile, we found that while pSMAD1/5/9 is stable during this timeframe, an accompanying gradient of SOX2 shifts dynamically. Third, we see through joint decoding maps of pSMAD1/5/9 and SOX2 that there is a high-fidelity mapping between signaling activity and position in the regions soon to become Kollikers organ and the organ of Corti, where radial patterns are more intricate than lateral regions. Mapping is ambiguous in the prosensory domain precursory to the outer sulcus, where cell fates are uniform. Altogether, this research provides new insights into the precision of early morphogenetic patterning cues in the radial cochlea prosensory domain. Summary ParagraphThe organ of Corti is the precisely patterned group of cells in the cochlea responsible for transforming sound energy into our perception of hearing. Morphogenetic signals encoding positional information are crucial for the early stages of patterning along the developing cochleas radial axis. SOX2 and pSMAD1/5/9 are transcription factors that together serve as an integrative readout of morphogen activity during E12.5 to E14.5 in the developing mouse cochlea. However, the role of spatiotemporal precision in these signals is unknown. Here we show that pSMAD1/5/9 forms a linear profile to establish a domain spanning reference frame of positional information and that SOX2 further refines precision. We found that the pSMAD1/5/9 signal retains its linear shape across at least 24 h of development while SOX2 dynamically shifts. The stable linear pSMAD1/5/9 profile provides a global reference point of radial positional information, while the SOX2 profile improves local precision with steep slopes. Furthermore, a linear profile from a diffusive ligand is unexpected, suggesting unidentified mechanisms of BMP regulation unique to this system. A version of the source-sink model for creating a linear morphogen profile modified from its original formulation3 is explored in this system, enabling a tight fit between the BMP model and pSMAD1/5/9 data. We expect the methods and results shown here to be a starting point for increased precision in cochlear morphogen activity measurements to enable further modeling and experimental inquiry. This combination of quantitative mechanistic explanation for how signals form, along with quantitative interpretations of their decoding properties, revealing why they form a certain way, together form a potent basis for biological discovery and may even be applied to the design of synthetic systems.

developmental biology↗

bioRxiv2022

Phenotype integration improves power and preserves specificity in biobank-based genetic studies of MDD

Biobanks often contain several phenotypes relevant to a given disorder, and researchers face complex tradeoffs between shallow phenotypes (high sample size, low specificity and sensitivity) and deep phenotypes (low sample size, high specificity and sensitivity). Here, we study an extreme case: Major Depressive Disorder (MDD) in UK Biobank. Previous studies found that shallow and deep MDD phenotypes have qualitatively distinct genetic architectures, but it remains unclear which are optimal for scientific study or clinical prediction. We propose a new framework to get the best of both worlds by integrating together information across hundreds of MDD-relevant phenotypes. First, we use phenotype imputation to increase sample size for the deepest available MDD phenotype, which dramatically improves GWAS power (increases #loci ~10 fold) and PRS accuracy (increases R2 ~2 fold). Further, we show the genetic architecture of the imputed phenotype remains specific to MDD using genetic correlation, PRS prediction in external clinical cohorts, and a novel PRS-based pleiotropy metric. We also develop a complementary approach to improve specificity of GWAS on shallow MDD phenotypes by adjusting for phenome-wide PCs. Finally, we study phenotype integration at the level of GWAS summary statistics, which can increase GWAS and PRS power but introduces non-MDD-specific signals. Our work provides a simple and scalable recipe to improve genetic studies in large biobanks by combining the sample size of shallow phenotypes with the sensitivity and specificity of deep phenotypes.

genetics↗

bioRxiv2022

Mice regulate their attentional intensity and arousal to exploit increases in task utility

Changes in autonomic arousal, such as mounting sleep pressure, and changes in motivation, such as fluctuating environmental reward statistics, both profoundly influence behavior. Our experience tells us that we have some capacity to control our arousal when doing so is important, such as staying awake while driving a motor vehicle. However, little is known about how decision computations are jointly influenced by arousal and motivation, including whether animals, such as rodents, can adapt their arousal state to their needs. Here, we developed and show results from an auditory feature-based sustained-attention task with intermittently shifting task utility. We use pupil size to estimate arousal across a wide range of states and apply novel signal detection theoretic and accumulation-to-bound modeling approaches in a large behavioral cohort. We find that both pupil-linked arousal and task utility have major impacts on multiple aspects of performance. Although substantial arousal fluctuations persist across utility conditions, mice partially stabilize their arousal near an intermediate, and optimal, level when task utility is high. Behavioral analyses show that multiple elements of behavior improve during high task utility and that arousal influences some, but not all, of them. Specifically, arousal influences the likelihood and timescale of sensory evidence accumulation, but not the quantity of evidence accumulated per time step while attending. In sum, the results establish specific decision-computational signatures of arousal, motivation, and their interaction, in attention. So doing, we provide an experimental and analysis framework for studying arousal self-regulation in neurotypical brains and diseases such as attention-deficit/hyperactivity disorder.

neuroscience↗

bioRxiv2021

Inhibition of adrenergic b1-AR/Gas signaling promotes cardiomyocyte proliferation through activation of RhoA-YAP axis

The regeneration potential of the mammalian heart is incredibly limited, as cardiomyocyte proliferation ceases shortly after birth. {beta}-adrenergic receptor ({beta}-AR) blockade has been shown to improve heart functions in response to injury; however, the underlying mechanisms remain poorly understood. Here we inhibited {beta}-AR signaling in the heart using a cardiomyocyte specific {beta}1-adrenergic receptor ({beta}1-AR) blocker (metoprolol) to examine its role in heart maturation and regeneration at the neonatal stage. We found that metoprolol robustly enhanced cardiomyocyte proliferation and promoted cardiac regeneration post myocardial infarction, resulting in reduced scar formation and improved cardiac function. Moreover, the increased cardiomyocyte proliferation was also induced by the genetic deletion of Gnas, the gene encoding G protein alpha subunit (Gs), a downstream effector of {beta}-AR. Genome wide transcriptome analysis revealed that the cardiomyocytes of {beta}-blocker treated and Gnas cKO hearts maintained an immature proliferating status even at the young-adult age, and that the loss of Gs function enhanced the activity of the Hippo-effector YAP, which is associated with immature cardiomyocyte proliferation. Moreover, the increased YAP activity is modulated by RhoA signaling. Our pharmacological and genetic studies reveal a previously unrecognized {beta}1-AR-Gs-YAP signaling axis for regulating cardiac regeneration. These results suggest that inhibiting {beta}-AR-Gs signaling promotes the regenerative capacity and extends the cardiac regenerative window in mice by activating YAP-mediated transcriptional programs. Thus, targeting {beta}-AR-Gs signaling may serve as a novel therapeutic target for the treatment of ischemic heart.

developmental biology↗

bioRxiv2021

The effects of age, sex, weight and breed on canid methylomes

Unlike genomes, which are static throughout the lifespan of an organism, DNA methylomes are dynamic. To study these dynamics we developed quantitative models that measure the effect of multiple factors on DNA methylomes including, age, sex, weight and genetics. We conducted our study in canids, which prove to be an ideal species to assess epigenetic moderators due to their extreme variability in size and well-characterized genetic structure. We collected buccal swabs from 217 canids (207 domestic dogs and 10 gray wolves) and used targeted bisulfite sequencing to measure methylomes. We also measured genotypes at over one thousand single nucleotide polymorphisms (SNPs). We found that DNA methylomes are strongly associated with age, enabling the construction of epigenetic clocks. We also show that methylomes are strongly impacted by sex, weight and sterilization status, leading to accurate predators of these factors. Methylomes are also affected by genetics and we observe multiple associations between SNP loci and methylated CpGs. Finally, we show that several factors moderate the relationship between epigenetic ages and real ages, such as body weight, which increases epigenetic aging. In conclusion, we demonstrate that the plasticity of DNA methylomes is impacted by myriad genetic and physiological factors, and that DNA methylation biomarkers are accurate predictors of age, sex and sterilization status.

bioinformatics↗

bioRxiv2021

Multi-context genetic modeling of transcriptional regulation resolves novel disease loci

A majority of the variants identified in genome-wide association studies fall in non-coding regions of the genome, indicating their mechanism of impact is mediated via gene expression. Leveraging this hypothesis, transcriptome-wide association studies (TWAS) have assisted in both the interpretation and discovery of additional genes associated with complex traits. However, existing methods for conducting TWAS do not take full advantage of the intra-individual correlation inherently present in multi-context expression studies and do not properly adjust for multiple testing across contexts. We developed CONTENT-- a computationally efficient method with proper cross-context false discovery correction that leverages correlation structure across contexts to improve power and generate context-specific and context-shared components of expression. We applied CONTENT to bulk multi-tissue and single-cell RNA-seq data sets and show that CONTENT leads to a 42% (bulk) and 110% (single cell) increase in the number of genetically predicted genes relative to previous approaches. Interestingly, we find the context-specific component of expression comprises 30% of heritability in tissue-level bulk data and 75% in single-cell data, consistent with cell type heterogeneity in bulk tissue. In the context of TWAS, CONTENT increased the number of gene-phenotype associations discovered by over 47% relative to previous methods across 22 complex traits.

genomics↗

bioRxiv2021

Fast and powerful statistical method for context-specific QTL mapping in multi-context genomic studies

Context-specific eQTLs mediate genetic risk for complex diseases. However, limitations in current methods for identifying these eQTLs have hindered their comprehensive characterization and downstream interpretation of disease-associated variants. Here, we introduce FastGxC, a method to efficiently and powerfully map context-specific eQTLs by leveraging the correlation structure in genomic studies with repeated sampling, e.g., single-cell RNA-seq studies. Using simulations, we demonstrate that FastGxC is up to nine times more powerful and 106 times faster than existing approaches, reducing computation time from years to minutes. We applied FastGxC to bulk multi-tissue (N=698) and single-cell PBMC (N=1,218) RNA-seq datasets, generating comprehensive tissue- and cell-type-specific eQTL maps. These eQTLs exhibited up to four-fold enrichment in open chromatin regions from matched contexts and were twice as enriched as standard context-specific eQTLs, highlighting their biological relevance. Furthermore, we examined the relationship between context-specific eQTLs and complex human traits and diseases. FastGxC improved precision in identifying relevant contexts for each trait by three-fold and expanded candidate causal genes by 25% in cell types and 6% in tissues compared to standard eQTLs. In summary, FastGxC provides a powerful framework for mapping context-specific eQTLs, advancing our understanding of gene regulatory mechanisms underlying complex human traits and diseases.

genomics↗

bioRxiv2021

Apis mellifera cognition as a tool for scientific engagement

In addition to the crowdsourcing of experimental data, citizen science, and scientific engagement more broadly, serve as a bridge between researchers and the wider community. This serves to foster a greater understanding of the scientific method and science-based solutions generally. Apis mellifera (honeybees) are a well-established model for the study of learning and cognition and can serve as an engaging outreach system for this wider community. Here, we developed and implemented a protocol using well established honeybee conditioning protocols to safely study the effects of caffeine and dopamine on learning performance. Using this protocol, a group of high-school aged students as part of the Ryukyu Girls program demonstrated that caffeine, but not dopamine, significantly reduced the number of trials required for a successful conditioning response. This allowed these students to explore the scientific method in a relatable and engaging way. Simple SummaryGlobal scientific literacy can be improved through widespread and effective community engagement by researchers. We propose Apis mellifera (honeybee) as an public engagement tool due to widespread awareness of colony collapse and the bees importance in food production. Moreover, their cognitive abilities make for engaging experiments. Their relative ease of cultivation means that studies can be performed cost-effectively, especially when partnering with local aperists. Using a proxy for honeybee learning, a group of non-specialist high-school-aged participants obtained data suggesting that caffeine, but not dopamine, improved learning. This hands-on experience facilitated student understanding of the scientific method, factors that shape learning and the importance of learning for hive health.

animal behavior and cognition↗

bioRxiv2020

Evaluating Specimen Quality and Results from a Community-Wide, Home-Based Respiratory Surveillance Study

IntroductionWhile influenza and other respiratory pathogens cause significant morbidity and mortality, the community-based burden of these infections remains incompletely understood. The development of novel methods to detect respiratory infections is essential for mitigating epidemics and developing pandemic-preparedness infrastructure. MethodsFrom October 2019 to March 2020, we conducted a home-based cross-sectional study in the greater Seattle area, utilizing electronic consent and data collection instruments. Participants received nasal swab collection kits via rapid delivery within 24 hours of self-reporting respiratory symptoms. Samples were returned to the laboratory and were screened for 26 respiratory pathogens and a human marker. Participant data were recorded via online survey at the time of sample collection and one week later. ResultsOf the 4,572 consented participants, 4,359 (95.3%) received a home swab kit, and 3,648 (83.7%) returned a nasal specimen for respiratory pathogen screening. The 3,638 testable samples had a mean RNase P CRT value of 19.0 (SD: 3.4) and 1,232 (33.9%) samples had positive results for one or more pathogens, including 645 (17.7%) influenza-positive specimens. Among the testable samples, the median time between shipment of the home swab kit and completion of laboratory testing was 8 days [IQR: 7.0-14.0]. DiscussionHome-based surveillance using online participant enrollment and specimen self-collection is a feasible method for community-level monitoring of influenza and other respiratory pathogens, which can readily be adapted for use during pandemics.

microbiology↗

bioRxiv2020

BiSulfite Bolt: A BiSulfite Sequencing Analysis Platform

BackgroundBisulfite sequencing is commonly employed to measure DNA methylation. Processing bisulfite sequencing data is often challenging due to the computational demands of mapping a low complexity, asymmetrical library and the lack of a unified processing toolset to produce an analysis ready methylation matrix from read alignments. To address these shortcomings, we have developed BiSulfite Bolt (BSBolt); a fast and scalable bisulfite sequencing analysis platform. BSBolt performs a pre-alignment sequencing read assessment step to improve efficiency when handling asymmetrical bisulfite sequencing libraries. FindingsWe evaluated BSBolt against simulated and real bisulfite sequencing libraries. We found that BSBolt provides accurate and fast bisulfite sequencing alignments and methylation calls. We also compared BSBolt to several existing bisulfite alignment tools and found BSBolt outperforms Bismark, BSSeeker2, BISCUIT, and BWA-Meth based on alignment accuracy and methylation calling accuracy. ConclusionBSBolt offers streamlined processing of bisulfite sequencing data through an integrated toolset that offers support for simulation, alignment, methylation calling, and data aggregation. BSBolt is implemented as a python package and command line utility for flexibility when building informatics pipelines. BSBolt is available at https://github.com/NuttyLogic/BSBolt under an MIT license.

bioinformatics↗

bioRxiv2020

Functional analysis of the fatty acid and alcohol metabolism of Pseudomonas putida using RB-TnSeq

ABSTRACTWith its ability to catabolize a wide variety of carbon sources and a growing engineering toolkit, Pseudomonas putida KT2440 is emerging as an important chassis organism for metabolic engineering. Despite advances in our understanding of this organism, many gaps remain in our knowledge of the genetic basis of its metabolic capabilities. These gaps are particularly noticeable in our understanding of both fatty acid and alcohol catabolism, where many paralogs putatively coding for similar enzymes co-exist making biochemical assignment via sequence homology difficult. To rapidly assign function to the enzymes responsible for these metabolisms, we leveraged Random Barcode Transposon Sequencing (RB-TnSeq). Global fitness analyses of transposon libraries grown on 13 fatty acids and 10 alcohols produced strong phenotypes for hundreds of genes. Fitness data from mutant pools grown on varying chain length fatty acids indicated specific enzyme substrate preferences, and enabled us to hypothesize that DUF1302/DUF1329 family proteins potentially function as esterases. From the data we also postulate catabolic routes for the two biogasoline molecules isoprenol and isopentanol, which are catabolized via leucine metabolism after initial oxidation and activation with CoA. Because fatty acids and alcohols may serve as both feedstocks or final products of metabolic engineering efforts, the fitness data presented here will help guide future genomic modifications towards higher titers, rates, and yields.IMPORTANCE To engineer novel metabolic pathways into P. putida, a comprehensive understanding of the genetic basis of its versatile metabolism is essential. Here we provide functional evidence for the putative roles of hundreds of genes involved in the fatty acid and alcohol metabolism of this bacterium. These data provide a framework facilitating precise genetic changes to prevent product degradation and channel the flux of specific pathway intermediates as desired.Competing Interest StatementJ.D.K. has financial interests in Amyris, Lygos, Demetrix, Napigen, Maple Bio, and Apertor Labs. C.B.E has a financial interest in Perlumi Chemicals.View Full Text

microbiology↗

bioRxiv2020

Low Intensity Vibration Restores Nuclear YAP Levels and Acute YAP Nuclear Shuttling in Mesenchymal Stem Cells Subjected to Simulated Microgravity

Reducing the bone deterioration that astronauts experience in microgravity requires countermeasures that can improve the effectiveness of rigorous and time-expensive exercise regimens under microgravity. The ability of low intensity vibrations (LIV) to activate force-responsive signaling pathways in cells suggests LIV as a potential countermeasure to improve cell responsiveness to subsequent mechanical challenge. Mechanoresponse of mesenchymal stem cells (MSC) which maintain bone-making osteoblasts is in part controlled by the "mechanotransducer" protein YAP (Yes-associated protein) which is shuttled into the nucleus in response cyto-mechanical forces. Here, using YAP nuclear shuttling as a measure of MSC mechanoresponse, we tested the effect of 72 hours of simulated microgravity (SMG) and daily LIV application (LIVDT) on the YAP nuclear entry driven by either acute LIV (LIVAT) or Lysophosphohaditic acid (LPA), applied at the end of the 72h period. We hypothesized that SMG-induced impairment of acute YAP nuclear entry will be alleviated by daily application of LIVDT. Results showed that while both acute LIVAT and LPA treatments increased nuclear YAP entry by 50% and 87% over the basal levels in SMG-treated MSCs, nuclear YAP levels of all SMG groups were significantly lower than non-SMG controls. Daily dosing of LIVDT, applied in parallel to SMG, restored the SMG-driven decrease in basal nuclear YAP to control levels as well as increased the LPA-induced but not LIVAT-induced YAP nuclear entry over the non-LIVDT treated, SMG only, counterparts. These cell level observations suggest that utilizing daily LIV treatments is a feasible countermeasure for increasing the YAP-mediated anabolic responsiveness of MSCs to subsequent mechanical challenge under SMG.

bioengineering↗

bioRxiv2020

Population dynamics analysis of Saccharomyces cerevisiae deletion library during fed-batch cultivation using Bar-seq

To understand the genetic basis of changes in strain physiology during industrial fermentation, and the corresponding roles these genes play in strain performance, we employed a barcoded yeast deletion library to assess genome-wide strain fitness across a simulated industrial fermentation regime. Our results demonstrate the utility of Bar-seq to assess fermentation associated stresses in yeast populations under industrial conditions. We find that mutant population diversity is maintained through multiple seed trains, enabling for large scale fermentation selective pressures to act upon the community. We identify specific deletion mutants that were enriched in all processes, independent of the cultivation conditions, which include MCK1, RIM11, MRK1, and YGK3 that encode homologues of mammalian glycogen synthase kinase 3 (GSK-3). Further, we show that significant changes in the population diversity during fed-batch cultivations reflect the presence of significant external stresses, such as the accumulation of the fermentative byproduct ethanol. The mutants that were lost during the time of most extreme population selection suggest that specific biological processes may be required to cope with these specific stresses. Overall our work highlights a promising avenue to identify genetic loci and biological stress responses required for fitness under industrial conditions.

microbiology↗