Search bioRxiv⌕ Search

SEARCH · Search bioRxiv

Search Search bioRxiv

Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
bioRxiv2018

150 years of research on Vierordt’s law - Fechner’s fault?

150 years ago, the physiologist Karl Vierordt discovered one type of systematic errors in time perception - an overestimation of long durations and underestimation of short durations, now known as Vierordt's law. Here we review the original study in its historical context and ask whether Vierordt's law is a result of an unnatural experimental randomization protocol. Using iterative Bayesian updating, we simulated the original results with astonishing accuracy. To validate whether the experimental protocol matters, we compared duration reproduction from two sequences with the same sampled distribution and found that trial-wise variation determines the reproduction error. We conclude that Vierordt's law is caused by an unnatural yet widely used experimental protocol.

neuroscience↗
bioRxiv2018

Polygenic Adaptation: From sweeps to subtle frequency shifts

1Evolutionary theory has produced two conflicting paradigms for the adaptation of a polygenic trait. While population genetics views adaptation as a sequence of selective sweeps at single loci underlying the trait, quantitative genetics posits a collective response, where phenotypic adaptation results from subtle allele frequency shifts at many loci. Yet, a synthesis of these views is largely missing and the population genetic factors that favor each scenario are not well understood. Here, we study the architecture of adaptation of a binary polygenic trait (such as resistance) with negative epistasis among the loci of its basis. The genetic structure of this trait allows for a full range of potential architectures of adaptation, ranging from sweeps to small frequency shifts. By combining computer simulations and a newly devised analytical framework based on Yule branching processes, we gain a detailed understanding of the adaptation dynamics for this trait. Our key analytical result is an expression for the joint distribution of mutant alleles at the end of the adaptive phase. This distribution characterizes the polygenic pattern of adaptation at the underlying genotype when phenotypic adaptation has been accomplished. We find that a single compound parameter, the population-scaled background mutation rate {Theta}bg, explains the main differences among these patterns. For a focal locus, {Theta}bg measures the mutation rate at all redundant loci in its genetic background that offer alternative ways for adaptation. For adaptation starting from mutation-selection-drift balance, we observe different patterns in three parameter regions. Adaptation proceeds by sweeps for small {Theta}bg [prsim] 0.1, while small polygenic allele frequency shifts require large {Theta}bg [scsim] 100. In the large intermediate regime, we observe a heterogeneous pattern of partial sweeps at several interacting loci. 2 Author summaryIt is still an open question how complex traits adapt to new selection pressures. While population genetics champions the search for selective sweeps, quantitative genetics proclaims adaptation via small concerted frequency shifts. To date the empirical evidence of clear sweep signals is more scarce than expected, while subtle shifts remain notoriously hard to detect. In the current study we develop a theoretical framework to predict the expected adaptive architecture of a simple polygenic trait, depending on parameters such as mutation rate, effective population size, size of the trait basis, and the available genetic variability at the onset of selection. For a population in mutation-selection-drift balance we find that adaptation proceeds via complete or partial sweeps for a large set of parameter values. We predict adaptation by small frequency shifts for two main cases. First, for traits with a large mutational target size and high levels of genetic redundancy among loci, and second if the starting frequencies of mutant alleles are more homogeneous than expected in mutation-selection-drift equilibrium, e.g. due to population structure or balancing selection.

evolutionary biology↗
bioRxiv2018

Subthalamic nucleus optogenetic manipulations: a glimpse at deep brain stimulation mechanisms

Although deep brain stimulation (DBS) is now a widely used therapeutic strategy, its precise mechanism remains largely unclear. Since this approach is progressively extended to treat non-motor disorders such as depression, obsessive-compulsive disorders, the comprehension of its effects on motivated behaviors appears of the upmost importance for a possible application for addiction. In intact rats, we used inhibition and high frequency optogenetic activation of subthalamic nucleus (STN) neurons to test whether or not we could reproduce the effects of electric deep brain stimulation on rats motivation for sweet food and cocaine. Rats motivation was assessed using fixed-ratio 5 and progressive ratio schedules of reinforcement for both rewards and illumination was applied during behavioral testing. Efficiency of optogenetic manipulations has been validated using in-vitro electrophysiological recordings. Optogenetic inhibition of STN increased motivation for food and reduced motivation for cocaine. In contrast, optogenetic high frequency stimulation reduced the motivation for food without impacting motivation for cocaine. Optical inhibition mimics the effect of electric deep brain stimulation on food and cocaine motivation, confirming that the effects observed under electric DBS result from a specific inactivation of the STN. In contrast, optogenetic high frequency stimulation induces opposite effects to those of electric one, suggesting a stimulation of the STN that only seems to affect food motivation.

neuroscience↗
bioRxiv2018

Transgenic Mice and Pluripotent Stem Cells Express EGFP under the Control of miR-302 Promoter

MicroRNAs are a group of short non-coding RNAs that undertake various roles in different cell signaling pathways and developmental stages. They regulate gene expression levels at the post-transcriptional stage, which results in cleavage of mRNAs or repression of their translation. Some miRNAs, including the miR-302 cluster, are critical regulators for the stemness state of embryonic stem cells and cell fate patterning. The miR-302 cluster is located in the intron of a non-coding gene that has no other reported function, other than hosting miR-302, and grant a complex expression regulation through upstream its regulatory sequences. To date, analysis of the miR-302 expression pattern in a transgenic mouse model has not been reported. In this study, we generated transgenic mice that expressed EGFP driven by miR-302 upstream regulatory sequences that harbored the core promoter of its host gene. We examined the activity of the miR-302 promotor in somatic tissues of transgenic mice, transgenic blastocysts, and embryonic stem cells derived from transgenic blastocysts. Our results showed that miR-302 highly expressed in both blastocysts and the first passages of transgenic embryonic stem cells, and has low expression in the somatic tissues of transgenic mice. It could be concluded that different temporal and spatial gene expression patterns occur during the embryonic and adult stages in mice.

developmental biology↗
bioRxiv2018

The amplitude in periodic neural state trajectories underlies the tempo of rhythmic tapping

Our motor commands can be exquisitely timed according to the demands of the environment, and the ability to generate rhythms of different tempos is a hallmark of musical cognition. Yet, the neuronal basis behind rhythmic tapping remains elusive. Here we found that the activity of hundreds of primate MPC neurons show a strong periodic pattern that becomes evident when their activity is projected into a lower dimensional state space. We show that different tempos are encoded by circular trajectories that travelled at a constant speed but with different radii, and that this neuronal code is highly resilient to the number of participating neurons. Crucially, the changes in the amplitude of the oscillatory dynamics in neuronal state space are a signature of beat-based timing, regardless of whether it is guided by an external metronome or is internally controlled and is not the result of repetitive motor commands. Furthermore, the increase in amplitude and variability of the neural trajectories accounted for the scalar property of interval timing. In addition, we found that the interval-dependent increments in the radius of periodic neural trajectories are the result of larger number of neurons engaged in the production of longer intervals. Our results support the notion that beat-based timing during rhythmic behaviors is encoded in the radial curvature of periodic MPC neural population trajectories.

neuroscience↗
bioRxiv2018

Pre- and postsynaptically expressed spiking-timing-dependent plasticity contribute differentially to neuronal learning

A plethora of experimental studies have shown that long-term plasticity can be expressed pre- or postsynaptically depending on a range of factors such as developmental stage, synapse type, and activity patterns. The functional consequences of this diversity are unknown. However, in models of neuronal learning, long-term synaptic plasticity is implemented as changes in connective weights. Whereas postsynaptic expression of plasticity predominantly affects synaptic response amplitude, presynaptic expression alters both synaptic response amplitude and short-term dynamics. In other words, the consideration of long-term plasticity as a fixed change in amplitude corresponds more closely to post- than to presynaptic expression, which means theoretical outcomes based on this choice of implementation may have a postsynaptic bias. To explore the functional implications of the diversity of expression of long-term synaptic plasticity, we modelled spike-timing-dependent plasticity (STDP) such that it was expressed either pre- or postsynaptically, or both. We tested pair-based standard STDP models and a biologically tuned triplet STDP model, and investigated the outcome in a feed-forward setting, with two different learning schemes: either inputs were triggered at different latencies, or a subset of inputs were temporally correlated. Across different STDP models and learning paradigms, we found that presynaptic changes adjusted the speed of learning, while postsynaptic expression was better at regulating spike timing and frequency. When combining both expression loci, postsynaptic changes amplified the response range, while presynaptic plasticity maintained control over postsynaptic firing rates, potentially providing a form of activity homeostasis. Our findings highlight how the seemingly innocuous choice of implementing synaptic plasticity by direct weight modification may unwittingly introduce a postsynaptic bias in modelling outcomes. We conclude that pre- and postsynaptically expressed plasticity are not interchangeable, but enable complimentary functions.

neuroscience↗
bioRxiv2018

Comparative metabonomic investigations of Schistosoma japonicum from SCID mice and BALB/c mice: clues to developmental abnormality of schistosome in the immunodeficient host

It has been discovered that the development of schistosome is hampered in immunodeficient mice, e.g. nude mice lacking T-lymphocytes and the severe combined immune deficient (SCID) mice lacking both T- and B-lymphocytes. However, its still unresolved about the underlying regulatory mechanisms of the retarded growth and development of schistosomes in their immunodeficient definitive host. In this study, therefore, five replicates of male or female Schistosoma japonicum samples with twenty male or female worms in each sample, were collected from SCID mice or BALB/c mice at five weeks post infection and used to perform metabonomic analysis using liquid chromatography tandem mass spectrometry (LC-MS/MS) platform, for elucidating the growth and development regulation of schistosome in their definitive hosts from the metabolomic aspect. Based on the identified 1015 ion features in ESI+ mode and 342 ion features in ESI-mode, multivariate modelling methods including the Principal Component Analysis (PCA), Partial Least Squares Discriminant Analysis (PLS-DA) and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) identified distinct metabolic profiles that clearly differentiated both male and female worms in SCID mice from those in BALB/c mice, respectively. Common and uniquely perturbed metabolites and their involved metabolic pathways were identified in male and female worms from SCID mice when compared with those from BALB/c mice. The results also revealed that more differential metabolites were found in female worms (one metabolite was up-regulated and forty metabolites were down-regulated) than male worms (nine metabolites were up-regulated and twenty metabolites were down-regulated) between SCID mice and BALB/c mice. The top five increased metabolites of male worms in SCID mice when compared with those in BALB/c mice were PC(22:6/20:1), L-allothreonine, L-serine, glycerophosphocholine and 5-aminoimidazole ribonucleotide. And the top five decreased metabolites of male worms in SCID mice when compared with those in BALB/c mice were PC(16:0/0:0), PAF C-16, PE(18:1/0:0), adenosine and butenoyl PAF. Most of the differential metabolites of female worms in SCID mice had lower levels when compared with the normal female worms in BALB/c mice, except for retinyl ester with a higher level. The top five decreased metabolites of female worms in SCID mice when compared with those in BALB/c mice were adrenic acid, 5-phosphoribosylamine, PC(16:0/0:0), PC(22:6/20:1) and ergothioneine. The involved metabolic pathways of the differential metabolites in male worms between SCID mice and BALB/c mice mainly included taurine and hypotaurine metabolism, glycerophospholipid metabolism, sphingolipid metabolism, arachidonic acid metabolism, alpha-linolenic acid metabolism, etc. The involved metabolic pathways of differential metabolites in female worms included mainly pyrimidine metabolism, sphingolipid metabolism, arachidonic acid metabolism, glycerophospholipid metabolism, tryptophan metabolism, etc. These findings suggested a correlation between the retarded growth and development of schistosome in SCID mice and their perturbed metabolic profiles, which also provided a new insight into the regulation mechanisms of growth and development of S. japonicum worms from the metabolic level, and provided clues for discovery of drugs or vaccines against the parasites and parasitic disease.\n\nAuthor summaryThe growth and development of schistosome has been discovered hampered in the immunodeficient hosts. But it remains unresolved about the molecular mechanisms involved in this. In this study, we tested and compared the metabolic profiles of the male and female Schistosoma japonicum worms collected from SCID mice or BALB/c mice at five weeks post infection using liquid chromatography tandem mass spectrometry (LC-MS/MS) platform. There were 1015 ion features in ESI+ mode and 342 ion features in ESI-mode were identified, and distinct metabolic profiles were found to clearly differentiate both male and female worms in SCID mice from those in BALB/c mice, respectively. The results also found more differential metabolites in female worms than in male worms between SCID mice and BALB/c mice. The enriched metabolic pathways of the differential metabolites in male worms between SCID mice and BALB/c mice included taurine and hypotaurine metabolism, glycerophospholipid metabolism, sphingolipid metabolism, arachidonic acid metabolism, alpha-linolenic acid metabolism, etc. And the enriched metabolic pathways of differential metabolites in female worms included pyrimidine metabolism, sphingolipid metabolism, arachidonic acid metabolism, glycerophospholipid metabolism, tryptophan metabolism, etc. The findings in this study suggested an association between the developmentally stunted schistosome and their perturbed metabolites and metabolic pathways, which provided a new insight into the regulation mechanisms of growth and development of S. japonicum worms from the metabolic level, and clues for discovery of drugs or vaccines against the parasites and disease.

biochemistry↗
bioRxiv2018

Homogenization of capillary flow and oxygenation in deeper cortical layers correlates with increased oxygen extraction

Our understanding of how capillary blood flow and oxygen distribute across cortical layers to meet the local metabolic demand is incomplete. We addressed this question by using two-photon imaging of microvascular oxygen partial pressure (PO2) and flow in the whisker barrel cortex in awake mice at rest. Our measurements in layers I-V show that the capillary red-blood-cell flux and oxygenation heterogeneity, and the intracapillary resistance to oxygen delivery, all decrease with depth, reaching a minimum around layer IV, while the depth-dependent oxygen extraction fraction is increased in layer IV, where oxygen demand is presumably the highest. Our findings suggest that homogenization of physiological observables relevant to oxygen transport to tissue is an important part of the microvascular network adaptation to a local brain metabolism increase. These results will inform the biophysical models of layer-specific cerebral oxygen delivery and consumption and improve our understanding of diseases that affect the cerebral microcirculation.\n\nIMPACT STATEMENTHomogenization of cortical capillary blood flow and oxygenation underpins an important mechanism, by which the microvascular network adapts to an increase in the local brain oxidative metabolism.

neuroscience↗
bioRxiv2018

Imaging Oxysterols in Mouse Brain by On-Tissue Derivatisation-Robotic Liquid Micro-Extraction Surface Analysis-Liquid Chromatography Mass Spectrometry

Dysregulated cholesterol metabolism is implicated in a number of neurological disorders. Many sterols, including cholesterol and its precursors and metabolites, are biologically active and important for proper brain function. However, spatial cholesterol metabolism in brain and the resulting sterol distributions are poorly defined. To better understand cholesterol metabolism in situ across the complex functional regions of brain, we have developed on-tissue enzyme-assisted derivatisation in combination with micro-liquid-extraction for surface analysis and liquid chromatography - mass spectrometry to image sterols in tissue slices (10 {micro}m) of mouse brain. The method provides sterolomic analysis at 400 {micro}m spot diameter with a limit of quantification of 0.01 ng/mm2. It overcomes the limitations of previous mass spectrometry imaging techniques in analysis of low abundance and difficult to ionise sterol molecules, allowing isomer differentiation and structure identification. Here we demonstrate the spatial distribution and quantification of multiple sterols involved in cholesterol metabolic pathways in wild type and cholesterol 24S-hydroxylase knock-out mouse brain. The technology described provides a powerful tool for future studies of spatial cholesterol metabolism in healthy and diseased tissues.\n\nSignificanceThe brain is a remarkably complex organ and cholesterol homeostasis underpins brain function. It is known that cholesterol is not evenly distributed across different brain regions, however, the precise map of cholesterol metabolism in the brain remains unclear. If cholesterol metabolism is to be correlated with brain function it is essential to generate such a map. Here we describe an advanced mass spectrometry imaging platform to reveal spatial cholesterol metabolism in situ at 400 {micro}m resolution on 10 {micro}m tissue slices from mouse brain. We mapped, not only cholesterol, but also other biologically active sterols arising from cholesterol turnover in both wild type and mice lacking cholesterol 24-hydroxylase (Cyp46a1), the major cholesterol metabolising enzyme.

neuroscience↗
bioRxiv2018

Sequential digestion with Trypsin and Elastase in cross-linking/mass spectrometry

Cross-linking/mass spectrometry has become an important approach for studying protein structures and protein-protein interactions. The amino acid composition of some protein regions impedes the detection of cross-linked residues, although it would yield invaluable information for protein modelling. Here, we report on a sequential digestion strategy with trypsin and elastase to penetrate regions with a low density of trypsin cleavage sites. We exploited intrinsic substrate recognition properties of elastase to specifically target larger tryptic peptides. Our application of this protocol to the TAF4-12 complex allowed us to identify cross-links in previously inaccessible regions.

biochemistry↗
bioRxiv2018

RERconverge: an R package for associating evolutionary rates with convergent traits

Motivation: When different lineages of organisms independently adapt to similar environments, selection often acts repeatedly upon the same genes, leading to signatures of convergent evolutionary rate shifts at these genes. With the increasing availability of genome sequences for organisms displaying a variety of convergent traits, the ability to identify genes with such convergent rate signatures would enable new insights into the molecular basis of these traits.\n\nResults: Here we present the R package RERconverge, which tests for association between relative evolutionary rates of genes and the evolution of traits across a phylogeny. RERconverge can perform associations with binary and continuous traits, and it contains tools for visualization and enrichment analyses of association results.\n\nAvailability: RERconverge source code, documentation, and a detailed usage walk-through are freely available at https://github.com/nclark-lab/RERconverge. Datasets for mammals, Drosophila, and yeast are available at https://bit.ly/2J2QBnj.\n\nContact: mchikina@pitt.edu\n\nSupplementary information: Supplementary information, containing detailed vignettes for usage of RERconverge, are available at Bioinformatics online.

evolutionary biology↗
bioRxiv2018

Split-QF system for fine-tuned transgene expression in Drosophila

The Q-system is a binary expression system that works well across species. Here we report the development of a split-QF system that drives strong expression, is repressible by QS and inducible by quinic acid. The split-QF system is fully compatible with existing split-GAL4 and split-LexA lines for advanced intersectional experiments, thus greatly expanding the range of possible anatomical, physiological and behavioural assays in Drosophila.

neuroscience↗
bioRxiv2018

Communicating compositional patterns

How do people perceive and communicate structure? We investigate this question by letting participants play a communication game, where one player describes a pattern, and another player redraws it based on the description alone. We use this paradigm to compare two models of pattern description, one compositional (complex structures built out of simpler ones) and one non-compositional. We find that compositional patterns are communicated more effectively than non-compositional patterns, that a compositional model of pattern description predicts which patterns are harder to describe, and that this model can be used to evaluate participants drawings, producing human-like quality ratings. Our results suggest that natural language can tap into a compositionally structured pattern description language.

animal behavior and cognition↗
bioRxiv2018

High-dimensional representation of texture in the somatosensory cortex of primates

In the somatosensory nerves, the tactile perception of texture is driven by spatial and temporal patterns of activation distributed across three populations of afferents. These disparate streams of information must then be integrated centrally to achieve a unified percept of texture. To investigate the representation of texture in somatosensory cortex, we scanned a wide range of natural textures across the fingertips of Rhesus macaques and recorded the responses evoked in Brodmann's areas 3b, 1, and 2. We found that texture identity is reliably encoded in the idiosyncratic responses of populations of cortical neurons, giving rise to a high-dimensional representation of texture. Cortical neurons fall along a continuum in their sensitivity to fine vs. coarse texture, and neurons at the extrema of this continuum seem to receive their major input from different afferent populations. Finally, we show that cortical responses can account for several aspects of texture perception in humans.

neuroscience↗
bioRxiv2018

The hippocampus is necessary for the sleep-dependent consolidation of a task that does not require the hippocampus for initial learning

During sleep, the hippocampus plays an active role in consolidating memories that depend on it for initial encoding. There are hints in the literature that the hippocampus may have a broader influence, contributing to the consolidation of memories that may not initially require the area. We tested this possibility by evaluating learning and consolidation of the motor sequence task (MST) in hippocampal amnesics and demographically matched control participants. While the groups showed similar initial learning, only controls exhibited evidence of sleep-dependent consolidation. These results demonstrate that the hippocampus can be required for normal consolidation of a task without being required for its acquisition, suggesting that the area plays a broader role in coordinating sleep-dependent memory consolidation than has previously been assumed.

neuroscience↗
bioRxiv2018

Reversing compulsive cocaine seeking with low frequency deep brain stimulation of the subthalamic nucleus

Cocaine seeking despite a foot-shock contingency is used to model compulsive drug seeking, a core component of drug addiction, in rodents. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is efficient on other addiction criteria models and we show here that 30-Hz STN stimulation reduces pathological cocaine seeking in compulsive-like rats. This confirms STN DBS as a potential strategy to treat addiction. We also observed that only compulsive-like rats displayed a progressive increase in STN low frequency oscillations, especially in the alpha/theta band (6-13 Hz), during cocaine escalation. Conversely, applying 8-Hz STN DBS to mimic alpha/theta oscillations in non-compulsive animals changed them into compulsive ones. We have thus identified a predictive neuronal biomarker of compulsivity. Since one critical challenge in addiction research is to identify vulnerable individuals before they transition to harmful drug consumption pattern, our results could lead to new diagnostic tools and prevention strategies.

neuroscience↗
bioRxiv2018

PGC-1α regulates mitochondrial calcium homeostasis, SR stress and cell death to mitigate skeletal muscle aging

Age-related impairment of muscle function severely affects the health of an increasing elderly population. While causality and the underlying mechanisms remain poorly understood, exercise is an efficient intervention to blunt these aging effects. We thus investigated the role of the peroxisome proliferator-activated receptor {gamma} coactivator 1 (PGC-1), a potent regulator of mitochondrial function and exercise adaptation, in skeletal muscle during aging. We demonstrate that PGC-1 overexpression improves mitochondrial dynamics and calcium buffering in an estrogen-related receptor (ERR)-dependent manner. Moreover, we show that sarcoplasmic reticulum stress is attenuated by PGC-1. As a result, PGC-1 prevents tubular aggregate formation and fiber apoptosis in old muscle. Similarly, the pro-apoptotic effects of ceramide and thapsigargin were blunted by PGC-1 in muscle cells. Accordingly, mice with muscle-specific gain- and loss-of-function of PGC-1 exhibit a delayed and premature aging phenotype, respectively. Together, our data reveal a key protective effect of PGC-1 on muscle function and overall health span in aging.\n\nStatement of significanceThe loss of muscle function in aging results in a massive impairment in life quality, e.g. by reducing motor function, strength, endurance, the ability to perform daily tasks or social interactions. Unfortunately, the mechanistic aspects underlying age-related muscle disorders remain poorly understood and treatments improving the disease are extremely limited. We now show that PGC-1, a transcriptional coactivator, is a key regulator of mitochondrial calcium homeostasis, cellular stress and death, all of which are linked to muscle aging and dysfunction. As a result, inhibition of the age-related decline in muscle PGC-1 considerably reduces aging of muscle and constitutes a promising target to prevent and treat the deterioration of muscle function in the elderly.\n\nAbbreviationsBNIP3, BCL2/Adenovirus E1B 19kDa interacting protein 3; Cpt1b, carnitine palmitoyltransferase 1B; CSQ1, calsequestrin 1; Drp1, dynamin-related protein 1; ER stress, endoplasmic reticulum stress; ERR, estrogen-related receptor ; Fis1, fission 1; GRP75, Glucose-Regulated Protein 75; IGFBP5, insulin like growth factor binding protein 5; IP3, inositol 1,4,5-trisphosphate; IP3R1, inositol 1,4,5-trisphosphate receptor type 1; Letm1, leucine zipper and EF-hand containing transmembrane protein 1; MAMs, mitochondria-associated ER membranes; Mcad, medium-chain acyl-CoA dehydrogenase; Opa1, optic atrophy 1; OXPHOS, oxidative phosphorylation; PGC-1, peroxisome proliferator-activated receptor {gamma} coactivator 1; pH2AX, phospho-H2A Histone Family Member X; ppRB, phospho-preproretinoblastoma-associated protein; Puma, BCL2 Binding Component 3; ROS, reactive oxygen species; SR, sarcoplasmic reticulum; TA, tibialis anterior; TBP, TATA binding protein; TPG, thapsigargin; Ucp3, uncoupling protein 3; VDAC, voltage-dependent anion channel; XBP1, X-Box Binding Protein 1; Xiap, X-linked inhibitor of apoptosis protein

cell biology↗
bioRxiv2018

Convective forces increase CXCR4-dependent glioblastoma cell invasion in GL261 murine model

Glioblastoma is the most common and malignant form of brain cancer. Its invasive nature limits treatment efficacy and promotes inevitable recurrence. Previous in vitro studies have shown that interstitial fluid flow, a factor characteristically increased in cancer, increases glioma cell invasion via CXCR4-CXCL12. It is currently unknown if these effects translate in vivo. Using the therapeutic technique of convection enhanced delivery (CED), we tested if convective flow alters glioma invasion in vivo using the syngeneic GL261 mouse model of glioblastoma. We first confirmed that GL261 invasion in vitro increased under flow in a CXCR4-CXCL12 dependent manner. Additionally, approximately 65.4% and 6.59% of GL261 express CXCR4 and CXCL12 in vivo, respectively, with 3.38% expressing both. Inducing convective flow within implanted tumors indeed increased glioma cell invasion over untreated controls, and administering CXCR4 antagonist AMD3100 (5 mg/kg) effectively eliminated this response. Therefore, glioma invasion is in fact stimulated by convective flow in vivo through CXCR4. We also analyzed patient samples to show that expression of CXCR4 and CXCL12 increase in patients following therapy. These results suggesting that targeting flow-stimulated invasion may prove beneficial as a second line of therapy, particularly in patients chosen to receive convection enhanced drug delivery.

cancer biology↗