Gene Regulatory Level Research Articles

Noncoding RNAs: the crucial role of programmed cell death in osteoporosis.

Osteoporosis is the most common skeletal disease characterized by an imbalance between bone resorption and bone remodeling. Osteoporosis can lead to bone loss and bone microstructural deterioration. This increases the risk of bone fragility and fracture, severely reducing patients' mobility and quality of life. However, the specific molecular mechanisms involved in the development of osteoporosis remain unclear. Increasing evidence suggests that multiple noncoding RNAs show differential expression in the osteoporosis state. Meanwhile, noncoding RNAs have been associated with an increased risk of osteoporosis and fracture. Noncoding RNAs are an important class of factors at the level of gene regulation and are mainly involved in cell proliferation, cell differentiation, and cell death. Programmed cell death is a genetically-regulated form of cell death involved in regulating the homeostasis of the internal environment. Noncoding RNA plays an important role in the programmed cell death process. The exploration of the noncoding RNA-programmed cell death axis has become an interesting area of research and has been shown to play a role in many diseases such as osteoporosis. In this review, we summarize the latest findings on the mechanism of noncoding RNA-mediated programmed cell death on bone homeostasis imbalance leading to osteoporosis. And we provide a deeper understanding of the role played by the noncoding RNA-programmed cell death axis at the gene regulatory level of osteoporosis. We hope to provide a unique opportunity to develop novel diagnostic and therapeutic approaches for osteoporosis.

Regulatory networks in plant responses to drought and cold stress.

Drought and cold represent distinct types of abiotic stress, each initiating unique primary signaling pathways in response to dehydration and temperature changes, respectively. However, a convergence at the gene regulatory level is observed where a common set of stress-responsive genes is activated to mitigate the impacts of both stresses. In this review, we explore these intricate regulatory networks, illustrating how plants coordinate distinct stress signals into a collective transcriptional strategy. We delve into the molecular mechanisms of stress perception, stress signaling, and the activation of gene regulatory pathways, with a focus on insights gained from model species. By elucidating both the shared and distinct aspects of plant responses to drought and cold, we provide insight into the adaptive strategies of plants, paving the way for the engineering of stress-resilient crop varieties that can withstand a changing climate.

Spatially constrained gene regulation identifies key genetic contributions of preeclampsia, hypertension, and proteinuria†.

Preeclampsia (PE) is a relatively common but severe pregnancy disorder (with very limited effective treatments) characterized by hypertension (HTN) and usually proteinuria (PRO) or other organ damage. Genome-wide association studies (GWAS) of PE, HTN, and PRO have mostly identified risk loci single nucleotide polymorphisms (SNPs) located in noncoding genomic regions, likely impacting the regulation of distal gene expression. The latest GWAS associated (P < 1 × 10-6) SNPs to PE (n = 25), HTN (n = 1926), and PRO (n = 170). Our algorithmic analysis (CoDeS3D) used chromatin connection data (Hi-C) derived from 70 cell lines followed by analysis of two expression quantitative trail loci (eQTL) cohorts: GTEx (838 donors, 54 tissues, totaling 15 253 samples) and DICE (91 donors, 13 blood tissue types). We identified spatially constrained eQTLs which implicate gene targets in PE (n = 16), HTN (n = 3561), and PRO (n = 335). By overlapping these target genes and their molecular pathways (protein-protein interaction networks), we identified shared functional impacts between PE and HTN, which are significantly enriched for regulatory interactions which target genes intolerant to loss-of-function mutations. While the disease-associated SNP loci mostly do not overlap, the regulatory signals (target genes and pathways) overlap, informing on PE risk mechanisms. This demonstrates a model in which genetic predisposition to HTN and PRO lays a molecular groundwork toward risk for PE pathogenesis. This overlap at the gene regulatory network level identifies possible shared therapeutic targets for future study.

Come together now: Dynamic body-formation of key regulators integrates environmental cues in plant development.

Plants as sessile organisms are constantly exposed to changing environmental conditions, challenging their growth and development. Indeed, not only above-ground organs but also the underground root system must adapt accordingly. Consequently, plants respond to these constraints at a gene-regulatory level to ensure their survival and well-being through key transcriptional regulators involved in different developmental processes. Recently, intrinsically disordered domains within these regulators are emerging as central nodes necessary not only for interactions with other factors but also for their partitioning into biomolecular condensates, so-called bodies, possibly driven by phase separation. Here, we summarize the current knowledge about body-forming transcriptional regulators important for plant development and highlight their functions in a possible environmental context. In this perspective article, we discuss potential mechanisms for the formation of membrane-less bodies as an efficient and dynamic program needed for the adaptation to external cues with a particular focus on the Arabidopsis root. Hereby, we aim to provide a perspective for future research on transcriptional regulators to investigate body formation as an expeditious mechanism of plant-environment interactions.

Creating a User-Friendly and Open-Access Gene Expression Database for Comparing Embryonic Development and Regeneration in Nematostella vectensis.

The sea anemone Nematostella vectensis has emerged as a powerful research model to understand at the gene regulatory network level, to what extend regeneration recapitulates embryonic development. Such comparison involves massive transcriptomic analysis, a routine approach for identifying differential gene expression. Here we present a workflow to build a user-friendly, mineable, and open-access database providing access to the scientific community to various RNAseq datasets.

Purification of an insect juvenile hormone receptor complex enables insights into its post-translational phosphorylation

Juvenile hormone (JH) plays vital roles in insect reproduction, development, and in many aspects of physiology. JH primarily acts at the gene-regulatory level through interaction with an intracellular receptor (JH receptor [JHR]), a ligand-activated complex of transcription factors consisting of the JH-binding protein methoprene-tolerant (MET) and its partner taiman (TAI). Initial studies indicated significance of post-transcriptional phosphorylation, subunit assembly, and nucleocytoplasmic transport of JHR in JH signaling. However, our knowledge of JHR regulation at the protein level remains rudimentary, partly because of the difficulty of obtaining purified and functional JHR proteins. Here, we present a method for high-yield expression and purification of JHR complexes from two insect species, the beetle T. castaneum and the mosquito Aedes aegypti. Recombinant JHR subunits from each species were coexpressed in an insect cell line using a baculovirus system. MET–TAI complexes were purified through affinity chromatography and anion exchange columns to yield proteins capable of binding both the hormonal ligand (JH III) and DNA bearing cognate JH-response elements. We further examined the beetle JHR complex in greater detail. Biochemical analyses and MS confirmed that T. castaneum JHR was a 1:1 heterodimer consisting of MET and Taiman proteins, stabilized by the JHR agonist ligand methoprene. Phosphoproteomics uncovered multiple phosphorylation sites in the MET protein, some of which were induced by methoprene treatment. Finally, we report a functional bipartite nuclear localization signal, straddled by phosphorylated residues, within the disordered C-terminal region of MET. Our present characterization of the recombinant JHR is an initial step toward understanding JHR structure and function.

Effects of the antidepressant mirtazapine on the swimming behaviour and gene expression rate of Danio rerio embryos – Is the sedating effect seen in humans also evident for fish?

In the last decade, mirtazapine has become an important antidepressant in clinical use and has also been found at many different environmental sampling sites. Several homologies between the zebrafish Danio rerio and humans, combined with a number of advantages for behavioural and gene expression research using zebrafish embryos, make their use for the analysis of mirtazapine appropriate. The sedative effect of mirtazapine in humans was also found for a specific concentration range in zebrafish embryos (1333.4 μg/L – 2666.9 μg/L). Specifically, 116 hpf old zebrafish embryos showed a reduced swimming distance when exposed to 1334.4 μg/L mirtazapine. Furthermore, changes at the gene regulatory level could be measured (1333.4 μg/L), in particular in the superordinate regulatory systems. For selected transporters of all regulatory systems, an up regulation of the genes by a factor of more than five times could be measured at the highest mirtazapine exposure concentration that was tested. Finally, studies on the protein levels demonstrated an increase in acetylcholinesterase activity for several exposure concentrations(83.3 μg/L and 666.7 μg/L). The physiological changes in zebrafish embryos caused by mirtazapine demonstrate the relevance of these types of studies in aquatic non-target organisms. Such neuroactive substances could pose a potential risk for aquatic organisms below the previously considered concentration threshold for morphological effects.

Microbial exposure in early life alters the ontogeny and function of CD8+ T cells

Abstract Evidence has shown that microbial exposure in early life can have long-lasting effects on the health status of an individual. However, the underlying basis of how microbes shape the immune system is not well understood. In this study, we utilized a novel pet shop mouse model and compared the immune development and function of laboratory mice raised in either a clean (SPF) or dirty (pet-shop) environment. When we challenged the two groups with an intracellular pathogen in adulthood, we found that mice raised in the dirty environment mounted a more robust CD8+ T cell response and were highly resistant to infection. Adoptive transfer experiments with CD8+ T cells from clean and dirty mice into T cell deficient recipients indicated that differences in immune susceptibility were linked to changes in the CD8+ T cell compartment. Moreover, the dirty mice had an increased accumulation of antigen-specific CD8+ T cells and produced more effector molecules. To understand how the ontogeny of the CD8+ T cell compartment was altered in the dirty mice, we used our fate-mapping timestamp mice and found a higher proportion of fast-acting fetal-derived CD8+ T cells and fewer slow-acting adult-derived CD8+ T cells present in the dirty mice. We found that immune susceptibility could be normalized between clean and dirty mice by depleting the fetal layer of CD8+ T cells. Collectively, these findings suggest that microbial exposure leads to permanent changes in the immune system by altering the developmental layering of the peripheral T cell compartment. We are currently using a combination of RNA- and ATAC-seq to gain a deeper understanding of how the microbial environment mediates changes to CD8+ T cells at the gene regulatory level.

Multi-Omic Analysis Identifies Epigenetic Evolution in Relapsed Acute Myeloid Leukemia

Introduction: Acute myeloid leukemia (AML) is associated with a poor prognosis even with aggressive treatments including high dose chemotherapy. While most patients enter clinical remission, these remissions are often short-lived leading to chemotherapy-resistant relapsed disease that accounts for the majority of deaths. We undertook a meta-analysis of published datasets consisting of 142 genotyped paired diagnosis-relapse AML samples to understand the genetic evolution of AML between the two disease states. This analysis determined that a plurality of cases exhibited the same mutations at diagnosis and relapse, and that genetically stable clones were associated with an increased probability of relapse. The finding that many cases exhibited no clonal genetic evolution upon relapse, yet exhibited chemotherapy resistance, lead us to hypothesize that epigenetic evolution plays a significant role in AML relapse. Here, our objective was to investigate the epigenetic evolution and cis and trans regulatory elements that correlate with AML relapse. Methods: We identified 27 paired diagnosis and relapse specimens from patients treated at Stanford with high dose chemotherapy regimens. Leukemic blasts, and in some cases leukemia stem cell (LSC)-enriched fractions, were purified by FACS. Cells were then analyzed through a multi-omic platform including genotyping with a myeloid malignancy targeted panel, RNA-seq, and ATAC-seq to obtain a molecular and chromatin accessibility profile of each sample. The resulting data set was analyzed to investigate epigenetic evolution in relapsed AML. Results: Genotyping analysis of banked AML specimens identified a similar pattern of genetic evolution as our meta-analysis, with several samples exhibiting the same mutations at diagnosis and relapse. We used an epigenetic matrix of chromatin accessibility data obtained from purified cell populations within the hematopoietic hierarchy and implemented this with the CIBERSORT algorithm to map the regulatory programs active in diagnosis and relapsed AML blasts. This analysis revealed a general trend of epigenetic states associated with more primitive cells (such as hematopoietic stem and progenitor cells) active at relapse, as opposed to more differentiated myeloid cell programs active at diagnosis. Focusing further on samples with no genetic changes between the two disease states, we observed several samples with substantial epigenetic evolution at relapse, with AML blasts shifting from a more differentiated myeloid cell profile to that of stem and progenitor cells. These changes were associated with a loss of accessibility in PU.1 and CEBPα transcription factor motifs, with a corresponding increase in GATA and RUNX motifs, suggesting epigenetic remodeling contributes to relapse even in the absence of genetic changes. We have additionally identified various categories of relapse samples in our cohort that share similar epigenetic profiles relating to genotype; NPM1 and FLT3 double mutant samples, for example, shared active chromatin accessibility features. Given the key importance of LSCs in AML pathogenesis and their potential role in chemotherapy resistance, we further undertook an analysis of cellular subpopulations enriched for these cells in a subset of our sample cohort. ATAC-seq analysis of CD34+CD38- cell fractions revealed these cells share many epigenetic features between samples, yet also have distinct regulatory programs from those active in leukemia non-stem cells and exhibit similar epigenetic reprogramming between diagnosis and relapse. This analysis further indicates that epigenetic evolution at relapse occurs at the single cell level, rather than reflecting selection of cellular subpopulations at relapse. Ongoing work involves identifying the specific regulatory programs upregulated in relapse samples, and LSCs specifically, to understand how these programs contribute to relapse at the gene regulatory level. Conclusion: Our results indicate a substantial role for epigenetic evolution in AML, with the activation of more primitive stem and progenitor programs upon relapse. We have also identified epigenetic classifications for several relapse samples that correspond to genotype and characterized the regulatory programs associated with relapse. We hope this work will permit a deeper understanding of the evolutionary factors that guide AML relapse. Disclosures Majeti: Zenshine Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Coherus BioSciences: Membership on an entity's Board of Directors or advisory committees; CircBio Inc.: Research Funding; BeyondSpring Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Stanford University: Patents &amp; Royalties: pending patent application on CD93 CAR ; Forty-Seven Inc.: Divested equity in a private or publicly-traded company in the past 24 months; Kodikaz Therapeutic Solutions Inc.: Membership on an entity's Board of Directors or advisory committees; Gilead Sciences, Inc.: Patents &amp; Royalties: inventor on patents related to CD47 cancer immunotherapy.

Rapid evolutionary changes in gene expression in response to climate fluctuations.

There is now abundant evidence of rapid evolution in natural populations, but the genetic mechanisms of these changes remain unclear. One possible route to rapid evolution is through changes in the expression of genes that influence traits under selection. We examined contemporary evolutionary gene expression changes in plant populations responding to environmental fluctuations. We compared genome‐wide gene expression, using RNA‐seq, in two populations of Brassica rapa collected over four time points between 1997 and 2014, during which precipitation in southern California fluctuated dramatically and phenotypic and genotypic changes occurred. By combining transcriptome profiling with the resurrection approach, we directly examined evolutionary changes in gene expression over time. For both populations, we found a substantial number of differentially expressed genes between generations, indicating rapid evolution in the expression of many genes. Using existing gene annotations, we found that many changes occurred in genes involved in regulating stress responses and flowering time. These appeared related to the fluctuations in precipitation and were potentially adaptive. However, the evolutionary changes in gene expression differed across generations within and between populations, indicating largely independent evolutionary trajectories across populations and over time. Our study provides strong evidence for rapid evolution in gene expression, and indicates that changes in gene expression can be one mechanism of rapid evolutionary responses to selection episodes. This study also illustrates that combining resurrection studies with transcriptomics is a powerful approach for investigating evolutionary changes at the gene regulatory level, and will provide new insights into the genetic basis of contemporary evolution.

Transcriptome analysis of maize inbred lines differing in drought tolerance provides novel insights into the molecular mechanisms of drought responses in roots

Maize (Zea mays) is an important food and forage crop, as well as an industrial raw material, that plays important roles in agriculture and national economies. Drought stress has negative effects on seed germination and seedling growth, and it decreases crop production. In this study, we selected two maize inbred lines with different drought-tolerance levels: drought-tolerant 287M and drought-sensitive 753F. The physiological results showed that drought stress resulted in a large accumulation of reactive oxygen species (ROS) in maize root cells. However, in 287M, the activity levels of the ROS scavenging enzymes superoxide dismutase and ascorbate peroxidase also increased, resulting in a higher ROS scavenging ability than 753F. We used Illumina RNA sequencing to obtain the gene expression profiles of the two maize inbred lines at the seedling stage in response to drought stress. The transcriptome data were analyzed to reveal the mechanisms underlying the drought tolerance of 287M at the gene regulatory level. The differences in drought tolerance between 287M and 753F may be associated with different ROS scavenging capabilities, signal interaction networks, and some transcription factors. Our results will aid in understanding the molecular mechanisms involved in plant responses to drought stress.

MA04.06 Lung Epithelium Whole Transcriptome Signatures That Reflect Incident Lung Cancer Case-Control Status

Focusing early detection and prevention efforts on those at high risk for lung cancer is central to leveraging such strategies. Notably, that risk persists even after removal of a lung cancer, as reflected in lung recurrences, which are common, and usually occur remote from the surgical removal site. This implies risk for future incident lung cancer is represented in the biology of broad areas of lung epithelium, before, during, and after diagnosis. Given that somatic mutations in the bronchial tree are known to persist for decades, there is a suggestion that smoking transforms the entire epithelium at several somatic and gene regulatory levels. We hypothesize that the normal lung epithelium contains expression and epigenetic epithelial signatures that are representative of donor case-control status, that is poised for carcinogenesis. As a first step, in order to identify differentially expressed genes (DEGs) associated with aging, smoking and cancer case-control status, we analyzed RNA-seq transcriptome data of laser capture microdissected (LCM) bronchial and alveolar epithelium separately, in paired tissue sets of 40- and 74 respective individuals, summarized here. Read count was the main normalization variable. We also measured differentially methylated sites (DME) by whole genome bisulfite genome sequencing (WGBSeq), covering >60% of the genome/methylome [as of this deadline, these methylome data are not yet fully analyzed]. Mean subject age for 77 total subjects was 65 (+/-9.9), 19% current-, 76% former, 5% never smokers. For each cell type, we modeled gene expression level as a result of aging, gender, smoking and case-control status. We put all four clinical variables age, gender, smoking status, case-control status) along with cell type (alveolar/bronchial) into the model, to avoid potential confounding effects. We discovered 175 DEGs discriminating case-control status (FDR p<0.05) in alveolar and bronchial cells combined, and 420 case-control DEGs with bronchial cells alone. Bronchial cells displayed 31 DEGs discriminating current versus former smokers (FDR-adjusted P<0.05). Gene ontology (David) clusters for case-control discrimination in these “normal” bronchial epithelia included energetics pathways (GO 0042776/0006754; ATP biosynthesis) as well as transcriptional and translational regulation pathways; KEGG clusters also included oxidative phosphorylation pathways (hsa00190), among others. There is a donor case-control discriminant expression signature for human lung bronchial captured cells, emphasizing bioenergetically-deranged metabolic pathways, among others. If confirmed in larger studies that measure deranged metabolites directly, metabolomics biomarkers representing bioenergetics and other pathways may serve to define those individuals whose epithelia is tilted toward carcinogenesis, and therefore are at increased risk for lung cancer.

Neurogenomic insights into paternal care and its relation to territorial aggression

Motherhood is characterized by dramatic changes in brain and behavior, but less is known about fatherhood. Here we report that male sticklebacks—a small fish in which fathers provide care—experience dramatic changes in neurogenomic state as they become fathers. Some genes are unique to different stages of paternal care, some genes are shared across stages, and some genes are added to the previously acquired neurogenomic state. Comparative genomic analysis suggests that some of these neurogenomic dynamics resemble changes associated with pregnancy and reproduction in mammalian mothers. Moreover, gene regulatory analysis identifies transcription factors that are regulated in opposite directions in response to a territorial challenge versus during paternal care. Altogether these results show that some of the molecular mechanisms of parental care might be deeply conserved and might not be sex-specific, and suggest that tradeoffs between opposing social behaviors are managed at the gene regulatory level.

Transcriptome-wide identification of microRNAs and functional insights inferred from microRNA—target pairs in Physalis angulata L

ABSTRACTPhysalis angulata L., a member of the family Solanaceae, is widely used as the folk medicine in various countries. Continuous research efforts are devoted to the discovery of the effective medicinal ingredients from Physalis angulata. However, due to the limited resources of genome and transcriptome sequencing data, only a few studies have been performed at the gene regulatory level. In this study, the transcriptomes of five organs (roots, stems, leaves, flowers and fruits) of Physalis angulata were reported. Based on the transcriptome assembly containing 196,117 unique transcripts, a total of 17,556 SSRs (simple sequence repeats) were identified, which could be useful RNA-based barcoding for discrimination of the plants closely relative to Physalis angulata. Additionally, 24 transcripts were discovered to be the potential microRNA (miRNA) precursors which encode a total of 31 distinct mature miRNAs. Some of these precursors showed organ-specific expression patterns. Target prediction revealed 116 miRNA–target pairs, involving 31 miRNAs and 83 target transcripts in Physalis angulata. Taken together, our results could serve as the data resource for in-depth studies on the molecular regulatory mechanisms related to the production of medicinal ingredients in Physalis angulata.

Crosstalk between BMP and Notch Induces Sox2 in Cerebral Endothelial Cells.

Bone morphogenetic protein (BMP) and Notch signaling are critical for endothelial cell (EC) differentiation in vascular development. Recent studies have shown that excess BMP activity induces Notch signaling in cerebral ECs resulting in arteriovenous malformation (AVMs). However, it is unclear how the crosstalk between BMP and Notch signaling affects cerebral EC differentiation at the gene regulatory level. Here, we report that BMP6 activates the activin receptor-like kinase (ALK) 3, a BMP type 1 receptor, to induce Notch1 receptor and Jagged1 and Jagged2 ligands. We show that increased expression of the Notch components alters the transcriptional regulatory complex in the SRY-Box 2 (Sox2) promoter region so as to induce its expression in cerebral ECs. Together, our results identify Sox2 as a direct target of BMP and Notch signaling and provide information on how altered BMP and Notch signaling affects the endothelial transcriptional landscape.

Evolutionarily significant A-to-I RNA editing events originated through G-to-A mutations in primates

BackgroundRecent studies have revealed thousands of A-to-I RNA editing events in primates, but the origination and general functions of these events are not well addressed.ResultsHere, we perform a comparative editome study in human and rhesus macaque and uncover a substantial proportion of macaque A-to-I editing sites that are genomically polymorphic in some animals or encoded as non-editable nucleotides in human. The occurrence of these recent gain and loss of RNA editing through DNA point mutation is significantly more prevalent than that expected for the nearby regions. Ancestral state analyses further demonstrate that an increase in recent gain of editing events contribute to the over-representation, with G-to-A mutation site as a favorable location for the origination of robust A-to-I editing events. Population genetics analyses of the focal editing sites further reveal that a portion of these young editing events are evolutionarily significant, indicating general functional relevance for at least a fraction of these sites.ConclusionsOverall, we report a list of A-to-I editing events that recently originated through G-to-A mutations in primates, representing a valuable resource to investigate the features and evolutionary significance of A-to-I editing events at the population and species levels. The unique subset of primate editome also illuminates the general functions of RNA editing by connecting it to particular gene regulatory processes, based on the characterized outcome of a gene regulatory level in different individuals or primate species with or without these editing events.

Modulation of inflammatory responses in heart failure via activation of alpha-7 nicotinic acetylcholine receptor agonist GTS-21

Abstract Heart failure (HF) is a prominent health concern amongst the public with prevalence rate being over 5.8 million in the USA. Inflammation and cytokine signaling are two main factors that lead to the pathogenesis of HF because of their effects on the heart and peripheral circulation. The “smoker’s paradox” showed associations between improvements in short-term acute myocardial infarction (MI) and smokers via activation of α7 nicotinic acetylcholine receptor (α7 nAChR) that can inhibit inflammatory responses in HF. Studies showed that the vagus nerve can modulate these inflammatory responses by activating the cholinergic anti-inflammatory pathway via stimulation of α7 nAChR. Hence, stimulation of α7 nAChR with specific agonists can be a potential therapeutic target for HF because it can inhibit pro-inflammatory responses. In this study, the anti-inflammatory effects of 3-(2,4-dimethoxybenzylident)-anabaseine (GTS-21), a partial agonist of α7 nAChR, were observed in an in vivo zebrafish model for HF. For four consecutive days, the zebrafishes were pre-treated with GTS-21 (0.113 μM) for 20 minutes per day. On the fourth day after pre-treatment with GTS-21, the zebrafishes were induced with MI by oligo-[2-(2-ethoxy)- ethoxyethyl)-guanidinium-chloride] (PGH) and survival was recorded. Using reverse transcription PCR (rt-PCR) for analysis, results showed that pre-treatment with GTS-21 modified the gene regulatory protein levels and reduced cytokine expression in the myocardium tissue. Other α7 nAChR agonists were investigated for their potential therapeutic effect in inhibiting inflammatory responses, but GTS-21 was more efficacious in inhibiting cytokine expression. Thus, GTS-21 may be used as a novel therapeutic for HF.

Abstract TP254: Effects of Inducible Nitric Oxide Synthase on Behavior and Functional Outcomes in a Novel “Humanized” Transgenic Mouse Model of Ischemic Stroke

Introduction: Inducible nitric oxide synthase (iNOS) is a critical regulator of brain and systemic inflammatory responses in many neurological disorders. Intriguingly, iNOS null mice have produced equivocal outcomes in mouse models of ischemic stroke, a result that may be due, in part, to species-specific differences between the mouse and human iNOS genes. Due to numerous differences at the gene regulatory level, mouse iNOS naturally produces much higher levels of nitric oxide (NO) than the human gene. To resolve the functional differences between mouse and human iNOS in ischemic stroke, we employed a novel mouse that expresses human iNOS on a mouse iNOS null genetic background, termed the HN mouse. Our study objective was to compare functional and behavioral outcomes following ischemic stroke between wildtype (WT) and HN mice. Hypothesis: We hypothesized that post-stroke functional outcomes would be more severe in HN male mice than in WT mice. Methods: Male C57BL/6J (WT) and HN mice (4-6 months) were subjected to 60 minutes of transient middle cerebral artery occlusion (tMCAO) followed by reperfusion and behavioral assessments at seven-day intervals for 30 days. Laser-Doppler flowmetry pre- and post-tMCAO was used to assess the effect of iNOS on blood flow. A comprehensive neurological battery was used to assess sensorimotor ability, reflexes, and balance, followed by open field, wire hang, and rotarod testing to evaluate locomotor activity, limb strength, and coordination. Results and Conclusion: Blood flow was significantly decreased in the ipsilateral hemisphere of both WT and HN mice following acute ischemic stroke; however, HN mice exhibited a sustained global decrease in blood flow following reperfusion. HN mice also demonstrated decreased locomotor activity and coordination, as well as greater neurological deficits compared to WT mice. Overall, these results suggest that the HN mouse model recapitulates more neurological deficits associated with human ischemic stroke than WT mice. Thus, the HN mouse may represent a more “humanized” model of ischemic stroke than more commonly used mouse models that express the mouse iNOS gene.

Estimating drivers of cell state transitions using gene regulatory network models

BackgroundSpecific cellular states are often associated with distinct gene expression patterns. These states are plastic, changing during development, or in the transition from health to disease. One relatively simple extension of this concept is to recognize that we can classify different cell-types by their active gene regulatory networks and that, consequently, transitions between cellular states can be modeled by changes in these underlying regulatory networks.ResultsHere we describe MONSTER, MOdeling Network State Transitions from Expression and Regulatory data, a regression-based method for inferring transcription factor drivers of cell state conditions at the gene regulatory network level. As a demonstration, we apply MONSTER to four different studies of chronic obstructive pulmonary disease to identify transcription factors that alter the network structure as the cell state progresses toward the disease-state.ConclusionsWe demonstrate that MONSTER can find strong regulatory signals that persist across studies and tissues of the same disease and that are not detectable using conventional analysis methods based on differential expression. An R package implementing MONSTER is available at github.com/QuackenbushLab/MONSTER.

Soldier-biased gene expression in a subterranean termite implies functional specialization of the defensive caste.

In a termite colony, reproduction is typically monopolized by a small number of sexuals that are supported by reproductively altruistic soldiers and workers. We expect caste differentiation to be associated with clear-cut differences in gene expression, and for these differences to reflect caste function and development. Here, we use RNA-Sequencing to compare the gene expression profiles of sexual nymphs and two non-reproductive helper castes (i.e., workers and soldiers) of the Eastern subterranean termite Reticulitermes flavipes. We found that of n = 93 genes that are strictly expressed as a function of caste, a majority (78%) show a soldier-specific pattern. This conspicuous soldier-bias in genome-wide expression suggests that this defensively specialized caste is functionally well-differentiated from both the reproductive and the other non-reproductive caste of this species, despite a shared developmental program with workers. Gene ontology analysis supports the notion of functional specialization by soldiers, as soldier-biased gene sets are enriched for novel biological processes. Whether this pattern reflects ancient or more recent bouts of selection for caste novelty at the gene-regulatory level is not known, but because soldiers are sterile and thus have no direct fitness, any selection for novelty must have been mediated indirectly, through reproducing relatives.