Biology subjects

Yun, S.

Publications and source records attributed to Yun, S..

At least 37 records · Page 2Linked to original sources

bioRxiv2023

Modulation of the spatiotemporal dynamics of striatal direct pathway neurons and motor output by mGluR5

Striatal spiny-projection neurons (SPNs) integrate glutamatergic inputs from the motor cortex and thalamus with neuromodulatory signals to regulate motor output. In vivo Ca2+ imaging has demonstrated that spatially overlapping ensembles of direct and indirect pathway SPNs (dSPNs, iSPNs) are co-active during spontaneous movement. This co-activity is statistically greater among nearby neurons, correlates with behavioral state, and changes in an SPN-type-specific manner under pathological conditions. How this co-activity arises and whether is important for movement are not well understood. Co-activity likely arises from shared excitatory inputs, the strength of which are scaled by well-characterized mechanisms of synaptic plasticity. Here, we show that the Group I metabotropic glutamate receptor 5 (mGluR5), which regulates the strength of corticostriatal synapses, is a key mediator of behaviorally relevant SPN co-activity. Pharmacological modulation of mGluR5 signaling bidirectionally altered movement and co-activity, but not the absolute level of activity in dSPNs. Targeted deletion of mGluR5 in dSPNs recapitulated the effects on spatiotemporal neural dynamics and movement, consistent with a striatum-specific effect of mGluR5 modulation. Targeted deletion of mGluR5 also produced changes in the synaptic properties of dSPNs. Separate from any effects on overall activity, our results show that excitatory synaptic modulation influences motor function by coordinating the spatial co-activation of dSPNs in vivo.

neuroscience↗

bioRxiv2023

Microglial depletion worsens lesion in female but not male C57BL/6J mice after P10 hypoxia-ischemia

BackgroundRodent models for perinatal hypoxic ischemic (HI) encephalopathy have reported sex differences such as the same injury causing larger lesions in the brains of males compared to females. Microglia, the resident immune cells of the brain that have sex-dependent developmental trajectories and gene expression patterns, likely play a different role in females and males following HI. However, there is conflicting literature on whether depletion of microglia worsens or improves HI-induced lesions and whether this differs by sex. Here we tested the effect of pharmacologic microglia depletion on HI lesion size in male and female mice. MethodsAn initial cohort of C57BL/6J mouse pups underwent HI at postnatal day 10 (P10) using a modified Vannucci procedure or a Sham insult followed by brain collection at P13. Another cohort of mice received daily intraperitoneal injections from P7 to P12 of either 25mg/kg PLX3397 (PLX, a CSF1R inhibitor) or vehicle (Veh). These mice also underwent HI or Sham at P10, resulting in four groups (Veh-Sham, Veh-HI, PLX-Sham, PLX-HI). All groups included female and male mice. Behavioral testing was performed both pre-HI (forelimb grasping [P8, P9]) and post-HI (open field traversal [P12], behavior and appearance observations [P13]). P13 brain sections underwent immunohistochemistry for Iba1 or cresyl violet staining for lesion scoring. ResultsP13 HI hippocampal sections had more Iba1 signal than Sham, with more variance in Male-HI vs Female-HI mice. PLX led to >95% depletion of Iba1+ cells at P10 or P13, and effective elimination of microglia did not differ by sex. In the hippocampus, Female-PLX-HI mice had worse lesion scores than Female-Veh-HI mice; this was not true in male mice, where there was a trend in the opposite direction. Female-PLX-HI mice also had worse lesion scores than Male-PLX-HI mice. In contrast to this sex-dependent effect of PLX on lesion score, there was no difference among groups in developmental milestones. ConclusionPLX3397 injection P7-P9 or P7-P12 effectively depletes microglia by P10 or P13, respectively. Microglial depletion via PLX worsens HI-induced injury in female mice but not in male mice.

neuroscience↗

bioRxiv2023

A Novel Subtype of Myeloproliferative Neoplasms Driven by a MYC-Alarmin Axis

Despite advances in understanding the genetic abnormalities in myeloproliferative neoplasms (MPNs) and the development of JAK2 inhibitors, there is an urgent need to devise new treatment strategies, particularly for triple negative myelofibrosis (MF) patients whose MPNs lack mutations in the JAK2 kinase pathway and have very poor clinical outcomes. Here we report that MYC copy number gain and increased MYC expression frequently occur in triple negative MF, and that MYC-directed activation of S100A9, an alarmin protein that plays pivotal roles in inflammation and innate immunity, is necessary and sufficient to drive development and progression of MF. Notably, the MYC-S100A9 circuit provokes a complex network of inflammatory signaling that involves various hematopoietic cell types in the bone marrow microenvironment. Accordingly, genetic ablation of S100A9 or treatment with small molecules targeting the MYC-S100A9 pathway effectively ameliorates MF phenotypes, highlighting the MYC-alarmin axis as a novel therapeutic vulnerability for this subgroup of MPNs. SIGNIFICANCEThis study establishes that MYC expression is increased in triple negative MPNs via trisomy 8, that a MYC-S100A9 circuit manifest in these cases is sufficient to provoke myelofibrosis and inflammation in diverse hematopoietic cell types in the BM niche, and that the MYC-S100A9 circuit is targetable in triple negative MPN.

cancer biology↗

bioRxiv2023

Highly effective gene inactivation in tetraploid Xenopus laevis with low-temperature-active engineered Cas12a

Gene knockout using the CRISPR/Cas (clustered regulatory interspaced short palindromic repeats/CRISPR-associated protein) system revolutionized reverse genetic studies in model and non-model organisms, as almost all genetic elements can be targeted with few limitations. Although the CRISPR/Cas system with SpCas9 (Cas9 derived from Streptococcus pyogenes) remains the most popular for genome editing, another CRISPR/Cas system with Cas12a (Cpf1) has expanded its application. However, Cas12a is challenging to use in some aquatic model organisms, such as Xenopus laevis, because of its low activity at the temperature at which X. laevis embryos are usually raised (lower than 25{degrees}C). Recently, an engineered Cas12a called Cas12a-Ultra was developed, which has improved in vivo endonuclease activity with reduced temperature dependency. Here, we evaluated the performance of these engineered Cas12a enzymes in X. laevis embryos. We first confirmed that they were more active than SpCas9 at the low temperature at which X. laevis embryos are mostly raised (20-22{degrees}C), based on in vitro digestion experiments. Then, we evaluated in vivo activities of Cas12a-Ultra by disrupting several genes in X. laevis whose phenotypic consequences are previously reported. LbCpf1 (Cas12a derived from Lachnospiraceae bacterium)-Ultra outperformed the other enzymes, producing more than 80% of embryos with severely defective phenotypes even in low-temperature conditions. In addition, duplicated copies of two paralogous lysine demethylases (kdm5b and kdm5c) were successfully disrupted, which recapitulated the previously reported phenotypes observed upon morpholino-mediated knockdown. This study demonstrated that this engineered Cas12a is valuable for gene function studies in Xenopus and other model organisms with low growth temperatures.

bioengineering↗

bioRxiv2023

Behavioral pattern separation and cognitive flexibility are enhanced in a mouse model of increased lateral entorhinal cortex-dentate gyrus circuit activity

Behavioral pattern separation and cognitive flexibility are essential cognitive abilities which are disrupted in many brain disorders. Better understanding of the neural circuitry involved in these abilities will open paths to treatment. In humans and mice, discrimination and adaptation rely on integrity of the hippocampal dentate gyrus (DG) which both receive glutamatergic input from the entorhinal cortex (EC), including the lateral EC (LEC). Inducible increase of EC-DG circuit activity improves simple hippocampal-dependent associative learning and increases DG neurogenesis. Here we asked if the activity of LEC fan cells that directly project to the DG (LECDG neurons) regulates behavioral pattern separation or cognitive flexibility. C57BL6/J male mice received bilateral LEC infusions of a virus expressing shRNA TRIP8b, an auxiliary protein of an HCN channel or a control virus (SCR shRNA); this approach increases the activity of LECDG neurons. Four weeks later, mice underwent testing for behavioral pattern separation and reversal learning (touchscreen-based Location Discrimination Reversal [LDR] task) and innate fear of open spaces (elevated plus maze [EPM]) followed by counting of new DG neurons (doublecortin-immunoreactive cells [DCX+] cells). TRIP8b and SCR shRNA mice performed similarly in general touchscreen training and LDR training. However, in late LDR testing, TRIP8b shRNA mice reached the first reversal more quickly and had more accurate discrimination vs. SCR shRNA mice, specifically when pattern separation was challenging (lit squares close together or "small separation"). Also, TRIP8b shRNA mice achieved more reversals in late LDR testing vs. SCR shRNA mice. Supporting a specific influence on cognitive behavior, SCR shRNA and TRIP8b shRNA mice did not differ in total distance traveled or in time spent in the closed arms of the EPM. Supporting an inducible increase in LEC-DG activity, DG neurogenesis was increased. These data indicate TRIP8b shRNA mice had better pattern separation and reversal learning and more neurogenesis vs. SCR shRNA mice. This work advances fundamental and translational neuroscience knowledge relevant to two cognitive functions critical for adaptation and survival -- behavioral pattern separation and cognitive flexibility -- and suggests the activity of LECDG neurons merits exploration as a therapeutic target to normalize dysfunctional DG behavioral output.

animal behavior and cognition↗

bioRxiv2022

SAYSD1 senses UFMylated ribosome to safeguard co-translational protein translocation at the endoplasmic reticulum

Translocon clogging at the endoplasmic reticulum (ER) as a result of translation stalling triggers ribosome UFMylation, activating a Translocation-Associated Quality Control (TAQC) mechanism that degrades clogged substrates. How cells sense ribosome UFMylation to initiate TAQC is unclear. Here we use a genome-wide CRISPR/Cas9 screen to identify an uncharacterized membrane protein named SAYSD1 that facilitates TAQC. SAYSD1 associates with the Sec61 translocon, and also recognizes both ribosome and UFM1 directly, engaging a stalled nascent chain to ensure its transport via the TRAPP complex to lysosomes for degradation. Like UFM1 deficiency, SAYSD1 depletion causes the accumulation of translocation-stalled proteins at the ER and triggers ER stress. Importantly, disrupting UFM1- and SAYSD1-dependent TAQC in Drosophila leads to intracellular accumulation of translocation-stalled collagens, defective collagen deposition, abnormal basement membranes, and reduced stress tolerance. Together, our data support a model that SAYSD1 acts as a UFM1 sensor that collaborates with ribosome UFMylation at the site of clogged translocon, safeguarding ER homeostasis during animal development.

cell biology↗

bioRxiv2022

Differential metabolic adaptations define responses of winner and loser oncogenic mutant stem cells in skin epidermis in vivo

Skin epithelial stem cells detect and correct aberrancies induced by oncogenic mutations. Different oncogenes invoke different mechanisms of epithelial tolerance: while wild-type cells outcompete {beta}-catenin-Gain-of-Function ({beta}catGOF) mutant cells, HrasG12V mutant cells outcompete wild-type cells1,2. Here we ask how metabolic states change as wild-type stem cells interface with mutant cells, and how this ultimately drives different cell competition outcomes. By adapting our live-imaging platform to track endogenous redox ratio (NAD(P)H/FAD) with single cell resolution in the same mice over time, we show that wild-type epidermal stem cells maintain robust redox ratio despite their heterogeneous cell cycle states. We discover that both {beta}catGOF and HrasG12V models lead to a rapid drop in redox ratios. However, the "winner" cells in each model (wild-type in {beta}catGOF and mutant in HrasG12V), rapidly recover their redox ratios, irrespective of the mutation induced. Using mass spectrometry (13C-LC-MS/MS)3, we find that both mutants increase flux through the oxidative tricarboxylic acid cycle, but the "winner" HrasG12V cells and the "loser" {beta}catGOF cells modulate glycolytic flux differently. Hence, we reveal the metabolic adaptations that define the hallmarks of winners and losers during cell competition in vivo and uncover the nodes of regulation unique to each cell fate.

cancer biology↗

bioRxiv2022

Live imaging reveals chromatin compaction transitions and dynamic transcriptional bursting during stem cell differentiation in vivo

Stem cell differentiation requires dramatic changes in gene expression and global remodeling of chromatin architecture. How and when chromatin remodels relative to the transcriptional, behavioral, and morphological changes during differentiation remain unclear, particularly in an intact tissue context. Here, we develop a quantitative pipeline which leverages fluorescently-tagged histones and longitudinal imaging to track large-scale chromatin compaction changes within individual cells in a live mouse. Applying this pipeline to epidermal stem cells, we reveal that cell-to-cell chromatin compaction heterogeneity within the stem cell compartment emerges independent of cell cycle status, and instead is reflective of differentiation status. Chromatin compaction state gradually transitions over days as differentiating cells exit the stem cell compartment. Moreover, establishing live imaging of keratin-10 nascent RNA, which marks the onset of stem cell differentiation, we find that keratin-10 transcription is highly dynamic and largely precedes the global chromatin compaction changes associated with differentiation. Together, these analyses reveal that stem cell differentiation involves dynamic transcriptional states and gradual chromatin rearrangement.

genetics↗

bioRxiv2022

Selective Nigrostriatal Dopamine Excess Impairs Behaviors Linked to the Cognitive and Negative Symptoms of Psychosis

BACKGROUNDExcess dopamine release in the dorsal striatum (DS) is linked to psychosis. Antipsychotics are thought to work for positive symptoms by blocking striatal D2 dopamine receptors, but they lack efficacy for the negative and cognitive symptoms. Further, broadly increasing dopamine release improves cognitive function. These observations fueled the dogma that excess dopamine is not involved in negative and cognitive symptoms, but this has never been tested with dopamine pathway specificity. METHODSWe selectively re-expressed excitatory TRPV1 receptors in DS-projecting dopamine neurons of male and female Trpv1 knockout mice. We treated these mice with capsaicin (TRPV1 agonist) to selectively activate these neurons, validated this approach with fiber photometry, and assessed its effects on social and cognitive function. We combined this manipulation with antipsychotic treatment (haloperidol) and compared the pathway-specific manipulation to treatment with the non-selective dopamine releaser amphetamine. RESULTSSelectively activating DS-projecting dopamine neurons increased DS (but not cortical) dopamine release and increased locomotor activity. Surprisingly, this manipulation also impaired behavioral processes linked to negative and cognitive symptoms (social drive and working memory). Haloperidol normalized locomotion, only partially rescued working memory, and had no effect on social interaction. By contrast, amphetamine increased locomotion but did not impair social interaction or working memory. CONCLUSIONSExcess dopamine release, when restricted to the DS, causes behavioral deficits linked to negative and cognitive symptoms. Previous studies using non-selective approaches to release dopamine likely overlooked these contributions of excess dopamine to psychosis. Future therapies should address this disregarded role for excess striatal dopamine in the treatment-resistant symptoms of psychosis.

neuroscience↗

bioRxiv2022

Integrative Multiomic Analyses of Diabetic Neuropathic Pain in Dorsal Root Ganglia: Proteomics, Phospho-proteomics, and Metabolomics

Diabetic peripheral neuropathy (DPN) is characterized by spontaneous pain in the extremities. Incidence of DPN continues to rise with the global diabetes epidemic. However, there remains a lack of safe, effective analgesics to control this chronic painful condition. Dorsal root ganglia (DRG) contain soma of sensory neurons and modulate sensory signal transduction into the central nervous system. In this study, we aimed to gain a deeper understanding of changes in molecular pathways in the DRG of DPN patients with chronic pain. We recently reported transcriptomic changes in the DRG with DPN. Here, we expand upon those results with integrated metabolomic, proteomic, and phospho-proteomic analyses to compare the molecular profiles of DRG from DPN donors and DRG from control donors without diabetes or chronic pain. Our analyses identified decreases of select amino acids and phospholipid metabolites in the DRG from DPN donors, which are important for cellular maintenance. Additionally, our analyses revealed changes suggestive of extracellular matrix (ECM) remodeling and altered mRNA processing. These results reveal new insights into changes in the molecular profiles associated with DPN.

neuroscience↗

bioRxiv2022

Injury suppresses Ras cell competitive advantage through enhanced wild-type cell proliferation

Healthy skin is a tapestry of wild-type and mutant clones. Although injury can cooperate with Ras mutations to promote tumorigenesis, the consequences in genetically mosaic skin are unknown. Here, we show that wild-type cells prevent oncogenic Ras-induced aberrant growth after injury. Although HrasG12V/+ and KrasG12D/+ cells outcompete wild-type cells in uninjured, mosaic tissue, their competitive advantage is suppressed after injury due to a selective increase in wild-type cell proliferation. EGFR inhibition abolishes the competitive advantage of wild-type cells after injury of HrasG12V/+-mosaic skin. Global loss of the cell cycle inhibitor p21 increases wild-type cell proliferation even without injury, suppressing the competitive advantage of HrasG12V/+ cells. Thus, injury plays an unanticipated role in switching the competitive balance between oncogenic and wild-type cells in genetically mosaic skin. One sentence SummaryInjury-repair selectively induces wild-type cell proliferation to suppress oncogenic growth in Ras-mosaic skin epithelium.

cell biology↗

bioRxiv2021

Iba1+ cell density and morphology classification at postnatal day 10 in four hippocampal subregions of female and male C57BL/6J mice

Microglia, the resident immune cells of the brain, support normal brain function and the brains response to disease and injury. The hippocampal dentate gyrus (DG) is an area of microglial study due to its central role in many behavioral and cognitive functions. Interestingly, microglia and related cells are distinct in female vs. male rodents, even in early life. Indeed, postnatal day (P)-dependent sex differences in number, density, and morphology of microglia have been reported in certain hippocampal subregions at specific ages. However, sex differences in the DG have not yet been assessed at P10, a rodent developmental time point translationally relevant to human term gestation. To address this knowledge gap, Iba1+ cells in the DG (which are enriched in the Hilus and Molecular Layer) in female and male C57BL/6J mice were analyzed for their number (via stereology) and density (via stereology and via sampling). Next, Iba1+ cells were classified into published morphology categories. Finally, the percent of Iba1+ cells in each morphology category was multiplied by total cell number to generate a total number of Iba1+ cells in each morphological category. Results show no sex difference in Iba1+ cell number, density, or morphology in the P10 Hilus or Molecular Layer. The lack of sex difference in Iba1+ cells in P10 DG using commonly-employed methodologies (sampling, stereology, morphology classification) provides a baseline from which to interpret microglia changes seen after injury. HIGHLIGHTSO_LISex differences in Iba1+ cells were assessed in the dentate gyrus (DG) of P10 mice C_LIO_LIIba1+ cells were assessed in DG microglia-rich subregions: Hilus and Molecular Layer C_LIO_LIBoth stereology and sampling approaches were used to quantify Iba1+ cells C_LIO_LINo sex difference found in Iba1+ cell number, density, or morphology in P10 mice DG C_LI

neuroscience↗

bioRxiv2021

Modulating D1 rather than D2 receptor-expressing spiny-projection neurons corresponds to optimal antipsychotic effect

Overactive dopamine transmission in psychosis is predicted to unbalance striatal output via D1- and D2-dopamine receptor-expressing spiny-projection neurons (SPNs). Antipsychotic drugs are thought to re-balance this output by blocking D2-receptor signaling. Here we imaged D1- and D2-SPN Ca2+ dynamics in mice to determine the neural signatures of antipsychotic effect. Initially we compared effective (clozapine and haloperidol) antipsychotics to a candidate drug that failed in clinical trials (MP-10). Clozapine and haloperidol normalized hyperdopaminergic D1-SPN dynamics, while MP-10 only normalized D2-SPN activity. Clozapine, haloperidol or chemogenetic manipulations of D1-SPNs also normalized sensorimotor gating. Given the surprising correlation between clinical efficacy and D1-SPN modulation, we evaluated compounds that selectively target D1-SPNs. D1R partial agonism, antagonism, or positive M4 cholinergic receptor modulation all normalized the levels of D1-SPN activity, locomotion, and sensorimotor gating. Our results suggest that D1-SPN activity is a more relevant therapeutic target than D2-SPN activity for the development of effective antipsychotics.

neuroscience↗

bioRxiv2021

Transcriptomic Analysis of Human Sensory Neurons in Painful Diabetic Neuropathy Reveals Inflammation and Neuronal Loss

Pathological sensations caused by peripheral painful neuropathy occurring in Type 2 diabetes mellitus (T2DM) are often described as sharp and burning and are commonly spontaneous in origin. Proposed etiologies implicate dysfunction of nociceptive sensory neurons in dorsal root ganglia (DRG) induced by generation of reactive oxygen species, microvascular defects, and ongoing axonal degeneration and regeneration. To investigate the molecular mechanisms contributing to diabetic pain, DRGs were acquired postmortem from patients who had been experiencing painful diabetic peripheral neuropathy (DPN) and subjected to transcriptome analyses to identify genes contributing to pathological processes and neuropathic pain. DPN occurs in distal extremities resulting in the characteristic "glove and stocking" pattern. Accordingly, the L4 and L5 DRGs, which contain the perikarya of primary afferent neurons innervating the foot, were analyzed from five DPN patients and compared with seven controls. Transcriptom e analyses identified 844 differentially expressed genes. We observed increases in levels of inflammation-associated genes from macrophages in DPN patients that may contribute to increased pain hypersensitivity and, conversely, there were frequent decreases in neuronally-related genes. The elevated inflammatory gene profile and the accompanying downregulation of multiple neuronal genes provide new insights into intraganglionic pathology and mechanisms causing neuropathic pain in DPN patients with T2DM.

neuroscience↗

bioRxiv2021

Effects of a 33-sequential beam galactic cosmic ray analog on male mouse behavior and evaluation of CDDO-EA as a radiation countermeasure

In long-term spaceflight, astronauts will face unique cognitive loads and social challenges which will be complicated by communication delays with Earth. It is important to understand the central nervous system (CNS) effects of deep spaceflight and the associated unavoidable exposure to galactic cosmic radiation (GCR). Rodent studies show single- or simple-particle combination exposure alters CNS endpoints, including hippocampal-dependent behavior. An even better Earth-based simulation of GCR is now available, consisting of a 33-beam (33-GCR) exposure. However, the effect of whole-body 33-GCR exposure on rodent behavior is unknown, and no 33-GCR CNS countermeasures have been tested. Here astronaut-age-equivalent (6mo-old) C57BL/6J male mice were exposed to 33-GCR (75cGy, a Mars mission dose). Pre-/during/post-Sham or 33-GCR exposure, mice received a diet containing a vehicle formulation alone or with the antioxidant/anti-inflammatory compound CDDO-EA as a potential countermeasure. Behavioral testing beginning 4mo post-irradiation suggested radiation and diet did not affect measures of exploration/anxiety-like behaviors (open field, elevated plus maze) or recognition of a novel object. However, in 3-Chamber Social Interaction (3-CSI), CDDO-EA/33-GCR mice failed to spend more time exploring a holder containing a novel mouse vs. a novel object (empty holder), suggesting sociability deficits. Also, Vehicle/33-GCR and CDDO-EA/Sham mice failed to discriminate between a novel stranger vs. familiarized stranger mouse, suggesting blunted preference for social novelty. CDDO-EA given pre-/during/post-irradiation did not attenuate the 33-GCR-induced blunting of preference for social novelty. Future elucidation of the mechanisms underlying 33-GCR-induced blunting of preference for social novelty will improve risk analysis for astronauts which may in-turn improve countermeasures.

animal behavior and cognition↗

bioRxiv2021

Multi-domain touchscreen-based cognitive assessment of C57BL/6J female mice shows whole body exposure to 56Fe particle space radiation in maturity improves discrimination learning yet impairs stimulus-response habit learning

Astronauts during interplanetary missions will be exposed to galactic cosmic radiation, including charged particles like 56Fe. Preclinical studies with mature, "astronaut-aged" rodents suggest space radiation diminishes performance in classical hippocampal- and prefrontal cortex-dependent tasks. However, a rodent cognitive touchscreen battery unexpectedly revealed 56Fe radiation improves the performance of C57BL/6J male mice in a hippocampal-dependent task (discrimination learning) without changing performance in a striatal-dependent task (rule-based learning). As other preclinical work suggests the female rodent brain may be relatively resistant to charged particle-induced injury, and as the proportion of female vs. male astronauts is increasing, further study on how charged particles influence the touchscreen cognitive performance of female mice is warranted. We hypothesized that, similar to mature male mice, mature female C57BL/6J mice exposed to whole-body 56Fe irradiation (3 x 6.7cGy 56Fe over 5 days, 600MeV/n) would improve performance vs.Sham conditions in touchscreen tasks relevant to hippocampal and prefrontal cortical function (e.g. location discrimination reversal [LDR] and extinction, respectively). In LDR, 56Fe female mice more accurately discriminated two discrete conditioned stimuli relative to Sham mice, suggesting improved hippocampal function. However, 56Fe and Sham female mice acquired a new simple stimulus-response behavior and extinguished this acquired behavior at similar rates, suggesting similar prefrontal cortical function. Based on prior work on multiple memory systems, we next tested whether improved hippocampal-dependent function (discrimination learning) came at the expense of striatal rule-based learning (visuomotor conditional learning). Interestingly, 56Fe female mice took more days to reach criteria in this striatal-dependent rule-based test relative to Sham mice. Together, our data support the idea of competition between memory systems, as an 56Fe-induced decrease in striatal-based learning is associated with enhanced hippocampal-based learning. These data emphasize the power of using a touchscreen-based battery to advance our understanding of the effects of space radiation on mission critical cognitive function in females, and underscore the importance of preclinical space radiation risk studies measuring multiple cognitive processes, thereby preventing NASAs risk assessments from being based on a single cognitive domain.

animal behavior and cognition↗

bioRxiv2021

Defective flow-migration coupling causes arteriovenous malformations in hereditary hemorrhagic telangiectasia

BackgroundActivin receptor-like kinase 1 (ACVRL1, hereafter ALK1) is an endothelial transmembrane serine threonine kinase receptor for BMP family ligands that plays a critical role in cardiovascular development and pathology. Loss-of-function mutations in the ALK1 gene cause type 2 hereditary hemorrhagic telangiectasia (HHT), a devastating disorder that leads to arteriovenous malformations (AVMs). Here we show that ALK1 controls endothelial cell polarization against the direction of blood flow and flow-induced endothelial migration from veins through capillaries into arterioles. MethodsUsing Cre lines that recombine in different subsets of arterial, capillary-venous or endothelial tip cells, we showed that capillary-venous Alk1 deletion was sufficient to induce AVM formation in the postnatal retina. ResultsALK1 deletion impaired capillary-venous endothelial cell polarization against the direction of blood flow in vivo and in vitro. Mechanistically, ALK1 deficient cells exhibited increased integrin signaling interaction with VEGFR2, which enhanced downstream YAP/TAZ nuclear translocation. Pharmacological inhibition of integrin or YAP/TAZ signaling rescued flow migration coupling and prevented vascular malformations in Alk1 deficient mice. ConclusionsOur study reveals ALK1 as an essential driver of flow-induced endothelial cell migration and identifies loss of flow-migration coupling as a driver of AVM formation in HHT disease. Integrin-YAP/TAZ signaling blockers are new potential targets to prevent vascular malformations in HHT patients.

cell biology↗

bioRxiv2021

ANALYSIS OF CHD-7 DEFECTIVE DAUER NEMATODES IMPLICATES COLLAGEN MISREGULATION IN CHARGE SYNDROME FEATURES.

CHARGE syndrome is a complex developmental disorder caused by mutations in the chromodomain helicase DNA-binding protein7 (CHD7) and characterized by retarded growth and malformations in the heart and nervous system. Despite the public health relevance of this disorder, relevant targets of CHD7 that relate to disease pathology are still poorly understood. Here we report that chd-7, the nematode ortholog of Chd7, is required for dauer morphogenesis, lifespan determination, and stress response. Consistent with our discoveries, we found chd-7 to be allelic to scd-3, a previously identified dauer suppressor from the TGF-{beta} pathway. Notably, DAF-12 promoted chd-7 expression, which is necessary to repress daf-9 for execution of the dauer program. Transcriptomic analysis comparing chd-7-defective and normal dauers showed enrichment of collagen genes, consistent with a conserved role for the TGF-{beta} pathway in formation of the extracellular matrix. To validate a conserved function for chd-7 in vertebrates, we used Xenopus laevis embryos, an established model to study craniofacial development. Morpholino mediated knockdown of Chd7 led to a reduction in col2a1 mRNA levels. Both embryonic lethality and craniofacial defects in Chd7-depleted tadpoles were partially rescued by over-expression of col2a1 mRNA. We suggest that pathogenic features of CHARGE syndrome caused by Chd7 mutations, such as craniofacial malformations, result from the reduction of collagen levels, implying that the extracellular matrix might represent a critical target of Chd7 in CHARGE development. SIGNIFICANCE STATEMENTCHARGE Syndrome is a complex developmental disorder caused by mutations in the chromodomain helicase DNA-binding protein-7 (CHD7). Unfortunately, the cellular events that lead to CHARGE syndrome are still poorly understood. In C. elegans, we identified chd-7 in a screen for suppressors of dauer formation, an alternative larval stage that develops in response to sensory signals of a harsh environment. We found that chd-7 regulates expression of collagens, which constitute the worms cuticle, a specialized extracellular matrix. In frogs embryos, we show that Chd7 inhibition leads to poor Col2a1, which is necessary and sufficient to exhibit CHARGE features. These studies establish C. elegans as an amenable animal model to study the etiology of the developmental defects associated with pathogenic Chd7.

genetics↗