The Characterization of Hematopoiesis in Murine Fetal Bone Marrow

Hematopoietic stem cells (HSCs) and their downstream progenitors are a heterogeneous population of cells that are indispensable for lifelong hematopoiesis and are often utilized in the clinic for the treatment of hematologic maladies via hematopoietic stem cell transplantation (HSCT). Over several decades, it has been discovered that HSCs arise in the dorsal aorta of the developing embryo, migrate to the fetal liver (FL), and undergo a large expansion before reaching their final resting place in the bone marrow (BM). Many resources have been invested in understanding the roles of the different niches HSCs encounter along their journey. A greater understanding of HSC niche regulation could provide clues for HSC maintenance and expansion in vitro. One critical niche during HSC ontogeny that has been greatly overlooked is the fetal BM (FBM), of which the hematopoietic and HSC niche compartments are poorly understood. For this reason, we meticulously characterized the hematopoietic progenitor compartment of the whole skeleton FBM from its colonization until after birth via competitive transplantation, immunophenotypic analysis of the hematopoietic stem and progenitor cell (HSPC) compartment, functional assessment of specific progenitor populations, and single-cell RNA-sequencing (scRNA-Seq) of the hematopoietic and stromal FBM environment. Here, we provide the first report of the presence of bona fide HSCs within the E15.5 FBM. We also found that HSCs were present in the all sources of BM, including the forelimbs, hindlimbs, and trunk of E15.5 embryos. We are also the first to assess the BM immunophenotypic HSPC compartment from initial seeding to adulthood and found that specific multipotent progenitor (MPP) cells (MPP2s) are the predominant HSPC population in the FBM, appearing to have the ability to migrate to and seed the FBM directly from the FL. Interestingly, immunophenotypic MPP2s are not functional in vitro or in vivo until birth (E18.5-P0), and display reduced repopulating capacity compared to adult BM and time-matched FL MPP2s. Also, the frequencies of the different FBM HSPCs shift around birth from an MPP2-dominant phenotype to the MPP3/MPP4-dominant phenotype seen in adult BM. To identify the intrinsic and extrinsic mechanisms controlling MPP2 functional maturation, we isolated stromal and hematopoietic progenitor (HP) populations from E16.5, E18.5, P0, and adult BM, and constructed the first known scRNA-Seq dataset spanning the HP and stromal compartment across BM ontogeny. Preliminary analysis of our scRNA-Seq datasets show that the FBM stroma and HP compartments are compositionally distinct from the adult BM compartments, and this disparity in composition is even more drastic at E16.5, suggesting that the reduced function of FBM MPP2s may be due to a semi-incompatible FBM niche. Our future studies will focus on identifying intrinsic differences between immunophenotypic HSPC populations across FBM ontogeny in our HP scRNA-Seq dataset, as well as defining putative niches for HSPCs in the FBM. We hope that these analyses will identify novel hematopoietic factors in the FBM niche that can be therapeutically exploited to enhance HSC expansion/function/differentiation in the clinic

Monon Greenway – Carmel, IN: Before and After

We will take a comprehensive look at the transformation of the Monon Greenway from a 12-ft-wide trail, to a pedestrian-prioritized, multi-modal street running through the heart of the City of Carmel. Topics covered include: reviewing key project objectives and evaluating if they were met; analyzing bicycle and pre- and post-pedestrian usage and the benefits of designing to prioritize pedestrian connectivity; the realized benefits of the project due to stakeholder involvement and infrastructure investment; and lessons learned

Radically open dialectical behavior therapy: Social signaling, transdiagnostic utility and current evidence

At the core of an overcontrolled personality and coping style is a tendency to have too much self-control, exhibiting as behavioral and cognitive inflexibility, high inhibition of emotion, high detail-focused processing and perfectionism, and a lack of social connectedness. Overcontrol underlies a wide variety of psychiatric illnesses and as such, an innovative transdiagnostic therapy called Radically Open Dialectical Behavior Therapy (RO DBT) has been developed to treat disorders characterized by overcontrol. RO DBT targets maladaptive social signaling in order to help individuals rejoin the tribe, hypothesizing that increasing social connectedness by means of targeting social signaling is the central mechanism of change in treatment. Because RO DBT is used for individuals with an overcontrolled personality style, rather than individual disordered symptoms, it can be used transdiagnostically across a range of comorbid disorders, including treatment-resistant depression and anxiety, anorexia nervosa, and personality disorders such as obsessive-compulsive personality disorder. The current article introduces this novel treatment approach and discusses its emphasis on social signaling and its transdiagnostic nature. We then provide the first review of existing literature testing the efficacy of RO DBT across clinical populations, discuss issues related to assessment of overcontrol, and speculate on future directions for this novel therapy

Regulation and Function of Activity-Dependent Homer in Synaptic Plasticity

Alterations in synaptic signaling and plasticity occur during the refinement of neural circuits over the course of development and the adult processes of learning and memory. Synaptic plasticity requires the rearrangement of protein complexes in the postsynaptic density (PSD), trafficking of receptors and ion channels and the synthesis of new proteins. Activity-induced short Homer proteins, Homer1a and Ania-3, are recruited to active excitatory synapses, where they act as dominant negative regulators of constitutively expressed, longer Homer isoforms. The expression of Homer1a and Ania-3 initiates critical processes of PSD remodeling, the modulation of glutamate receptor-mediated functions, and the regulation of calcium signaling. Together, available data support the view that Homer1a and Ania-3 are responsible for the selective, transient destabilization of postsynaptic signaling complexes to facilitate plasticity of the excitatory synapse. The interruption of activity-dependent Homer proteins disrupts disease-relevant processes and leads to memory impairments, reflecting their likely contribution to neurological disorders

Rescue of long-term memory after reconsolidation blockade

Memory reconsolidation is considered to be the process whereby stored memories become labile on recall, allowing updating. Blocking the restabilization of a memory during reconsolidation is held to result in a permanent amnesia. The targeted knockdown of either Zif268 or Arc levels in the brain, and inhibition of protein synthesis, after a brief recall results in a non-recoverable retrograde amnesia, known as reconsolidation blockade. These experimental manipulations are seen as key proof for the existence of reconsolidation. However, here we demonstrate that despite disrupting the molecular correlates of reconsolidation in the hippocampus, rodents are still able to recover contextual memories. Our results challenge the view that reconsolidation is a separate memory process and instead suggest that the molecular events activated initially at recall act to constrain premature extinction

Cyfip1 Haploinsufficiency Does Not Alter GABAA Receptor δ-Subunit Expression and Tonic Inhibition in Dentate Gyrus PV+ Interneurons and Granule Cells

Copy number variation (CNV) at chromosomal region 15q11.2 is linked to increased risk of neurodevelopmental disorders including autism and schizophrenia. A significant gene at this locus is cytoplasmic fragile X mental retardation protein (FMRP) interacting protein 1 (CYFIP1). CYFIP1 protein interacts with FMRP, whose monogenic absence causes fragile X syndrome (FXS). Fmrp knock-out has been shown to reduce tonic GABAergic inhibition by interacting with the δ-subunit of the GABAA receptor (GABAAR). Using in situ hybridization (ISH), qPCR, Western blotting techniques, and patch clamp electrophysiology in brain slices from a Cyfip1 haploinsufficient mouse, we examined δ-subunit mediated tonic inhibition in the dentate gyrus (DG). In wild-type (WT) mice, DG granule cells (DGGCs) responded to the δ-subunit-selective agonist THIP with significantly increased tonic currents. In heterozygous mice, no significant difference was observed in THIP-evoked currents in DGGCs. Phasic GABAergic inhibition in DGGC was also unaltered with no difference in properties of spontaneous IPSCs (sIPSCs). Additionally, we demonstrate that DG granule cell layer (GCL) parvalbumin-positive interneurons (PV+-INs) have functional δ-subunit-mediated tonic GABAergic currents which, unlike DGGC, are also modulated by the α1-selective drug zolpidem. Similar to DGGC, both IPSCs and THIP-evoked currents in PV+-INs were not different between Cyfip1 heterozygous and WT mice. Supporting our electrophysiological data, we found no significant change in hippocampal δ-subunit mRNA expression or protein level and no change in α1/α4-subunit mRNA expression. Thus, Cyfip1 haploinsufficiency, mimicking human 15q11.2 microdeletion syndrome, does not alter hippocampal phasic or tonic GABAergic inhibition, substantially differing from the Fmrp knock-out mouse model

Serial subtraction by sevens significantly alters limb knee adduction during lateral step-down when compared to the Stroop color-word test

"Dual tasking pairs movement and cognitive tasks to simulate real-world movement conditions. Dual tasking can lead to increased injury risk while performing dynamic lower limb movements. Bilateral asymmetry in neuromuscular control is suggested to play a role in the risk for lower limb injuries. Lower limb dominance influences motor control."--Introduction

Hippocampal Regulation of Postsynaptic Density Homer1 by Associative Learning

Genes involved in synaptic plasticity, particularly genes encoding postsynaptic density proteins, have been recurrently linked to psychiatric disorders including schizophrenia and autism. Postsynaptic density Homer1 proteins contribute to synaptic plasticity through the competing actions of short and long isoforms. The activity-induced expression of shortHomer1isoforms,Homer1aandAnia-3, is thought to be related to processes of learning and memory. However, the precise regulation ofHomer1aandAnia-3with different components of learning has not been investigated. Here, we used in situ hybridization to quantify short and longHomer1expression in the hippocampus following consolidation, retrieval, and extinction of associative fear memory, using contextual fear conditioning in rats.Homer1aandAnia-3, but not longHomer1, were regulated by contextual fear learning or novelty detection, although their precise patterns of expression in hippocampal subregions were dependent on the isoform. We also show for the first time that the two short Homer1 isoforms are regulated after the retrieval and extinction of contextual fear memory, albeit with distinct temporal and spatial profiles. These findings support a role of activity-induced Homer1 isoforms in learning and memory processes in discrete hippocampal subregions and suggest that Homer1a and Ania-3 may play separable roles in synaptic plasticity.</jats:p

FMRP and CYFIP1 at the synapse and their role in psychiatric vulnerability

There is increasing awareness of the role genetic risk variants have in mediating vulnerability to psychiatric disorders such as schizophrenia and autism. Many of these risk variants encode synaptic proteins, influencing biological pathways of the postsynaptic density and, ultimately, synaptic plasticity. Fragile X Mental Retardation 1 (FMR1) and Cytoplasmic FRMP-Interacting Protein (CYFIP1) contain two such examples of highly penetrant risk variants and encode synaptic proteins with shared functional significance. In this Review, we will discuss the biological actions of FMRP and CYFIP1, including their regulation of i) protein translation and specifically FMRP targets, ii) dendritic and spine morphology and iii) forms of synaptic plasticity such as long-term depression. We draw upon a range of preclinical studies that have used genetic dosage models of FMR1 and CYFIP1 to determine their biological function. In parallel, we discuss how clinical studies of Fragile X Syndrome or 15q11.2 deletion patients have informed our understanding of FMRP and CYFIP1 proteins, and highlight the latest psychiatric genomic findings that continue to implicate FMRP and CYFIP1. Lastly, we assess the current limitations in our understanding of FMRP and CYFIP1 biology and how they must be addressed before mechanism-led therapeutic strategies can be developed for psychiatric disorders