Touch neurons underlying dopaminergic pleasurable touch and sexual receptivity.

Pleasurable touch is paramount during social behavior, including sexual encounters. However, the identity and precise role of sensory neurons that transduce sexual touch remain unknown. A population of sensory neurons labeled by developmental expression of the G protein-coupled receptor Mrgprb4 detects mechanical stimulation in mice. Here, we study the social relevance of Mrgprb4-lineage neurons and reveal that these neurons are required for sexual receptivity and sufficient to induce dopamine release in the brain. Even in social isolation, optogenetic stimulation of Mrgprb4-lineage neurons through the back skin is sufficient to induce a conditioned place preference and a striking dorsiflexion resembling the lordotic copulatory posture. In the absence of Mrgprb4-lineage neurons, female mice no longer find male mounts rewarding: sexual receptivity is supplanted by aggression and a coincident decline in dopamine release in the nucleus accumbens. Together, these findings establish that Mrgprb4-lineage neurons initiate a skin-to-brain circuit encoding the rewarding quality of social touch.

Diverse CMT2 neuropathies are linked to aberrant G3BP interactions in stress granules.

Complex diseases often involve the interplay between genetic and environmental factors. Charcot-Marie-Tooth type 2 neuropathies (CMT2) are a group of genetically heterogeneous disorders, in which similar peripheral neuropathology is inexplicably caused by various mutated genes. Their possible molecular links remain elusive. Here, we found that upon environmental stress, many CMT2-causing mutant proteins adopt similar properties by entering stress granules (SGs), where they aberrantly interact with G3BP and integrate into SG pathways. For example, glycyl-tRNA synthetase (GlyRS) is translocated from the cytoplasm into SGs upon stress, where the mutant GlyRS perturbs the G3BP-centric SG network by aberrantly binding to G3BP. This disrupts SG-mediated stress responses, leading to increased stress vulnerability in motoneurons. Disrupting this aberrant interaction rescues SG abnormalities and alleviates motor deficits in CMT2D mice. These findings reveal a stress-dependent molecular link across diverse CMT2 mutants and provide a conceptual framework for understanding genetic heterogeneity in light of environmental stress.

Epigenetic memory of coronavirus infection in innate immune cells and their progenitors.

Inflammation can trigger lasting phenotypes in immune and non-immune cells. Whether and how human infections and associated inflammation can form innate immune memory in hematopoietic stem and progenitor cells (HSPC) has remained unclear. We found that circulating HSPC, enriched from peripheral blood, captured the diversity of bone marrow HSPC, enabling investigation of their epigenomic reprogramming following coronavirus disease 2019 (COVID-19). Alterations in innate immune phenotypes and epigenetic programs of HSPC persisted for months to 1 year following severe COVID-19 and were associated with distinct transcription factor (TF) activities, altered regulation of inflammatory programs, and durable increases in myelopoiesis. HSPC epigenomic alterations were conveyed, through differentiation, to progeny innate immune cells. Early activity of IL-6 contributed to these persistent phenotypes in human COVID-19 and a mouse coronavirus infection model. Epigenetic reprogramming of HSPC may underlie altered immune function following infection and be broadly relevant, especially for millions of COVID-19 survivors.

Mechanoreceptor synapses in the brainstem shape the central representation of touch.

Mammals use glabrous (hairless) skin of their hands and feet to navigate and manipulate their environment. Cortical maps of the body surface across species contain disproportionately large numbers of neurons dedicated to glabrous skin sensation, in part reflecting a higher density of mechanoreceptors that innervate these skin regions. Here, we find that disproportionate representation of glabrous skin emerges over postnatal development at the first synapse between peripheral mechanoreceptors and their central targets in the brainstem. Mechanoreceptor synapses undergo developmental refinement that depends on proximity of their terminals to glabrous skin, such that those innervating glabrous skin make synaptic connections that expand their central representation. In mice incapable of sensing gentle touch, mechanoreceptors innervating glabrous skin still make more powerful synapses in the brainstem. We propose that the skin region a mechanoreceptor innervates controls the developmental refinement of its central synapses to shape the representation of touch in the brain.

Neurobiology, Stem Cell Biology, and Immunology: An Emerging Triad for Understanding Tissue Homeostasis and Repair.

The peripheral nervous system (PNS) endows animals with the remarkable ability to sense and respond to a dynamic world. Emerging evidence shows the PNS also participates in tissue homeostasis and repair by integrating local changes with organismal and environmental changes. Here, we provide an in-depth summary of findings delineating the diverse roles of peripheral nerves in modulating stem cell behaviors and immune responses under steady-state conditions and in response to injury and duress, with a specific focus on the skin and the hematopoietic system. These examples showcase how elucidating neuro-stem cell and neuro-immune cell interactions provides a conceptual framework that connects tissue biology and local immunity with systemic bodily changes to meet varying demands. They also demonstrate how changes in these interactions can manifest in stress, aging, cancer, and inflammation, as well as how these findings can be harnessed to guide the development of new therapeutics.

Microbiota-Induced Type I Interferons Instruct a Poised Basal State of Dendritic Cells.

Environmental signals shape host physiology and fitness. Microbiota-derived cues are required to program conventional dendritic cells (cDCs) during the steady state so that they can promptly respond and initiate adaptive immune responses when encountering pathogens. However, the molecular underpinnings of microbiota-guided instructive programs are not well understood. Here, we report that the indigenous microbiota controls constitutive production of type I interferons (IFN-I) by plasmacytoid DCs. Using genome-wide analysis of transcriptional and epigenetic regulomes of cDCs from germ-free and IFN-I receptor (IFNAR)-deficient mice, we found that tonic IFNAR signaling instructs a specific epigenomic and metabolic basal state that poises cDCs for future pathogen combat. However, such beneficial biological function comes with a trade-off. Instructed cDCs can prime T cell responses against harmless peripheral antigens when removing roadblocks of peripheral tolerance. Our data provide fresh insights into the evolutionary trade-offs that come with successful adaptation of vertebrates to their microbial environment.

An Airway Protection Program Revealed by Sweeping Genetic Control of Vagal Afferents.

Sensory neurons initiate defensive reflexes that ensure airway integrity. Dysfunction of laryngeal neurons is life-threatening, causing pulmonary aspiration, dysphagia, and choking, yet relevant sensory pathways remain poorly understood. Here, we discover rare throat-innervating neurons (∼100 neurons/mouse) that guard the airways against assault. We used genetic tools that broadly cover a vagal/glossopharyngeal sensory neuron atlas to map, ablate, and control specific afferent populations. Optogenetic activation of vagal P2RY1 neurons evokes a coordinated airway defense program-apnea, vocal fold adduction, swallowing, and expiratory reflexes. Ablation of vagal P2RY1 neurons eliminates protective responses to laryngeal water and acid challenge. Anatomical mapping revealed numerous laryngeal terminal types, with P2RY1 neurons forming corpuscular endings that appose laryngeal taste buds. Epithelial cells are primary airway sentinels that communicate with second-order P2RY1 neurons through ATP. These findings provide mechanistic insights into airway defense and a general molecular/genetic roadmap for internal organ sensation by the vagus nerve.

Natural Killer Cells Degenerate Intact Sensory Afferents following Nerve Injury.

Sensory axons degenerate following separation from their cell body, but partial injury to peripheral nerves may leave the integrity of damaged axons preserved. We show that an endogenous ligand for the natural killer (NK) cell receptor NKG2D, Retinoic Acid Early 1 (RAE1), is re-expressed in adult dorsal root ganglion neurons following peripheral nerve injury, triggering selective degeneration of injured axons. Infiltration of cytotoxic NK cells into the sciatic nerve by extravasation occurs within 3 days following crush injury. Using a combination of genetic cell ablation and cytokine-antibody complex stimulation, we show that NK cell function correlates with loss of sensation due to degeneration of injured afferents and reduced incidence of post-injury hypersensitivity. This neuro-immune mechanism of selective NK cell-mediated degeneration of damaged but intact sensory axons complements Wallerian degeneration and suggests the therapeutic potential of modulating NK cell function to resolve painful neuropathy through the clearance of partially damaged nerves.

Antigen-presenting cells as specialized drivers of intestinal T cell functions.

The immune system recognizes a multitude of innocuous antigens from food and intestinal commensal microbes toward which it orchestrates appropriate, non-inflammatory responses. This process requires antigen-presenting cells (APCs) that induce T cells with either regulatory or effector functions. Compromised APC function disrupts the T cell balance, leading to inflammation and dysbiosis. Although their precise identities continue to be debated, it has become clear that multiple APC lineages direct the differentiation of distinct microbiota-specific CD4+ T cell programs. Here, we review how unique APC subsets instruct T cell differentiation and function in response to microbiota and dietary antigens. These discoveries provide new opportunities to investigate T cell-APC regulatory networks controlling immune homeostasis and perturbations associated with inflammatory and allergic diseases.

CD4+ T cell activation distinguishes response to anti-PD-L1+anti-CTLA4 therapy from anti-PD-L1 monotherapy.

Cancer patients often receive a combination of antibodies targeting programmed death-ligand 1 (PD-L1) and cytotoxic T lymphocyte antigen-4 (CTLA4). We conducted a window-of-opportunity study in head and neck squamous cell carcinoma (HNSCC) to examine the contribution of anti-CTLA4 to anti-PD-L1 therapy. Single-cell profiling of on- versus pre-treatment biopsies identified T cell expansion as an early response marker. In tumors, anti-PD-L1 triggered the expansion of mostly CD8+ T cells, whereas combination therapy expanded both CD4+ and CD8+ T cells. Such CD4+ T cells exhibited an activated T helper 1 (Th1) phenotype. CD4+ and CD8+ T cells co-localized with and were surrounded by dendritic cells expressing T cell homing factors or antibody-producing plasma cells. T cell receptor tracing suggests that anti-CTLA4, but not anti-PD-L1, triggers the trafficking of CD4+ naive/central-memory T cells from tumor-draining lymph nodes (tdLNs), via blood, to the tumor wherein T cells acquire a Th1 phenotype. Thus, CD4+ T cell activation and recruitment from tdLNs are hallmarks of early response to anti-PD-L1 plus anti-CTLA4 in HNSCC.

Spheromers reveal robust T cell responses to the Pfizer/BioNTech vaccine and attenuated peripheral CD8+ T cell responses post SARS-CoV-2 infection.

T cells are a critical component of the response to SARS-CoV-2, but their kinetics after infection and vaccination are insufficiently understood. Using "spheromer" peptide-MHC multimer reagents, we analyzed healthy subjects receiving two doses of the Pfizer/BioNTech BNT162b2 vaccine. Vaccination resulted in robust spike-specific T cell responses for the dominant CD4+ (HLA-DRB1∗15:01/S191) and CD8+ (HLA-A∗02/S691) T cell epitopes. Antigen-specific CD4+ and CD8+ T cell responses were asynchronous, with the peak CD4+ T cell responses occurring 1 week post the second vaccination (boost), whereas CD8+ T cells peaked 2 weeks later. These peripheral T cell responses were elevated compared with COVID-19 patients. We also found that previous SARS-CoV-2 infection resulted in decreased CD8+ T cell activation and expansion, suggesting that previous infection can influence the T cell response to vaccination.

Macrophages facilitate peripheral nerve regeneration by organizing regeneration tracks through Plexin-B2.

The regeneration of peripheral nerves is guided by regeneration tracks formed through an interplay of many cell types, but the underlying signaling pathways remain unclear. Here, we demonstrate that macrophages are mobilized ahead of Schwann cells in the nerve bridge after transection injury to participate in building regeneration tracks. This requires the function of guidance receptor Plexin-B2, which is robustly up-regulated in infiltrating macrophages in injured nerves. Conditional deletion of Plexin-B2 in myeloid lineage resulted in not only macrophage misalignment but also matrix disarray and Schwann cell disorganization, leading to misguided axons and delayed functional recovery. Plexin-B2 is not required for macrophage recruitment or activation but enables macrophages to steer clear of colliding axons, in particular the growth cones at the tip of regenerating axons, leading to parallel alignment postcollision. Together, our studies unveil a novel reparative function of macrophages and the importance of Plexin-B2-mediated collision-dependent contact avoidance between macrophages and regenerating axons in forming regeneration tracks during peripheral nerve regeneration.

Shaping hematopoietic cell ecosystems through galectin-glycan interactions.

Hematopoiesis- the formation of blood cell components- continually replenishes the blood system during embryonic development and postnatal lifespans. This coordinated process requires the synchronized action of a broad range of cell surface associated proteins and soluble mediators, including growth factors, cytokines and lectins. Collectively, these mediators control cellular communication, signalling, commitment, proliferation, survival and differentiation. Here we discuss the role of galectins - an evolutionarily conserved family of glycan-binding proteins - in the establishment and dynamic remodelling of hematopoietic niches. We focus on the contribution of galectins to B and T lymphocyte development and selection, as well as studies highlighting the role of these proteins in myelopoiesis, with particular emphasis on erythropoiesis and megakaryopoiesis. Finally, we also highlight recent findings suggesting the role of galectin-1, a prototype member of this protein family, as a key pathogenic factor and therapeutic target in myelofibrosis. Through extracellular or intracellular mechanisms, galectins can influence the fate and function of distinct hematopoietic progenitors and fine-tune the final repertoire of blood cells, with critical implications in a wide range of physiologically vital processes including innate and adaptive immunity, immune tolerance programs, tissue repair, regeneration, angiogenesis, inflammation, coagulation and oxygen delivery. Additionally, positive or negative regulation of galectin-driven circuits may contribute to a broad range of blood cell disorders.

Sodium Channels in Human Pain Disorders: Genetics and Pharmacogenomics.

Acute pain is adaptive, but chronic pain is a global challenge. Many chronic pain syndromes are peripheral in origin and reflect hyperactivity of peripheral pain-signaling neurons. Current treatments are ineffective or only partially effective and in some cases can be addictive, underscoring the need for better therapies. Molecular genetic studies have now linked multiple human pain disorders to voltage-gated sodium channels, including disorders characterized by insensitivity or reduced sensitivity to pain and others characterized by exaggerated pain in response to normally innocuous stimuli. Here, we review recent developments that have enhanced our understanding of pathophysiological mechanisms in human pain and advances in targeting sodium channels in peripheral neurons for the treatment of pain using novel and existing sodium channel blockers.

A neuro-lymphatic communication guides lymphatic development by CXCL12/CXCR4 signaling.

Lymphatic vessels grow through active sprouting and mature into a vascular complex including lymphatic capillaries and collecting vessels that ensure fluid transport. However, the signaling cues that direct lymphatic sprouting and patterning remains unclear. In this study, we demonstrated the chemokine signaling, specifically through CXCL12/CXCR4 plays critical roles in regulating lymphatic development. We showed that LEC specific CXCR4 deficient embryos and CXCL12 mutant embryos exhibited server defects in lymphatic sprouting, migration, and lymphatic valve formation. We also discovered that CXCL12, originating from peripheral nerves, directs the migration of dermal lymphatic vessels to align with nerves in developing skin. Deletion CXCR4 or blockage of CXCL12/CXCR4 activity results in reduced VEGFR3 levels on the LEC surface. This, in turn, impairs VEGFC mediated VEGFR3 signaling and downstream PI3K/AKT activities. Taken together, these data identify previously unknown chemokine signaling originating from peripheral nerves that guides dermal lymphatic sprouting and patterning. Our work identifies for the first time a neuro-lymphatics communications during mouse development and reveals a novel mechanism by which CXCR4 modulates VEGFC/VEGFR3/AKT signaling.

The rapidly changing landscape in mature T-cell lymphoma (MTCL) biology and management.

Historical advances in the care of patients with non-Hodgkin lymphoma (NHL) have been restricted largely to patients with B-cell lymphoma. The peripheral T-cell lymphomas (PTCLs), which are rare and heterogeneous in nature, have yet to experience the same degree of improvement in outcome over the past 20 to 30 years. It is estimated that there are approximately 80,000 and 14,000 cases, respectively, of NHL and Hodgkin lymphoma per year in the United States. As a subgroup of NHL, the PTCLs account for 6% to 10% of all cases of NHL, making them exceedingly rare. In addition, the World Health Organization 2017 classification describes 29 distinct subtypes of PTCL. This intrinsic diversity, coupled with its rarity, has stymied progress in the disease. In addition, most subtypes carry an inferior prognosis compared with their B-cell counterparts, an outcome largely attributed to the fact that most treatment paradigms for patients with PTCL have been derived from B-cell neoplasms, a radically different disease. In fact, the first drug ever approved for patients with PTCL was approved only a decade ago. The plethora of recent drug approvals in PTCL, coupled with a deeper understanding of the molecular pathogenesis of the disease, has stimulated the field to pursue new avenues of research that are now largely predicated on the development of novel, targeted small molecules, which include a host of epigenetic modifiers and biologics. There is an expectation these advances may begin to favorably challenge the chemotherapy paradigms that have been used in the T-cell malignancies.

An Isoprene Lipid-Binding Protein Promotes Eukaryotic Coenzyme Q Biosynthesis.

The biosynthesis of coenzyme Q presents a paradigm for how cells surmount hydrophobic barriers in lipid biology. In eukaryotes, CoQ precursors-among nature's most hydrophobic molecules-must somehow be presented to a series of enzymes peripherally associated with the mitochondrial inner membrane. Here, we reveal that this process relies on custom lipid-binding properties of COQ9. We show that COQ9 repurposes the bacterial TetR fold to bind aromatic isoprenes with high specificity, including CoQ intermediates that likely reside entirely within the bilayer. We reveal a process by which COQ9 associates with cardiolipin-rich membranes and warps the membrane surface to access this cargo. Finally, we identify a molecular interface between COQ9 and the hydroxylase COQ7, motivating a model whereby COQ9 presents intermediates directly to CoQ enzymes. Overall, our results provide a mechanism for how a lipid-binding protein might access, select, and deliver specific cargo from a membrane to promote biosynthesis.

Capturing RAS oligomerization on a membrane.

RAS GTPases associate with the biological membrane where they function as molecular switches to regulate cell growth. Recent studies indicate that RAS proteins oligomerize on membranes, and disrupting these assemblies represents an alternative therapeutic strategy. However, conflicting reports on RAS assemblies, ranging in size from dimers to nanoclusters, have brought to the fore key questions regarding the stoichiometry and parameters that influence oligomerization. Here, we probe three isoforms of RAS [Kirsten Rat Sarcoma viral oncogene (KRAS), Harvey Rat Sarcoma viral oncogene (HRAS), and Neuroblastoma oncogene (NRAS)] directly from membranes using mass spectrometry. We show that KRAS on membranes in the inactive state (GDP-bound) is monomeric but forms dimers in the active state (GTP-bound). We demonstrate that the small molecule BI2852 can induce dimerization of KRAS, whereas the binding of effector proteins disrupts dimerization. We also show that RAS dimerization is dependent on lipid composition and reveal that oligomerization of NRAS is regulated by palmitoylation. By monitoring the intrinsic GTPase activity of RAS, we capture the emergence of a dimer containing either mixed nucleotides or GDP on membranes. We find that the interaction of RAS with the catalytic domain of Son of Sevenless (SOScat) is influenced by membrane composition. We also capture the activation and monomer to dimer conversion of KRAS by SOScat. These results not only reveal the stoichiometry of RAS assemblies on membranes but also uncover the impact of critical factors on oligomerization, encompassing regulation by nucleotides, lipids, and palmitoylation.

Different temporal dynamics of foveal and peripheral visual processing during fixation.

Humans explore visual scenes by alternating short fixations with saccades directing the fovea to points of interest. During fixation, the visual system not only examines the foveal stimulus at high resolution, but it also processes the extrafoveal input to plan the next saccade. Although foveal analysis and peripheral selection occur in parallel, little is known about the temporal dynamics of foveal and peripheral processing upon saccade landing, during fixation. Here we investigate whether the ability to localize changes across the visual field differs depending on when the change occurs during fixation, and on whether the change localization involves foveal, extrafoveal processing, or both. Our findings reveal that the ability to localize changes in peripheral areas of the visual field improves as a function of time after fixation onset, whereas localization accuracy for foveal stimuli remains approximately constant. Importantly, this pattern holds regardless of whether individuals monitor only foveal or peripheral stimuli, or both simultaneously. Altogether, these results show that the visual system is more attuned to the foveal input early on during fixation, whereas change localization for peripheral stimuli progressively improves throughout fixation, possibly as a consequence of an increased readiness to plan the next saccade.

Propagation of distinct CWD prion strains during peripheral and intracerebral challenges of gene-targeted mice.

Since prion diseases result from infection and neurodegeneration of the central nervous system (CNS), experimental characterizations of prion strain properties customarily rely on the outcomes of intracerebral challenges. However, natural transmission of certain prions, including those causing chronic wasting disease (CWD) in elk and deer, depends on propagation in peripheral host compartments prior to CNS infection. Using gene-targeted GtE and GtQ mice, which accurately control cellular elk or deer PrP expression, we assessed the impact that peripheral or intracerebral exposures play on CWD prion strain propagation and resulting CNS abnormalities. Whereas oral and intraperitoneal transmissions produced identical neuropathological outcomes in GtE and GtQ mice and preserved the naturally convergent conformations of elk and deer CWD prions, intracerebral transmissions generated CNS prion strains with divergent biochemical properties in GtE and GtQ mice that were changed compared to their native counterparts. While CWD replication kinetics remained constant during iterative peripheral transmissions and brain titers reflected those found in native hosts, serial intracerebral transmissions produced 10-fold higher prion titers and accelerated incubation times. Our demonstration that peripherally and intracerebrally challenged Gt mice develop dissimilar CNS diseases which result from the propagation of distinct CWD prion strains points to the involvement of tissue-specific cofactors during strain selection in different host compartments. Since peripheral transmissions preserved the natural features of elk and deer prions, whereas intracerebral propagation produced divergent strains, our findings illustrate the importance of experimental characterizations using hosts that not only abrogate species barriers but also accurately recapitulate natural transmission routes of native strains.