The transcription factor c-Maf controls touch receptor development and function

Terminal differentiation and persistence of effector regulatory T cells essential for preventing intestinal inflammation

Regulatory T (Treg) cells are a specialized CD4+ T cell lineage with essential anti-inflammatory functions. Analysis of Treg cell adaptations to non-lymphoid tissues that enable their specialized immunosuppressive and tissue-supportive functions raises questions about the underlying mechanisms of these adaptations and whether they represent stable differentiation or reversible activation states. Here, we characterize distinct colonic effector Treg cell transcriptional programs. Attenuated T cell receptor (TCR) signaling and acquisition of substantial TCR-independent functionality seems to facilitate the terminal differentiation of a population of colonic effector Treg cells that are distinguished by stable expression of the immunomodulatory cytokine IL-10. Functional studies show that this subset of effector Treg cells, but not their expression of IL-10, is indispensable for colonic health. These findings identify core features of the terminal differentiation of effector Treg cells in non-lymphoid tissues and their function.

The activation thresholds and inactivation kinetics of poking-evoked PIEZO1 and PIEZO2 currents are sensitive to subtle variations in mechanical stimulation parameters

PIEZO1 and PIEZO2 are mechanically activated ion channels that confer mechanosensitivity to various cell types. PIEZO channels are commonly examined using the so-called poking technique, where currents are recorded in the whole-cell configuration of the patch-clamp technique, while the cell surface is mechanically stimulated with a small fire-polished patch pipette. Currently, there is no gold standard for mechanical stimulation, and therefore, stimulation protocols differ significantly between laboratories with regard to stimulation velocity, angle, and size of the stimulation probe. Here, we systematically examined the impact of variations in these three stimulation parameters on the outcomes of patch-clamp recordings of PIEZO1 and PIEZO2. We show that the inactivation kinetics of PIEZO1 and, to a lesser extent, of PIEZO2 change with the angle at which the probe that is used for mechanical stimulation is positioned and, even more prominently, with the size of its tip. Moreover, we found that the mechanical activation threshold of PIEZO2, but not PIEZO1, decreased with increasing stimulation speeds. Thus, our data show that two key outcome parameters of PIEZO-related patch-clamp studies are significantly affected by common variations in the mechanical stimulation protocols, which calls for caution when comparing data from different laboratories and highlights the need to establish a gold standard for mechanical stimulation to improve comparability and reproducibility of data obtained with the poking technique.

Restriction of innate Tγδ17 cell plasticity by an AP-1 regulatory axis

IL-17-producing γδ T (Tγδ17) cells are innate-like mediators of intestinal barrier immunity. While Th17 cell and ILC3 plasticity have been extensively studied, the mechanisms governing Tγδ17 cell effector flexibility remain undefined. Here, we combined type 3 fate-mapping with single cell ATAC/RNA-seq multiome profiling to define the cellular features and regulatory networks underlying Tγδ17 cell plasticity. During homeostasis, Tγδ17 cell effector identity was stable across tissues, including for intestinal T-bet+ Tγδ17 cells that restrained IFNγ production. However, S. typhimurium infection induced intestinal Vγ6+ Tγδ17 cell conversion into type 1 effectors, with loss of IL-17A production and partial RORγt downregulation. Multiome analysis revealed a trajectory along Vγ6+ Tγδ17 effector conversion, with TIM-3 marking ex-Tγδ17 cells with enhanced type 1 functionality. Lastly, we characterized and validated a critical AP-1 regulatory axis centered around JunB and Fosl2 that controls Vγ6+ Tγδ17 cell plasticity by stabilizing type 3 identity and restricting type 1 effector conversion.

Maf expression in B cells restricts reactive plasmablast and germinal center B cell expansion

Precise regulation of B cell differentiation is essential for an effective adaptive immune response. Here, we show that B cell development in mice with B cell-specific Maf deletion is unaffected, but marginal zone B cells, germinal centre B cells, and plasmablasts are significantly more frequent in the spleen of naive Maf-deficient mice compared to wild type controls. In the context of a T cell-dependent immunization, Maf deletion causes increased proliferation of germinal centre B cells and extrafollicular plasmablasts. This is accompanied by higher production of antigen-specific IgG1 antibodies with minimal modification of early memory B cells, but a reduction in plasma cell numbers. Single-cell RNA sequencing shows upregulation of genes associated with DNA replication and cell cycle progression, confirming the role of Maf in cell proliferation. Subsequent pathway analysis reveals that Maf influences cellular metabolism, transporter activity, and mitochondrial proteins, which have been implicated in controlling the germinal centre reaction. In summary, our findings demonstrate that Maf acts intrinsically in B cells as a negative regulator of late B cell differentiation, plasmablast proliferation and germinal centre B cell formation.

Molecular regulation of axon termination in mechanosensory neurons

Spatially and temporally accurate termination of axon outgrowth, a process called axon termination, is required for efficient, precise nervous system construction and wiring. The mechanosensory neurons that sense low-threshold mechanical stimulation or gentle touch have proven exceptionally valuable for studying axon termination over the past 40 years. In this Review, we discuss progress made in deciphering the molecular and genetic mechanisms that govern axon termination in touch receptor neurons. Findings across model organisms, including Caenorhabditis elegans, Drosophila, zebrafish and mice, have revealed that complex signaling is required for termination with conserved principles and players beginning to surface. A key emerging theme is that axon termination is mediated by complex signaling networks that include ubiquitin ligase signaling hubs, kinase cascades, transcription factors, guidance/adhesion receptors and growth factors. Here, we begin a discussion about how these signaling networks could represent termination codes that trigger cessation of axon outgrowth in different species and types of mechanosensory neurons.

Recruited atypical Ly6G+ macrophages license alveolar regeneration after lung injury

The lung is constantly exposed to airborne pathogens and particles that can cause alveolar damage. Hence, appropriate repair responses are essential for gas exchange and life. Here, we deciphered the spatiotemporal trajectory and function of an atypical population of macrophages after lung injury. Post-influenza A virus (IAV) infection, short-lived monocyte-derived Ly6G-expressing macrophages (Ly6G+ Macs) were recruited to the alveoli of lung perilesional areas. Ly6G+ Macs engulfed immune cells, exhibited a high metabolic potential, and clustered with alveolar type 2 epithelial cells (AT2s) in zones of active epithelial regeneration. Ly6G+ Macs were partially dependent on granulocyte-macrophage colony-stimulating factor and interleukin-4 receptor signaling and were essential for AT2-dependent alveolar regeneration. Similar macrophages were recruited in other models of injury and in the airspaces of lungs from patients with suspected pneumonia. This study identifies perilesional alveolar Ly6G+ Macs as a spatially restricted, short-lived macrophage subset promoting epithelial regeneration postinjury, thus representing an attractive therapeutic target for treating lung damage.

Molecular and functional profiling of cell diversity and identity in the lateral superior olive, an auditory brainstem center with ascending and descending projections

The lateral superior olive (LSO), a prominent integration center in the auditory brainstem, contains a remarkably heterogeneous population of neurons. Ascending neurons, predominantly principal neurons (pLSOs), process interaural level differences for sound localization. Descending neurons (lateral olivocochlear neurons, LOCs) provide feedback into the cochlea and are thought to protect against acoustic overload. The molecular determinants of the neuronal diversity in the LSO are largely unknown. Here, we used patch-seq analysis in mice at postnatal days P10-12 to classify developing LSO neurons according to their functional and molecular profiles. Across the entire sample (n = 86 neurons), genes involved in ATP synthesis were particularly highly expressed, confirming the energy expenditure of auditory neurons. Two clusters were identified, pLSOs and LOCs. They were distinguished by 353 differentially expressed genes (DEGs), most of which were novel for the LSO. Electrophysiological analysis confirmed the transcriptomic clustering. We focused on genes affecting neuronal input-output properties and validated some of them by immunohistochemistry, electrophysiology, and pharmacology. These genes encode proteins such as osteopontin, Kv11.3, and Kvβ3 (pLSO-specific), calcitonin-gene-related peptide (LOC-specific), or Kv7.2 and Kv7.3 (no DEGs). We identified 12 "Super DEGs" and 12 genes showing "Cluster similarity." Collectively, we provide fundamental and comprehensive insights into the molecular composition of individual ascending and descending neurons in the juvenile auditory brainstem and how this may relate to their specific functions, including developmental aspects.

Blimp-1 and c-Maf regulate immune gene networks to protect against distinct pathways of pathobiont-induced colitis

Intestinal immune responses to microbes are controlled by the cytokine IL-10 to avoid immune pathology. Here, we use single-cell RNA sequencing of colon lamina propria leukocytes (LPLs) along with RNA-seq and ATAC-seq of purified CD4+ T cells to show that the transcription factors Blimp-1 (encoded by Prdm1) and c-Maf co-dominantly regulate Il10 while negatively regulating proinflammatory cytokines in effector T cells. Double-deficient Prdm1fl/flMaffl/flCd4Cre mice infected with Helicobacter hepaticus developed severe colitis with an increase in TH1/NK/ILC1 effector genes in LPLs, while Prdm1fl/flCd4Cre and Maffl/flCd4Cre mice exhibited moderate pathology and a less-marked type 1 effector response. LPLs from infected Maffl/flCd4Cre mice had increased type 17 responses with increased Il17a and Il22 expression and an increase in granulocytes and myeloid cell numbers, resulting in increased T cell-myeloid-neutrophil interactions. Genes over-expressed in human inflammatory bowel disease showed differential expression in LPLs from infected mice in the absence of Prdm1 or Maf, revealing potential mechanisms of human disease.

A mouse DRG genetic toolkit reveals morphological and physiological diversity of somatosensory neuron subtypes

Dorsal root ganglia (DRG) somatosensory neurons detect mechanical, thermal, and chemical stimuli acting on the body. Achieving a holistic view of how different DRG neuron subtypes relay neural signals from the periphery to the CNS has been challenging with existing tools. Here, we develop and curate a mouse genetic toolkit that allows for interrogating the properties and functions of distinct cutaneous targeting DRG neuron subtypes. These tools have enabled a broad morphological analysis, which revealed distinct cutaneous axon arborization areas and branching patterns of the transcriptionally distinct DRG neuron subtypes. Moreover, in vivo physiological analysis revealed that each subtype has a distinct threshold and range of responses to mechanical and/or thermal stimuli. These findings support a model in which morphologically and physiologically distinct cutaneous DRG sensory neuron subtypes tile mechanical and thermal stimulus space to collectively encode a wide range of natural stimuli.

TGF-β specifies TFH versus TH17 cell fates in murine CD4+ T cells through c-Maf

T follicular helper (TFH) cells are essential for effective antibody responses, but deciphering the intrinsic wiring of mouse TFH cells has long been hampered by the lack of a reliable protocol for their generation in vitro. We report that transforming growth factor-β (TGF-β) induces robust expression of TFH hallmark molecules CXCR5 and Bcl6 in activated mouse CD4+ T cells in vitro. TGF-β-induced mouse CXCR5+ TFH cells are phenotypically, transcriptionally, and functionally similar to in vivo-generated TFH cells and provide critical help to B cells. The study further reveals that TGF-β-induced CXCR5 expression is independent of Bcl6 but requires the transcription factor c-Maf. Classical TGF-β-containing T helper 17 (TH17)-inducing conditions also yield separate CXCR5+ and IL-17A-producing cells, highlighting shared and distinct cell fate trajectories of TFH and TH17 cells. We demonstrate that excess IL-2 in high-density T cell cultures interferes with the TGF-β-induced TFH cell program, that TFH and TH17 cells share a common developmental stage, and that c-Maf acts as a switch factor for TFH versus TH17 cell fates in TGF-β-rich environments in vitro and in vivo.

Touch receptor end-organ innervation and function require sensory neuron expression of the transcription factor Meis2

Touch sensation is primarily encoded by mechanoreceptors, called low-threshold mechanoreceptors (LTMRs), with their cell bodies in the dorsal root ganglia. Because of their great diversity in terms of molecular signature, terminal endings morphology, and electrophysiological properties, mirroring the complexity of tactile experience, LTMRs are a model of choice to study the molecular cues differentially controlling neuronal diversification. While the transcriptional codes that define different LTMR subtypes have been extensively studied, the molecular players that participate in their late maturation and in particular in the striking diversity of their end-organ morphological specialization are largely unknown. Here we identified the TALE homeodomain transcription factor Meis2 as a key regulator of LTMRs target-field innervation in mice. Meis2 is specifically expressed in cutaneous LTMRs, and its expression depends on target-derived signals. While LTMRs lacking Meis2 survived and are normally specified, their end-organ innervations, electrophysiological properties, and transcriptome are differentially and markedly affected, resulting in impaired sensory-evoked behavioral responses. These data establish Meis2 as a major transcriptional regulator controlling the orderly formation of sensory neurons innervating peripheral end organs required for light touch.

Intestinal microbiota-specific Th17 cells possess regulatory properties and suppress effector T cells via c-MAF and IL-10

Commensal microbes induce cytokine-producing effector tissue-resident CD4+ T cells, but the function of these T cells in mucosal homeostasis is not well understood. Here, we report that commensal-specific intestinal Th17 cells possess an anti-inflammatory phenotype marked by expression of interleukin (IL)-10 and co-inhibitory receptors. The anti-inflammatory phenotype of gut-resident commensal-specific Th17 cells was driven by the transcription factor c-MAF. IL-10-producing commensal-specific Th17 cells were heterogeneous and derived from a TCF1+ gut-resident progenitor Th17 cell population. Th17 cells acquired IL-10 expression and anti-inflammatory phenotype in the small-intestinal lamina propria. IL-10 production by CD4+ T cells and IL-10 signaling in intestinal macrophages drove IL-10 expression by commensal-specific Th17 cells. Intestinal commensal-specific Th17 cells possessed immunoregulatory functions and curbed effector T cell activity in vitro and in vivo in an IL-10-dependent and c-MAF-dependent manner. Our results suggest that tissue-resident commensal-specific Th17 cells perform regulatory functions in mucosal homeostasis.

Blimp-1 and c-Maf regulate Il10 and negatively regulate common and unique proinflammatory gene networks in IL-12 plus IL-27-driven T helper-1 cells

Background

CD4 + Th1 cells producing IFN-γ are required to eradicate intracellular pathogens, however if uncontrolled these cells can cause immunopathology. The cytokine IL-10 is produced by multiple immune cells including Th1 cells during infection and regulates the immune response to minimise collateral host damage. In this study we aimed to elucidate the transcriptional network of genes controlling the expression of Il10 and proinflammatory cytokines, including Ifng in Th1 cells differentiated from mouse naive CD4 + T cells.

Methods

We applied computational analysis of gene regulation derived from temporal profiling of gene expression clusters obtained from bulk RNA sequencing (RNA-seq) of flow cytometry sorted naïve CD4 + T cells from mouse spleens differentiated in vitro into Th1 effector cells with IL-12 and IL-27 to produce Ifng and Il10, compared to IL-27 alone which express Il10 only , or IL-12 alone which express Ifng and no Il10, or medium control driven-CD4 + T cells which do not express effector cytokines . Data were integrated with analysis of active genomic regions from these T cells using an assay for transposase-accessible chromatin with sequencing (ATAC)-seq, integrated with literature derived-Chromatin-immunoprecipitation (ChIP)-seq data and the RNA-seq data, to elucidate the transcriptional network of genes controlling expression of Il10 and pro-inflammatory effector genes in Th1 cells. The co-dominant role for the transcription factors, Prdm1 (encoding Blimp-1) and Maf (encoding c-Maf) , in cytokine gene regulation in Th1 cells, was confirmed using T cells obtained from mice with T-cell specific deletion of these transcription factors.

Results

We show that the transcription factors Blimp-1 and c-Maf each have unique and common effects on cytokine gene regulation and not only co-operate to induce Il10 gene expression in IL-12 plus IL-27 differentiated mouse Th1 cells, but additionally directly negatively regulate key proinflammatory cytokines including Ifng, thus providing mechanisms for reinforcement of regulated Th1 cell responses.

Conclusions

These data show that Blimp-1 and c-Maf positively and negatively regulate a network of both unique and common anti-inflammatory and pro-inflammatory genes to reinforce a Th1 response in mice that will eradicate pathogens with minimum immunopathology.

Exploring Large MAF Transcription Factors: Functions, Pathology, and Mouse Models with Point Mutations

Large musculoaponeurotic fibrosarcoma (MAF) transcription factors contain acidic, basic, and leucine zipper regions. Four types of MAF have been elucidated in mice and humans, namely c-MAF, MAFA, MAFB, and NRL. This review aimed to elaborate on the functions of MAF transcription factors that have been studied in vivo so far, as well as describe the pathology of human patients and corresponding mouse models with c-MAF, MAFA, and MAFB point mutations. To identify the functions of MAF transcription factors in vivo, we generated genetically modified mice lacking c-MAF, MAFA, and MAFB and analyzed their phenotypes. Further, in recent years, c-MAF, MAFA, and MAFB have been identified as causative genes underpinning many rare diseases. Careful observation of human patients and animal models is important to examine the pathophysiological mechanisms underlying these conditions for targeted therapies. Murine models exhibit phenotypes similar to those of human patients with c-MAF, MAFA, and MAFB mutations. Therefore, generating these animal models emphasizes their usefulness for research uncovering the pathophysiology of point mutations in MAF transcription factors and the development of etiology-based therapies.

Labeling PIEZO2 activity in the peripheral nervous system

Sensory neurons detect mechanical forces from both the environment and internal organs to regulate physiology. PIEZO2 is a mechanosensory ion channel critical for touch, proprioception, and bladder stretch sensation, yet its broad expression in sensory neurons suggests it has undiscovered physiological roles. To fully understand mechanosensory physiology, we must know where and when PIEZO2-expressing neurons detect force. The fluorescent styryl dye FM 1-43 was previously shown to label sensory neurons. Surprisingly, we find that the vast majority of FM 1-43 somatosensory neuron labeling in mice in vivo is dependent on PIEZO2 activity within the peripheral nerve endings. We illustrate the potential of FM 1-43 by using it to identify novel PIEZO2-expressing urethral neurons that are engaged by urination. These data reveal that FM 1-43 is a functional probe for mechanosensitivity via PIEZO2 activation in vivo and will facilitate the characterization of known and novel mechanosensory processes in multiple organ systems.

Opposing gene regulatory programs governing myofiber development and maturation revealed at single nucleus resolution

Skeletal muscle fibers express distinct gene programs during development and maturation, but the underlying gene regulatory networks that confer stage-specific myofiber properties remain unknown. To decipher these distinctive gene programs and how they respond to neural activity, we generated a combined multi-omic single-nucleus RNA-seq and ATAC-seq atlas of mouse skeletal muscle development at multiple stages of embryonic, fetal, and postnatal life. We found that Myogenin, Klf5, and Tead4 form a transcriptional complex that synergistically activates the expression of muscle genes in developing myofibers. During myofiber maturation, the transcription factor Maf acts as a transcriptional switch to activate the mature fast muscle gene program. In skeletal muscles of mutant mice lacking voltage-gated L-type Ca²⁺ channels (Cav1.1), Maf expression and myofiber maturation are impaired. These findings provide a transcriptional atlas of muscle development and reveal genetic links between myofiber formation, maturation, and contraction.

Optogenetic and Chemogenic Control of Pain Signaling: Molecular Markers

Pain is a complex experience that involves physical, emotional, and cognitive aspects. This review focuses specifically on the physiological processes underlying pain perception, with a particular emphasis on the various types of sensory neurons involved in transmitting pain signals to the central nervous system. Recent advances in techniques like optogenetics and chemogenetics have allowed researchers to selectively activate or inactivate specific neuronal circuits, offering a promising avenue for developing more effective pain management strategies. The article delves into the molecular targets of different types of sensory fibers such as channels, for example, TRPV1 in C-peptidergic fiber, TRPA1 in C-non-peptidergic receptors expressed differentially as MOR and DOR, and transcription factors, and their colocalization with the vesicular transporter of glutamate, which enable researchers to identify specific subtypes of neurons within the pain pathway and allows for selective transfection and expression of opsins to modulate their activity.

A bifurcated role for c-Maf in Th2 and Tfh2 cells during helminth infection

Differences in transcriptomes, transcription factor usage, and function have identified T follicular helper 2 (Tfh2) cells and T helper 2 (Th2) cells as distinct clusters of differentiation 4+",(CD4) T-cell subsets in settings of type-2 inflammation. Although the transcriptional programs driving Th2 cell differentiation and cytokine production are well defined, dependence on these classical Th2 programs by Tfh2 cells is less clear. Using cytokine reporter mice in combination with transcription factor inference analysis, the b-Zip transcription factor c-Maf and its targets were identified as an important regulon in both Th2 and Tfh2 cells. Conditional deletion of c-Maf in T cells confirmed its importance in type-2 cytokine expression by Th2 and Tfh2 cells. However, while c-Maf was not required for Th2-driven helminth clearance or lung eosinophilia, it was required for Tfh2-driven Immunoglobulin E production and germinal center formation. This differential regulation of cell-mediated and humoral immunity by c-Maf was a result of redundant pathways in Th2 cells that were absent in Tfh2 cells, and c-Maf-specific mechanisms in Tfh2 cells that were absent in Th2 cells. Thus, despite shared expression by Tfh2 and Th2 cells, c-Maf serves as a unique regulator of Tfh2-driven humoral hallmarks during type-2 immunity.

c-Maf-positive spinal cord neurons are critical elements of a dorsal horn circuit for mechanical hypersensitivity in neuropathy

Corticospinal tract (CST) neurons innervate the deep spinal dorsal horn to sustain chronic neuropathic pain. The majority of neurons targeted by the CST are interneurons expressing the transcription factor c-Maf. Here, we used intersectional genetics to decipher the function of these neurons in dorsal horn sensory circuits. We find that excitatory c-Maf (c-MafEX) neurons receive sensory input mainly from myelinated fibers and target deep dorsal horn parabrachial projection neurons and superficial dorsal horn neurons, thereby connecting non-nociceptive input to nociceptive output structures. Silencing c-MafEX neurons has little effect in healthy mice but alleviates mechanical hypersensitivity in neuropathic mice. c-MafEX neurons also receive input from inhibitory c-Maf and parvalbumin neurons, and compromising inhibition by these neurons caused mechanical hypersensitivity and spontaneous aversive behaviors reminiscent of c-MafEX neuron activation. Our study identifies c-MafEX neurons as normally silent second-order nociceptors that become engaged in pathological pain signaling upon loss of inhibitory control.

A DRG genetic toolkit reveals molecular, morphological, and functional diversity of somatosensory neuron subtypes

Mechanical and thermal stimuli acting on the skin are detected by morphologically and physiologically distinct sensory neurons of the dorsal root ganglia (DRG). Achieving a holistic view of how this diverse neuronal population relays sensory information from the skin to the central nervous system (CNS) has been challenging with existing tools. Here, we used transcriptomic datasets of the mouse DRG to guide development and curation of a genetic toolkit to interrogate transcriptionally defined DRG neuron subtypes. Morphological analysis revealed unique cutaneous axon arborization areas and branching patterns of each subtype. Physiological analysis showed that subtypes exhibit distinct thresholds and ranges of responses to mechanical and/or thermal stimuli. The somatosensory neuron toolbox thus enables comprehensive phenotyping of most principal sensory neuron subtypes. Moreover, our findings support a population coding scheme in which the activation thresholds of morphologically and physiologically distinct cutaneous DRG neuron subtypes tile multiple dimensions of stimulus space.

Tumor-suppressive role of the musculoaponeurotic fibrosarcoma gene in colorectal cancer

Somatic cell reprogramming using the microRNAs miR-200c, miR-302s, and miR-369s leads to increased expression of cyclin-dependent kinase inhibitors in human colorectal cancer (CRC) cells and suppressed tumor growth. Here, we investigated whether these microRNAs inhibit colorectal tumorigenesis in CPC;Apc mice, which are prone to colon and rectal polyps. Repeated administration of microRNAs inhibited polyp formation. Microarray analysis indicated that c-MAF, which reportedly shows oncogene-like behavior in multiple myeloma and T cell lymphoma, decreased in tumor samples but increased in microRNA-treated normal mucosa. Immunohistochemistry identified downregulation of c-MAF as an early tumorigenesis event in CRC, with low c-MAF expression associated with poor prognosis. Of note, c-MAF expression and p53 protein levels were inversely correlated in CRC samples. c-MAF knockout led to enhanced tumor formation in azoxymethane/dextran sodium sulfate-treated mice, with activation of cancer-promoting genes. c-MAF may play a tumor-suppressive role in CRC development.

The gut microbiota promotes distal tissue regeneration via RORγ+ regulatory T cell emissaries

Specific microbial signals induce the differentiation of a distinct pool of RORγ+ regulatory T (Treg) cells crucial for intestinal homeostasis. We discovered highly analogous populations of microbiota-dependent Treg cells that promoted tissue regeneration at extra-gut sites, notably acutely injured skeletal muscle and fatty liver. Inflammatory meditators elicited by tissue damage combined with MHC-class-II-dependent T cell activation to drive the accumulation of gut-derived RORγ+ Treg cells in injured muscle, wherein they regulated the dynamics and tenor of early inflammation and helped balance the proliferation vs. differentiation of local stem cells. Reining in IL-17A-producing T cells was a major mechanism underlying the rheostatic functions of RORγ+ Treg cells in compromised tissues. Our findings highlight the importance of gut-trained Treg cell emissaries in controlling the response to sterile injury of non-mucosal tissues.

MafB-restricted local monocyte proliferation precedes lung interstitial macrophage differentiation

Resident tissue macrophages (RTMs) are differentiated immune cells that populate distinct niches and exert important tissue-supportive functions. RTM maintenance is thought to rely either on differentiation from monocytes or on RTM self-renewal. Here, we used a mouse model of inducible lung interstitial macrophage (IM) niche depletion and refilling to investigate the development of IMs in vivo. Using time-course single-cell RNA-sequencing analyses, bone marrow chimeras and gene targeting, we found that engrafted Ly6C⁺ classical monocytes proliferated locally in a Csf1 receptor-dependent manner before differentiating into IMs. The transition from monocyte proliferation toward IM subset specification was controlled by the transcription factor MafB, while c-Maf specifically regulated the identity of the CD206⁺ IM subset. Our data provide evidence that, in the mononuclear phagocyte system, the ability to proliferate is not merely restricted to myeloid progenitor cells and mature RTMs but is also a tightly regulated capability of monocytes developing into RTMs in vivo.

Novel cataract-causing variant c.177dupC in c-MAF regulates the expression of crystallin genes for cell apoptosis via a mitochondria-dependent pathway

Congenital cataract (CC) is regarded as the most common hereditary ophthalmic disease in children. Mutations in CC-associated genes play important roles in CC formation, which provides the basis for molecular diagnosis and therapy. Among these CC-associated genes, v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog (c-MAF) is considered an important transcription factor for eye and lens development. In this study, we recruited a three-generation Chinese Han family with CC. Gene sequencing revealed a novel duplication mutation in c-MAF (NM_005360.5: c.177dup) that caused frameshifting at residue 60 (p. M60fs) of c-MAF. Additionally, in the patient blood samples, the expression levels of related crystallin and noncrystallin genes confirmed that this novel duplication variant impaired the transactivation of c-MAF. Further functional analyses suggested that the c-MAF mutant induces the transcriptional inhibition of CRYAA and CRYGA and subsequently influences ME and G6PD expression levels, ultimately resulting in ROS generation and further leading to cell apoptosis via mitochondria-dependent pathways. In conclusion, we report a novel c-MAF heterozygous mutation that plays a vital role in CC formation in a Chinese family, broadening the genetic spectrum of CC.

Inhibitory Kcnip2 neurons of the spinal dorsal horn control behavioral sensitivity to environmental cold

Proper sensing of ambient temperature is of utmost importance for the survival of euthermic animals, including humans. While considerable progress has been made in our understanding of temperature sensors and transduction mechanisms, the higher-order neural circuits processing such information are still only incompletely understood. Using intersectional genetics in combination with circuit tracing and functional neuron manipulation, we identified Kcnip2-expressing inhibitory (Kcnip2^GlyT2) interneurons of the mouse spinal dorsal horn as critical elements of a neural circuit that tunes sensitivity to cold. Diphtheria toxin-mediated ablation of these neurons increased cold sensitivity without affecting responses to other somatosensory modalities, while their chemogenetic activation reduced cold and also heat sensitivity. We also show that Kcnip2^GlyT2 neurons become activated preferentially upon exposure to cold temperatures and subsequently inhibit spinal nociceptive output neurons that project to the lateral parabrachial nucleus. Our results thus identify a hitherto unknown spinal circuit that tunes cold sensitivity.

Intestinal epithelial c-Maf expression determines enterocyte differentiation and nutrient uptake in mice

The primary function of the small intestine (SI) is to absorb nutrients to maintain whole-body energy homeostasis. Enterocytes are the major epithelial cell type facilitating nutrient sensing and uptake. However, the molecular regulators governing enterocytes have remained undefined. Here, we identify c-Maf as an enterocyte-specific transcription factor within the SI epithelium. c-Maf expression was determined by opposing Noggin/BMP signals and overlapped with the zonated enrichment of nutrient transporters in the mid-villus region. Functionally, enterocytes required c-Maf to appropriately differentiate along the villus axis. Specifically, gene programs controlling carbohydrate and protein absorption were c-Maf-dependent. Consequently, epithelial cell-specific c-Maf deletion resulted in impaired enterocyte maturation and nutrient uptake, including defects in the adaptation to different nutrient availability. Concomitantly, intraepithelial lymphocytes were less abundant, while commensal epithelial cell-attaching SFB overgrew in a c-Maf-deficient environment, highlighting the close interdependence between the intestinal epithelium, immune system, and microbiota. Collectively, our data identified c-Maf as a key regulator of SI enterocyte differentiation and function, essential for nutrient, immune, and microbial homeostasis.

Maf family transcription factors are required for nutrient uptake in the mouse neonatal gut

There are fundamental differences in how neonatal and adult intestines absorb nutrients. In adults, macromolecules are broken down into simpler molecular components in the lumen of the small intestine, then absorbed. In contrast, neonates are thought to rely on internalization of whole macromolecules and subsequent degradation in the lysosome. Here, we identify the Maf family transcription factors MAFB and c-MAF as markers of terminally differentiated intestinal enterocytes throughout life. The expression of these factors is regulated by HNF4α and HNF4γ, master regulators of enterocyte cell fate. Loss of Maf factors results in a neonatal-specific failure to thrive and loss of macromolecular nutrient uptake. RNA-Seq and CUT&RUN analyses defined an endo-lysosomal program as being downstream of these transcription factors. We demonstrate major transcriptional changes in metabolic pathways, including fatty acid oxidation and increases in peroxisome number, in response to loss of Maf proteins. Finally, we show that loss of BLIMP1, a repressor of adult enterocyte genes, shows highly overlapping changes in gene expression and similar defects in macromolecular uptake. This work defines transcriptional regulators that are necessary for nutrient uptake in neonatal enterocytes.

Broadening the genotypic and phenotypic spectrum of MAF in three Chinese Han congenital cataracts families

Pathogenic variants in the v-maf avian musculoaponeurotic fibrosarcoma oncogene homologue (MAF) encoding a transcription factor (from a unique subclass of basic leucine zipper transcription factors) are associated with isolated congenital cataracts (CCs) and Aymé-Gripp syndrome (AYGRPS). We collected detailed disease histories from, and performed comprehensive ophthalmic and systemic examinations in 269 patients with CCs; we then performed whole-exome sequencing. Pathogenicity assessments were evaluated using multiple predictive tools. The clinical validities of the reported gene-disease relationships for MAF genes (MAF-CCs and MAF-AYGRPS) were assessed using the ClinGen gene curation framework. We identified two novel (c.173C>A, p.Thr58Asn and c.947T>C, p. Leu316Pro) variants and one known (c.173C>T, p.Thr58Ile) MAF missense variant in three patients. We described novel phenotypes including cleft palate, macular hypoplasia, and retinal neovascularization in the peripheral avascular area and analyzed the genotype-phenotype correlations. We demonstrated associations of variants in the MAF C-terminal DNA-binding domain with CCs and associations of variants in the N-terminal transactivation domain of MAF with AYGRPS. We thus expand the genotypic and phenotypic spectrum of the MAF gene. The ClinGen gene curation framework results suggested that variants in different domains of MAF are associated with different diseases.

Human Stem Cell-Derived TRPV1-Positive Sensory Neurons: A New Tool to Study Mechanisms of Sensitization

Somatosensation, the detection and transduction of external and internal stimuli such as temperature or mechanical force, is vital to sustaining our bodily integrity. But still, some of the mechanisms of distinct stimuli detection and transduction are not entirely understood, especially when noxious perception turns into chronic pain. Over the past decade major progress has increased our understanding in areas such as mechanotransduction or sensory neuron classification. However, it is in particular the access to human pluripotent stem cells and the possibility of generating and studying human sensory neurons that has enriched the somatosensory research field. Based on our previous work, we describe here the generation of human stem cell-derived nociceptor-like cells. We show that by varying the differentiation strategy, we can produce different nociceptive subpopulations with different responsiveness to nociceptive stimuli such as capsaicin. Functional as well as deep sequencing analysis demonstrated that one protocol in particular allowed the generation of a mechano-nociceptive sensory neuron population, homogeneously expressing TRPV1. Accordingly, we find the cells to homogenously respond to capsaicin, to become sensitized upon inflammatory stimuli, and to respond to temperature stimulation. The efficient and homogenous generation of these neurons make them an ideal translational tool to study mechanisms of sensitization, also in the context of chronic pain.

Targeting the oncogenic transcription factor c-Maf for the treatment of multiple myeloma

Multiple myeloma (MM) is a hematologic malignancy derived from clonal expansion of plasma cells within the bone marrow and it may progress to the extramedullary region in late stage of the disease course. c-Maf, an oncogenic zipper leucine transcription factor, is overexpressed in more than 50% MM cell lines and primary species in association with chromosomal translocation, aberrant signaling transduction and modulation of stability. By triggering the transcription of critical genes including CCND2, ITGB7, CCR1, ARK5, c-Maf promotes MM progress, proliferation, survival and chemoresistance. Notably, c-Maf is usually expressed at the embryonic stage to promote cell differentiation but less expressed in healthy adult cells. c-Maf has long been proposed as a promising therapeutic target of MM and a panel of small molecule compounds have been identified to downregulate c-Maf and display potent anti-myeloma activities. In the current article, we take a concise summary on the advances in c-Maf biology, pathophysiology, and targeted drug discovery in the potential treatment of MM.

Mafa-dependent GABAergic activity promotes mouse neonatal apneas

While apneas are associated with multiple pathological and fatal conditions, the underlying molecular mechanisms remain elusive. We report that a mutated form of the transcription factor Mafa (Mafa^4A) that prevents phosphorylation of the Mafa protein leads to an abnormally high incidence of breath holding apneas and death in newborn Mafa^4A/4A mutant mice. This apneic breathing is phenocopied by restricting the mutation to central GABAergic inhibitory neurons and by activation of inhibitory Mafa neurons while reversed by inhibiting GABAergic transmission centrally. We find that Mafa activates the Gad2 promoter in vitro and that this activation is enhanced by the mutation that likely results in increased inhibitory drives onto target neurons. We also find that Mafa inhibitory neurons are absent from respiratory, sensory (primary and secondary) and pontine structures but are present in the vicinity of the hypoglossal motor nucleus including premotor neurons that innervate the geniohyoid muscle, to control upper airway patency. Altogether, our data reveal a role for Mafa phosphorylation in regulation of GABAergic drives and suggest a mechanism whereby reduced premotor drives to upper airway muscles may cause apneic breathing at birth.

Apneas are associated with many pathological conditions. Here, the authors show in a mouse model that stabilization of the transcription factor Mafa in brainstem GABAergic neurons may contribute to apnea, by decreasing motor drive to muscles controlling the airways.

c-Maf enforces cytokine production and promotes memory-like responses in mouse and human type 2 innate lymphoid cells

Group‐2 innate lymphoid cells (ILC2s), which are involved in type 2 inflammatory diseases such as allergy, can exhibit immunological memory, but the basis of this ILC2 "trained immunity" has remained unclear. Here, we found that stimulation with IL‐33/IL‐25 or exposure to the allergen papain induces the expression of the transcription factor c‐Maf in mouse ILC2s. Chronic papain exposure results in high production of IL‐5 and IL‐13 cytokines and lung eosinophil recruitment, effects that are blocked by c‐Maf deletion in ILCs. Transcriptomic analysis revealed that knockdown of c‐Maf in ILC2s suppresses expression of type 2 cytokine genes, as well as of genes linked to a memory‐like phenotype. Consistently, c‐Maf was found highly expressed in human adult ILC2s but absent in cord blood and required for cytokine production in isolated human ILC2s. Furthermore, c‐Maf‐deficient mouse or human ILC2s failed to exhibit strengthened (“trained”) responses upon repeated challenge. Thus, the expression of c‐Maf is indispensable for optimal type 2 cytokine production and proper memory‐like responses in group‐2 innate lymphoid cells.

Specification of fetal liver endothelial progenitors to functional zonated adult sinusoids requires c-Maf induction

The liver vascular network is patterned by sinusoidal and hepatocyte co-zonation. How intra-liver vessels acquire their hierarchical specialized functions is unknown. We study heterogeneity of hepatic vascular cells during mouse development through functional and single-cell RNA-sequencing. The acquisition of sinusoidal endothelial cell identity is initiated during early development and completed postnatally, originating from a pool of undifferentiated vascular progenitors at E12. The peri-natal induction of the transcription factor c-Maf is a critical switch for the sinusoidal identity determination. Endothelium-restricted deletion of c-Maf disrupts liver sinusoidal development, aberrantly expands postnatal liver hematopoiesis, promotes excessive postnatal sinusoidal proliferation, and aggravates liver pro-fibrotic sensitivity to chemical insult. Enforced c-Maf overexpression in generic human endothelial cells switches on a liver sinusoidal transcriptional program that maintains hepatocyte function. c-Maf represents an inducible intra-organotypic and niche-responsive molecular determinant of hepatic sinusoidal cell identity and lays the foundation for the strategies for vasculature-driven liver repair.

Intrinsically disordered intracellular domains control key features of the mechanically-gated ion channel PIEZO2

A central question in mechanobiology is how mechanical forces acting in or on cells are transmitted to mechanically-gated PIEZO channels that convert these forces into biochemical signals. Here we examined the role of the intracellular domains of PIEZO2, which account for 25% of the channel, and demonstrate that these domains fine-tune properties such as poking and stretch-sensitivity, velocity coding and single channel conductance. Moreover, we show that the intrinsically disordered linker between the transmembrane helices twelve and thirteen (IDR5) is required for the activation of PIEZO2 by cytoskeleton-transmitted forces. The deletion of IDR5 abolishes PIEZO2-mediated inhibition of neurite outgrowth, while it only partially affected its sensitivity to cell indentation and does not alter its stretch sensitivity. Thus, we propose that PIEZO2 is a polymodal mechanosensor that detects different types of mechanical stimuli via different force transmission pathways, which highlights the importance of utilizing multiple complementary assays when investigating PIEZO function.

A key question in mechanobiology is how mechanical forces are transmitted to PIEZO ion channels. Here, Verkest et al. identify an intracellular channel domain that is required for the activation of PIEZO2 by cytoskeleton-transmitted forces.

Joint actions of diverse transcription factor families establish neuron-type identities and promote enhancer selectivity

To systematically investigate the complexity of neuron specification regulatory networks, we performed an RNA interference (RNAi) screen against all 875 transcription factors (TFs) encoded in Caenorhabditis elegans genome and searched for defects in nine different neuron types of the monoaminergic (MA) superclass and two cholinergic motoneurons. We identified 91 TF candidates to be required for correct generation of these neuron types, of which 28 were confirmed by mutant analysis. We found that correct reporter expression in each individual neuron type requires at least nine different TFs. Individual neuron types do not usually share TFs involved in their specification but share a common pattern of TFs belonging to the five most common TF families: homeodomain (HD), basic helix loop helix (bHLH), zinc finger (ZF), basic leucine zipper domain (bZIP), and nuclear hormone receptors (NHR). HD TF members are overrepresented, supporting a key role for this family in the establishment of neuronal identities. These five TF families are also prevalent when considering mutant alleles with previously reported neuronal phenotypes in C. elegans, Drosophila, and mouse. In addition, we studied terminal differentiation complexity focusing on the dopaminergic terminal regulatory program. We found two HD TFs (UNC-62 and VAB-3) that work together with known dopaminergic terminal selectors (AST-1, CEH-43, CEH-20). Combined TF binding sites for these five TFs constitute a cis-regulatory signature enriched in the regulatory regions of dopaminergic effector genes. Our results provide new insights on neuron-type regulatory programs in C. elegans that could help better understand neuron specification and evolution of neuron types.

Influencers in the Somatosensory System: Extrinsic Control of Sensory Neuron Phenotypes

Somatosensory neurons in dorsal root ganglia (DRG) comprise several main subclasses: high threshold nociceptors/thermoceptors, high- and low-threshold mechanoreceptors, and proprioceptors. Recent years have seen an explosion in the identification of molecules that underlie the functional diversity of these sensory modalities. They also have begun to reveal the developmental mechanisms that channel the emergence of this subtype diversity, solidifying the importance of peripheral instructive signals. Somatic sensory neurons collectively serve numerous essential physiological and protective roles, and as such, an increased understanding of the processes that underlie the specialization of these sensory subtypes is not only biologically interesting but also clinically relevant.

Generation of hiPSC-derived low threshold mechanoreceptors containing axonal termini resembling bulbous sensory nerve endings and expressing Piezo1 and Piezo2

Somatosensory low threshold mechanoreceptors (LTMRs) sense innocuous mechanical forces, largely through specialized axon termini termed sensory nerve endings, where the mechanotransduction process initiates upon activation of mechanotransducers. In humans, a subset of sensory nerve endings is enlarged, forming bulb-like expansions, termed bulbous nerve endings. There is no in vitro human model to study these neuronal endings. Piezo2 is the main mechanotransducer found in LTMRs. Recent evidence shows that Piezo1, the other mechanotransducer considered absent in dorsal root ganglia (DRG), is expressed at low level in somatosensory neurons. We established a differentiation protocol to generate, from iPSC-derived neuronal precursor cells, human LTMR recapitulating bulbous sensory nerve endings and heterogeneous expression of Piezo1 and Piezo2. The derived neurons express LTMR-specific genes, convert mechanical stimuli into electrical signals and have specialized axon termini that morphologically resemble bulbous nerve endings. Piezo2 is concentrated within these enlarged axon termini. Some derived neurons express low level Piezo1, and a subset co-express both channels. Thus, we generated a unique, iPSCs-derived human model that can be used to investigate the physiology of bulbous sensory nerve endings, and the role of Piezo1 and 2 during mechanosensation.

c-MAF-dependent perivascular macrophages regulate diet-induced metabolic syndrome

[Figure: see text].

The cellular and molecular basis of somatosensory neuron development

Primary somatosensory neurons convey salient information about our external environment and internal state to the CNS, allowing us to detect, perceive, and react to a wide range of innocuous and noxious stimuli. Pseudo-unipolar in shape, and among the largest (longest) cells of most mammals, dorsal root ganglia (DRG) somatosensory neurons have peripheral axons that extend into skin, muscle, viscera, or bone and central axons that innervate the spinal cord and brainstem, where they synaptically engage the central somatosensory circuitry. Here, we review the diversity of mammalian DRG neuron subtypes and the intrinsic and extrinsic mechanisms that control their development. We describe classical and contemporary advances that frame our understanding of DRG neurogenesis, transcriptional specification of DRG neurons, and the establishment of morphological, physiological, and synaptic diversification across somatosensory neuron subtypes.

The structure of sensory afferent compartments in health and disease

Primary sensory neurons are a heterogeneous population of cells able to respond to both innocuous and noxious stimuli. Like most neurons they are highly compartmentalised, allowing them to detect, convey and transfer sensory information. These compartments include specialised sensory endings in the skin, the nodes of Ranvier in myelinated axons, the cell soma and their central terminals in the spinal cord. In this review, we will highlight the importance of these compartments to primary afferent function, describe how these structures are compromised following nerve damage and how this relates to neuropathic pain.

The mechanosensory neurons of touch and their mechanisms of activation

Our sense of touch emerges from an array of mechanosensory structures residing within the fabric of our skin. These tactile end organ structures convert innocuous forces acting on the skin into electrical signals that propagate to the CNS via the axons of low-threshold mechanoreceptors (LTMRs). Our rich capacity for tactile discrimination arises from the dissimilar intrinsic properties of the LTMR subtypes that innervate different regions of the skin and the structurally distinct end organ complexes with which they associate. These end organ structures comprise a range of non-neuronal cell types, which may themselves actively contribute to the transformation of tactile forces into neural impulses within the LTMR afferents. Although the mechanism and the site of transduction across end organs remain unclear, PIEZO2 has emerged as the principal mechanosensitive channel involved in light touch of the skin. Here we review the physiological properties of LTMR subtypes and discuss how features of their cutaneous end organ complexes shape subtype-specific tuning.

The SNAG Domain of Insm1 Regulates Pancreatic Endocrine Cell Differentiation and Represses β- to δ-Cell Transdifferentiation

The allocation and specification of pancreatic endocrine lineages are tightly regulated by transcription factors. Disturbances in differentiation of these lineages contribute to the development of various metabolic diseases, including diabetes. The insulinoma-associated protein 1 (Insm1), which encodes a protein containing one SNAG domain and five zinc fingers, plays essential roles in pancreatic endocrine cell differentiation and in mature β-cell function. In the current study, we compared the differentiation of pancreatic endocrine cells between Insm1 null and Insm1 SNAG domain mutants (Insm1delSNAG) to explore the specific function of the SNAG domain of Insm1. We show that the δ-cell number is increased in Insm1delSNAG but not in Insm1 null mutants as compared with the control mice. We also show a less severe reduction of the β-cell number in Insm1delSNAG as that in Insm1 null mutants. In addition, similar deficits are observed in α-, PP, and ε-cells in Insm1delSNAG and Insm1 null mutants. We further identified that the increased δ-cell number is due to β- to δ-cell transdifferentiation. Mechanistically, the SNAG domain of Insm1 interacts with Lsd1, the demethylase of H3K4me1/2. Mutation in the SNAG domain of Insm1 results in impaired recruitment of Lsd1 and increased H3K4me1/2 levels at hematopoietically expressed homeobox (Hhex) loci that are bound by Insm1, thereby promoting the transcriptional activity of the δ-cell-specific gene Hhex Our study has identified a novel function of the SNAG domain of Insm1 in the regulation of pancreatic endocrine cell differentiation, particularly in the repression of β- to δ-cell transdifferentiation.

Functional analysis of large MAF transcription factors and elucidation of their relationships with human diseases

The large MAF transcription factor group is a group of transcription factors with an acidic region, a basic region, and a leucine zipper region. Four types of MAF, MAFA, MAFB, c-MAF, and NRL, have been identified in humans and mice. In order to elucidate the functions of the large MAF transcription factor group in vivo, our research group created genetically modified MAFA-, MAFB-, and c-MAF-deficient mice and analyzed their phenotypes. MAFA is expressed in pancreatic β cells and is essential for insulin transcription and secretion. MAFB is essential for the development of pancreatic endocrine cells, formation of inner ears, podocyte function in the kidneys, and functional differentiation of macrophages. c-MAF is essential for lens formation and osteoblast differentiation. Furthermore, a single-base mutation in genes encoding the large MAF transcription factor group causes congenital renal disease, eye disease, bone disease, diabetes, and tumors in humans. This review describes the functions of large MAF transcription factors in vivo and their relationships with human diseases.

Transcriptional Programming of Human Mechanosensory Neuron Subtypes from Pluripotent Stem Cells

Efficient and homogeneous in vitro generation of peripheral sensory neurons may provide a framework for novel drug screening platforms and disease models of touch and pain. We discover that, by ovesssrexpressing NGN2 and BRN3A, human pluripotent stem cells can be transcriptionally programmed to differentiate into a surprisingly uniform culture of cold- and mechano-sensing neurons. Although such a neuronal subtype is not found in mice, we identify molecular evidence for its existence in human sensory ganglia. Combining NGN2 and BRN3A programming with neural crest patterning, we produce two additional populations of sensory neurons, including a specialized touch receptor neuron subtype. Finally, we apply this system to model a rare inherited sensory disorder of touch and proprioception caused by inactivating mutations in PIEZO2. Together, these findings establish an approach to specify distinct sensory neuron subtypes in vitro, underscoring the utility of stem cell technology to capture human-specific features of physiology and disease.

Nickolls et al. develop a method, using human stem cells, to generate specific types of sensory neurons that detect cold temperature and mechanical force. This approach uncovers a class of neuron found in humans, but not mice, and enables the modeling of a rare sensory disorder of touch and proprioception.

A Functional Topographic Map for Spinal Sensorimotor Reflexes

Cutaneous somatosensory modalities play pivotal roles in generating a wide range of sensorimotor behaviors, including protective and corrective reflexes that dynamically adapt ongoing movement and posture. How interneurons (INs) in the dorsal horn encode these modalities and transform them into stimulus-appropriate motor behaviors is not known. Here, we use an intersectional genetic approach to functionally assess the contribution that eight classes of dorsal excitatory INs make to sensorimotor reflex responses. We demonstrate that the dorsal horn is organized into spatially restricted excitatory modules composed of molecularly heterogeneous cell types. Laminae I/II INs drive chemical itch-induced scratching, laminae II/III INs generate paw withdrawal movements, and laminae III/IV INs modulate dynamic corrective reflexes. These data reveal a key principle in spinal somatosensory processing, namely, sensorimotor reflexes are driven by the differential spatial recruitment of excitatory neurons.

USH2A is a Meissner's corpuscle protein necessary for normal vibration sensing in mice and humans

Fingertip mechanoreceptors comprise sensory neuron endings together with specialized skin cells that form the end-organ. Exquisitely sensitive, vibration-sensing neurons are associated with Meissner's corpuscles in the skin. In the present study, we found that USH2A, a transmembrane protein with a very large extracellular domain, was found in terminal Schwann cells within Meissner's corpuscles. Pathogenic USH2A mutations cause Usher's syndrome, associated with hearing loss and visual impairment. We show that patients with biallelic pathogenic USH2A mutations also have clear and specific impairments in vibrotactile touch perception, as do mutant mice lacking USH2A. Forepaw rapidly adapting mechanoreceptors innervating Meissner's corpuscles, recorded from Ush2a^-/- mice, showed large reductions in vibration sensitivity. However, the USH2A protein was not found in sensory neurons. Thus, loss of USH2A in corpuscular end-organs reduced mechanoreceptor sensitivity as well as vibration perception. Thus, a tether-like protein is required to facilitate detection of small-amplitude vibrations essential for the perception of fine-grained tactile surfaces.

An IL-27-Driven Transcriptional Network Identifies Regulators of IL-10 Expression across T Helper Cell Subsets

Interleukin-27 (IL-27) is an immunoregulatory cytokine that suppresses inflammation through multiple mechanisms, including induction of IL-10, but the transcriptional network mediating its diverse functions remains unclear. Combining temporal RNA profiling with computational algorithms, we predict 79 transcription factors induced by IL-27 in T cells. We validate 11 known and discover 5 positive (Cebpb, Fosl2, Tbx21, Hlx, and Atf3) and 2 negative (Irf9 and Irf8) Il10 regulators, generating an experimentally refined regulatory network for Il10. We report two central regulators, Prdm1 and Maf, that cooperatively drive the expression of signature genes induced by IL-27 in type 1 regulatory T cells, mediate IL-10 expression in all T helper cells, and determine the regulatory phenotype of colonic Foxp3+ regulatory T cells. Prdm1/Maf double-knockout mice develop spontaneous colitis, phenocopying ll10-deficient mice. Our work provides insights into IL-27-driven transcriptional networks and identifies two shared Il10 regulators that orchestrate immunoregulatory programs across T helper cell subsets.

Vertebrate Sensory Ganglia: Common and Divergent Features of the Transcriptional Programs Generating Their Functional Specialization

Sensory fibers of the peripheral nervous system carry sensation from specific sense structures or use different tissues and organs as receptive fields, and convey this information to the central nervous system. In the head of vertebrates, each cranial sensory ganglia and associated nerves perform specific functions. Sensory ganglia are composed of different types of specialized neurons in which two broad categories can be distinguished, somatosensory neurons relaying all sensations that are felt and visceral sensory neurons sensing the internal milieu and controlling body homeostasis. While in the trunk somatosensory neurons composing the dorsal root ganglia are derived exclusively from neural crest cells, somato- and visceral sensory neurons of cranial sensory ganglia have a dual origin, with contributions from both neural crest and placodes. As most studies on sensory neurogenesis have focused on dorsal root ganglia, our understanding of the molecular mechanisms underlying the embryonic development of the different cranial sensory ganglia remains today rudimentary. However, using single-cell RNA sequencing, recent studies have made significant advances in the characterization of the neuronal diversity of most sensory ganglia. Here we summarize the general anatomy, function and neuronal diversity of cranial sensory ganglia. We then provide an overview of our current knowledge of the transcriptional networks controlling neurogenesis and neuronal diversification in the developing sensory system, focusing on cranial sensory ganglia, highlighting specific aspects of their development and comparing it to that of trunk sensory ganglia.

Peripheral Mechanobiology of Touch-Studies on Vertebrate Cutaneous Sensory Corpuscles

The vertebrate skin contains sensory corpuscles that are receptors for different qualities of mechanosensitivity like light brush, touch, pressure, stretch or vibration. These specialized sensory organs are linked anatomically and functionally to mechanosensory neurons, which function as low-threshold mechanoreceptors connected to peripheral skin through Aβ nerve fibers. Furthermore, low-threshold mechanoreceptors associated with Aδ and C nerve fibers have been identified in hairy skin. The process of mechanotransduction requires the conversion of a mechanical stimulus into electrical signals (action potentials) through the activation of mechanosensible ion channels present both in the axon and the periaxonal cells of sensory corpuscles (i.e., Schwann-, endoneurial- and perineurial-related cells). Most of those putative ion channels belong to the degenerin/epithelial sodium channel (especially the family of acid-sensing ion channels), the transient receptor potential channel superfamilies, and the Piezo family. This review updates the current data about the occurrence and distribution of putative mechanosensitive ion channels in cutaneous mechanoreceptors including primary sensory neurons and sensory corpuscles.