Cross-species analysis defines the conservation of anatomically segregated VMH neuron populations

Development and characterization of an Sf-1-Flp mouse model

The use of genetically engineered tools, including combinations of Cre-LoxP and Flp-FRT systems, enables the interrogation of complex biology. Steroidogenic factor-1 (SF-1) is expressed in the ventromedial hypothalamic nucleus (VMH). Development of genetic tools, such as mice expressing Flp recombinase (Flp) in SF-1 neurons (Sf-1-Flp), will be useful for future studies that unravel the complex physiology regulated by the VMH. Here, we developed and characterized Sf-1-Flp mice and demonstrated their utility. The Flp sequence was inserted into the Sf-1 locus with P2A. This insertion did not affect Sf-1 mRNA expression levels and Sf-1-Flp mice do not have any visible phenotypes. They are fertile and metabolically comparable to wild-type littermate mice. Optogenetic stimulation using adeno-associated virus (AAV) carrying Flp-dependent channelrhodopsin-2 (ChR2) increased blood glucose and skeletal muscle PGC-1α in Sf-1-Flp mice. This was similar to SF-1 neuronal activation using Sf-1-BAC-Cre and AAV carrying Cre-dependent ChR2. Finally, we generated Sf-1-Flp mice that lack β2-adrenergic receptors (Adrb2) only in skeletal muscle with a combination of Cre/LoxP technology (Sf-1-Flp:SKMΔAdrb2). Optogenetic stimulation of SF-1 neurons failed to increase skeletal muscle PGC-1α in Sf-1-Flp:SKMΔAdrb2 mice, suggesting that Adrb2 in skeletal muscle is required for augmented skeletal muscle PGC-1α by SF-1 neuronal activation. Our data demonstrate that Sf-1-Flp mice are useful for interrogating complex physiology.

Population coding of predator imminence in the hypothalamus

Hypothalamic VMHdmSF1 neurons are activated by predator cues and are necessary and sufficient for instinctive defensive responses. However, such data do not distinguish which features of a predator encounter are encoded by VMHdmSF1 neural activity. To address this issue, we imaged VMHdmSF1 neurons at single-cell resolution in freely behaving mice exposed to a natural predator in varying contexts. Our results reveal that VMHdmSF1 neurons do not encode different defensive behaviors but rather represent predator identity and multiple predator-evoked internal states, including threat-evoked fear/anxiety, arousal or neophobia, predator imminence, and safety. Notably, threat and safety are encoded bi-directionally by anti-correlated subpopulations. Strikingly, individual differences in predator defensiveness are correlated with individual differences in VMHdmSF1 response dynamics. Thus, different threat-related internal state variables are encoded by distinct neuronal subpopulations within a genetically defined, anatomically restricted hypothalamic cell class.

Hypothalamic GABAergic neurons: their roles in health and metabolic diseases

Hypothalamic GABAergic neurons are important in regulating metabolic homeostasis and energy balance. Serving as critical integrators of catabolic and anabolic processes, these neurons orchestrate a broad spectrum of metabolic functions, including feeding, nutrient metabolism, fluid homeostasis, basal metabolism, thermoregulation, and circadian rhythms. Recent advances in neuroscience have facilitated a deeper exploration of the role of hypothalamic GABAergic neurons in metabolic regulation. Emerging research has uncovered key mechanisms through which these neurons modulate energy balance and maintain metabolic balance. These findings not only enhance our understanding of obesity and related metabolic disorders but also underscore the link between hypothalamic dysfunction and prevalent metabolic diseases such as obesity and type 2 diabetes. This review summarizes the latest advancements in our understanding of the role of hypothalamic GABAergic neurons in metabolic regulation. It aims to elucidate the neural and molecular mechanisms underlying hypothalamic control of metabolism, offering new perspectives for the diagnosis and treatment of metabolic disorders.

Development and Characterization of a Sf-1-Flp Mouse Model

The use of genetically engineered tools, including combinations of Cre-LoxP and Flp-FRT systems, enable the interrogation of complex biology. Steroidogenic factor-1 (SF-1) is expressed in the ventromedial hypothalamic nucleus (VMH). Development of genetic tools, such as mice expressing Flp recombinase (Flp) in SF-1 neurons (Sf-1-Flp), will be useful for future studies that unravel the complex physiology regulated by the VMH. Here, we developed and characterized Sf-1-Flp mice and demonstrated its utility. Flp sequence was inserted into Sf-1 locus with P2A. This insertion did not affect Sf-1 mRNA expression levels and Sf-1-Flp mice do not have any visible phenotypes. They are fertile and metabolically comparable to wild-type littermate mice. Optogenetic stimulation using adeno-associated virus (AAV)-bearing Flp-dependent channelrhodopsin-2 (ChR2) increased blood glucose and skeletal muscle PGC-1α in Sf-1-Flp mice. This was similar to SF-1 neuronal activation using Sf-1-BAC-Cre and AAV-bearing Cre-dependent ChR2. Finally, we generated Sf-1-Flp mice that lack β2-adrenergic receptors (Adrβ2) only in skeletal muscle with a combination of Cre/LoxP technology (Sf-1-Flp::SKMΔAdrβ2). Optogenetic stimulation of SF-1 neurons failed to increase skeletal muscle PGC-1α in Sf-1-Flp::SKMΔAdrβ2 mice, suggesting that Adrβ2 in skeletal muscle is required for augmented skeletal muscle PGC-1α by SF-1 neuronal activation. Our data demonstrate that Sf-1-Flp mice are useful for interrogating complex physiology.

Functionally Separate Populations of Ventromedial Hypothalamic Neurons in Obesity and Diabetes: A Report on Research Supported by Pathway to Stop Diabetes

The ventromedial hypothalamic nucleus (VMN) maintains healthy metabolic function through several important roles. Collectively, homeostasis is maintained via intermingled cells within the VMN that raise blood glucose, lower blood glucose, and stimulate energy expenditure when needed. In this article I discuss the defining factors for the VMN cell types that govern distinct functions induced by the VMN, particularly in relation to energy balance and blood glucose levels. Special attention is given to distinct features of VMN cells responsible for these processes. Finally, these topics are reviewed in the context of research funded by the American Diabetes Association Pathway to Stop Diabetes initiative, with highlighting of key findings and current unresolved questions for future investigations.

Single-cell omics: experimental workflow, data analyses and applications

Cells are the fundamental units of biological systems and exhibit unique development trajectories and molecular features. Our exploration of how the genomes orchestrate the formation and maintenance of each cell, and control the cellular phenotypes of various organismsis, is both captivating and intricate. Since the inception of the first single-cell RNA technology, technologies related to single-cell sequencing have experienced rapid advancements in recent years. These technologies have expanded horizontally to include single-cell genome, epigenome, proteome, and metabolome, while vertically, they have progressed to integrate multiple omics data and incorporate additional information such as spatial scRNA-seq and CRISPR screening. Single-cell omics represent a groundbreaking advancement in the biomedical field, offering profound insights into the understanding of complex diseases, including cancers. Here, we comprehensively summarize recent advances in single-cell omics technologies, with a specific focus on the methodology section. This overview aims to guide researchers in selecting appropriate methods for single-cell sequencing and related data analysis.

NR5A1 and cell population heterogeneity: Insights into developmental and functional disparities and regulatory mechanisms

Background

NR5A1 plays essential roles in the development of various tissues, including the ventromedial hypothalamus, pituitary gonadotrope, adrenal cortex, spleen, testis, and ovary. Additionally, NR5A1-positive cells in these tissues exhibit developmental and functional heterogeneity.

Methods

This review summarizes recent knowledge on the relationships between physiological functions and gene cascades regulated by NR5A1 in each tissue. In addition, we also present several intriguing examples of disparities in Nr5a1 gene regulation within the same tissues, which are relevant to developmentally and functionally heterogeneous cell populations.

Main Findings

The adrenal cortex and testicular Leydig cells exhibit clear biphasic developmental processes, resulting in functionally distinct fetal and adult cell populations in which Nr5a1 is regulated by distinct enhancers. Similar heterogeneity of cell populations has been suggested in other tissues. However, functional differences in each cell population remain unclear, and Nr5a1 gene regulation disparities have not been reported.

Conclusion

Some steroidogenic tissues demonstrate biphasic development, with fetal and adult cell populations playing distinct and crucial physiological roles. Nr5a1 regulation varies across cell populations, and analyses of gene cascades centered on NR5A1 will aid in understanding the mechanisms underlying the development and maturation of reproductive capabilities.

LCoRL Regulates Growth and Metabolism

Genome-wide association studies (GWAS) in humans and livestock have identified genes associated with metabolic traits. However, the causality of many of these genes on metabolic homeostasis is largely unclear due to a lack of detailed functional analyses. Here we report ligand-dependent corepressor-like (LCoRL) as a metabolic regulator for body weight and glucose homeostasis. Although GWAS data show that LCoRL is strongly associated with body size, glucose homeostasis, and other metabolic traits in humans and livestock, functional investigations had not been performed. We generated Lcorl knockout mice (Lcorl-/-) and characterized the metabolic traits. We found that Lcorl-/- pups are born smaller than the wild-type (WT) littermates before reaching normal weight by 7 to 9 weeks of age. While aging, Lcorl-/- mice remain lean compared to WT mice, which is associated with a decrease in daily food intake. Glucose tolerance and insulin sensitivity are improved in Lcorl-/- mice. Mechanistically, this stunted growth is linked to a reduction of circulating levels of IGF-1. The expression of the genes downstream of GH signaling and the genes involved in glucose and lipid metabolism are altered in the liver of Lcorl-/- mice. Furthermore, Lcorl-/- mice are protected against a high-fat diet challenge and show reduced exercise capacity in an exercise stress test. Collectively, our results are congruent with many of the metabolic parameters linked to the Lcorl locus as reported in GWAS in humans and livestock.

Concerted transcriptional regulation of the morphogenesis of hypothalamic neurons by ONECUT3

Acquisition of specialized cellular features is controlled by the ordered expression of transcription factors (TFs) along differentiation trajectories. Here, we find a member of the Onecut TF family, ONECUT3, expressed in postmitotic neurons that leave their Ascl1+/Onecut1/2+ proliferative domain in the vertebrate hypothalamus to instruct neuronal differentiation. We combined single-cell RNA-seq and gain-of-function experiments for gene network reconstruction to show that ONECUT3 affects the polarization and morphogenesis of both hypothalamic GABA-derived dopamine and thyrotropin-releasing hormone (TRH)+ glutamate neurons through neuron navigator-2 (NAV2). In vivo, siRNA-mediated knockdown of ONECUT3 in neonatal mice reduced NAV2 mRNA, as well as neurite complexity in Onecut3-containing neurons, while genetic deletion of Onecut3/ceh-48 in C. elegans impaired neurocircuit wiring, and sensory discrimination-based behaviors. Thus, ONECUT3, conserved across neuronal subtypes and many species, underpins the polarization and morphological plasticity of phenotypically distinct neurons that descend from a common pool of Ascl1+ progenitors in the hypothalamus.

Dentate gyrus granule cells are a locus of pathology in Scn8a developmental encephalopathy

Gain-of-function mutations in SCN8A cause developmental and epileptic encephalopathy (DEE), a disorder characterized by early-onset refractory seizures, deficits in motor and intellectual functions, and increased risk of sudden unexpected death in epilepsy. Altered activity of neurons in the corticohippocampal circuit has been reported in mouse models of DEE. We examined the effect of chronic seizures on gene expression in the hippocampus by single-nucleus RNA sequencing in mice expressing the patient mutation SCN8A-p.Asn1768Asp (N1768D). One hundred and eighty four differentially expressed genes were identified in dentate gyrus granule cells, many more than in other cell types. Electrophysiological recording from dentate gyrus granule cells demonstrated an elevated firing rate. Targeted reduction of Scn8a expression in the dentate gyrus by viral delivery of an shRNA resulted in doubling of median survival time from 4 months to 8 months, whereas delivery of shRNA to the CA1 and CA3 regions did not result in lengthened survival. These data indicate that granule cells of the dentate gyrus are a specific locus of pathology in SCN8A-DEE.

Role of the central nervous system in cell non-autonomous signaling mechanisms of aging and longevity in mammals

Multiple organs orchestrate the maintenance of proper physiological function in organisms throughout their lifetimes. Recent studies have uncovered that aging and longevity are regulated by cell non-autonomous signaling mechanisms in several organisms. In the brain, particularly in the hypothalamus, aging and longevity are regulated by such cell non-autonomous signaling mechanisms. Several hypothalamic neurons have been identified as regulators of mammalian longevity, and manipulating them promotes lifespan extension or shortens the lifespan in rodent models. The hypothalamic structure and function are evolutionally highly conserved across species. Thus, elucidation of hypothalamic function during the aging process will shed some light on the mechanisms of aging and longevity and, thereby benefiting to human health.

Population coding of predator imminence in the hypothalamus

Hypothalamic VMHdm SF1 neurons are activated by predator cues and are necessary and sufficient for instinctive defensive responses. However, such data do not distinguish which features of a predator encounter are encoded by VMHdm SF1 neural activity. To address this issue, we imaged VMHdm SF1 neurons at single-cell resolution in freely behaving mice exposed to a natural predator in varying contexts. Our results reveal that VMHdm SF1 neurons do not represent different defensive behaviors, but rather encode predator identity and multiple predator-evoked internal states, including threat-evoked fear/anxiety; neophobia or arousal; predator imminence; and safety. Notably, threat and safety are encoded bi-directionally by anti-correlated subpopulations. Finally, individual differences in predator defensiveness are correlated with differences in VMHdm SF1 response dynamics. Thus, different threat-related internal state variables are encoded by distinct neuronal subpopulations within a genetically defined, anatomically restricted hypothalamic cell class.

Highlights

Distinct subsets of VMHdm SF1 neurons encode multiple predator-evoked internal states. Anti-correlated subsets encode safety vs. threat in a bi-directional mannerA population code for predator imminence is identified using a novel assay VMHdm SF1 dynamics correlate with individual variation in predator defensiveness.

Cell-type-specific cholinergic control of granular retrosplenial cortex with implications for angular velocity coding across brain states

Cholinergic receptor activation enables the persistent firing of cortical pyramidal neurons, providing a key cellular basis for theories of spatial navigation involving working memory, path integration, and head direction encoding. The granular retrosplenial cortex (RSG) is important for spatially-guided behaviors, but how acetylcholine impacts RSG neurons is unknown. Here, we show that a transcriptomically, morphologically, and biophysically distinct RSG cell-type - the low-rheobase (LR) neuron - has a very distinct expression profile of cholinergic muscarinic receptors compared to all other neighboring excitatory neuronal subtypes. LR neurons do not fire persistently in response to cholinergic agonists, in stark contrast to all other principal neuronal subtypes examined within the RSG and across midline cortex. This lack of persistence allows LR neuron models to rapidly compute angular head velocity (AHV), independent of cholinergic changes seen during navigation. Thus, LR neurons can consistently compute AHV across brain states, highlighting the specialized RSG neural codes supporting navigation.

Molecularly stratified hypothalamic astrocytes are cellular foci for obesity

Astrocytes safeguard the homeostasis of the central nervous system1,2. Despite their prominent morphological plasticity under conditions that challenge the brain's adaptive capacity3-5, the classification of astrocytes, and relating their molecular make-up to spatially devolved neuronal operations that specify behavior or metabolism, remained mostly futile6,7. Although it seems unexpected in the era of single-cell biology, the lack of a major advance in stratifying astrocytes under physiological conditions rests on the incompatibility of 'neurocentric' algorithms that rely on stable developmental endpoints, lifelong transcriptional, neurotransmitter, and neuropeptide signatures for classification6-8 with the dynamic functional states, anatomic allocation, and allostatic plasticity of astrocytes1. Simplistically, therefore, astrocytes are still grouped as 'resting' vs. 'reactive', the latter referring to pathological states marked by various inducible genes3,9,10. Here, we introduced a machine learning-based feature recognition algorithm that benefits from the cumulative power of published single-cell RNA-seq data on astrocytes as a reference map to stepwise eliminate pleiotropic and inducible cellular features. For the healthy hypothalamus, this walk-back approach revealed gene regulatory networks (GRNs) that specified subsets of astrocytes, and could be used as landmarking tools for their anatomical assignment. The core molecular censuses retained by astrocyte subsets were sufficient to stratify them by allostatic competence, chiefly their signaling and metabolic interplay with neurons. Particularly, we found differentially expressed mitochondrial genes in insulin-sensing astrocytes and demonstrated their reciprocal signaling with neurons that work antagonistically within the food intake circuitry. As a proof-of-concept, we showed that disrupting Mfn2 expression in astrocytes reduced their ability to support dynamic circuit reorganization, a time-locked feature of satiety in the hypothalamus, thus leading to obesity in mice. Overall, our results suggest that astrocytes in the healthy brain are fundamentally more heterogeneous than previously thought and topologically mirror the specificity of local neurocircuits.

Gpr149 is involved in energy homeostasis in the male mouse

GPR149 is an orphan receptor about which little is known. Accordingly, in the present study, we mapped the tissue expression of Gpr149 in mice using three complementary approaches: quantitative PCR, in situ hybridization, and a newly generated Gpr149-Cre reporter mouse model. The strongest expressions of Gpr149 were observed in neurons of the islands of Calleja, the ventromedial hypothalamus, and the rostral interpeduncular nucleus. Moderate-to-low expression was also observed in the basal forebrain, striatum, hypothalamus, brainstem, and spinal cord. Some Gpr149 expression was also detected in the primary afferent neurons, enteric neurons, and pituitary endocrine cells. This expression pattern is consistent with the involvement of GPR149 signaling in the regulation of energy balance. To explore the physiological function of GPR149 in vivo, we used CRISPR-Cas9 to generate a global knockout allele with mice lacking Gpr149 exon 1. Preliminary metabolic findings indicated that Gpr149-/- mice partially resist weight gain when fed with a high-fat diet and have greater sensitivity to insulin than control mice. In summary, our data may serve as a resource for future in vivo studies on GPR149 in the context of diet-induced obesity.

Single-cell genomics reveals region-specific developmental trajectories underlying neuronal diversity in the human hypothalamus

The development and diversity of neuronal subtypes in the human hypothalamus has been insufficiently characterized. To address this, we integrated transcriptomic data from 241,096 cells (126,840 newly generated) in the prenatal and adult human hypothalamus to reveal a temporal trajectory from proliferative stem cell populations to mature hypothalamic cell types. Iterative clustering of the adult neurons identified 108 robust transcriptionally distinct neuronal subtypes representing 10 hypothalamic nuclei. Pseudotime trajectories provided insights into the genes driving formation of these nuclei. Comparisons to single-cell transcriptomic data from the mouse hypothalamus suggested extensive conservation of neuronal subtypes despite certain differences in species-enriched gene expression. The uniqueness of hypothalamic neuronal lineages was examined developmentally by comparing excitatory lineages present in cortex and inhibitory lineages in ganglionic eminence, revealing both distinct and shared drivers of neuronal maturation across the human forebrain. These results provide a comprehensive transcriptomic view of human hypothalamus development through gestation and adulthood at cellular resolution.

VMHdm/cSF-1 neuronal circuits regulate skeletal muscle PGC1-α via the sympathoadrenal drive

OBJECTIVE

To adapt to metabolically challenging environments, the central nervous system (CNS) orchestrates metabolism of peripheral organs including skeletal muscle. The organ-communication between the CNS and skeletal muscle has been investigated, yet our understanding of the neuronal pathway from the CNS to skeletal muscle is still limited. Neurons in the dorsomedial and central parts of the ventromedial hypothalamic nucleus (VMHdm/c) expressing steroidogenic factor-1 (VMHdm/cSF-1 neurons) are key for metabolic adaptations to exercise, including increased basal metabolic rate and skeletal muscle mass in mice. However, the mechanisms by which VMHdm/cSF-1 neurons regulate skeletal muscle function remain unclear. Here, we show that VMHdm/cSF-1 neurons increase the sympathoadrenal activity and regulate skeletal muscle peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) in mice via multiple downstream nodes.

METHODS

Optogenetics was used to specifically manipulate VMHdm/cSF-1 neurons combined with genetically-engineered mice and surgical manipulation of the sympathoadrenal activity.

RESULTS

Optogenetic activation of VMHdm/cSF-1 neurons dramatically elevates mRNA levels of skeletal muscle Pgc-1α, which regulates a spectrum of skeletal muscle function including protein synthesis and metabolism. Mechanistically, the sympathoadrenal drive coupled with β2 adrenergic receptor (β2AdR) is essential for VMHdm/cSF-1 neurons-mediated increases in skeletal muscle PGC1-α. Specifically, both adrenalectomy and β2AdR knockout block augmented skeletal muscle PGC1-α by VMHdm/cSF-1 neuronal activation. Optogenetic functional mapping reveals that downstream nodes of VMHdm/cSF-1 neurons are functionally redundant to increase circulating epinephrine and skeletal muscle PGC1-α.

CONCLUSIONS

Collectively, we propose that VMHdm/cSF-1 neurons-skeletal muscle pathway, VMHdm/cSF-1 neurons→multiple downstream nodes→the adrenal gland→skeletal muscle β2AdR, underlies augmented skeletal muscle function for metabolic adaptations.

Suppression of food intake by Glp1r/Lepr-coexpressing neurons prevents obesity in mouse models

The adipose-derived hormone leptin acts via its receptor (LepRb) in the brain to control energy balance. A potentially unidentified population of GABAergic hypothalamic LepRb neurons plays key roles in the restraint of food intake and body weight by leptin. To identify markers for candidate populations of LepRb neurons in an unbiased manner, we performed single-nucleus RNA-Seq of enriched mouse hypothalamic LepRb cells, identifying several previously unrecognized populations of hypothalamic LepRb neurons. Many of these populations displayed strong conservation across species, including GABAergic Glp1r-expressing LepRb (LepRbGlp1r) neurons, which expressed more Lepr than other LepRb cell populations. Ablating Lepr from LepRbGlp1r cells provoked hyperphagic obesity without impairing energy expenditure. Similarly, improvements in energy balance caused by Lepr reactivation in GABA neurons of otherwise Lepr-null mice required Lepr expression in GABAergic Glp1r-expressing neurons. Furthermore, restoration of Glp1r expression in LepRbGlp1r neurons in otherwise Glp1r-null mice enabled food intake suppression by the GLP1R agonist, liraglutide. Thus, the conserved GABAergic LepRbGlp1r neuron population plays crucial roles in the suppression of food intake by leptin and GLP1R agonists.

Anoctamin 4 channel currents activate glucose-inhibited neurons in the mouse ventromedial hypothalamus during hypoglycemia

Glucose is the basic fuel essential for maintenance of viability and functionality of all cells. However, some neurons - namely, glucose-inhibited (GI) neurons - paradoxically increase their firing activity in low-glucose conditions and decrease that activity in high-glucose conditions. The ionic mechanisms mediating electric responses of GI neurons to glucose fluctuations remain unclear. Here, we showed that currents mediated by the anoctamin 4 (Ano4) channel are only detected in GI neurons in the ventromedial hypothalamic nucleus (VMH) and are functionally required for their activation in response to low glucose. Genetic disruption of the Ano4 gene in VMH neurons reduced blood glucose and impaired counterregulatory responses during hypoglycemia in mice. Activation of VMHAno4 neurons increased food intake and blood glucose, while chronic inhibition of VMHAno4 neurons ameliorated hyperglycemia in a type 1 diabetic mouse model. Finally, we showed that VMHAno4 neurons represent a unique orexigenic VMH population and transmit a positive valence, while stimulation of neurons that do not express Ano4 in the VMH (VMHnon-Ano4) suppress feeding and transmit a negative valence. Together, our results indicate that the Ano4 channel and VMHAno4 neurons are potential therapeutic targets for human diseases with abnormal feeding behavior or glucose imbalance.

Brain-wide mapping of efferent projections of glutamatergic (Onecut3+ ) neurons in the lateral mouse hypothalamus

AIM

This study mapped the spatiotemporal positions and connectivity of Onecut3+ neuronal populations in the developing and adult mouse brain.

METHODS

We generated fluorescent reporter mice to chart Onecut3+ neurons for brain-wide analysis. Moreover, we crossed Onecut3-iCre and Mapt-mGFP (Tau-mGFP) mice to visualize axonal projections. A dual Cre/Flp-dependent AAV construct in Onecut3-iCre cross-bred with Slc17a6-FLPo mice was used in an intersectional strategy to map the connectivity of glutamatergic lateral hypothalamic neurons in the adult mouse.

RESULTS

We first found that Onecut3 marks a hitherto undescribed Slc17a6+ /Vglut2+ neuronal cohort in the lateral hypothalamus, with the majority expressing thyrotropin-releasing hormone. In the adult, Onecut3+ /Vglut2+ neurons of the lateral hypothalamus had both intra- and extrahypothalamic efferents, particularly to the septal complex and habenula, where they targeted other cohorts of Onecut3+ neurons and additionally to the neocortex and hippocampus. This arrangement suggests that intrinsic reinforcement loops could exist for Onecut3+ neurons to coordinate their activity along the brain's midline axis.

CONCLUSION

We present both a toolbox to manipulate novel subtypes of hypothalamic neurons and an anatomical arrangement by which extrahypothalamic targets can be simultaneously entrained.

Inhibition of high-fat diet-induced inflammatory responses in adipose tissue by SF1-expressing neurons of the ventromedial hypothalamus

Inflammation and thermogenesis in white adipose tissue (WAT) at different sites influence the overall effects of obesity on metabolic health. In mice fed a high-fat diet (HFD), inflammatory responses are less pronounced in inguinal WAT (ingWAT) than in epididymal WAT (epiWAT). Here we show that ablation and activation of steroidogenic factor 1 (SF1)-expressing neurons in the ventromedial hypothalamus (VMH) oppositely affect the expression of inflammation-related genes and the formation of crown-like structures by infiltrating macrophages in ingWAT, but not in epiWAT, of HFD-fed mice, with these effects being mediated by sympathetic nerves innervating ingWAT. In contrast, SF1 neurons of the VMH preferentially regulated the expression of thermogenesis-related genes in interscapular brown adipose tissue (BAT) of HFD-fed mice. These results suggest that SF1 neurons of the VMH differentially regulate inflammatory responses and thermogenesis among various adipose tissue depots and restrain inflammation associated with diet-induced obesity specifically in ingWAT.

Enteric glial hub cells coordinate intestinal motility

Enteric glia are the predominant cell type in the enteric nervous system yet their identities and roles in gastrointestinal function are not well classified. Using our optimized single nucleus RNA-sequencing method, we identified distinct molecular classes of enteric glia and defined their morphological and spatial diversity. Our findings revealed a functionally specialized biosensor subtype of enteric glia that we call "hub cells." Deletion of the mechanosensory ion channel PIEZO2 from adult enteric glial hub cells, but not other subtypes of enteric glia, led to defects in intestinal motility and gastric emptying in mice. These results provide insight into the multifaceted functions of different enteric glial cell subtypes in gut health and emphasize that therapies targeting enteric glia could advance the treatment of gastrointestinal diseases.

Obesity wars: hypothalamic sEVs a new hope

There are currently several pharmacological therapies available for the treatment of obesity, targeting both the central nervous system (CNS) and peripheral tissues. In recent years, small extracellular vesicles (sEVs) have been shown to be involved in many pathophysiological conditions. Because of their special nanosized structure and contents, sEVs can activate receptors and trigger intracellular pathways in recipient cells. Notably, in addition to transferring molecules between cells, sEVs can also alter their phenotypic characteristics. The purpose of this review is to discuss how sEVs can be used as a CNS-targeted strategy for treating obesity. Furthermore, we will evaluate current findings, such as the sEV-mediated targeting of hypothalamic AMP-activated protein kinase (AMPK), and discuss how they can be translated into clinical application.

Populational heterogeneity and partial migratory origin of the ventromedial hypothalamic nucleus: genoarchitectonic analysis in the mouse

The ventromedial hypothalamic nucleus (VMH) is one of the most distinctive hypothalamic tuberal structures, subject of numerous classic and modern functional studies. Commonly, the adult VMH has been divided in several portions, attending to differences in cell aggregation, cell type, connectivity, and function. Consensus VMH partitions in the literature comprise the dorsomedial (VMHdm), and ventrolateral (VMHvl) subnuclei, which are separated by an intermediate or central (VMHc) population (topographic names based on the columnar axis). However, some recent transcriptome analyses have identified a higher number of different cell types in the VMH, suggesting additional subdivisions, as well as the possibility of separate origins. We offer a topologic and genoarchitectonic developmental study of the mouse VMH complex using the prosomeric axis as a reference. We analyzed genes labeling specific VMH subpopulations, with particular focus upon the Nkx2.2 transcription factor, a marker of the alar-basal boundary territory of the prosencephalon, from where some cells seem to migrate dorsoventrally into VMH. We also identified separate neuroepithelial origins of a Nr2f1-positive subpopulation, and a new Six3-positive component, as well as subtle differences in origin of Nr5a1 positive versus Nkx2.2-positive cell populations entering dorsoventrally the VMH. Several of these migrating cell types are born in the dorsal tuberal domain and translocate ventralwards to reach the intermediate tuberal domain, where the adult VMH mass is located in the adult. This work provides a more detailed area map on the intrinsic organization of the postmigratory VMH complex, helpful for deeper functional studies of this basal hypothalamic entity.

Relaxin/insulin-like family peptide receptor 4 (Rxfp4) expressing hypothalamic neurons modulate food intake and preference in mice

OBJECTIVE

Insulin-like peptide 5 (INSL5) signalling, through its cognate receptor relaxin/insulin-like family peptide receptor 4 (RXFP4), has been reported to be orexigenic, and the high fat diet (HFD) preference observed in wildtype mice is altered in Rxfp4 knock-out mice. In this study, we used a new Rxfp4-Cre mouse model to investigate the mechanisms underlying these observations.

METHODS

We generated transgenic Rxfp4-Cre mice and investigated central expression of Rxfp4 by RT-qPCR, RNAscope and intraparenchymal infusion of INSL5. Rxfp4-expressing cells were chemogenetically manipulated in global Cre-reporter mice using designer receptors exclusively activated by designer drugs (DREADDs) or after stereotactic injection of a Cre-dependent AAV-DIO-Dq-DREADD targeting a population located in the ventromedial hypothalamus (RXFP4VMH). Food intake and feeding motivation were assessed in the presence and absence of a DREADD agonist. Rxfp4-expressing cells in the hypothalamus were characterised by single-cell RNA-sequencing (scRNAseq) and the connectivity of RXFP4VMH cells was investigated using viral tracing.

RESULTS

Rxfp4-Cre mice displayed Cre-reporter expression in the hypothalamus. Active expression of Rxfp4 in the adult mouse brain was confirmed by RT-qPCR and RNAscope. Functional receptor expression was supported by cyclic AMP-responses to INSL5 application in ex vivo brain slices and increased HFD and highly palatable liquid meal (HPM), but not chow, intake after intra-VMH INSL5 infusion. scRNAseq of hypothalamic RXFP4 neurons defined a cluster expressing VMH markers, alongside known appetite-modulating neuropeptide receptors (Mc4r, Cckar and Nmur2). Viral tracing demonstrated RXFP4VMH neural projections to nuclei implicated in hedonic feeding behaviour. Whole body chemogenetic inhibition (Di-DREADD) of Rxfp4-expressing cells, mimicking physiological INSL5-RXFP4 Gi-signalling, increased intake of the HFD and HPM, but not chow, whilst activation (Dq-DREADD), either at whole body level or specifically within the VMH, reduced HFD and HPM intake and motivation to work for the HPM.

CONCLUSION

These findings identify RXFP4VMH neurons as regulators of food intake and preference, and hypothalamic RXFP4 signalling as a target for feeding behaviour manipulation.

A web-based database server using 43,710 public RNA-seq samples for the analysis of gene expression and alternative splicing in livestock animals

BACKGROUND

Livestock animals is of great significance in agricultural production. However, the role of specific gene expression, especially alternative splicing in determining phenotype, is not well understood. The livestock research community needs a gene expression and alternative splicing database contributing to livestock genetic improvement.

DESCRIPTION

We report the construction of LivestockExp ( https://bioinfo.njau.edu.cn/livestockExp ), a web-based database server for the exploration of gene expression and alternative splicing using 43,710 uniformly processed RNA-seq samples from livestock animals and several relative species across six orders. The database is equipped with basic querying functions and multiple online analysis modules including differential/specific expression analysis, co-expression network analysis, and cross-species gene expression conservation analysis. In addition to the re-analysis of public datasets, users can upload personal datasets to perform co-analysis with public datasets. The database also offers a wide range of visualization tools and diverse links to external databases enabling users to efficiently explore the results and to gain additional insights.

CONCLUSION

LivestockExp covers by far the largest number of livestock animal species and RNA-seq samples and provides a valuable data resource and analysis platform for the convenient utilization of public RNA-seq datasets.

Single nucleus RNA-sequencing: how it's done, applications and limitations

Single nuclei RNA-sequencing (sNuc-Seq) is a methodology which uses isolated nuclei instead of whole cells to profile gene expression. By using droplet microfluidic technologies, users are able to profile thousands of single transcriptomes at high throughput from their chosen tissue. This article aims to introduce sNuc-Seq as a method and its utility in multiple tissue types. Furthermore, we discuss the risks associated with the use of nuclei, which must be considered before committing to a methodology.

Cross-species analysis defines the conservation of anatomically segregated VMH neuron populations

The ventromedial hypothalamic nucleus (VMH) controls diverse behaviors and physiologic functions, suggesting the existence of multiple VMH neural subtypes with distinct functions. Combing translating ribosome affinity purification with RNA-sequencing (TRAP-seq) data with single-nucleus RNA-sequencing (snRNA-seq) data, we identified 24 mouse VMH neuron clusters. Further analysis, including snRNA-seq data from macaque tissue, defined a more tractable VMH parceling scheme consisting of six major genetically and anatomically differentiated VMH neuron classes with good cross-species conservation. In addition to two major ventrolateral classes, we identified three distinct classes of dorsomedial VMH neurons. Consistent with previously suggested unique roles for leptin receptor (Lepr)-expressing VMH neurons, Lepr expression marked a single dorsomedial class. We also identified a class of glutamatergic VMH neurons that resides in the tuberal region, anterolateral to the neuroanatomical core of the VMH. This atlas of conserved VMH neuron populations provides an unbiased starting point for the analysis of VMH circuitry and function.