Biology subjects

Hoang, T.

Publications and source records attributed to Hoang, T..

At least 37 records · Page 2Linked to original sources

bioRxiv2022

Ectopic insert-dependent neuronal expression of GFAP promoter-driven AAV constructs in adult mouse retina.

Direct reprogramming of retinal Muller glia is a promising avenue for replacing photoreceptors and retinal ganglion cells lost to retinal dystrophies. However, questions have recently been raised about the accuracy of studies claiming efficient glia-to-neuron reprogramming in retina that were conducted using GFAP mini promoter-driven adeno-associated virus (AAV) vectors. In this study, we have addressed these questions using GFAP mini promoter-driven AAV constructs to simultaneously overexpress the mCherry reporter and candidate transcription factors predicted to induce glia-to-neuron conversion, in combination with prospective genetic labeling of retinal Muller glia using inducible Cre-dependent GFP reporters. We find that, while control GFAP-mCherry constructs express faithfully in Muller glia, 5 out of 7 transcription factor overexpression constructs tested are predominantly expressed in amacrine and retinal ganglion cells. However, genetic cell lineage analysis shows no evidence for glia-to-neuron conversion. These findings demonstrate strong insert-dependent effects on AAV-based GFAP mini promoter specificity that preclude its use in inferring cell lineage relationships when studying glia-to-neuron conversion in retina.

neuroscience↗

bioRxiv2021

Notch inhibition promotes regeneration and immunosuppression supports cone survival in a zebrafish model of inherited retinal dystrophy

Photoreceptor degeneration leads to irreversible vision loss in humans with retinal dystrophies such as Retinitis Pigmentosa. Whereas photoreceptor loss is permanent in mammals, zebrafish possesses the ability to regenerate retinal neurons and restore visual function. Following acute damage, Muller glia (MG) re-enter the cell cycle and produce multipotent progenitors whose progeny differentiate into mature neurons. Both MG reprogramming and proliferation of retinal progenitor cells require reactive microglia and associated inflammatory signaling. Paradoxically, MG in zebrafish models of photoreceptor degeneration fail to re-enter the cell cycle and regenerate lost cells. Here, we used the zebrafish cep290 mutant to demonstrate that progressive cone degeneration generates an immune response but does not stimulate MG proliferation. Acute light damage triggered photoreceptor regeneration in cep290 mutants but cones were only restored to pre-lesion densities. Using irf8 mutant zebrafish, we found that the chronic absence of microglia reduced inflammation and rescued cone degeneration in cep290 mutants. Finally, single-cell RNA-sequencing revealed sustained expression of notch3 in MG of cep290 mutants and inhibition of Notch signaling induced MG to re-enter the cell cycle. Our findings provide new insights on the requirements for MG to proliferate and the potential for immunosuppression to prolong photoreceptor survival.

neuroscience↗

bioRxiv2021

An intranasally administrated SARS-CoV-2 beta variant subunit booster vaccine prevents beta variant viral replication in rhesus macaques

Emerging of SARS-CoV-2 variants and waning of vaccine/infection-induced immunity poses threats to curbing the COVID-19 pandemic. An effective, safe, and convenient booster vaccine will be needed. We hypothesized that a variant-modified mucosal booster vaccine might induce local immunity to prevent SARS-CoV-2 infection at the port of entry. The beta-variant is hardest to cross-neutralize. Herein we assessed the protective efficacy of an intranasal booster composed of beta variant-spike protein S1 with IL-15 and TLR agonists in previously immunized macaques. The macaques were first vaccinated with Wuhan strain S1 with the same adjuvant. One year later, negligibly detectable SARS-CoV-2-specific antibody remained. Nevertheless, the booster induced vigorous humoral immunity including serum- and bronchoalveolar lavage (BAL)-IgG, secretory nasal- and BAL-IgA, and neutralizing antibody against the original strain and/or beta variant. Beta-variant S1-specifc CD4+ and CD8+ T cell responses were also elicited in PBMC and BAL. Following SARS-CoV-2 beta variant challenge, the vaccinated group demonstrated significant protection against viral replication in the upper and lower respiratory tracts, with almost full protection in the nasal cavity. The fact that one intranasal beta-variant booster administrated one year after the first vaccination provoked protective immunity against beta variant infections may inform future SARS-CoV-2 booster design and administration timing.

immunology↗

bioRxiv2021

Ptbp1 deletion does not induce glia-to-neuron conversion in adult mouse retina and brain.

Direct reprogramming of glia into neurons is a potentially promising approach for the replacement of neurons lost to injury or neurodegenerative disorders. Knockdown of the polypyrimidine tract-binding protein Ptbp1 has been recently reported to induce efficient conversion of retinal Muller glia and brain astrocytes into functional neurons. However, genetic analysis of Ptbp1 function in adult glia has not been conducted. Here, we use a combination of genetic lineage tracing, scRNA-Seq, and electrophysiological analysis to show that specific deletion of Ptbp1 in adult retinal Muller glia and brain astrocytes does not lead to any detectable level of glia-to-neuron conversion. Only a few changes in gene expression are observed in glia following Ptbp1 deletion, and glial identity is maintained. These findings highlight the importance of using genetic manipulation and lineage tracing methods in studying cell type conversion.

neuroscience↗

bioRxiv2021

Fatty acid-binding proteins and fatty acid synthase influence glial reactivity and promote the formation of Müller glia-derived progenitor cells in the avian retina

The capacity for retinal regeneration varies greatly across vertebrates species. A recent comparative epigenetic and transcriptomic investigation of Muller glial (MG) in the retinas of fish, birds and mice revealed that Fatty Acid Binding Proteins (FABPs) are among the most highly up-regulated genes in activated chick MG (Hoang et al., 2020). Herein we provide an in-depth follow-up investigation to describe patterns of expression and how FABPs and fatty acid synthase (FASN) influence glial cells in the chick retina. During development, FABP7 is highly expressed by embryonic retinal progenitor cells (eRPCs) and maturing MG, whereas FABP5 is gradually up-regulated in maturing MG and remains elevated in mature glial cells. PMP2 (FABP8) is expressed by oligodendrocytes and FABP5 is expressed by non-astrocytic inner retinal glial cells, and both of these FABPs are significantly up-regulated in activated MG in damaged or growth factor-treated retinas. In addition to suppressing the formation of MGPCs, we find that FABP-inhibition suppressed the accumulation of proliferating microglia, although the microglia appeared highly reactive. scRNA-seq analyses of cells treated with FABP-inhibitor revealed distinct changes in patterns of expression suggesting that FABPs are involved in the transitions of MG from a resting state to a reactive state and conversion from reactive MG to MGPCs. Inhibition of FABPs in undamaged retinas had a significant impact upon the transcriptomic profiles of MG, with up-regulation of genes associated with gliogenesis, decreases in genes associated with neurogenesis, and suppression of the ability of MG to become MGPCs. scRNA-seq analyses of microglia indicated that FABP inhibition enhances gene modules related to reactivity, proliferation and cytokine signaling. We find that the proliferation of retinal progenitors in the circumferential marginal zone (CMZ) is unaffected by FABP-inhibitor. Upstream of FABP activity, we inhibited FASN in damaged retinas, which reduced numbers of dying cells, increased the proliferation of microglia, and potently suppressed the formation MGPCs in damaged retinas. We conclude that the activity of FASN and FABPs are required early during the formation of proliferating MGPCs. Fatty acid metabolism and cell signaling involving fatty acids are important in regulating glial homeostasis in the retina, and the dedifferentiation and proliferation of microglia and MGPCs.

developmental biology↗

bioRxiv2021

Gene regulatory networks controlling temporal patterning, neurogenesis and cell fate specification in the mammalian retina.

Gene regulatory networks (GRNs), consisting of transcription factors and their target cis- regulatory sequences, control neurogenesis and cell fate specification in the developing central nervous system, but their organization is poorly characterized. In this study, we performed integrated single-cell RNA- and scATAC-seq analysis in both mouse and human retina to profile dynamic changes in gene expression, chromatin accessibility and transcription factor footprinting during retinal neurogenesis. We identified multiple interconnected, evolutionarily-conserved GRNs consisting of cell type-specific transcription factors that both activate expression of genes within their own network and often inhibit expression of genes in other networks. These GRNs control state transitions within primary retinal progenitors that underlie temporal patterning, regulate the transition from primary to neurogenic progenitors, and drive specification of each major retinal cell type. We confirmed the prediction of this analysis that the NFI transcription factors Nfia, Nfib, and Nfix selectively activate expression of genes that promote late-stage temporal identity in primary retinal progenitors. We also used GRNs to identify additional transcription factors that promote (Insm1/2) and inhibit (Tbx3, Tcf7l1/2) rod photoreceptor specification in postnatal retina. This study provides an inventory of cis- and trans-acting factors that control retinal development, identifies transcription factors that control the temporal identity of retinal progenitors and cell fate specification, and will potentially guide cell-based therapies aimed at replacing retinal neurons lost due to disease.

neuroscience↗

bioRxiv2021

Multi-omic Analysis of Developing Human Retina and Organoids Reveals Cell-Specific Cis-Regulatory Elements and Mechanisms of Non-Coding Genetic Disease Risk.

Cis-regulatory elements (CREs) play a critical role in the development, maintenance, and disease-states of all human cell types. In the human retina, CREs have been implicated in a variety of inherited retinal disorders. To characterize cell-class-specific CREs in the human retina and elucidate their potential functions in development and disease, we performed single-nucleus (sn)ATAC-seq and snRNA-seq on the developing and adult human retina and on human retinal organoids. These analyses allowed us to identify cell-class-specific CREs, enriched transcription factor binding motifs, putative target genes, and to examine how these features change over development. By comparing DNA accessibility between the human retina and retinal organoids we found that CREs in organoids are highly correlated at the single-cell level, validating the use of organoids as a model for studying disease-associated CREs. As a proof of concept, we studied the function of a disease-associated CRE at 5q14.3 in organoids, identifying its principal target gene as the miR-9-2 primary transcript and demonstrating a dual role for this CRE in regulating neurogenesis and gene regulatory programs in mature glia. This study provides a rich resource for characterizing cell-class-specific CREs in the human retina and showcases retinal organoids as a model in which to study the function of retinal CREs that influence retinal development and disease. HIGHLIGHTSO_LISingle-cell map of cis-regulatory elements in developing and adult human retina. C_LIO_LICorrelation of single-cell DNA accessibility between human retina and retinal organoids. C_LIO_LIAssociation of disease risk loci with cell-class-specific accessibility. C_LIO_LIModeling of enhancer function at the 5q14.3 retinal disease-risk locus. C_LI

developmental biology↗

bioRxiv2021

Transcriptomic profiling of human orbital fat and differentiating orbital fibroblasts

Structured AbstractO_ST_ABSPurposeC_ST_ABSOrbital fat hyperplasia has a central role in the manifestations of thyroid-associated orbitopathy (TAO). To better understand the pathways involved in adipogenesis in TAO, we have used transcriptomic methods to analyze gene expression in control and TAO patients, as well as in differentiating orbital fibroblasts (OFs). MethodsWe performed bulk RNA sequencing (RNA-Seq) on intraconal orbital fat to compare gene expression in control and TAO patients. We treated cultured OFs derived from TAO patients with media containing dexamethasone, insulin, rosiglitazone, and isobutylmethylxanthine (IBMX) to induce adipogenesis. We used single nuclear RNA-Seq (snRNA-Seq) profiling of treated OFs to compare gene expression over time in order to identify pathways that are involved in orbital adipogenesis in vitro and compared the dynamic patterns of gene expression identify differences in gene expression in control and TAO orbital fat. ResultsOrbital fat from TAO and control patients segregate with principal component analysis (PCA). Numerous signaling pathways are enriched in orbital fat isolated from TAO patients. SnRNA-Seq of orbital fibroblasts undergoing adipogenesis reveals differential expression of adipocyte-specific genes over the developmental time course. Furthermore, genes that are enriched in TAO orbital fat are also upregulated in orbital adipocytes that differentiate in vitro, while genes that are enriched in control orbital fat are enriched in orbital fibroblasts prior to differentiation. ConclusionsDifferentiating orbital fibroblasts serve as a model to study orbital fat hyperplasia seen in TAO. We demonstrate that the insulin-like growth factor-1 receptor (IGF-1R) and Wnt signaling pathways are differentially expressed early in orbital adipogenesis. PrecisTo understand the pathways involved in adipogenesis in TAO, we used transcriptomic methods to analyze gene expression in control and TAO patients, as well as in differentiating OFs. We demonstrate that the IGF-1R and Wnt signaling pathways are differentially expressed during orbital adipogenesis.

molecular biology↗

bioRxiv2021

Cannabinoid signaling promotes the reprogramming of Muller glia into proliferating progenitor cells.

Endocannabinoids (eCB) are lipid-based neurotransmitters that are known to influence synaptic function in the visual system. eCBs are also known to suppress neuroinflammation in different pathological states. However, nothing is known about the roles of the eCB system during reprogramming of Muller glia (MG) into proliferating progenitor-like cells in the retina. Accordingly, we used the chick and mouse model to characterize expression patterns of eCB-related genes and applied pharmacological agents to examine how the eCB system impacts glial reactivity and the capacity of MG to become Muller glia-derived progenitor cells (MGPCs). We probed single cell RNA-seq libraries to identify eCB-related genes and identify cells with dynamic patterns of expression in damaged retinas. MG and inner retinal neurons expressed the eCB receptor CNR1, as well as enzymes involved in eCB metabolism. In the chick, intraocular injections of 2-Arachidonoylglycerol (2-AG) and Anandamide (AEA) potentiated the formation of MGPCs. Consistent with these findings, CNR1-agonists and MGLL-inhibitor promoted reprogramming, whereas CNR1-antagonist and inhibitors of eCB synthesis suppressed reprogramming. Surprisingly, retinal microglia were largely unaffected by increases or decreases in eCB signaling in both chick and mouse models. However, eCB-signaling suppressed the activation of NFkB-reporter in MG in damaged mouse retinas. We conclude that the eCB system in the retina influences the reactivity of MG and is important for regulating glial reactivity and the reprogramming of MG into proliferating MGPCs, but not for regulating the reactivity of immune cells in the retina. Main PointsMuller glia express CNR1 receptor and endocannabinoid synthesis genes. Endocannabinoids after retinal damage promote the formation of Muller glia derived progenitor cells in chick. Endocannabinoids reduce NFkB activity in mouse Muller glia.

molecular biology↗

bioRxiv2020

Control of neurogenic competence in mammalian hypothalamic tanycytes.

Hypothalamic tanycytes, radial glial cells that share many features with neuronal progenitors, generate small numbers of neurons in the postnatal hypothalamus, but the identity of these neurons and the molecular mechanisms that control tanycyte-derived neurogenesis are unknown. In this study, we demonstrate that tanycyte-specific disruption of the NFI family of transcription factors (Nfia/b/x) robustly stimulates tanycyte proliferation and tanycyte-derived neurogenesis. Single-cell RNA- and ATAC-Seq analysis reveals that NFI factors repress Shh and Wnt signaling in tanycytes, and small molecule modulation of these pathways blocks proliferation and tanycyte-derived neurogenesis in Nfia/b/x-deficient mice. We show that Nfia/b/x-deficient tanycytes give rise to multiple mediobasal hypothalamic neuronal subtypes that can mature, integrate into hypothalamic synaptic circuitry, and selectively respond to changes in internal states. These findings identify molecular mechanisms that control tanycyte-derived neurogenesis, suggesting a new therapeutic approach to selectively remodel the hypothalamic neural circuitry that controls homeostatic physiological processes.

neuroscience↗

bioRxiv2020

Midkine in chick and mouse retinas: neuroprotection, glial reactivity and the formation of Müller glia-derived progenitor cells

Recent studies have shown that midkine (MDK), a basic heparin-binding growth factor, is involved in the development and regeneration of the zebrafish retina. However, very little is known about MDK in the retinas of warm-blooded vertebrates. We investigate the expression patterns of MDK and related factors, roles in neuronal survival, and influence upon the formation of Muller glia-derived progenitor cells (MGPCs) in chick and mouse model systems. By using single-cell RNA-sequencing, we find that MDK is upregulated during Muller glia (MG) maturation in chick development and when stimulated to reprogram into MGPCs after NMDA damage or FGF2/Insulin treatment. Interestingly, MDK is significantly up-regulated by MG in damaged chick retinas, but down-regulated by MG in damaged mouse retinas. In both chick and mouse retinas, exogenous MDK selectively up-regulates cFOS and pS6 (a readout of mTOR-signaling) in MG. In the chick, intraocular injections of MDK before injury is neuroprotective with an observed decrease in dying neurons and microglial reactivity, inducing fewer proliferating MGPCs. Blocking MDK signaling with Na3VO4 following blocks neuroprotective effects with an increase the number of dying cells and negates the pro-proliferative effects on MGPCs. Inhibitors of PP2A and Pak1 associated with MDK integrin {beta}1 signaling had MG specific inhibitory effects on MGPC formation. In mice, MDK administration with NMDA damage drives a small but significant increase in MGPCs. We conclude that MDK expression is dynamically regulated in reactive Muller glia and during reprogramming into MGPCs. MDK acts to coordinate glial activity, neuronal survival, and may act in an autocrine manner to influence the re-programming of Muller glia into proliferating MGPCs.

neuroscience↗

bioRxiv2020

Validation of a Single-step, Single-tube Reverse Transcription-Loop-Mediated Isothermal Amplification Assay for Rapid Detection of SARS-CoV-2 RNA

2.IntroductionThe SARS-CoV-2 pandemic of 2020 has resulted in unparalleled requirements for RNA extraction kits and enzymes required for virus detection, leading to global shortages. This has necessitated the exploration of alternative diagnostic options to alleviate supply chain issues. AimTo establish and validate a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for the detection of SARS-CoV-2 from nasopharyngeal swabs. MethodologyWe used a commercial RT-LAMP mastermix from OptiGene Ltd in combination with a primer set designed to detect the CDC N1 region of the SARS-CoV-2 nucleocapsid (N) gene. A single-tube, single-step fluorescence assay was implemented whereby as little as 1 L of universal transport medium (UTM) directly from a nasopharyngeal swab could be used as template, bypassing the requirement for RNA purification. Amplification and detection could be conducted in any thermocycler capable of holding 65{degrees}C for 30 minutes and measure fluorescence in the FAM channel at one-minute intervals. ResultsAssay evaluation by assessment of 157 clinical specimens previously screened by E-gene RT-qPCR revealed assay sensitivity and specificity of 87% and 100%, respectively. Results were fast, with an average time-to-positive (Tp) for 93 clinical samples of 14 minutes (SD {+/-}7 minutes). Using dilutions of SARS-CoV-2 virus spiked into UTM, we also evaluated assay performance against FDA guidelines for implementation of emergency-use diagnostics and established a limit-of-detection of 54 Tissue Culture Infectious Dose 50 per ml (TCID50 mL-1), with satisfactory assay sensitivity and specificity. A comparison of 20 clinical specimens between four laboratories showed excellent interlaboratory concordance; performing equally well on three different, commonly used thermocyclers, pointing to the robustness of the assay. ConclusionWith a simplified workflow, N1-STOP-LAMP is a powerful, scalable option for specific and rapid detection of SARS-CoV-2 and an additional resource in the diagnostic armamentarium against COVID-19. 3. Data summaryThe authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files.

microbiology↗

bioRxiv2020

An In Vitro Vascularized Micro-Tumor Model of Human Colorectal Cancer Recapitulates In Vivo Drug Responses

Around 95% of anti-cancer drugs that show promise during preclinical study fail to gain FDA-approval for clinical use. This failure of the preclinical pipeline highlights the need for improved, physiologically-relevant in vitro models that can better serve as reliable drug-screening tools. The vascularized micro-tumor (VMT) is a novel three-dimensional model system that recapitulates the complex human tumor microenvironment, including perfused vasculature, within a transparent microfluidic device, allowing real-time study of drug responses and tumor-stromal interactions. Here we have validated the VMT platform for the study of colorectal cancer (CRC), the second leading cause of cancer-related deaths, by showing that gene expression, tumor heterogeneity, and treatment response in the VMT more closely model CRC tumor clinicopathology than current standard drug screening modalities, including 2-dimensional (2D) monolayer culture and 3-dimensional (3D) spheroids.

cancer biology↗

bioRxiv2019

Single-cell analysis of human retina identifies evolutionarily conserved and species-specific mechanisms controlling development.

The development of single-cell RNA-Sequencing (scRNA-Seq) has allowed high resolution analysis of cell type diversity and transcriptional networks controlling cell fate specification. To identify the transcriptional networks governing human retinal development, we performed scRNA-Seq over retinal organoid and in vivo retinal development, across 20 timepoints. Using both pseudotemporal and cross-species analyses, we examined the conservation of gene expression across retinal progenitor maturation and specification of all seven major retinal cell types. Furthermore, we examined gene expression differences between developing macula and periphery and between two distinct populations of horizontal cells. We also identify both shared and species-specific patterns of gene expression during human and mouse retinal development. Finally, we identify an unexpected role for ATOH7 expression in regulation of photoreceptor specification during late retinogenesis. These results provide a roadmap to future studies of human retinal development, and may help guide the design of cell-based therapies for treating retinal dystrophies.

neuroscience↗

bioRxiv2019

Therapeutically Exploring Persister Metabolism In Bacteria

Bacterial persisters are rare phenotypic variants that are temporarily tolerant to high concentrations of antibiotics. We have previously discovered that persisters are mostly derived from stationary-phase cells with high redox activities that are maintained by endogenous protein and RNA degradation. This intracellular degradation resulted in self-inflicted damage that transiently repressed the cellular functions targeted by antibiotics. Leveraging this knowledge, we developed an assay integrating a degradable fluorescent protein system and a small library, containing FDA-approved drugs and antibiotics, to detect chemicals that target persister metabolism. We identified several metabolic inhibitors, including anti-psychotic drugs, that can reduce Escherichia coli persistence. These chemical inhibitors also reduce Pseudomonas aeruginosa persistence, potentially verifying the existence of similar mechanisms in a medically relevant organism.

microbiology↗

bioRxiv2019

Comparative transcriptomic and epigenomic analysis identifies key regulators of injury response and neurogenic competence in retinal glia

Injury induces retinal Muller glia of cold-blooded, but not mammalian, vertebrates to regenerate neurons. To identify gene regulatory networks that control neuronal reprogramming in retinal glia, we comprehensively profiled injury-dependent changes in gene expression and chromatin accessibility in Muller glia from zebrafish, chick and mice using bulk RNA-Seq and ATAC-Seq, as well as single-cell RNA-Seq. Cross-species integrative analysis of these data, together with functional validation, identified evolutionarily conserved and species-specific gene networks controlling glial quiescence, gliosis and neurogenesis. In zebrafish and chick, transition from the resting state to gliosis is essential for initiation of retinal regeneration, while in mice a dedicated network suppresses neurogenic competence and restores quiescence. Selective disruption of NFI family transcription factors, which maintain and restore quiescence, enables Muller glia to proliferate and generate neurons in adult mice following retinal injury. These findings may aid in the design of cell-based therapies aimed at restoring retinal neurons lost to degenerative disease. Summary sentenceThis study identifies gene regulatory networks controlling proliferative and neurogenic competence in retinal Muller glia.

neuroscience↗

bioRxiv2019

The Evolution of Placental Invasion and Cancer Metastasis are Causally Linked

Among mammals, the extent of placental invasion is correlated with vulnerability to malignancy. Animals with more invasive placentation (e.g. humans) are more vulnerable to malignancy, whereas animals with a non-invasive placenta (e.g. ruminants) are less likely to develop malignant cancer. To explain this correlation, we propose the hypothesis of Evolved Levels of Invasibility (ELI) positing that the permissiveness of stromal tissue to invasion is a unitary character affecting both placental and cancer invasion. We provide evidence for this hypothesis by contrasting invasion of human and bovine cancer and placental cells into a lawn of stromal cells from different species. We find that both bovine endometrial and skin fibroblasts are more resistant to invasion of placental and cancer cells than their human counterparts. Gene expression profiling identified genes with high expression in human but not bovine fibroblasts. Knocking down of a subset of them in human fibroblasts leads to significantly stronger resistance to cancer cell invasion. Comparative analysis of gene expression among mammals suggests that humans evolved higher vulnerability to malignancy than the eutherian ancestor, possibly as a correlate of more invasive placentation, and boroeutherians evolved to decrease stromal invasibility. Identifying the evolutionary determinants of stromal invasibility can provide significant insights to develop rational anti-metastatic therapeutics.

cancer biology↗

bioRxiv2019

Tanycyte-independent control of hypothalamic leptin signaling

Leptin is secreted by adipocytes to regulate appetite and body weight. Recent studies have reported that tanycytes actively transport circulating leptin across the brain barrier into the hypothalamus, and are required for normal levels of hypothalamic leptin signaling. However, direct evidence for leptin receptor (LepR) expression is lacking, and the effect of tanycyte-specific deletion of LepR has not been investigated. In this study, we analyze the expression and function of the tanycytic LepR in mice. Using single-molecule fluorescent in situ hybridization (smfISH), RT-qPCR, single-cell RNA sequencing (scRNA-Seq), and selective deletion of the LepR in tanycytes, we are unable to detect expression of LepR in the tanycytes. Tanycyte-specific deletion of LepR likewise did not affect leptin-induced pSTAT3 expression in hypothalamic neurons, regardless of whether leptin was delivered by intraperitoneal or intracerebroventricular injection. Finally, we use activity-regulated scRNA-Seq (act-Seq) to comprehensively profile leptin-induced changes in gene expression in all cell types in mediobasal hypothalamus. Clear evidence for leptin signaling is only seen in endothelial cells and subsets of neurons, although virtually all cell types show leptin-induced changes in gene expression. We thus conclude that LepR expression in tanycytes is either absent or undetectably low, that tanycytes do not directly regulate hypothalamic leptin signaling through a LepR-dependent mechanism, and that leptin regulates gene expression in diverse hypothalamic cell types through both direct and indirect mechanisms.

neuroscience↗