Liu Y, Feng J, Li J, Zhao H, Ho TV, Chai Y.
PMID: 26293299
Coordination between the Hertwig’s Epithelial Root Sheath (HERS) and apical papilla (AP) is crucial for proper tooth root development. The Hedgehog (Hh) signaling pathway and Nfic are both involved in tooth root development, however their relationship has yet to be elucidated. Here we establish a time course of mouse molar root development by histological staining of sections and demonstrate that Hh signaling is active before and during root development in the AP and HERS using Gli1 reporter mice. The proper pattern of Hh signaling activity in the AP is critical for the proliferation of dental mesenchymal cells, because either inhibition with Hh inhibitors or constitutive activation of Hh signaling activity in transgenic mice leads to decreased proliferation in the AP and shorter roots. Moreover, Hh activity is elevated in Nfic-/- mice, a root defect model, whereas RNA sequencing and in situ hybridization show that Hh attenuator Hhip is down-regulated. ChIP and RNAscope analyses suggest that Nfic binds to the promoter region of Hhip. Treatment of Nfic-/- mice with Hh inhibitor partially restores cell proliferation, AP growth and root development. Taken together, our results demonstrate that an Nfic-Hhip-Hh signaling pathway is critical for apical papilla growth and proper root formation. This discovery provides insight into the molecular mechanisms regulating tooth root development.
Yan, JJ;Ding, XJ;He, T;Chen, AX;Zhang, W;Yu, ZX;Cheng, XY;Wei, CY;Hu, QD;Liu, XY;Zhang, YL;He, M;Xie, ZY;Zha, X;Xu, C;Cao, P;Li, H;Xu, XH;
PMID: 36463200 | DOI: 10.1038/s41467-022-35211-7
Behavioral observations suggest a connection between anxiety and predator defense, but the underlying neural mechanisms remain unclear. Here we examine the role of the anterior hypothalamic nucleus (AHN), a node in the predator defense network, in anxiety-like behaviors. By in vivo recordings in male mice, we find that activity of AHN GABAergic (AHNVgat+) neurons shows individually stable increases when animals approach unfamiliar objects in an open field (OF) or when they explore the open-arm of an elevated plus-maze (EPM). Moreover, object-evoked AHN activity overlap with predator cue responses and correlate with the object and open-arm avoidance. Crucially, exploration-triggered optogenetic inhibition of AHNVgat+ neurons reduces object and open-arm avoidance. Furthermore, retrograde viral tracing identifies the ventral subiculum (vSub) of the hippocampal formation as a significant input to AHNVgat+ neurons in driving avoidance behaviors in anxiogenic situations. Thus, convergent activation of AHNVgat+ neurons serves as a shared mechanism between anxiety and predator defense to promote behavioral avoidance.
Ilanges, A;Shiao, R;Shaked, J;Luo, JD;Yu, X;Friedman, JM;
PMID: 36071158 | DOI: 10.1038/s41586-022-05161-7
Infections induce a set of pleiotropic responses in animals, including anorexia, adipsia, lethargy and changes in temperature, collectively termed sickness behaviours1. Although these responses have been shown to be adaptive, the underlying neural mechanisms have not been elucidated2-4. Here we use of a set of unbiased methodologies to show that a specific subpopulation of neurons in the brainstem can control the diverse responses to a bacterial endotoxin (lipopolysaccharide (LPS)) that potently induces sickness behaviour. Whole-brain activity mapping revealed that subsets of neurons in the nucleus of the solitary tract (NTS) and the area postrema (AP) acutely express FOS after LPS treatment, and we found that subsequent reactivation of these specific neurons in FOS2A-iCreERT2 (also known as TRAP2) mice replicates the behavioural and thermal component of sickness. In addition, inhibition of LPS-activated neurons diminished all of the behavioural responses to LPS. Single-nucleus RNA sequencing of the NTS-AP was used to identify LPS-activated neural populations, and we found that activation of ADCYAP1+ neurons in the NTS-AP fully recapitulates the responses elicited by LPS. Furthermore, inhibition of these neurons significantly diminished the anorexia, adipsia and locomotor cessation seen after LPS injection. Together these studies map the pleiotropic effects of LPS to a neural population that is both necessary and sufficient for canonical elements of the sickness response, thus establishing a critical link between the brain and the response to infection.
Brain Struct Funct. 2014 Nov 27.
de Kloet AD, Wang L, Ludin JA, Smith JA, Pioquinto DJ, Hiller H, Steckelings UM, Scheuer DA, Sumners C, Krause EG.
PMID: 25427952
Angiotensin-II acts at its type-1 receptor (AT1R) in the brain to regulate body fluid homeostasis, sympathetic outflow and blood pressure. However, the role of the angiotensin type-2 receptor (AT2R) in the neural control of these processes has received far less attention, largely because of limited ability to effectively localize these receptors at a cellular level in the brain. The present studies combine the use of a bacterial artificial chromosome transgenic AT2R-enhanced green fluorescent protein (eGFP) reporter mouse with recent advances in in situ hybridization (ISH) to circumvent this obstacle. Dual immunohistochemistry (IHC)/ISH studies conducted in AT2R-eGFP reporter mice found that eGFP and AT2R mRNA were highly co-localized within the brain. Qualitative analysis of eGFP immunoreactivity in the brain then revealed localization to neurons within nuclei that regulate blood pressure, metabolism, and fluid balance (e.g., NTS and median preoptic nucleus [MnPO]), as well as limbic and cortical areas known to impact stress responding and mood. Subsequently, dual IHC/ISH studies uncovered the phenotype of specific populations of AT2R-eGFP cells. For example, within the NTS, AT2R-eGFP neurons primarily express glutamic acid decarboxylase-1 (80.3 ± 2.8 %), while a smaller subset express vesicular glutamate transporter-2 (18.2 ± 2.9 %) or AT1R (8.7 ± 1.0 %). No co-localization was observed with tyrosine hydroxylase in the NTS. Although AT2R-eGFP neurons were not observed within the paraventricular nucleus (PVN) of the hypothalamus, eGFP immunoreactivity is localized to efferents terminating in the PVN and within GABAergic neurons surrounding this nucleus. These studies demonstrate that central AT2R are positioned to regulate blood pressure, metabolism, and stress responses.
Yang N, Leung EL, Liu C, Li L, Eguether T, Jun Yao XJ, Jones EC, Norris DA, Liu A, Clark RA, Roop DR, Pazour GJ, Shroyer KR, Chen J.
PMID: 28459465 | DOI: 10.1038/onc.2017.117
Inturned (INTU), a cilia and planar polarity effector, performs prominent ciliogenic functions during morphogenesis, such as in the skin. INTU is expressed in adult tissues but its role in tissue maintenance is unknown. Here, we report that the expression of the INTU gene is aberrantly elevated in human basal cell carcinoma (BCC), coinciding with increased primary cilia formation and activated hedgehog (Hh) signaling. Disrupting Intu in an oncogenic mutant Smo (SmoM2)-driven BCC mouse model prevented the formation of BCC through suppressing primary cilia formation and Hh signaling, suggesting that Intu performs a permissive role during BCC formation. INTU is essential for intraflagellar transport A complex assembly during ciliogenesis. To further determine whether Intu is directly involved in the activation of Hh signaling downstream of ciliogenesis, we examined the Hh signaling pathway in mouse embryonic fibroblasts, which readily responds to the Hh pathway activation. Depleting Intu blocked Smo agonist-induced Hh pathway activation, whereas the expression of Gli2ΔN, a constitutively active Gli2, restored Hh pathway activation in Intu-deficient cells, suggesting that INTU functions upstream of Gli2 activation. In contrast, overexpressing Intu did not promote ciliogenesis or Hh signaling. Taken together, data obtained from this study suggest that INTU is indispensable during BCC tumorigenesis and that its aberrant upregulation is likely a prerequisite for primary cilia formation during Hh-dependent tumorigenesis.
Sun, L;Zhu, M;Wang, M;Hao, Y;Hao, Y;Jing, X;Yu, H;Shi, Y;Zhang, X;Wang, S;Yuan, F;Yuan, XS;
PMID: 37348822 | DOI: 10.1016/j.brainresbull.2023.110693
The nucleus tractus solitarii (NTS) is the primary central station that integrates visceral afferent information and regulates respiratory, gastrointestinal, cardiovascular, and other physiological functions. Leptin receptor b (LepRb)-expressing neurons of the NTS (NTSLepRb neurons) are implicated in central respiration regulation, respiratory facilitation, and respiratory drive enhancement. Furthermore, LepRb dysfunction is involved in obesity, insulin resistance, and sleep-disordered breathing. However, the monosynaptic inputs and outputs of NTSLepRb neurons in whole-brain mapping remain to be elucidated. Therefore, the exploration of its whole-brain connection system may provide strong support for comprehensively understanding the physiological and pathological functions of NTSLepRb neurons. In the present study, we used a cell type-specific, modified rabies virus and adeno-associated virus with the Cre-loxp system to map monosynaptic inputs and outputs of NTSLepRb neurons in LepRb-Cre mice. The results showed that NTSLepRb neurons received inputs from 48 nuclei in the whole brain from five brain regions, including especially the medulla. We found that NTSLepRb neurons received inputs from nuclei associated with respiration, such as the pre-Bötzinger complex, ambiguus nucleus, and parabrachial nucleus. Interestingly, some brain areas related to cardiovascular regulation-i.e., the ventrolateral periaqueductal gray and locus coeruleus-also sent a small number of inputs to NTSLepRb neurons. In addition, anterograde tracing results demonstrated that NTSLepRb neurons sent efferent projections to 15 nuclei, including the dorsomedial hypothalamic nucleus and arcuate hypothalamic nucleus, which are involved in regulation of energy metabolism and feeding behaviors. Quantitative statistical analysis revealed that the inputs of the whole brain to NTSLepRb neurons were significantly greater than the outputs. Our study comprehensively revealed neuronal connections of NTSLepRb neurons in the whole brain and provided a neuroanatomical basis for further research on physiological and pathological functions of NTSLepRb neurons.
Kennedy, EA;Aggarwal, S;Dhar, A;Karst, SM;Wilen, CB;Baldridge, MT;
PMID: 37188813 | DOI: 10.1038/s41564-023-01383-1
Norovirus (NoV) is the leading global cause of viral gastroenteritis. Young children bear the highest burden of disease and play a key role in viral transmission throughout the population. However, which host factors contribute to age-associated variability in NoV severity and shedding are not well-defined. The murine NoV (MNoV) strain CR6 causes persistent infection in adult mice and targets intestinal tuft cells. Here we find that natural transmission of CR6 from infected dams occurred only in juvenile mice. Direct oral CR6 inoculation of wild-type neonatal mice led to accumulation of viral RNA in the ileum and prolonged shedding in the stool that was replication-independent. This viral exposure induced both innate and adaptive immune responses including interferon-stimulated gene expression and MNoV-specific antibody responses. Interestingly, viral uptake depended on passive ileal absorption of luminal virus, a process blocked by cortisone acetate administration, which prevented ileal viral RNA accumulation. Neonates lacking interferon signalling in haematopoietic cells were susceptible to productive infection, viral dissemination and lethality, which depended on the canonical MNoV receptor CD300LF. Together, our findings reveal developmentally associated aspects of persistent MNoV infection, including distinct tissue and cellular tropism, mechanisms of interferon regulation and severity of infection in the absence of interferon signalling. These emphasize the importance of defining viral pathogenesis phenotypes across the developmental spectrum and highlight passive viral uptake as an important contributor to enteric infections in early life.
Xu J, Molinas AJR, Mukerjee S, Morgan DA, Rahmouni K, Zsombok A, Lazartigues E.
PMID: 31006330 | DOI: 10.1161/HYPERTENSIONAHA.119.12832
Chronic activation of the brain renin-angiotensin system contributes to the development of hypertension by altering autonomic balance. Beyond the essential role of Ang II (angiotensin II) type 1 receptors, ADAM17 (A disintegrin and metalloprotease 17) is also found to promote brain renin-angiotensin system overactivation. ADAM17 is robustly expressed in various cell types within the central nervous system. The aim of this study was to determine whether ADAM17 modulates presympathetic neuronal activity to promote autonomic dysregulation in salt-sensitive hypertension. To test our hypothesis, ADAM17 was selectively knocked down in glutamatergic neurons using Cre-loxP technology. In mice lacking ADAM17 in glutamatergic neurons, the blood pressure increase induced by deoxycorticosterone acetate-salt treatment was blunted. Deoxycorticosterone acetate-salt significantly elevated cardiac and vascular sympathetic drive in control mice, while such effects were reduced in mice with ADAM17 knockdown. This blunted sympathoexcitation was extended to the spleen, with a lesser activation of the peripheral immune system, translating into a sequestration of circulating T cells within this organ, compared with controls. Within the paraventricular nucleus, Ang II-induced activation of kidney-related presympathetic glutamatergic neurons was reduced in ADAM17 knockdown mice, with the majority of cells no longer responding to Ang II stimulation, confirming the supportive role of ADAM17 in increasing presympathetic neuronal activity. Overall, our data highlight the pivotal role of neuronal ADAM17 in regulating sympathetic activity and demonstrate that activation of ADAM17 in glutamatergic neurons leads to a selective increase of sympathetic output, but not vagal tone, to specific organs, ultimately contributing to dysautonomia and salt-sensitive hypertension.
Kroeger, D;Thundercliffe, J;Phung, A;De Luca, R;Geraci, C;Bragg, S;McCafferty, KJ;Bandaru, SS;Arrigoni, E;Scammell, TE;
PMID: 36170177 | DOI: 10.1093/sleep/zsac242
The pedunculopontine tegmental nucleus (PPT) is implicated in many brain functions, ranging from sleep/wake control and locomotion, to reward mechanisms and learning. The PPT contains cholinergic, GABAergic and glutamatergic neurons with extensive ascending and descending axonal projections. Glutamatergic PPT (PPT vGlut2) neurons are thought to promote wakefulness, but the mechanisms through which this occurs are unknown. In addition, some researchers propose that PPT vGlut2 neurons promote locomotion, yet even though the PPT is a target for deep brain stimulation in Parkinson's disease, the role of the PPT in locomotion is debated. We hypothesized that PPT vGluT2 neurons drive arousal and specific waking behaviors via certain projections and modulate locomotion via others.We mapped the axonal projections of PPT vGlut2 neurons using conditional anterograde tracing and then photostimulated PPT vGlut2 soma or their axon terminal fields across sleep/wake states and analyzed sleep/wake behavior, muscle activity, and locomotion in transgenic mice.We found that stimulation of PPT vGlut2 soma and their axon terminals rapidly triggered arousals from NREM sleep, especially with activation of terminals in the basal forebrain (BF) and lateral hypothalamus (LH). With photoactivation of PPT vGlut2 terminals in the BF and LH, this wakefulness was accompanied by locomotion and other active behaviors, but stimulation of PPT vGlut2 soma and terminals in the substantia nigra triggered only quiet wakefulness without locomotion.These findings demonstrate the importance of the PPT vGluT2 neurons in driving various aspects of arousal and show that heterogeneous brain nuclei, such as the PPT, can promote a variety of behaviors via distinct axonal projections.
VGLUT2 is a determinant of dopamine neuron resilience in a rotenone model of dopamine neurodegeneration
The Journal of neuroscience : the official journal of the Society for Neuroscience
Buck, SA;Miranda, BR;Logan, RW;Fish, KN;Greenamyre, JT;Freyberg, Z;
PMID: 33893220 | DOI: 10.1523/JNEUROSCI.2770-20.2021
Parkinson's disease (PD) is characterized by progressive dopamine (DA) neuron loss in the substantia nigra pars compacta (SNc). In contrast, DA neurons in the ventral tegmental area (VTA) are relatively protected from neurodegeneration, but the underlying mechanisms for this resilience remain poorly understood. Recent work suggests that expression of the vesicular glutamate transporter 2 (VGLUT2) selectively impacts midbrain DA neuron vulnerability. We investigated whether altered DA neuron VGLUT2 expression determines neuronal resilience in rats exposed to rotenone, a mitochondrial complex I inhibitor and toxicant model of PD. We discovered that VTA/SNc DA neurons that expressed VGLUT2 are more resilient to rotenone-induced DA neurodegeneration. Surprisingly, the density of neurons with detectable VGLUT2 expression in the VTA and SNc increases in response to rotenone. Furthermore, dopaminergic terminals within the nucleus accumbens, where the majority of VGLUT2-expressing DA neurons project, exhibit greater resilience compared to DA terminals in the caudate/putamen. More broadly, VGLUT2-expressing terminals are protected throughout the striatum from rotenone-induced degeneration. Together, our data demonstrate that a distinct subpopulation of VGLUT2-expressing DA neurons are relatively protected from rotenone neurotoxicity. Rotenone-induced upregulation of the glutamatergic machinery in VTA and SNc neurons and their projections may be part of a broader neuroprotective mechanism. These findings offer a putative new target for neuronal resilience that can be manipulated to prevent toxicant-induced DA neurodegeneration in PD.SIGNIFICANCE STATEMENT:Environmental exposures to pesticides contribute significantly to pathological processes that culminate in Parkinson's disease (PD). The pesticide rotenone has been used to generate a PD model that replicates key features of the illness including dopamine neurodegeneration. To date, longstanding questions remain: are there dopamine neuron subpopulations resilient to rotenone, and if so, what are the molecular determinants of this resilience? Here we show that the subpopulation of midbrain dopaminergic neurons that express the vesicular glutamate transporter 2 (VGLUT2) are more resilient to rotenone-induced neurodegeneration. Rotenone also upregulates VGLUT2 more broadly in the midbrain, suggesting VGLUT2 expression generally confers increased resilience to rotenone. VGLUT2 may therefore be a new target for boosting neuronal resilience to prevent toxicant-induced DA neurodegeneration in PD.
Gao Y, Fang X, Vincent DF, Threadgill DW, Bartholin L, Li Q.
PMID: 29221447 | DOI: 10.1186/s12958-017-0312-z
Abstract
BACKGROUND:
Transforming growth factor beta (TGFB) superfamily signaling is implicated in the development of sex cord-stromal tumors, a category of poorly defined gonadal tumors. The aim of this study was to determine potential effects of dysregulated TGFB signaling in the ovary using Cre recombinase driven by growth differentiation factor 9 (Gdf9) promoter known to be expressed in oocytes.
METHODS:
A mouse model containing constitutively active TGFBR1 (TGFBR1CA) using Gdf9-iCre (termed TGFBR1-CAG9Cre) was generated. Hematoxylin and eosin (H & E) staining, follicle counting, and immunohistochemistry and immunofluorescence analyses using antibodies directed to Ki67, forkhead box L2 (FOXL2), forkhead box O1 (FOXO1), inhibin alpha (INHA), and SRY (sex determining region Y)-box 9 were performed to determine the characteristics of the TGFBR1-CAG9Cre ovary. Terminal deoxynucleotidyl transferase (TdT) labeling of 3'-OH ends of DNA fragments, real-time PCR, and western blotting were used to examine apoptosis, select gene expression, and TGFBR1 activation. RNAscope in situ hybridization was used to localize the expression of GLI-Kruppel family member GLI1 (Gli1) in ovarian tumortissues.
RESULTS:
TGFBR1-CAG9Cre females were sterile. Sustained activation of TGFBR1 led to altered granulosa cell proliferation evidenced by high expression of Ki67. At an early age, these mice demonstrated follicular defects and development of ovarian granulosa cell tumors, which were immunoreactive for granulosa cell markers including FOXL2, FOXO1, and INHA. Further histochemical and molecular analyses provided evidence of overactivation of TGFBR1 in the granulosa cell compartment during ovarian pathogenesis in TGFBR1-CAG9Cre mice, along with upregulation of Gli1 and Gli2 and downregulation of Tgfbr3 in ovarian tumor tissues.
CONCLUSIONS:
These results reinforce the role of constitutively active TGFBR1 in promoting ovarian tumorigenesis in mice. The mouse model created in this study may be further exploited to define the cellular and molecular mechanisms of TGFB/activin downstream signaling in granulosa cell tumor development. Future studies are needed to test whether activation of TGFB/activin signaling contributes to the development of human granulosa cell tumors.
Journal of chemical neuroanatomy
Beebe, NL;Silveira, MA;Goyer, D;Noftz, WA;Roberts, MT;Schofield, BR;
PMID: 36375740 | DOI: 10.1016/j.jchemneu.2022.102189
Neurons in the inferior colliculus (IC), the midbrain hub of the central auditory pathway, send ascending and descending projections to other auditory brain regions, as well as projections to other sensory and non-sensory brain regions. However, the axonal projection patterns of individual classes of IC neurons remain largely unknown. Vasoactive intestinal polypeptide (VIP) is a neuropeptide expressed by subsets of neurons in many brain regions. We recently identified a class of IC stellate neurons that we called VIP neurons because they are labeled by tdTomato (tdT) expression in VIP-IRES-Cre x Ai14 mice. Here, using fluorescence in situ hybridization, we found that tdT+ neurons in VIP-IRES-Cre x Ai14 mice express Vglut2, a marker of glutamatergic neurons, and VIP, suggesting that VIP neurons use both glutamatergic and VIPergic signaling to influence their postsynaptic targets. Next, using viral transfections with a Cre-dependent eGFP construct, we labeled the axonal projections of VIP neurons. As a group, VIP neurons project intrinsically, within the ipsilateral and contralateral IC, and extrinsically to all the major targets of the IC. Within the auditory system, VIP neurons sent axons and formed axonal boutons in higher centers, including the medial geniculate nucleus and the nucleus of the brachium of the IC. Less dense projections terminated in lower centers, including the nuclei of the lateral lemniscus, superior olivary complex, and dorsal cochlear nucleus. VIP neurons also project to several non-auditory brain regions, including the superior colliculus, periaqueductal gray, and cuneiform nucleus. The diversity of VIP projections compared to the homogeneity of VIP neuron intrinsic properties suggests that VIP neurons play a conserved role at the microcircuit level, likely involving neuromodulation through glutamatergic and VIPergic signaling, but support diverse functions at the systems level through their participation in different projection pathways.
