Neuroscience
Abstract
The opioid system plays crucial roles in modulating social behaviors in both humans and animals. However, the pharmacological profiles of opioids regarding social behavior and their therapeutic potential remain unclear. Multiple pharmacological, behavioral, and immunohistological c-Fos mapping approaches were used to characterize the effects of μ-opioid receptor agonists on social behavior and investigate the mechanisms in naive mice and autism spectrum disorder–like (ASD-like) mouse models, such as prenatally valproic acid–treated mice and Fmr1-KO mice. Here, we report that low-dose morphine, a μ-opioid receptor agonist, promoted social behavior by selectively activating neurons in prosocial brain regions, including the nucleus accumbens, but not those in the dorsomedial periaqueductal gray (dmPAG), which are only activated by analgesic high-dose morphine. Critically, intra-dmPAG morphine injection counteracted the prosocial effect of low-dose morphine, suggesting that dmPAG neural activation suppresses social behavior. Moreover, buprenorphine, a μ-opioid receptor partial agonist with less abuse liability and a well-established safety profile, ameliorated social behavior deficits in two mouse models recapitulating ASD symptoms by selectively activating prosocial brain regions without dmPAG neural activation. Our findings highlight the therapeutic potential of brain region–specific neural activation induced by low-dose opioids for social behavior deficits in ASD.
Authors
Soichiro Ohnami, Megumi Naito, Haruki Kawase, Momoko Higuchi, Shigeru Hasebe, Keiko Takasu, Ryo Kanemaru, Yuki Azuma, Rei Yokoyama, Takahiro Kochi, Eiji Imado, Takeru Tahara, Yaichiro Kotake, Satoshi Asano, Naoya Oishi, Kazuhiro Takuma, Hitoshi Hashimoto, Koichi Ogawa, Atsushi Nakamura, Hidekuni Yamakawa, Yukio Ago
Abstract
In the mammalian cochlea, sensory hair cells are crucial for the transduction of acoustic stimuli into electrical signals, which are then relayed to the central auditory pathway via spiral ganglion neuron (SGN) afferent dendrites. The SGN output is directly modulated by inhibitory cholinergic axodendritic synapses from the efferent fibers originating in the superior olivary complex. When the adult cochlea is subjected to noxious stimuli or aging, the efferent system undergoes major rewiring, such that it reestablishes direct axosomatic contacts with the inner hair cells (IHCs), which occur only transiently during prehearing stages of development. The trigger, origin, and degree of efferent plasticity in the cochlea remains largely unknown. Using functional and morphological approaches, we demonstrate that efferent plasticity in the adult cochlea occurs as a direct consequence of mechanoelectrical transducer current dysfunction. We also show that, different from prehearing stages of development, the lateral olivocochlear — but not the medial olivocochlear — efferent fibers are those that form the axosomatic synapses with the IHCs. The study also demonstrates that in vivo restoration of IHC function using AAV-Myo7a rescue reestablishes the synaptic profile of adult IHCs and improves hearing, highlighting the potential of using gene-replacement therapy for progressive hearing loss.
Authors
Andrew P. O’Connor, Ana E. Amariutei, Alice Zanella, Sarah A. Hool, Adam J. Carlton, Fanbo Kong, Mauricio Saenz-Roldan, Jing-Yi Jeng, Marie-José Lecomte, Stuart L. Johnson, Saaid Safieddine, Walter Marcotti
Abstract
Brain arteriovenous malformations (bAVMs) are anomalies forming vascular tangles connecting the arteries and veins, which cause hemorrhagic stroke in young adults. Current surgical approaches are highly invasive, and alternative therapeutic methods are warranted. Recent genetic studies identified KRAS mutations in endothelial cells of bAVMs; however, the underlying process leading to malformation in the postnatal stage remains unknown. Here we established a mouse model of bAVM developing during the early postnatal stage. Among 4 methods tested, mutant KRAS specifically introduced in brain endothelial cells by brain endothelial cell–directed adeno-associated virus (AAV) and endothelial cell–specific Cdh5-CreERT2 mice successfully induced bAVMs in the postnatal period. Mutant KRAS led to the development of multiple vascular tangles and hemorrhage in the brain with increased MAPK/ERK signaling and growth in endothelial cells. Three-dimensional analyses in cleared tissue revealed dilated vascular networks connecting arteries and veins, similar to human bAVMs. Single-cell RNA-Seq revealed dysregulated gene expressions in endothelial cells and multiple cell types involved in the pathological process. Finally, we employed CRISPR/CasRx to knock down mutant KRAS expression, which efficiently suppressed bAVM development. The present model reveals pathological processes that lead to postnatal bAVMs and demonstrates the efficacy of therapeutic strategies with CRISPR/CasRx.
Authors
Shoji Saito, Yuka Nakamura, Satoshi Miyashita, Tokiharu Sato, Kana Hoshina, Masayasu Okada, Hitoshi Hasegawa, Makoto Oishi, Yukihiko Fujii, Jakob Körbelin, Yoshiaki Kubota, Kazuki Tainaka, Manabu Natsumeda, Masaki Ueno
Abstract
The availability and integration of electrophysiological and molecular data from the living brain is critical to understand and diagnose complex human disease. Intracranial stereo electroencephalography (SEEG) electrodes used for identifying the seizure focus on epilepsy patients could enable the integration of such multimodal data. Here, we report MoPEDE (Multimodal Profiling of Epileptic Brain Activity via Explanted Depth Electrodes), a method that recovers extensive protein-coding transcripts, including cell-type markers, DNA methylation and short variant profiles from explanted SEEG electrodes matched with electrophysiological and radiological data allowing for high-resolution reconstructions of brain structure and function. We find gene expression gradients that correspond with the neurophysiology-assigned epileptogenicity index but also outlier molecular fingerprints in some electrodes, potentially indicating seizure generation or propagation zones not detected during electroclinical assessments. Additionally, we identify DNA methylation profiles indicative of transcriptionally permissive or restrictive chromatin states and SEEG-adherent differentially expressed and methylated genes not previously associated with epilepsy. Together, these findings validate that RNA profiles and genome-wide epigenetic data from explanted SEEG electrodes offer high-resolution surrogate molecular landscapes of brain activity. The MoPEDE approach has the potential to enhance diagnostic decisions and deepen our understanding of epileptogenic network processes in the human brain.
Authors
Anuj Kumar Dwivedi, Arun Mahesh, Albert Sanfeliu, Julian Larkin, Rebecca A. Siwicki, Kieron J. Sweeney, Donncha F. O'Brien, Peter Widdess-Walsh, Simone Picelli, David C. Henshall, Vijay K. Tiwari
Abstract
The blood-brain barrier (BBB) is critical for maintaining brain homeostasis but is susceptible to inflammatory dysfunction. While transporter-dependent efflux of some lipophilic substrates across the BBB shows circadian variation due to rhythmic transporter expression, basal transporter–independent permeability and leakage is nonrhythmic. Whether daily timing influences BBB permeability in response to inflammation is unknown. Here, we induced systemic inflammation through repeated LPS injections either in the morning (ZT1) or evening (ZT13) under standard lighting conditions; we then examined BBB permeability to a polar molecule that is not a transporter substrate, sodium fluorescein. We observed clear diurnal variation in inflammatory BBB permeability, with a striking increase in paracellular leak across the BBB specifically following evening LPS injection. Evening LPS led to persisting glia activation as well as inflammation in the brain that was not observed in the periphery. The exaggerated evening neuroinflammation and BBB disruption were suppressed by microglial depletion or through keeping mice in constant darkness. Our data show that diurnal rhythms in microglial inflammatory responses to LPS drive daily variability in BBB breakdown and reveal time of day as a key regulator of inflammatory BBB disruption.
Authors
Jennifer H. Lawrence, Asha Patel, Melvin W. King, Collin J. Nadarajah, Richard Daneman, Erik S. Musiek
Abstract
Excessive aldosterone production increases the risk of heart disease, stroke, dementia, and death. Aldosterone increases both sodium retention and sodium consumption, and increased sodium consumption may worsen end-organ damage in patients with aldosteronism. Preventing this increase could improve outcomes, but the behavioral mechanisms of aldosterone-induced sodium appetite remain unclear. In rodents, we previously identified aldosterone-sensitive neurons, which express the mineralocorticoid receptor and its pre-receptor regulator, 11-beta-hydroxysteroid dehydrogenase 2 (HSD2). In the present study, we identified HSD2 neurons in the human brain, then used a mouse model to evaluate their role in aldosterone-induced salt intake. First, we confirmed that dietary sodium deprivation increases aldosterone production, salt intake, and HSD2 neuron activity. Next, we showed that continuous chemogenetic stimulation of HSD2 neurons causes a large and specific increase in salt intake. Finally, we use dose-response studies and genetically targeted ablation of HSD2 neurons to show that these neurons are necessary for aldosterone-induced salt intake. Identifying HSD2 neurons in the human brain and establishing their necessity for aldosterone-induced salt intake in mice improves our understanding of appetitive circuits and highlights this small cell population as a therapeutic target for moderating dietary sodium.
Authors
Silvia Gasparini, Lila Peltekian, Miriam C. McDonough, Chidera J.A. Mitchell, Marco Hefti, Jon M. Resch, Joel C. Geerling
Abstract
Solute carrier family 39, member 8 (SLC39A8), is a transmembrane transporter that mediates the cellular uptake of zinc, iron, and manganese (Mn). Human genetic studies document the involvement of SLC39A8 in Mn homeostasis, brain development, and function. However, the role and pathophysiological mechanisms of SLC39A8 in the central nervous system remain elusive. We generated Slc39a8 neuron-specific knockout (Slc39a8-NSKO) mice to study SLC39A8 function in neurons. The Slc39a8-NSKO mice displayed markedly decreased Mn levels in the whole brain and brain regions, especially the cerebellum. Radiotracer studies using 54Mn revealed that Slc39a8-NSKO mice had impaired brain uptake of Mn. Slc39a8-NSKO cerebellums exhibited morphological defects and abnormal dendritic arborization of Purkinje cells. Reduced neurogenesis and increased apoptotic cell death occurred in the cerebellar external granular layer of Slc39a8-NSKO mice. Brain Mn deficiency in Slc39a8-NSKO mice was associated with motor dysfunction. Unbiased RNA-Seq analysis revealed downregulation of key pathways relevant to neurodevelopment and synaptic plasticity, including cAMP signaling pathway genes. We further demonstrated that Slc39a8 was required for the optimal transcriptional response to the cAMP-mediated signaling pathway. In summary, our study highlighted the essential roles of SLC39A8 in brain Mn uptake and cerebellum development and functions.
Authors
Eun-Kyung Choi, Luisa Aring, Yujie Peng, Adele B. Correia, Andrew P. Lieberman, Shigeki Iwase, Young Ah Seo
Abstract
SCN8A developmental and epileptic encephalopathy (DEE) is a severe epilepsy syndrome resulting from mutations in the voltage-gated sodium channel Nav1.6, encoded by the gene SCN8A. Nav1.6 is expressed in excitatory and inhibitory neurons, yet previous studies primarily focus on how SCN8A mutations affect excitatory neurons, with limited studies on the importance of inhibitory interneurons. Parvalbumin (PV) interneurons are a prominent inhibitory interneuron subtype that expresses Nav1.6. To assess PV interneuron function within SCN8A DEE, we used 2 mouse models harboring patient-derived SCN8A gain-of-function variants, Scn8aD/+, where the SCN8A variant N1768D is expressed globally, and Scn8aW/+-PV, where the SCN8A variant R1872W is selectively expressed in PV interneurons. Expression of the R1872W SCN8A variant selectively in PV interneurons led to development of spontaneous seizures and seizure-induced death. Electrophysiology studies showed that Scn8aD/+ and Scn8aW/+-PV interneurons were susceptible to depolarization block and exhibited increased persistent sodium current. Evaluation of synaptic connections between PV interneurons and pyramidal cells showed synaptic transmission deficits in Scn8aD/+ and Scn8aW/+-PV interneurons. Together, our findings indicate that PV interneuron failure via depolarization block along with inhibitory synaptic impairment likely elicits an overall inhibitory reduction in SCN8A DEE, leading to unchecked excitation and ultimately resulting in seizures and seizure-induced death.
Authors
Raquel M. Miralles, Alexis R. Boscia, Shrinidhi Kittur, Jessica C. Hanflink, Payal S. Panchal, Matthew S. Yorek, Tyler C. J. Deutsch, Caeley M. Reever, Shreya R. Vundela, Eric R. Wengert, Manoj K. Patel
Abstract
Recent studies have identified multiple genetic variants of SEL1L-HRD1 ER-associated degradation (ERAD) in humans with neurodevelopmental disorders and locomotor dysfunctions, including ataxia. However, the relevance and importance of SEL1L-HRD1 ERAD in the pathogenesis of ataxia remain unexplored. Here we show that SEL1L deficiency in Purkinje cells leads to early-onset progressive cerebellar ataxia with progressive loss of Purkinje cells with age. Mice with Purkinje cell-specific deletion of SEL1L (Sel1LPcp2Cre) exhibit motor dysfunction beginning around 9 weeks of age. Transmission electron microscopy (TEM) analysis reveals dilated ER and fragmented nuclei in Purkinje cells of adult Sel1LPcp2Cre mice, indicative of altered ER homeostasis and cell death. Lastly, loss of Purkinje cells is associated with a secondary neurodegeneration of granular cells, as well as robust activation of astrocytes and proliferation of microglia, in the cerebellum of Sel1LPcp2Cre mice. These data demonstrate the pathophysiological importance of SEL1L-HRD1 ERAD in Purkinje cells in the pathogenesis of cerebellar ataxia.
Authors
Mauricio Torres, Brent Pederson, Hui Wang, Liangguang L. Lin, Huilun Wang, Amara Bugarin-Lapuz, Zhen Zhao, Ling Qi
Abstract
Gaucher disease, the most prevalent lysosomal storage disease, is caused by homozygous mutations at the GBA gene, responsible for encoding the enzyme glucocerebrosidase. Neuronopathic Gaucher disease is associated with microgliosis, astrogliosis, and neurodegeneration. However, the role that microglia, astrocytes, and neurons play in the disease remains to be determined. In the current study, we developed novel, inducible, cell-type specific GBA KO mice to understand the individual impacts of GBA deficiencies on microglia and neurons. GBA was conditionally knocked out either exclusively in microglia or neurons, or throughout the body. These novel mouse models were developed using a tamoxifen-inducible Cre system, with tamoxifen administration commencing at weaning. Microglia-specific GBA KO mice showed no signs of disease. However, the neuron-specific GBA KO resulted in a shortened lifespan, severe weight loss, and ataxia. These mice also had significant neurodegeneration, microgliosis, and astrogliosis accompanied by the accumulation of glucosylceramide and glucosylsphingosine, recapitulating Gaucher disease-like symptoms. These surprising findings reveal that, unlike the neuron-specific GBA deficiency, microglia-specific GBA deficiency alone does not induce disease. The novel neuronal Gaucher disease mouse model, with a median survival of 16 weeks, may be useful for future studies of pathogenesis and the evaluation of therapies.
Authors
Hannah B. D. Duffy, Colleen Byrnes, Hongling Zhu, Galina Tuymetova, Y. Terry Lee, Frances M. Platt, Richard L. Proia
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