Neuroscience
Abstract
The cellular etiology of seizures in CLN2 disease, a childhood-onset neurodegenerative lysosomal storage disorder caused by a deficiency of tripeptidyl peptidase 1 (TPP1), remains elusive. Given that Cln2R207X/R207X mice display fatal spontaneous seizures and an early loss of several cortical GABAergic interneuron populations, we hypothesized that these two events might be causally related. To study the cell-autonomous effects of interneuron-specific TPP1 deficiency, we first generated a transgenic mouse expressing loxP-flanked lysosomal membrane-tethered TPP1 (TPP1LAMP1) on the Cln2R207X/R207X genetic background, and then crossed TPP1LAMP1 mice with Vgat-Cre mice. These Vgat-Cre; TPP1LAMP1 mice accumulated storage in cortical and striatal interneurons. Vgat-Cre; TPP1LAMP1 mice also died more readily after pentylenetetrazole-induced seizures, indicating that interneuron-specific TPP1 deficiency renders these mice more susceptible to seizure-induced mortality. We also selectively activated interneurons using Designer Receptor Exclusively Activated by Designer Drugs (DREADDs) in Vgat-Cre; Cln2R207X/R207X mice. Electroencephalogram monitoring revealed that DREADD-mediated activation of interneurons markedly accelerated the onset of spontaneous seizures and seizure-associated death in Vgat-Cre; Cln2R207X/R207X mice, suggesting that modulating interneuron activity can exacerbate epileptiform abnormalities. Taken together, these results provide new mechanistic insights into the underlying etiology of seizures and premature death that characterize CLN2 disease.
Authors
Keigo Takahashi, Nicholas R. Rensing, Elizabeth M. Eultgen, Letitia L. Williams, Sophie H. Wang, Hemanth R. Nelvagal, Steven Q. Le, Marie S. Roberts, Balraj Doray, Edward B. Han, Patricia I. Dickson, Michael Wong, Mark S. Sands, Jonathan D. Cooper
Abstract
Skeletal muscle excitation-contraction (EC) coupling depends on the direct coupling between CaV1.1 on the sarcolemma and ryanodine receptor (RyR1) on the sarcoplasmic reticulum. A key regulator of this process is STAC3, a protein essential for both the functional expression of CaV1.1 and its conformational coupling with RyR1. Mutations in Stac3 cause STAC3 disorder, a congenital myopathy characterized by muscle weakness. STAC3 interacts with CaV1.1 in 2 key regions: the II-III loop and the proximal C-terminus. While the II-III loop has been previously found to be essential for skeletal muscle EC coupling, here we demonstrated that the interaction between STAC3 and the proximal C-terminus is necessary and sufficient for CaV1.1 functional expression and minimal EC coupling. In contrast, the interaction with the II-III loop is not essential for EC coupling, though it plays a facilitating role in enhancing the process. Supporting this finding, we identified a patient with STAC3 disorder carrying a mutation that deletes the domain of STAC3 involved in the II-III loop interaction. Collectively, our results established that STAC3 binding to CaV1.1 C-terminus is essential for its functional expression, whereas STAC3 interaction with the II-III loop serves to enhance the conformational coupling with RyR1.
Authors
Wietske E. Tuinte, Enikő Török, Petronel Tuluc, Fabiana Fattori, Adele D’Amico, Marta Campiglio
Abstract
Preterm white matter injury (PWMI) is a leading cause of cerebral palsy and chronic neurological disabilities in premature infants. It is characterized by defects in oligodendrocyte precursor cell (OPC) differentiation and dysmyelination. Currently, there are no effective therapeutic strategies available in clinical practice. Lipid homeostasis plays a crucial role in myelin development, yet the function of Lipin1 — a key phosphatidic acid phosphatase involved in phospholipid synthesis — remains unclear. In this study, we identified a significant downregulation of Lipin1 in OPCs from PWMI mice, which impaired OPC differentiation and myelin formation. Conversely, Lipin1 overexpression in these mice promoted OPC maturation and enhanced myelin development. We found evidence that N-acetyltransferase 10 (NAT10) acts as a regulator of Lipin1 expression through RNA pull-down and mass spectrometry. NAT10-mediated N4-acetylcytidine (ac4C) modification enhanced Lipin1 mRNA stability and translation, and NAT10 knockdown in OPCs impaired myelination, highlighting its crucial role in Lipin1-mediated myelination. Our study revealed that the downregulation of Lipin1 impaired OPC differentiation and myelination in PWMI, with NAT10-mediated ac4C modification playing a critical role in regulating Lipin1 expression. These findings highlight Lipin1 and NAT10 as promising therapeutic targets for treating myelination defects in PWMI, warranting further investigation into their potential in preterm birth–related neurological disorders.
Authors
Xinyu Li, Meng Zhang, Yanan Liu, Chunjie Guo, Yiwei Liu, Lei Han, Zhaowei Feng, Xiue Wei, Ruiqin Yao
N6-methyladenosine (m6A) dysregulation contributes to network excitability in temporal lobe epilepsy
Abstract
Analogous to DNA methylation and protein phosphorylation, it is now well understood that RNA is also subject to extensive processing and modification. N6-methyladenosine (m6A) is the most abundant internal RNA modification and regulates RNA fate in several ways, including stability and translational efficiency. The role of m6A in both experimental and human epilepsy remains unknown. Here, we used transcriptome-wide m6A arrays to obtain a detailed analysis of the hippocampal m6A-ome from both mouse and human epilepsy samples. We combined this with human proteomic analyses and show that epileptic tissue displays disrupted metabolic and autophagic pathways that may be directly linked to m6A processing. Specifically, our results suggest that m6A levels inversely correlate with protein pathway activation. Finally, we show that elevated levels of m6A decrease seizure susceptibility and severity in mice. Together, our findings indicate that m6A represents an additional layer of gene regulation complexity in epilepsy and may contribute to the pathomechanisms that drive the development and maintenance of hyperexcitable brain networks.
Authors
Justine Mathoux, Marc-Michel Wilson, Sujithra Srinivas, Gabrielle Litovskich, Leticia Villalba Benito, Cindy Tran, Jaideep Kesavan, Aileen Harnett, Theresa Auer, Amaya Sanz-Rodriguez, Mohammad Kh. A.E. Alkhayyat, Mairéad Sullivan, Zining Liu, Yifan Huang, Austin Lacey, Norman Delanty, Jane Cryan, Francesca M. Brett, Michael A. Farrell, Donncha F. O’Brien, Pablo M. Casillas-Espinosa, Eva M. Jimenez-Mateos, Jeffrey C. Glennon, Mary Canavan, David C. Henshall, Gary P. Brennan
Chronic integrated stress response causes dysregulated cholesterol synthesis in white matter disease
Abstract
Maladaptive integrated stress response (ISR) activation is observed in human diseases of the brain. Genetic mutations of eIF2B, a critical mediator of protein synthesis, cause chronic pathway activation resulting in a leukodystrophy but the precise mechanism is unknown. We generated N208Y eIF2Bα mice and found that this metabolite binding mutation leads to destabilization of eIF2Bα, a systemic ISR, and neonatal lethality. 2BAct, an eIF2B activator, rescued lethality and significantly extended the lifespan of this severe model, underscoring its therapeutic potential in pediatric disease. Continuous treatment was required for survival, as withdrawal led to ISR induction in all tissues and rapid deterioration, thereby providing a model to assess the impact of the ISR in vivo by tuning drug availability. Single nuclei RNA-sequencing of the CNS identified astrocytes, oligodendrocytes, and ependymal cells as the cell types most susceptible to eIF2B dysfunction and revealed dysfunctional maturation of oligodendrocytes. Moreover, ISR activation decreased cholesterol biosynthesis, a process critical for myelin formation and maintenance. As such, persistent ISR engagement may contribute to pathology in other demyelinating diseases.
Authors
Karin Lin, Nina Ly, Rejani B. Kunjamma, Ngoc Vu, Bryan King, Holly M. Robb, Eric G. Mohler, Janani Sridar, Qi Hao, José Zavala-Solorio, Chunlian Zhang, Varahram Shahryari, Nick van Bruggen, Caitlin F. Connelly, Bryson D. Bennett, James J. Lee, Carmela Sidrauski
Abstract
Parkinson’s disease (PD) is a neurodegenerative disorder with both genetic and environmental factors contributing to pathogenesis. Viral infections are potential environmental triggers that influence PD pathology. Using ViroFind, an unbiased platform for whole virome sequencing, along with quantitative PCR (qPCR), we identified human pegivirus (HPgV) in 5 of 10 (50%) of PD brains, confirmed by IHC in 2 of 2 cases, suggesting an association with PD. All 14 age- and sex-matched controls were HPgV negative. HPgV-brain positive patients with PD showed increased neuropathology by Braak stage and Complexin-2 levels, while those positive in the blood had higher IGF-1 and lower pS65-ubiquitin, supporting disruption in metabolism or mitophagy in response to HPgV. RNA-Seq revealed altered immune signaling in HPgV-infected PD samples, including consistent suppression of IL-4 signaling in both the brain and blood. Longitudinal analysis of blood samples showed a genotype-dependent viral response, with HPgV titers correlating directly with IL-4 signaling in a LRRK2 genotype–dependent manner. YWHAB was a key hub gene in the LRRK2 genotypic response, which exhibited an altered relationship with immune-related factors, including NFKB1, ITPR2, and LRRK2 itself, in patients with PD who are positive for HPgV. These results suggest a role for HPgV in shaping PD pathology and highlight the complex interplay between viral infection, immunity, and neuropathogenesis.
Authors
Barbara A. Hanson, Xin Dang, Pouya Jamshidi, Alicia Steffens, Kaleigh Copenhaver, Zachary S. Orban, Bernabe Bustos, Stephen J. Lubbe, Rudolph J. Castellani, Igor J. Koralnik
Abstract
High myopia (HM) and posterior staphyloma (PS) are major causes of vision loss worldwide. Genetic and environmental factors, especially light exposure, influence myopia. This study shows that LRP2 (Low-density lipoprotein-related receptor type 2) levels are decreased in the vitreous of patients with HM and PS, and that in human donor eyes affected by PS, LRP2 expression was reduced in the neural retina and retinal pigment epithelium (RPE), with morphologic changes similar to those observed in the Foxg1-Cre-Lrp2lox/lox mouse that also develops PS. In human iPSc-derived RPE cells (iRPE), LRP2 silencing regulated genes involved in eye and neuronal development, visual perception, tissue remodeling, hormone metabolism and RPE structure. Its expression increased under light exposure, particularly red light, but was downregulated by cortisol. These findings establish a link between LRP2, myopization, and environmental factors, highlighting its crucial role in nonsyndromic HM and PS. LRP2 appears to be a promising therapeutic target for high myopia treatment.
Authors
Kimberley Delaunay, Emilie Picard, Patricia Lassiaz, Laurent Jonet, Vidjea Cannaya, José Maria Ruiz-Moreno, Kentaro Kojima, Henrik Vorum, Bent Honoré, Jorge R. Medrano, Lasse Jørgensen Cehofski, Eric Pussard, Renata Kozyraki, Alicia Torriglia, Olivier Cases, Francine Behar-Cohen
Abstract
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by an expanded CAG repeat in the androgen receptor (AR) gene. To elucidate the cell type–specific temporal gene expression in SBMA, we performed single-nucleus RNA sequencing on the spinal cords of an SBMA mouse model (AR-97Q). Among all cell types, oligodendrocytes had the highest number of differentially expressed genes before disease onset. Analysis of oligodendrocyte clusters suggested that pathways associated with cation channels and synaptic function were activated before disease onset, with increased output from oligodendrocytes to neurons in AR-97Q mice compared with wild-type mice. These changes in the early stages were abrogated at the advanced stages. An oligodendrocyte model of SBMA showed phenotypes similar to those of AR-97Q mice at early stages, such as increased transcriptional changes in synapse organization, and Ca2+ imaging of oligodendrocytes in AR-97Q mice revealed the increased Ca2+ responses. A coculture system of primary rat oligodendrocytes and neurons revealed that the mutant AR in oligodendrocytes affected the activity and synchronization of neurons. These findings suggest that dysregulated cell-to-cell communication plays a critical role in early SBMA pathology and that synaptic or ion channel–related proteins, such as contactin associated protein 2 (Cntnap2) and NALCN channel auxiliary factor 1 (Fam155a), are potential therapeutic targets for SBMA.
Authors
Madoka Iida, Kentaro Sahashi, Tomoki Hirunagi, Kenji Sakakibara, Kentaro Maeda, Yohei Iguchi, Jiayi Li, Yosuke Ogura, Masaki Iizuka, Tomohiro Akashi, Kunihiko Hinohara, Shouta Sugio, Hiroaki Wake, Masahiro Nakatochi, Masahisa Katsuno
Abstract
Multiple sclerosis is characterized by CNS infiltration of auto-reactive immune cells that drive both acute inflammatory demyelination and chronic progressive axonal and neuronal injury. Expanding evidence implicates CD8+ anti-neural T cells in the irreversible neurodegeneration that underlies progression in multiple sclerosis, yet therapies specifically targeting this cell population are limited. CD8+ T cells from patients with MS exhibit increased engagement of the pentose phosphate pathway. Pharmacologic inhibition of the pentose phosphate pathway reduced glycolysis, glucose uptake, NADPH production, ATP production, proliferation, and proinflammatory cytokine secretion in CD8+ T cells activated by ligation of CD3 and CD28. Pentose phosphate pathway inhibition also prevented CD8+ T cell-mediated antigen-specific neuronal injury in vitro and in both an adoptive transfer-based cuprizone model of demyelination and in mice with experimental autoimmune encephalomyelitis. Notably, transcriptional profiling of CNS-infiltrating CD8+ T cells in patients with MS indicated increased pentose phosphate pathway engagement, suggesting that this pathway is involved in CD8+ T cell-mediated injury of axons and neurons in the demyelinated CNS. Inhibiting the pentose phosphate pathway disrupts CD8+ T cell metabolic reprogramming and effector functions, suggesting that such inhibition may serve as a therapeutic strategy to prevent neurodegeneration in patients with progressive MS.
Authors
Ethan M. Grund, Benjamin D.S. Clarkson, Susanna Pucci, Maria S. Westphal, Carolina Muniz Partida, Sara A. Muhammad, Charles L. Howe
Abstract
Loss-of-function mutations in the GBA1 gene are a prevalent risk factor for Parkinson’s disease (PD). Defining features are Lewy bodies that can be rich in α-synuclein (αS), vesicle- and other lipid membranes coupled with striatal dopamine loss and progressive motor dysfunction. Of these, lipid abnormalities are the least understood. An altered lipid metabolism in PD patient-derived neurons, carrying mutations in either GBA1, encoding for glucocerebrosidase, or αS can shift the physiological αS tetramer-monomer (T:M) equilibrium, resulting in PD phenotypes. We previously reported inhibition of stearoyl-CoA desaturase (SCD), the rate-limiting enzyme for fatty acid desaturation, stabilized αS tetramers and improved motor deficits in αS mice. Here we show that mutant GBA-PD cultured neurons have increased SCD products (monounsaturated fatty acids, MUFAS) and reduced αS T:M ratios that were improved by inhibiting SCD. Oral treatment of symptomatic L444P- and E326K Gba1 mutant mice with 5b also improved the αS T:M homeostasis and dopaminergic striatal integrity. Moreover, SCD inhibition normalized GCase maturation and dampened lysosomal and lipid-rich clustering, key features of neuropathology in GBA-PD. In conclusion, this study supports brain MUFA metabolism links GBA1 genotype and wildtype αS homeostasis to downstream neuronal and behavioral impairments, identifying SCD as a therapeutic target for GBA-PD.
Authors
Silke Nuber, Harrison Hsiang, Esra'a Keewan, Tim E. Moors, Sydney J. Reitz, Anupama Tiwari, Gary P. H. Ho, Elena Su, Wolf Hahn, Marie-Alexandre Adom, Riddhima Pathak, Matthew Blizzard, Sangjune Kim, Han Seok Ko, Xiaoqun Zhang, Per Svenningsson, Dennis J. Selkoe, Saranna Fanning
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