Neuroscience
Abstract
Maternal low thyroxine (T4) serum levels during the first trimester of pregnancy correlate with cerebral cortex volume and mental development of the progeny, but why neural cells during early fetal brain development are vulnerable to maternal T4 levels remains unknown. In this study, using iPSCs obtained from a boy with a loss-of-function mutation in MCT8—a transporter previously identified as critical for thyroid hormone uptake and action in neural cells—we demonstrate that thyroid hormones induce transcriptional changes that promote the progression of human neural precursor cells along the dorsal projection trajectory. Consistent with these findings, single-cell, spatial, and bulk transcriptomics from MCT8-deficient cerebral organoids and cultures of human neural precursor cells underscore the necessity for optimal thyroid hormone levels for these cells to differentiate into neurons. The controlled intracellular activation of T4 signaling occurs through the transient expression of the enzyme type 2 deiodinase, which converts T4 into its active form, T3, alongside the coordinated expression of thyroid hormone nuclear receptors. The intracellular activation of T4 in NPCs results in transcriptional changes important for their division mode and cell cycle progression. Thus, T4 is essential for fetal neurogenesis, highlighting the importance of adequate treatment for mothers with hypothyroidism.
Authors
Federico Salas-Lucia, Sergio Escamilla, Amanda Charest, Hanzi Jiang, Randy Stout, Antonio C. Bianco
Abstract
Type I interferons (IFNs) are critical cytokines for antiviral defense and are linked to painful diseases like rheumatoid arthritis, lupus, and neuropathic pain in humans. IFN-α therapy can cause myalgia, headache, joint and abdominal pain. Studies in rodent models demonstrate that direct action of IFNs on sensory neurons in the dorsal root ganglion (DRG) promotes hyperexcitability but rodent behavioral data on IFNs are conflicting, with reports of both pro- and anti-nociceptive actions. We sought to clarify the action of IFN-α and IFN-β on human DRG (hDRG) nociceptors. We found that IFN receptor subunits IFNAR1 and IFNAR2 are expressed by these neurons and their engagement induces canonical STAT1 signaling and non-canonical MAPK activation as measured by increased phosphorylation of the cap-binding protein eIF4E by MNK1/2 kinases. Using patch clamp electrophysiology, Ca2+-imaging, and multi-electrode arrays we demonstrate that IFN-α and -β increase the excitability of hDRG neurons with acute and long-term exposure. Type I IFNs prolong the duration of capsaicin responses, an effect that is blocked by inhibition of MNK1/2 with eFT508, a specific inhibitor of these kinases. This study supports the conclusion that type I IFNs induce hyperexcitability and TRPV1-sensitization when they interact with IFNAR1/2 in hDRG nociceptors.
Authors
Úrzula Franco-Enzástiga, Keerthana Natarajan, Felipe Espinosa, Rafael Granja-Vazquez, Hemanth Mydugolam, Theodore J. Price
Abstract
Epilepsy is a common neurological disorder resulting from an imbalance between neuronal excitation and inhibition. Synapses play a pivotal role in the pathogenesis of epilepsy. Src-homology 2 (SH2) domain–containing protein 5 (SH2D5) is highly expressed in the brain and is implicated in the regulation of synaptic function. However, its role and mechanism in epilepsy remain unclear. In this study, we found that SH2D5 was predominantly localized to pyramidal neurons in the mouse hippocampus and was upregulated in the hippocampus of epileptic brains. KO of Sh2d5 in the hippocampus alleviated both the susceptibility to and severity of epileptic activity. Mechanistically, SH2D5 regulated N-methyl-D-aspartate receptor–mediated (NMDAR–mediated) excitatory synaptic transmission by altering the protein expression levels of NMDAR subunits. We further demonstrated that SH2D5 modulated the transcription of NMDARs by promoting the autophagic degradation of STAT1. These findings suggest that targeting the SH2D5/STAT1/NMDAR pathway may offer a potential therapeutic strategy for epilepsy.
Authors
Haokun Guo, Hui Zhang, Chenlu Zhang, Yuanyuan Shen, Liumi Jiang, Min Yang, Yuansong Zhang, Ningning Zhang, Ruirui Zhang, Ran Yu, Yong Yang, Xin Tian
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
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