Research
Abstract
Dravet syndrome (DS) is an early-onset epilepsy caused by loss of function mutations in the SCN1A gene, which encodes Nav1.1 channels that preferentially regulate activity of inhibitory neurons early in development. DS is associated with a high incidence of sudden unexpected death in epilepsy (SUDEP) by a mechanism that may involve respiratory failure. Evidence also shows that loss of Scn1a impaired activity of neurons in the retrotrapezoid nucleus (RTN) that regulate breathing in response to CO2/H+, suggesting breathing problems precede seizures and serve as a biomarker of SUDEP. Consistent with this, we showed that Scn1a+/- mice exhibited a blunted ventilatory response to CO2/H+ prior to overt seizure activity that worsened with disease progression. Later in development, some Scn1a+/- mice also showed a blunted ventilatory response to hypoxia. Importantly, the severity of respiratory problems correlated with mortality. We also found that pharmacological activation of Nav1.1 rescued activity deficits of RTN neurons in Scn1a+/- mice. We conclude that disordered breathing may be an early biomarker of SUDEP in DS, and at the cellular level loss of Scn1a disrupts RTN neurons by mechanisms involving disinhibition and pharmacological activation of Nav1.1 re-establish inhibitory control of RTN neurons and rescue activity deficits.
Authors
Brenda M, Milla, Eliandra Silva, Cleyton R. Sobrinho, Monica Strain, Daniel K. Mulkey
Abstract
Spinal muscular atrophy (SMA) is a neuromuscular disease caused by low levels of SMN protein. Several therapeutic approaches boosting SMN are approved for human patients, delivering remarkable improvements in lifespan and symptoms. However, emerging phenotypes, including neurodevelopmental comorbidities, are being reported in some treated SMA patients, indicative of alterations in brain development. Here, using a mouse model of severe SMA, we revealed an underlying neurodevelopmental phenotype in SMA where prenatal SMN-dependent defects in translation drove disruptions in non-motile primary cilia across the central nervous system (CNS). Low levels of SMN caused widespread perturbations in translation at embryonic day (E) 14.5 targeting genes associated with primary cilia. The density of primary cilia in vivo, as well as cilial length in vitro, was significantly decreased in prenatal SMA mice. Proteomic analysis revealed downstream perturbations in primary cilia-regulated signalling pathways, including Wnt signalling. Cell proliferation was concomitantly reduced in the hippocampus of SMA mice. Prenatal transplacental therapeutic intervention with SMN-restoring risdiplam rescued primary cilia defects in SMA mouse embryos. Thus, SMN protein is required for normal cellular and molecular development of primary cilia in the CNS. Early, systemic treatment with SMN-restoring therapies can successfully target neurodevelopmental comorbidities in SMA.
Authors
Federica Genovese, Yu-Ting Huang, Anna A.L. Motyl, Martina Paganin, Gaurav Sharma, Ilaria Signoria, Deborah Donzel, Nicole C.H. Lai, Marie Pronot, Rachel A. Kline, Helena Chaytow, Kimberley J. Morris, Kiterie M.E. Faller, Thomas M. Wishart, Ewout J.N. Groen, Michael A. Cousin, Gabriella Viero, Thomas H. Gillingwater
Abstract
Impaired muscle regrowth in aging is underpinned by reduced pro-inflammatory macrophage function and subsequently impaired muscle cellular remodeling. Macrophage phenotype is metabolically controlled through TCA intermediate accumulation and activation of HIF1A. We hypothesized that transient hypoxia following disuse in old mice would enhance macrophage metabolic inflammatory function thereby improving muscle cellular remodeling and recovery. Old (20 months) and young adult mice (4 months) were exposed to acute (24h) normobaric hypoxia immediately following 14-days of hindlimb unloading and assessed during early re-ambulation (4- and 7-days) compared to age-matched controls. Treated aged mice had improved pro-inflammatory macrophage profiles, muscle cellular remodeling, and functional muscle recovery to the levels of young control mice. Likewise, young adult mice had enhanced muscle remodeling and functional recovery when treated with acute hypoxia. Treatment in aged mice restored the muscle molecular fingerprint and biochemical spectral patterns (Raman Spectroscopy) observed in young mice and strongly correlated to improved collagen remodeling. Finally, intramuscular delivery of hypoxia-treated macrophages recapitulated the muscle remodeling and recovery effects of whole-body hypoxic exposure in old mice. These results emphasize the role of pro-inflammatory macrophages during muscle regrowth in aging and highlight immunometabolic approaches as a route to improve muscle cellular dynamics and regrowth.
Authors
Zachary J. Fennel, Negar Kosari, Paul-Emile Bourrant, Elena M. Yee, Robert J. Castro, Anu S. Kurian, Jonathan Palmer, Morgan Christensen, Katsuhiko Funai, Ryan M. O'Connell, Anhong Zhou, Micah J. Drummond
Abstract
We conceived of a type of antitumor mechanism of action by which a soluble target in the tumor microenvironment, such as a tumor-driving growth factor, can be phagocytized along with cancer cells via antibody-dependent cellular phagocytosis (ADCP) using an antibody bispecific for the soluble target and a solid target overexpressed on the cancer cell surface. We explored this concept through engineering bispecific antibodies (BsAbs) co-targeting human epidermal growth factor receptor-2 (HER2) and vascular endothelial growth factor A (VEGFA) in an scFv-IgG format (VHS). We showed that the HER2-VEGFA BsAbs but not the parental antibodies alone or in combination induced co-phagocytosis of VEGFA and HER2-overexpressing cancer cells by tumor-associated macrophages via ADCP. In both immunocompromised and immunocompetent mice with aggressive tumors, the BsAbs demonstrated greater anti-metastasis activity and produced a greater survival benefit than the parental antibodies alone or in combination, in a manner dependent on Fcγ receptors on the macrophages. Our results provide proof of the concept that HER2-VEGFA BsAbs achieve enhanced antitumor activity by leveraging HER2 overexpressed on the cancer cell surface to induce co-phagocytosis of VEGFA. Our findings warrant clinical testing of the strategy to treat metastasis and recurrence of HER2-overexpressing solid tumors that respond to anti-VEGFA therapy.
Authors
Yang Lu, Songbo Qiu, Zhen Fan
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
In vitro studies have implicated orphan receptor GPRC5B in β-cell survival, proliferation and insulin secretion, but its relevance for glucose homeostasis in vivo is largely unknown. Using tamoxifen-inducible, β-cell-specific GPRC5B knockout mice (Ins-G5b-KOs) we show here that loss of GPRC5B does not affect β-cell function in the lean state, but results in strongly reduced insulin secretion and disturbed glucose tolerance in mice subjected to high fat diet for 16 weeks. Flow cytometry and single-cell expression analyses in islets from obese mice show a reduced β-cell abundance and a less mature β-cell phenotype in Ins-G5b-KOs. Expression of β-cell-specific transcription factor MafA is reduced both on the RNA and protein level, as are transcripts of MafA target genes. Mechanistically, we show that phosphorylation of cAMP response element-binding protein (CREB), a major regulator of MafA expression, is reduced in islets of obese Ins-G5b-KOs, and that this phenotype precedes the downregulation of MafA and MafA target genes. Taken together, GPRC5B helps to maintain mature β-cell function in obesity through cAMP/CREB-dependent regulation of MafA expression.
Authors
Tianpeng Wang, Remy Bonnavion, Janett Piesker, Stefan Günther, Nina Wettschureck
Abstract
Mutations on genes encoding polycystin-1 (PC1) and -2 (PC2) cause autosomal-dominant polycystic kidney disease. How these two proteins work together to exert anti-cystogenesis remains elusive. PC1 resembles adhesion G-protein coupled receptors and undergoes autocleavage in the extracellular N-terminus to expose a hidden “stalk” region, which is hypothesized to act as a “tethered agonist”. Here, we showed that wildtype PC1 and PC2 formed functional heteromeric channel complexes in Xenopus oocytes with different biophysical properties from PC2 homomeric channels. Deletion of PC1 N-terminus, which exposed the stalk, increased calcium permeability in PC1/PC2 heteromers that required the presence of stalk. Extracellular application of synthetic stalk peptide increased calcium permeation in stalkless PC1/PC2. Application of Wnt9B protein increased calcium permeability in PC1/PC2, but not in heteromers containing cleavage-resistant mutant PC1. Wnt9B interacted with N-terminal leucine-rich repeat (LRR) of PC1. Pretreatment with LRR blunted the increase in calcium permeability by Wnt9B. Thus, PC1 and PC2 form receptor-channel complexes that is activated by exposure of the stalk region following ligand binding to the PC1 N-terminus. The stalk peptide acts as a tethered agonist to activate PC1/PC2 by impacting ion selectivity of the complexes.
Authors
Runping Wang, Danish Idrees, Mohammad Amir, Biswajit Padhy, Jian Xie, Chou-Long Huang
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
Recent findings suggest that the small intestine (SI) is a novel site for B cell lymphopoiesis during fetal and neonatal life. However, the unique and/or conserved features that enable B cell development at this site remain unclear. To investigate the molecular and cellular scaffolds for B cell lymphopoiesis in mouse and human fetal intestines we leveraged single-cell RNA sequencing, in situ immunofluorescence, spatial transcriptomics and high-dimensional spectral flow cytometry. We found that SI mesenchymal and stromal cells expressed higher levels of chemokines known to recruit common lymphoid progenitors. Importantly, local lymphatic endothelial cells expressed IL7 and TSLP in proximity to IL7R+ precursor B cells, likely promoting their differentiation in the SI. Notably, we found that fetal-derived lymphoid tissue inducer (LTi) cells were required for B cell development and localization in the SI, but not fetal liver. These findings identify a lymphoid tissue development-independent role for this immune cell in B cell development. Collectively, our data reveal a conserved intestinal B cell niche in mice and humans, challenging traditional models of lymphopoiesis. The identification of a requisite cellular/molecular scaffold for fetal B cell development allows future studies to test the importance of this de novo B cell lymphopoiesis to long-term immunity.
Authors
Kimberly A. Carroll, Weihong Gu, Long Phan, Eduardo Gonzalez Santiago, Wenjia Wang, George C. Tseng, Liza Konnikova, Shruti Sharma
Abstract
To radically diminish TB incidence and mortality by 2035, as set out by the WHO End TB Strategy, there is a desperate need for improved TB therapies and a more effective vaccine against the deadly pathogen Mycobacterium tuberculosis (Mtb). Aerosol vaccination with the MtbΔsigH mutant protects two different species of NHPs against lethal TB challenge by invoking vastly superior T and B cell responses in the lungs through superior antigen-presentation and interferon-conditioning. Since the Geneva consensus on essential steps towards the development of live mycobacterial vaccines recommends that live TB vaccines must incorporate at least two independent gene knock outs, we have now generated several rationally designed, double (DKO)- and triple (TKO) knock-out mutants in Mtb, each containing the ΔsigH deletion. Here, we report preclinical studies in the rhesus macaque model of aerosol infection and SIV/HIV co-infection, aimed at assessing the safety of these MtbΔsigH - based DKOs and TKOs. We found that most of these mutant strains are attenuated in both immunocompetent and SIV-co-infected macaques and combinatorial infection with these generated strong cellular immune responses in the lung, akin to MtbΔsigH. Aerosol infection with these KO strains elicited inducible Bronchus Associated Lymphoid Tissue (iBALT), which is a correlate of protection from TB.
Authors
Garima Arora, Caden W. Munson, Mushtaq Ahmed, Vinay Shivanna, Annu Devi, Venkata S.R. Devireddy, Basil Antony, Shannan Hall-Ursone, Olga D. Gonzalez, Edward Dick Jr., Chinnaswamy Jagannath, Xavier Alvarez, Smriti Mehra, Shabaana A. Khader, Dhiraj K. Singh, Deepak Kaushal
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