Research Article
Abstract
Arcuate nucleus agouti–related peptide (AgRP) neurons play a central role in feeding and are under complex regulation by both homeostatic hormonal and nutrient signals and hypothalamic neuronal pathways. Feeding may also be influenced by environmental cues, sensory inputs, and other behaviors, implying the involvement of higher brain regions. However, whether such pathways modulate feeding through direct synaptic control of AgRP neuron activity is unknown. Here, we show that nociceptin-expressing neurons in the anterior bed nuclei of the stria terminalis (aBNST) make direct GABAergic inputs onto AgRP neurons. We found that activation of these neurons inhibited AgRP neurons and feeding. The activity of these neurons increased upon food availability, and their ablation resulted in obesity. Furthermore, these neurons received afferent inputs from a range of upstream brain regions as well as hypothalamic nuclei. Therefore, aBNST GABAergic nociceptin neurons may act as a gateway to feeding behavior by connecting AgRP neurons to both homeostatic and nonhomeostatic neuronal inputs.
Authors
Mark A. Smith, Agharul I. Choudhury, Justyna A. Glegola, Paulius Viskaitis, Elaine E. Irvine, Pedro Caldas Custodio de Campos Silva, Sanjay Khadayate, Hanns Ulrich Zeilhofer, Dominic J. Withers
Abstract
Inherited optic neuropathies include complex phenotypes, mostly driven by mitochondrial dysfunction. We report an optic atrophy spectrum disorder, including retinal macular dystrophy and kidney insufficiency leading to transplantation, associated with mitochondrial DNA (mtDNA) depletion without accumulation of multiple deletions. By whole-exome sequencing, we identified mutations affecting the mitochondrial single-strand binding protein (SSBP1) in 4 families with dominant and 1 with recessive inheritance. We show that SSBP1 mutations in patient-derived fibroblasts variably affect the amount of SSBP1 protein and alter multimer formation, but not the binding to ssDNA. SSBP1 mutations impaired mtDNA, nucleoids, and 7S-DNA amounts as well as mtDNA replication, affecting replisome machinery. The variable mtDNA depletion in cells was reflected in severity of mitochondrial dysfunction, including respiratory efficiency, OXPHOS subunits, and complex amount and assembly. mtDNA depletion and cytochrome c oxidase–negative cells were found ex vivo in biopsies of affected tissues, such as kidney and skeletal muscle. Reduced efficiency of mtDNA replication was also reproduced in vitro, confirming the pathogenic mechanism. Furthermore, ssbp1 suppression in zebrafish induced signs of nephropathy and reduced optic nerve size, the latter phenotype complemented by WT mRNA but not by SSBP1 mutant transcripts. This previously unrecognized disease of mtDNA maintenance implicates SSBP1 mutations as a cause of human pathology.
Authors
Valentina Del Dotto, Farid Ullah, Ivano Di Meo, Pamela Magini, Mirjana Gusic, Alessandra Maresca, Leonardo Caporali, Flavia Palombo, Francesca Tagliavini, Evan Harris Baugh, Bertil Macao, Zsolt Szilagyi, Camille Peron, Margaret A. Gustafson, Kamal Khan, Chiara La Morgia, Piero Barboni, Michele Carbonelli, Maria Lucia Valentino, Rocco Liguori, Vandana Shashi, Jennifer Sullivan, Shashi Nagaraj, Mays El-Dairi, Alessandro Iannaccone, Ioana Cutcutache, Enrico Bertini, Rosalba Carrozzo, Francesco Emma, Francesca Diomedi-Camassei, Claudia Zanna, Martin Armstrong, Matthew Page, Nicholas Stong, Sylvia Boesch, Robert Kopajtich, Saskia Wortmann, Wolfgang Sperl, Erica E. Davis, William C. Copeland, Marco Seri, Maria Falkenberg, Holger Prokisch, Nicholas Katsanis, Valeria Tiranti, Tommaso Pippucci, Valerio Carelli
Abstract
Currently, an effective targeted therapy for pancreatitis is lacking. Hereditary pancreatitis (HP) is a heritable, autosomal-dominant disorder with recurrent acute pancreatitis (AP) progressing to chronic pancreatitis (CP) and a markedly increased risk of pancreatic cancer. In 1996, mutations in PRSS1 were linked to the development of HP. Here, we developed a mouse model by inserting a full-length human PRSS1R122H gene, the most commonly mutated gene in human HP, into mice. Expression of PRSS1R122H protein in the pancreas markedly increased stress signaling pathways and exacerbated AP. After the attack of AP, all PRSS1R122H mice had disease progression to CP, with similar histologic features as those observed in human HP. By comparing PRSS1R122H mice with PRSS1WT mice as well as enzymatically inactivated Dead-PRSS1R122H mice, we unraveled that increased trypsin activity is the mechanism for R122H mutation to sensitize mice to the development of pancreatitis. We further discovered that trypsin inhibition, in combination with anticoagulation therapy, synergistically prevented progression to CP in PRSS1R122H mice. These animal models help us better understand the complex nature of this disease and provide powerful tools for developing and testing novel therapeutics for human pancreatitis.
Authors
Fu Gui, Yuebo Zhang, Jianhua Wan, Xianbao Zhan, Yao Yao, Yinghua Li, Ashley N. Haddock, Ji Shi, Jia Guo, Jiaxiang Chen, Xiaohui Zhu, Brandy H. Edenfield, Lu Zhuang, Cheng Hu, Ying Wang, Debabrata Mukhopadhyay, Evette S. Radisky, Lizhi Zhang, Aurelia Lugea, Stephen J. Pandol, Yan Bi, Baoan Ji
Abstract
Whether respiratory epithelial cells regulate the final transit of extravasated neutrophils into the inflamed airspace or are a passive barrier is poorly understood. Alveolar epithelial type 1 (AT1) cells, best known for solute transport and gas exchange, have few established immune roles. Epithelial membrane protein 2 (EMP2), a tetraspan protein that promotes recruitment of integrins to lipid rafts, is highly expressed in AT1 cells, but has no known function in lung biology. Here, we show that Emp2–/– mice exhibit reduced neutrophil influx into the airspace after a wide range of inhaled exposures. During bacterial pneumonia, Emp2–/– mice had attenuated neutrophilic lung injury and improved survival. Bone marrow chimeras, intravital neutrophil labeling, and in vitro assays suggested that defective transepithelial migration of neutrophils into the alveolar lumen occurs in Emp2–/– lungs. Emp2–/– AT1 cells had dysregulated surface display of multiple adhesion molecules, associated with reduced raft abundance. Epithelial raft abundance was dependent upon putative cholesterol-binding motifs in EMP2, whereas EMP2 supported adhesion molecule display and neutrophil transmigration through suppression of caveolins. Taken together, we propose that EMP2-dependent membrane organization ensures proper display on AT1 cells of a suite of proteins required to instruct paracellular neutrophil traffic into the alveolus.
Authors
Wan-Chi Lin, Kymberly M. Gowdy, Jennifer H. Madenspacher, Rachel L. Zemans, Kazuko Yamamoto, Miranda Lyons-Cohen, Hideki Nakano, Kyathanahalli Janardhan, Carmen J. Williams, Donald N. Cook, Joseph P. Mizgerd, Michael B. Fessler
Abstract
Mutations in genes encoding components of the mitochondrial DNA (mtDNA) replication machinery cause mtDNA depletion syndromes (MDSs), which associate ocular features with severe neurological syndromes. Here, we identified heterozygous missense mutations in single-strand binding protein 1 (SSBP1) in 5 unrelated families, leading to the R38Q and R107Q amino acid changes in the mitochondrial single-stranded DNA-binding protein, a crucial protein involved in mtDNA replication. All affected individuals presented optic atrophy, associated with foveopathy in half of the cases. To uncover the structural features underlying SSBP1 mutations, we determined a revised SSBP1 crystal structure. Structural analysis suggested that both mutations affect dimer interactions and presumably distort the DNA-binding region. Using patient fibroblasts, we validated that the R38Q variant destabilizes SSBP1 dimer/tetramer formation, affects mtDNA replication, and induces mtDNA depletion. Our study showing that mutations in SSBP1 cause a form of dominant optic atrophy frequently accompanied with foveopathy brings insights into mtDNA maintenance disorders.
Authors
Camille Piro-Mégy, Emmanuelle Sarzi, Aleix Tarrés-Solé, Marie Péquignot, Fenna Hensen, Mélanie Quilès, Gaël Manes, Arka Chakraborty, Audrey Sénéchal, Béatrice Bocquet, Chantal Cazevieille, Agathe Roubertie, Agnès Müller, Majida Charif, David Goudenège, Guy Lenaers, Helmut Wilhelm, Ulrich Kellner, Nicole Weisschuh, Bernd Wissinger, Xavier Zanlonghi, Christian Hamel, Johannes N. Spelbrink, Maria Sola, Cécile Delettre
Abstract
Mosaic-variegated aneuploidy (MVA) syndrome is a rare childhood disorder characterized by biallelic BUBR1, CEP57, or TRIP13 aberrations; increased chromosome missegregation; and a broad spectrum of clinical features, including various cancers, congenital defects, and progeroid pathologies. To investigate the mechanisms underlying this disorder and its phenotypic heterogeneity, we mimicked the BUBR1L1012P mutation in mice (BubR1L1002P) and combined it with 2 other MVA variants, BUBR1X753 and BUBR1H, generating a truncated protein and low amounts of wild-type protein, respectively. Whereas BubR1X753/L1002P and BubR1H/X753 mice died prematurely, BubR1H/L1002P mice were viable and exhibited many MVA features, including cancer predisposition and various progeroid phenotypes, such as short lifespan, dwarfism, lipodystrophy, sarcopenia, and low cardiac stress tolerance. Strikingly, although these mice had a reduction in total BUBR1 and spectrum of MVA phenotypes similar to that of BubR1H/H mice, several progeroid pathologies were attenuated in severity, which in skeletal muscle coincided with reduced senescence-associated secretory phenotype complexity. Additionally, mice carrying monoallelic BubR1 mutations were prone to select MVA-related pathologies later in life, with predisposition to sarcopenia correlating with mTORC1 hyperactivity. Together, these data demonstrate that BUBR1 allelic effects beyond protein level and aneuploidy contribute to disease heterogeneity in both MVA patients and heterozygous carriers of MVA mutations.
Authors
Cynthia J. Sieben, Karthik B. Jeganathan, Grace G. Nelson, Ines Sturmlechner, Cheng Zhang, Willemijn H. van Deursen, Bjorn Bakker, Floris Foijer, Hu Li, Darren J. Baker, Jan M. van Deursen
Apelin directs endothelial cell differentiation and vascular repair following immune-mediated injury
Abstract
Sustained, indolent immune injury of the vasculature of a heart transplant limits long-term graft and recipient survival. This injury is mitigated by a poorly characterized, maladaptive repair response. Vascular endothelial cells respond to proangiogenic cues in the embryo by differentiation to specialized phenotypes, associated with expression of apelin. In the adult, the role of developmental proangiogenic cues in repair of the established vasculature is largely unknown. We found that human and minor histocompatibility–mismatched donor mouse heart allografts with alloimmune-mediated vasculopathy upregulated expression of apelin in arteries and myocardial microvessels. In vivo, loss of donor heart expression of apelin facilitated graft immune cell infiltration, blunted vascular repair, and worsened occlusive vasculopathy in mice. In vitro, an apelin receptor agonist analog elicited endothelial nitric oxide synthase activation to promote endothelial monolayer wound repair, and reduce immune cell adhesion. Thus, apelin acted as an autocrine growth cue to sustain vascular repair and mitigate the effects of immune injury. Treatment with an apelin receptor agonist after vasculopathy was established markedly reduced progression of arterial occlusion in mice. Together, these initial data identify proangiogenic apelin as a key mediator of coronary vascular repair and a pharmacotherapeutic target for immune-mediated injury of the coronary vasculature.
Authors
Andrew G. Masoud, Jiaxin Lin, Abul K. Azad, Maikel A. Farhan, Conrad Fischer, Lin F. Zhu, Hao Zhang, Banu Sis, Zamaneh Kassiri, Ronald B. Moore, Daniel Kim, Colin C. Anderson, John C. Vederas, Benjamin A. Adam, Gavin Y. Oudit, Allan G. Murray
Abstract
The mineralocorticoid aldosterone is produced in the adrenal zona glomerulosa (ZG) under the control of the renin–angiotensin II (AngII) system. Primary aldosteronism (PA) results from renin-independent production of aldosterone and is a common cause of hypertension. PA is caused by dysregulated localization of the enzyme aldosterone synthase (Cyp11b2), which is normally restricted to the ZG. Cyp11b2 transcription and aldosterone production are predominantly regulated by AngII activation of the Gq signaling pathway. Here, we report the generation of transgenic mice with Gq-coupled designer receptors exclusively activated by designer drugs (DREADDs) specifically in the adrenal cortex. We show that adrenal-wide ligand activation of Gq DREADD receptors triggered disorganization of adrenal functional zonation, with induction of Cyp11b2 in glucocorticoid-producing zona fasciculata cells. This result was consistent with increased renin-independent aldosterone production and hypertension. All parameters were reversible following termination of DREADD-mediated Gq signaling. These findings demonstrate that Gq signaling is sufficient for adrenocortical aldosterone production and implicate this pathway in the determination of zone-specific steroid production within the adrenal cortex. This transgenic mouse also provides an inducible and reversible model of hyperaldosteronism to investigate PA therapeutics and the mechanisms leading to the damaging effects of aldosterone on the cardiovascular system.
Authors
Matthew J. Taylor, Matthew R. Ullenbruch, Emily C. Frucci, Juilee Rege, Mark S. Ansorge, Celso E. Gomez-Sanchez, Salma Begum, Edward Laufer, David T. Breault, William E. Rainey
Abstract
Gene therapy approaches are being deployed to treat recessive genetic disorders by restoring the expression of mutated genes. However, the feasibility of these approaches for dominantly inherited diseases — where treatment may require reduction in the expression of a toxic mutant protein resulting from a gain-of-function allele — is unclear. Here we show the efficacy of allele-specific RNAi as a potential therapy for Charcot-Marie-Tooth disease type 2D (CMT2D), caused by dominant mutations in glycyl-tRNA synthetase (GARS). A de novo mutation in GARS was identified in a patient with a severe peripheral neuropathy, and a mouse model precisely recreating the mutation was produced. These mice developed a neuropathy by 3–4 weeks of age, validating the pathogenicity of the mutation. RNAi sequences targeting mutant GARS mRNA, but not wild-type, were optimized and then packaged into AAV9 for in vivo delivery. This almost completely prevented the neuropathy in mice treated at birth. Delaying treatment until after disease onset showed modest benefit, though this effect decreased the longer treatment was delayed. These outcomes were reproduced in a second mouse model of CMT2D using a vector specifically targeting that allele. The effects were dose dependent, and persisted for at least 1 year. Our findings demonstrate the feasibility of AAV9-mediated allele-specific knockdown and provide proof of concept for gene therapy approaches for dominant neuromuscular diseases.
Authors
Kathryn H. Morelli, Laurie B. Griffin, Nettie K. Pyne, Lindsay M. Wallace, Allison M. Fowler, Stephanie N. Oprescu, Ryuichi Takase, Na Wei, Rebecca Meyer-Schuman, Dattatreya Mellacheruvu, Jacob O. Kitzman, Samuel G. Kocen, Timothy J. Hines, Emily L. Spaulding, James R. Lupski, Alexey Nesvizhskii, Pedro Mancias, Ian J. Butler, Xiang-Lei Yang, Ya-Ming Hou, Anthony Antonellis, Scott Q. Harper, Robert W. Burgess
Abstract
The microphthalmia family of transcription factors (MiT/TFEs) controls lysosomal biogenesis and is negatively regulated by the nutrient sensor mTORC1. However, the mechanisms by which cells with constitutive mTORC1 signaling maintain lysosomal catabolism remain to be elucidated. Using the murine epidermis as a model system, we found that epidermal Tsc1 deletion resulted in a phenotype characterized by wavy hair and curly whiskers, and was associated with increased EGFR and HER2 degradation. Unexpectedly, constitutive mTORC1 activation with Tsc1 loss increased lysosomal content via upregulated expression and activity of MiT/TFEs, whereas genetic deletion of Rheb or Rptor or prolonged pharmacologic mTORC1 inactivation had the reverse effect. This paradoxical increase in lysosomal biogenesis by mTORC1 was mediated by feedback inhibition of AKT, and a resulting suppression of AKT-induced MiT/TFE downregulation. Thus, inhibiting hyperactive AKT signaling in the context of mTORC1 loss-of-function fully restored MiT/TFE expression and activity. These data suggest that signaling feedback loops work to restrain or maintain cellular lysosomal content during chronically inhibited or constitutively active mTORC1 signaling, respectively, and reveal a mechanism by which mTORC1 regulates upstream receptor tyrosine kinase signaling.
Authors
Kaushal Asrani, Sanjana Murali, Brandon Lam, Chan-Hyun Na, Pornima Phatak, Akshay Sood, Harsimar Kaur, Zoya Khan, Michaël Noë, Ravi K. Anchoori, C. Conover Talbot Jr., Barbara Smith, Michael Skaro, Tamara L. Lotan
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Copyright © 2019 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)