Epithelial membrane protein 2 governs transepithelial migration of neutrophils into the airspace

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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 (AT)1 cells, best known for solute transport and gas exchange, have few established immune roles. Epithelial membrane protein (EMP)2, 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 labelling, 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 R. Lyons-Cohen, Hideki Nakano, Kyathanahalli Janardhan, Carmen J. Williams, Donald N. Cook, Joseph P. Mizgerd, Michael B. Fessler

Dominant mutations in mtDNA maintenance gene SSBP1 cause optic atrophy and foveopathy

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Abstract

Mutations in genes encoding components of the mitochondrial DNA (mtDNA) replication machinery cause mtDNA depletion syndromes (MDS), which associate ocular features with severe neurological syndromes. Here, we identified heterozygous missense mutations in SSBP1 in five 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 new revised SSBP1 crystal structure. Structural analysis suggests 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 novel form of dominant optic atrophy frequently accompanied with foveopathy, brings new 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 Solà, Cécile Delettre

SSBP1 mutations cause mtDNA depletion underlying a complex optic atrophy disorder

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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 four families with dominant and one with recessive inheritance. We show that SSBP1 mutations in patient-derived fibroblasts variably affect its amount and alter multimer formation, but not the binding to ssDNA. SSBP1 mutations impaired mtDNA, nucleoids and 7S-DNA amounts as well as mtDNA replication, impacting replisome machinery. The variable mtDNA depletion in cells reflected in severity of mitochondrial dysfunction, including respiratory efficiency, OXPHOS subunits and complexes amount and assembly. mtDNA depletion and cytochrome c oxidase-negative cells were found ex-vivo in biopsies of affected tissues, like 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 wild-type mRNA but not by SSBP1 mutant transcripts. This previously unrecognized disease of mtDNA maintenance implicates SSBP1 mutations as 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 H. Baugh, Bertil Macao, Zsolt Szilagyi, Camille Péron, Margaret A. Gustafson, Kamal Khan, Chiara La Morgia, Piero Barboni, Michele Carbonelli, Maria Lucia Valentino, Rocco Liguori, Vandana Shashi, Jennifer A. Sullivan, Shashi Nagaraj, Mays El-Dairi, Alessandro Iannaccone, Ioana Cutcutache, Enrico Bertini, Rosalba Carrozzo, Francesco Emma, Francesca Diomedi-Camassei, Claudia Zanna, Martin Armstrong, Matthew J Page, Sylvia Boesch, Saskia B. Wortmann, Robert Kopajtich, Nicholas Stong, Wolfgang Sperl, Erica Davis, William C. Copeland, Marco Seri, Maria Falkenberg, Holger Prokisch, Nicholas Katsanis, Valeria Tiranti, Tommaso Pippucci, Valerio Carelli

Manganese transporter Slc30a10 controls physiological manganese excretion and toxicity

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Abstract

Manganese (Mn), an essential metal and nutrient, is toxic in excess. Toxicity classically results from inhalational exposures in individuals working in industrial settings. Identified in 2012, the first known disease of inherited Mn excess is caused by mutations in the metal exporter SLC30A10 and is characterized by Mn excess, dystonia, cirrhosis, and polycythemia. To investigate the role of SLC30A10 in Mn homeostasis, we first generated mice with whole body Slc30a10 deficiency, which developed severe Mn excess and impaired systemic and biliary Mn excretion. Slc30a10 localized to canalicular membrane of hepatocytes, but mice with liver Slc30a10 deficiency developed minimal Mn excess despite impaired biliary Mn excretion. Slc30a10 also localized to the apical membrane of enterocytes, but mice with Slc30a10 deficiency in small intestines developed minimal Mn excess despite impaired Mn export into the lumen of the small intestines. Finally, mice with Slc30a10 deficiency in liver and small intestines developed Mn excess less severe than that observed in mice with whole body Slc30a10 deficiency, suggesting that additional sites of Slc30a10 expression contribute to Mn homeostasis. Overall, these results indicated that Slc30a10 is essential for Mn excretion and could be an effective target for pharmacological intervention for Mn toxicity.

Authors

Courtney J. Mercadante, Milankumar Prajapati, Heather L. Conboy, Miriam E. Dash, Carolina Herrera, Michael A. Pettiglio, Layra Cintron-Rivera, Madeleine A. Salesky, Deepa B. Rao, Thomas B. Bartnikas

mTORC1 feedback to AKT modulates lysosomal biogenesis through MiT/TFE regulation

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Abstract

The Microphthalmia family of transcription factors (MiT/TFE) 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 up-regulated expression and activity of MiT/TFEs, while 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 down-regulation. 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

Loss-of-function variants in myocardin cause congenital megabladder in humans and mice

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Abstract

Myocardin (MYOCD) is the founding member of a class of transcriptional co-activators that bind serum response factor to activate gene expression programs critical in smooth muscle (SM) and cardiac muscle development. Insights into the molecular functions of MYOCD have been obtained from cell culture studies and, to date, knowledge about in vivo roles of MYOCD comes exclusively from experimental animals. Here, we defined an often lethal congenital human disease associated with inheritance of pathogenic MYOCD variants. This disease manifested as a massively dilated urinary bladder, or megabladder, with disrupted SM in its wall. We provided evidence that monoallelic loss-of-function variants in MYOCD caused congenital megabladder in males only, whereas biallelic variants were associated with disease in both sexes, with a phenotype additionally involving the cardiovascular system. These results were supported by co-segregation of MYOCD variants with the phenotype in four unrelated families, by in vitro transactivation studies where pathogenic variants resulted in abrogated SM gene expression, and finding megabladder in two distinct mouse models with reduced Myocd activity. In conclusion, we have demonstrated that variants in MYOCD result in human disease, and the collective findings highlight a vital role for MYOCD in mammalian organogenesis.

Authors

Arjan C. Houweling, Glenda M. Beaman, Alex V. Postma, T. Blair Gainous, Klaske D. Lichtenbelt, Francesco Brancati, Filipa M. Lopes, Ingeborg van der Made, Abeltje M. Polstra, Michael L. Robinson, Kevin D. Wright, Jamie M. Ellingford, Ashley R. Jackson, Eline Overwater, Rita Genesio, Silvio Romano, Letizia Camerota, Emanuela D'Angelo, Elizabeth J. Meijers-Heijboer, Vincent M. Christoffels, Kirk M. McHugh, Brian L. Black, William G. Newman, Adrian S. Woolf, Esther E. Creemers

Dermal adipose tissue has high plasticity and undergoes reversible dedifferentiation in mice

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Abstract

Dermal adipose tissue (dWAT) has been the focus of much discussion in recent years. However, dWAT remains poorly characterized. The fate of the mature dermal adipocytes and the origin of the rapidly re-appearing dermal adipocytes at different stages remain unclear. Here, we isolated dermal adipocytes and characterized dermal fat at the cellular and molecular level. Together with its dynamic responses to external stimuli, we established that dermal adipocytes are a distinct class of white adipocytes with high plasticity. By combining pulse-chase lineage tracing and single cell RNA-sequencing, we observed that mature dermal adipocytes undergo de-differentiation and re-differentiation under physiological and pathophysiological conditions. Upon various challenges, the de-differentiated cells proliferate and re-differentiate into adipocytes. In addition, manipulation of dWAT highlighted an important role for mature dermal adipocytes for hair cycling and wound healing. Altogether, these observations unravel a surprising plasticity of dermal adipocytes and provide an explanation for the dynamic changes in dWAT mass that occur under physiological and pathophysiological conditions, and highlight the important contributions of dWAT towards maintaining skin homeostasis.

Authors

Zhuzhen Zhang, Mengle Shao, Chelsea Hepler, Zhenzhen Zi, Shangang Zhao, Yu A. An, Yi Zhu, Alexandra Ghaben, May-yun Wang, Na Li, Toshiharu Onodera, Nolwenn Joffin, Clair Crewe, Qingzhang Zhu, Lavanya Vishvanath, Ashwani Kumar, Chao Xing, Qiong A. Wang, Laurent Gautron, Yingfeng Deng, Ruth Gordillo, Ilja Kruglikov, Christine M. Kusminski, Rana K. Gupta, Philipp E. Scherer

Cannabidiol attenuates seizures and EEG abnormalities in Angelman syndrome model mice

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Abstract

Angelman syndrome (AS) is a neurodevelopmental disorder characterized by intellectual disability, lack of speech, ataxia, EEG abnormalities, and epilepsy. Seizures in AS individuals are common, debilitating, and often drug-resistant. Therefore, there is an unmet need for better treatment options. Cannabidiol (CBD), a major phytocannabinoid constituent of cannabis, has antiseizure activity and behavioral benefits in preclinical and clinical studies for some disorders associated with epilepsy, suggesting that the same could be true for AS. Here we show that acute CBD (100 mg/kg) attenuated hyperthermia- and acoustically-induced seizures in a mouse model of AS. However, neither acute CBD nor a two-weeklong course of CBD administered immediately after a kindling protocol could halt the pro-epileptogenic plasticity observed in AS model mice. CBD had a dose-dependent sedative effect, but did not have an impact on motor performance. CBD abrogated the enhanced intracortical local field potential power, including delta and theta rhythms observed in AS model mice, indicating that CBD administration could also help normalize the EEG deficits observed in individuals with AS. Our results provide critical preclinical evidence supporting CBD treatment of seizures and alleviation of EEG abnormalities in AS, and will thus help guide the rational development of CBD as an AS treatment.

Authors

Bin Gu, Manhua Zhu, Madison R. Glass, Marie Rougié, Viktoriya D. Nikolova, Sheryl S. Moy, Paul R. Carney, Benjamin D. Philpot

Myeloid loss of Beclin 1 promotes PD-L1^hi precursor B Cell lymphoma development

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Abstract

Beclin 1 (Becn1) is a key molecule of the autophagy pathway and has been implicated in cancer development. Due to the embryonic lethality of Becn1 homozygous deficient mice, the precise mechanisms and cell-type-specific role of Becn1 in the regulation of inflammation and tumor immunity remain elusive. Here, we report that myeloid-deficient Becn1 (Becn1ΔM) mice develop neutrophilia and hypersusceptible to LPS-induced septic shock, with a high risk of developing spontaneous precursor (pre)-B cell lymphoma with elevated expressions of immunosuppressive molecules PD-L1 and IL-10. Becn1 deficiency results in stabilization of neutrophil MEKK3, aberrant p38 activation, and neutrophil-B cell interaction through Cxcl9/Cxcr3 chemotaxis. Neutrophil-B cell interplay leads to activations of IL-21/STAT3/IRF1 and CD40L/ERK signaling, together regulates the programmed death ligand 1 (PD-L1) expression, and suppresses CD8+ T cell function. Ablation of p38 in Becn1ΔM mice prevents neutrophil-inflammation and B cell tumorigenesis. Importantly, low Becn1 expression in human neutrophils correlates with PD-L1 levels in pre-B ALL patients. Our findings have identified myeloid Becn1 as a therapeutic target of cancer immunity and immunotherapy for pre-B lymphomas.

Authors

Peng Tan, Lian He, Changsheng Xing, Jingrong Mao, Xiao Yu, Motao Zhu, Lixia Diao, Leng Han, Yubin Zhou, James M. You, Helen Y. Wang, Rong-Fu Wang

Sonic Hedgehog repression underlies gigaxonin mutation-induced motor deficits in giant axonal neuropathy

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Abstract

Growing evidence shows that alterations occurring at early developmental stages contribute to symptoms manifested in adulthood in the setting of neurodegenerative diseases. Here, we studied the molecular mechanisms causing giant axonal neuropathy (GAN), a severe neurodegenerative disease due to loss-of-function of the gigaxonin-E3 ligase. We showed that gigaxonin governs Sonic Hedgehog (Shh) induction, the developmental pathway patterning the dorso-ventral axis of the neural tube and muscles, by controlling the degradation of the Shh-bound Patched receptor. Similarly to Shh inhibition, repression of gigaxonin in zebrafish impaired motor neuron specification and somitogenesis and abolished neuromuscular junction formation and locomotion. Shh signaling was impaired in gigaxonin null zebrafish and was corrected by both pharmacological activation of the Shh pathway and human gigaxonin, pointing to an evolutionary-conserved mechanism regulating Shh signaling. Gigaxonin-dependent inhibition of Shh activation was also demonstrated in primary fibroblasts from GAN patients and in a Shh activity reporter line depleted in gigaxonin. Our findings establish gigaxonin as a key E3 ligase that positively controls the initiation of Shh transduction, reveal the causal role of Shh dysfunction in motor deficits, thus highlighting the developmental origin of GAN.

Authors

Yoan Arribat, Karolina S Mysiak, Léa Lescouzères, Alexia Boizot, Maxime Ruiz, Mireille Rossel, Pascale Bomont