Diabetes is a common complication of cystic fibrosis (CF) that affects approximately 20% of adolescents and 40% to 50% of adults with CF. The age-at-onset of CF-related diabetes (marked by clinical diagnosis and treatment initiation) is an important measure of the disease process. DNA variants associated with age-at-onset of CFRD reside in and near SLC26A9. Deep sequencing of the SLC26A9 gene in 762 individuals with CF revealed that two common DNA haplotypes formed by the risk variants account for the association with diabetes (high risk, P-value: 4.34E-3; low risk, P-value: 1.14E-3). Single-cell RNA (scRNA) sequencing indicated that SLC26A9 is predominantly expressed in pancreatic ductal cells, and frequently co-expressed with CFTR along with transcription factors that have binding sites 5′ of SLC26A9. These findings replicated upon re-analysis of scRNA data from 4 independent studies. DNA fragments derived from the 5′ region of SLC26A9 bearing variants from the low risk haplotype generated 12% to 20% higher levels of expression in PANC-1 and CFPAC-1 cells compared to the high risk haplotype (P-values: 2.00E-3 to 5.15E-9). Taken together, our findings indicate that an increase in SLC26A9 expression in ductal cells of the pancreas delays the age-at-onset of diabetes, thereby suggesting a CFTR-agnostic treatment for a major complication of CF.
Anh-Thu N. Lam, Melis A. Aksit, Briana Vecchio-Pagan, Celeste A. Shelton, Derek L. Osorio, Arianna F. Anzmann, Loyal A. Goff, David C. Whitcomb, Scott M. Blackman, Garry R. Cutting
Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the CNS. Although CD4 T cells are implicated in MS pathogenesis and have been the main focus of MS research using the animal model experimental autoimmune encephalomyelitis (EAE), substantial evidence from patients with MS points to a role for CD8 T cells in disease pathogenesis. We previously showed that an MHC class I-restricted epitope of myelin basic protein (MBP) is presented in the CNS during CD4 T cell-initiated EAE. Here, we investigated whether naïve MBP-specific CD8 T cells recruited to the CNS during CD4 T cell-initiated EAE engaged in determinant-spreading and influenced disease. We found that the MBP-specific CD8 T cells exacerbated brain but not spinal cord inflammation. We show that a higher frequency of monocytes and monocyte-derived cells presented the MHC class I-restricted MBP ligand in the brain compared to the spinal cord. Infiltration of MBP-specific CD8 T cells enhanced ROS production in the brain only in these cell-types and only when the MBP-specific CD8 T cells expressed Fas ligand (FasL). These results suggest that myelin-specific CD8 T cells may contribute to disease pathogenesis via a FasL-dependent mechanism that preferentially promotes lesion formation in the brain.
Catriona A. Wagner, Pamela J. Roqué, Trevor R. Mileur, Denny Liggitt, Joan M. Goverman
Brown adipose tissue (BAT), as the main site of adaptive thermogenesis, exerts beneficial metabolic effects on obesity and insulin resistance. BAT has been previously assumed to contain a homogeneous population of brown adipocytes. Utilizing multiple mouse models capable of genetically labeling different cellular populations, as well as single-cell RNA sequencing, and 3D tissue profiling, we discovered a new brown adipocyte subpopulation with low thermogenic activity co-existing with the classical high thermogenic brown adipocytes within the BAT. These low thermogenic brown adipocytes had significantly lower Ucp1 and Adipoq expression, larger lipid droplets, and lower mitochondrial content. Functional analyses showed that the low thermogenic brown adipocytes have significant lower basal mitochondrial respiration, and they are specialized in fatty acid uptake. Upon changes in environmental temperature, the two brown adipocyte subpopulations underwent dynamic inter-conversions. Cold exposure converted low thermogenic brown adipocytes into high thermogenic cells, and a thermoneutral environment had the opposite effect. This recruitment of high thermogenic brown adipocytes by cold stimulation is not affected by high fat diet feeding, but significantly declined with age. Our results revealed a high degree of functional heterogeneity of brown adipocytes.
Anying Song, Wenting Dai, Min Jee Jang, Leonard Medrano, Zhuo Li, Hu Zhao, Mengle Shao, Jiayi Tan, Aimin Li, Tinglu Ning, Marcia M. Miller, Brian Armstrong, Janice M. Huss, Yi Zhu, Yong Liu, Viviana Gradinaru, Xiwei Wu, Lei Jiang, Philipp E. Scherer, Qiong A. Wang
Catecholamines released by sympathetic nerves can activate adrenergic receptors present on nearly every cell type, including myeloid derived suppressor cells (MDSCs). Using in vitro systems and murine tumor models, in wild-type mice and genetically modified (β2-AR–/–) mice, as well adoptive transfer approaches, we found that the degree of β2-AR signaling significantly influences MDSC frequency and survival in tumors and other tissues, modulates their expression of immunosuppressive molecules such as arginase-I and PDL-1 and alters their ability to suppress the proliferation of T cells. The regulatory functions of β-AR signaling in MDSCs were found to be dependent upon STAT3 phosphorylation. Moreover, we observed that the β2-AR-mediated increase in survival of MDSCs is dependent upon Fas-FasL interactions, and this is consistent with gene expression analyses which reveal a greater expression of apoptosis-related genes in β2-AR–/– MDSCs. Our data reveals the potential of β2-AR signaling to increase the generation of MDSCs from both murine and human peripheral blood cells and that the immunosuppressive function of MDSCs could be mitigated by treatment with β-AR antagonists, or enhanced by β-AR agonists, strongly supporting the possibility that reducing stress-induced activation of β2-ARs could help to overcome immune suppression and enhance the efficacy of immunotherapy and other cancer therapies.
Hemn Mohammadpour, Cameron R. MacDonald, Guanxi Qiao, Minhui Chen, Bowen Dong, Bonnie L. Hylander, Philip L. McCarthy, Scott I. Abrams, Elizabeth A. Repasky
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 (GoF) allele—is unclear. Here we show the efficacy of allele-specific RNAi as a potential therapeutic for Charcot-Marie-Tooth 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 one 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.
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
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. 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 nociceptin/GABAergic neurons may act as a gateway to feeding behavior by connecting AgRP neurons to both homeostatic and non-homeostatic neuronal inputs.
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
Currently, an effective targeted therapy for pancreatitis is still 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 PRSS1R122Hgene, 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 anti-coagulation therapy, synergistically prevented the 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.
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
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.
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
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.
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
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.
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
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