| 1. |
- Alberro-Brage, Andres, et al.
(författare)
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Influenza virus decreases albumin uptake and megalin expression in alveolar epithelial cells
- 2023
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Ingår i: Frontiers in Immunology. - 1664-3224. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionAcute respiratory distress syndrome (ARDS) is a common complication of influenza virus (IV) infection. During ARDS, alveolar protein concentrations often reach 40-90% of plasma levels, causing severe impairment of gas exchange and promoting deleterious alveolar remodeling. Protein clearance from the alveolar space is at least in part facilitated by the multi-ligand receptor megalin through clathrin-mediated endocytosis.MethodsTo investigate whether IV infection impairs alveolar protein clearance, we examined albumin uptake and megalin expression in MLE-12 cells and alveolar epithelial cells (AEC) from murine precision-cut lung slices (PCLS) and in vivo, under IV infection conditions by flow cytometry and western blot. Transcriptional levels from AEC and broncho-alveolar lavage (BAL) cells were analyzed in an in-vivo mouse model by RNAseq.ResultsIV significantly downregulated albumin uptake, independently of activation of the TGF- β1/GSK3β axis that has been previously implicated in the regulation of megalin function. Decreased plasma membrane abundance, total protein levels, and mRNA expression of megalin were associated with this phenotype. In IV-infected mice, we identified a significant upregulation of matrix metalloproteinase (MMP)-14 in BAL fluid cells. Furthermore, the inhibition of this protease partially recovered total megalin levels and albumin uptake.DiscussionOur results suggest that the previously described MMP-driven shedding mechanisms are potentially involved in downregulation of megalin cell surface abundance and clearance of excess alveolar protein. As lower alveolar edema protein concentrations are associated with better outcomes in respiratory failure, our findings highlight the therapeutic potential of a timely MMP inhibition in the treatment of IV-induced ARDS.
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| 2. |
- Arcot Jayaram, Satish, 1979-
(författare)
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New roles for apical secretion and extracellular matrix assembly in Drosophila epithelial morphogenesis
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Branched tubular organs, such as the lung and vascular system fulfill the respiratory needs of most animals. Optimal tissue function relies on the uniform sizes and shapes of the constituting branches in each organ. The Drosophila tracheal airways provide a recognized genetic model system for identification and characterization of tube size regulators. We found that the programmed secretion and assembly of the apical extracellular matrix (ECM) is required for the expansion of the trachea and salivary glands (SG) tubes. We have characterized Vermiform (Verm) and Serpentine (Serp), two chitin-binding proteins with predicted polysaccharide deacetylase domains (ChLDs). Verm and Serp mutants show overelongated tubes, suggesting that luminal ECM modification restricts tracheal tube elongation. The luminal deposition of ChLDs, but not other secreted components, depends on paracellular septate junction integrity (SJs) in the tracheal epithelium. Deletion of the deacetylase domain renders Serp-GFP intracellular, arguing that the deacetylase domain harbors uncharacterized secretion signals. To explore this possibility we transferred the deacetylase domain from Serp to Gasp, another tracheal luminal protein, which requires the Emp24 adaptor for ER exit. The Gasp-Deac-GFP chimera was normally secreted in emp24 mutants indicating that the deacetylase domain contains potential ER-exit signals. To identify such signals we characterized conserved sequence motifs in the Serp deacetylase domain. Mutations of the N-glycosylation sites gradually reduced Serp-GFP luminal deposition suggesting that increased glycosylation enhances apical Serp secretion. By contrast, substitutions in three conserved amino acid stretches completely blocked the ER-exit of Serp-GFP. The mutated proteins were N-glycosylated suggesting that the motifs may be involved in a subsequent protein-folding step or facilitate ER exit through interactions with unidentified specific adaptors.
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| 3. |
- Bergenstråhle, Joseph, et al.
(författare)
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Spatial transcriptomic profiling of RespiratorySyncytial Virus (RSV) infection
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Despite the fact that the human Respiratory Syncytial Virus (RSV) was first discoveredback in 1956, it remains one of the leading causes of morbidity and mortality inyoung children. Transcriptome-wide spatially resolved transcriptomics is a technologyunder rapid development that introduces a new modality for exploratory examinationof cellular behavior. With this modality, we examine how RSV infection changes thelocal cellular environment in the lung by infecting mice with RSV and comparing itto control samples four days after infection. We find viral presence in all compartmentsof the tissue, well-defined induced tertiary lymphoid tissue within some of thesamples, compartmentalized infiltration of innate immune cells, as well as functionalenrichment of airway epithelial repair pathways.
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| 4. |
- Dabral, Swati, et al.
(författare)
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A RASSF1A-HIF1 alpha loop drives Warburg effect in cancer and pulmonary hypertension
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia signaling plays a major role in non-malignant and malignant hyperproliferative diseases. Pulmonary hypertension (PH), a hypoxia-driven vascular disease, is characterized by a glycolytic switch similar to the Warburg effect in cancer. Ras association domain family 1A (RASSF1A) is a scaffold protein that acts as a tumour suppressor. Here we show that hypoxia promotes stabilization of RASSF1A through NOX-1- and protein kinase C- dependent phosphorylation. In parallel, hypoxia inducible factor-1 alpha (HIF-1 alpha) activates RASSF1A transcription via HIF-binding sites in the RASSF1A promoter region. Vice versa, RASSF1A binds to HIF-1 alpha, blocks its prolyl-hydroxylation and proteasomal degradation, and thus enhances the activation of the glycolytic switch. We find that this mechanism operates in experimental hypoxia-induced PH, which is blocked in RASSF1A knockout mice, in human primary PH vascular cells, and in a subset of human lung cancer cells. We conclude that RASSF1A-HIF-1 alpha forms a feedforward loop driving hypoxia signaling in PH and cancer.
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| 5. |
- Firsova, Alexandra, et al.
(författare)
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Topographic atlas of cell states identifies regional gene expression in the adult human lung
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Single cell mRNA sequencing of the whole organ has become a popular technique to reveal rare types and subtypes of previously characterized cells as well as to distinguish and characterize gene expression of previously unknown cell types. Unsupervised clustering can reveal tens or even hundreds of variable genes that characterize cell types. Variation in gene expression is often observed within one cell type, and sometimes cannot be biologically explained without mapping of mRNA on tissue. In this study we aim to (i) map the majority of cell types of human lung, (ii) describe variability in their gene expression and (iii) relate this gene expression to cellular location and neighborhoods. Using three different spatial transcriptomics approaches, we mapped epithelial cell states of airways and submucosal gland, and defined cell type-unrelated gene expression variability along proximo-distal axis, including potential regulators and co-regulators of such cell states in the mesenchymal and immune cell niches. In addition, we mapped rare cell types, such as subtypes of neuroendocrine cells, ionocytes and tuft (brush) cells, revealing tracheal preference for ionocytes, and distal airways for GHRL-positive neuroendocrine cells. Finally, we used the created map as a reference for the diseased tissue from patients with stage II COPD and revealed perturbed cell states and COPD-specific imbalance of cell types, affecting immune and AT0 clusters.
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| 6. |
- Gallio, Marco, et al.
(författare)
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Rhomboid 3 orchestrates Slit-independent repulsion of tracheal branches at the CNS midline.
- 2004
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 131:15, s. 3605-3614
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Tidskriftsartikel (refereegranskat)abstract
- EGF-receptor ligands act as chemoattractants for migrating epithelial cells during organogenesis and wound healing. We present evidence that Rhomboid 3/EGF signalling, which originates from the midline of the Drosophila ventral nerve cord, repels tracheal ganglionic branches and prevents them from crossing it. rho3 acts independently from the main midline repellent Slit, and originates from a different sub-population of midline cells: the VUM neurons. Expression of dominant-negative Egfr or Ras induces midline crosses, whereas activation of the Egfr or Ras in the leading cell of the ganglionic branch can induce premature turns away from the midline. This suggests that the level of Egfr intracellular signalling, rather than the asymmetric activation of the receptor on the cell surface, is an important determinant in ganglionic branch repulsion. We propose that Egfr activation provides a necessary switch for the interpretation of a yet unknown repellent function of the midline.
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| 7. |
- He, Li, 1987-
(författare)
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Spatial and temporal regulation of neural stem cells in the developing brain by PRDM16
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mammalian brain comprises a large number and diversity of neurons and non-neural cells. Most of these cell types derive from a single sheet of neuroepithelium (NE) that contains a limited pool of neural stem cells (NSCs). NSCs in the developing brain are under complex regulation to achieve maximum daughter cell type diversity. In this thesis, we investigate how NSCs are regulated spatially and temporally by a critical transcription factor (TF), PRDM16, in the developing mouse brain. In the first paper, we study the mechanisms that guide specification of an essential brain structure, the Choroid plexus (ChP). The ChP localizes at the brain dorsal midline, and the cell identity of the ChP epithelium depends on the induction by Bone morphogenetic protein (BMP) morphogens. NSCs at the presumptive ChP exit cell cycle, lose neural potential and subsequently obtain the ChP epithelial cell identity. We found that PRDM16 is required for ChP epithelium specification, as proliferative NSCs failed to acquire quiescence in the Prdm16 mutant brain. To investigate the molecular mechanisms controlling NSC proliferation and quiescence, we determined transcriptional states of proliferative versus quiescent NSCs and profiled genomic binding patterns for the BMP signaling effectors SMAD4 and pSMAD1/5/8. We found that BMP signaling suppresses cell proliferation genes in NSCs, and this activity requires PRDM16 co-binding to the enhancers of these target genes. One of the PRDM16-SMAD co-regulated genes is the Wnt pathway ligand Wnt7b. Using a single-cell-resolution fluorescent in situ technique, we confirm that Wnt7band Wnt activity are upregulated in Prdm16 mutant ChP epithelial cells and that the increased Wnt activity correlates with NSC over-proliferation. Together, our work reveals the mechanism by which BMP signaling induces NSC quiescence and defines a regulatory circuit composed of BMP, Wnt signaling and PRDM16 in the specification of the ChP epithelium. NSCs sequentially generate cortical projection neurons in the neocortex. How the temporal progression of these stem cells is regulated remains unclear. We identify an essential role of PRDM16 in determining the transition of early to late neurogenesis. Prdm16 deficiency leads to delayed NSC progression, neuronal subtype mis-specification and severe defects in laminar organization. Our genomic profiling of PRDM16 binding sites reveals its enrichment at distal regulatory elements of genes that are differentially expressed between early and late neurogenesis. We further show that PRDM16 represses target gene expression by restricting the chromatin accessibility of the enhancer regions. Cell cycle regulators and genes involved in neuronal migration are direct targets of PRDM16 in regulating NSC behavior and neuronal specification. Together, the findings have broadened our understanding of spatial and temporal regulation on NSC identity by the interplay of morphogens and TFs. In particular, we reveal the molecular mechanisms by which BMP signaling together with PRDM16 induces stem cell quiescence to obtain tissue-specific identity and show the temporal dynamics of cortical NSC gene expression programs controlled by PRDM16.
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| 8. |
- Hemphälä, Johanna, 1970-
(författare)
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Genetic dissection of tubulogenesis in the Drosophila trachea
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The formation of branched tubular organs, such as the mammalian lung kidney and vascular system, is an essential process in animal development. The Drosophila tracheal (respiratory) system provides a genetic model system to study the highly ordered process of branch outgrowth and fusion required to form continuous tubular networks.In a transposon mutagenesis screen we identified several genes involved in the different steps of tracheal network formation, including branch fusion. We initially studied the differentiation of the fusion cell in the dorsal branches (DBs). The DBs consists of 5-6 cells, one of which acquires the fusion cell fate. Our results point to a role for Decapentaplegic (Dpp), the Drosophila homolog of transforming growth factor-b (TGFb), in inducing the DB fusion cells fate. The Delta/Notch pathway is then required to select and restrict the fusion cell fate to a single cell in the DBs.After the outgrowth and fusion of tracheal branches, the constituent tubes acquire distinct size and shapes to generate a functional tubular tissue. We have found that a mutation in the grainyhead (grh) gene cause the branches to elongate excessively. Cellular and ultrastructural analyses showed that this phenotype was generated by apical cell membrane overgrowth. It was further shown that the activity of Grh is modulated by Branchless, the key regulator of branch outgrowth. Mutations in the Na/K ATPase a subunit (ATP a) and the fasiclin II (fasII) genes, cause similar elongated tracheal tubes as the ones found in grh mutants, but instead these mutations affect the lateral subcellular compartment, independently of the function of Grh in the apical cell domain.In a search for downstream effectors of Grh, we found the krotzkopf verkehrt (kkv) gene, encoding a Drosophila chitin synthase. Analysis of kkv mutants suggests that a chitinous intralumenal cable, lacking in kkv embryos, is essential for the tracheal tubes to attain their correct length and diameter. The composition of the chitinous filament is also affected in mutants of various septate junction components, indicating that their tube size defects are at least in part caused by an inability to correctly assemble the intralumenal chitinous matrix formed by Kkv.
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