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Neurofibromatosis type 2 tumor suppressor protein is expressed in oligodendrocytes and regulates cell proliferation and process formation.

ABSTRACT: The neurofibromatosis type 2 (NF2) tumor suppressor protein Merlin functions as a negative regulator of cell growth and actin dynamics in different cell types amongst which Schwann cells have been extensively studied. In contrast, the presence and the role of Merlin in oligodendrocytes, the myelin forming cells within the CNS, have not been elucidated. In this work, we demonstrate that Merlin immunoreactivity was broadly distributed in the white matter throughout the central nervous system. Following Merlin expression during development in the cerebellum, Merlin could be detected in the cerebellar white matter tract at early postnatal stages as shown by its co-localization with Olig2-positive cells as well as in adult brain sections where it was aligned with myelin basic protein containing fibers. This suggests that Merlin is expressed in immature and mature oligodendrocytes. Expression levels of Merlin were low in oligodendrocytes as compared to astrocytes and neurons throughout development. Expression of Merlin in oligodendroglia was further supported by its identification in either immortalized cell lines of oligodendroglial origin or in primary oligodendrocyte cultures. In these cultures, the two main splice variants of Nf2 could be detected. Merlin was localized in clusters within the nuclei and in the cytoplasm. Overexpressing Merlin in oligodendrocyte cell lines strengthened reduced impedance in XCELLigence measurements and Ki67 stainings in cultures over time. In addition, the initiation and elongation of cellular projections were reduced by Merlin overexpression. Consistently, cell migration was retarded in scratch assays done on Nf2-transfected oligodendrocyte cell lines. These data suggest that Merlin actively modulates process outgrowth and migration in oligodendrocytes.

SUBMITTER: Toledo A

PROVIDER: S-EPMC5929554 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Neurofibromatosis type 2 tumor suppressor protein is expressed in oligodendrocytes and regulates cell proliferation and process formation.

Toledo Andrea A Grieger Elena E Karram Khalad K Morrison Helen H Baader Stephan L SL

PloS one 20180501 5

The neurofibromatosis type 2 (NF2) tumor suppressor protein Merlin functions as a negative regulator of cell growth and actin dynamics in different cell types amongst which Schwann cells have been extensively studied. In contrast, the presence and the role of Merlin in oligodendrocytes, the myelin forming cells within the CNS, have not been elucidated. In this work, we demonstrate that Merlin immunoreactivity was broadly distributed in the white matter throughout the central nervous system. Foll ...[more]

PMID: 29715273

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Project description:BackgroundMerlin, the product of the Neurofibromatosis type 2 (NF2) tumor suppressor gene, belongs to the ezrin-radixin-moesin (ERM) subgroup of the protein 4.1 superfamily, which links cell surface glycoproteins to the actin cytoskeleton. While merlin's functional activity has been examined in mammalian and Drosophila models, little is understood about its evolution, diversity, and overall distribution among different taxa.ResultsBy combining bioinformatic and phylogenetic approaches, we demonstrate that merlin homologs are present across a wide range of metazoan lineages. While the phylogenetic tree shows a monophyletic origin of the ERM family, the origin of the merlin proteins is robustly separated from that of the ERM proteins. The derivation of merlin is thought to be in early metazoa. We have also observed the expansion of the ERM-like proteins within the vertebrate clade, which occurred after its separation from Urochordata (Ciona intestinalis). Amino acid sequence alignment reveals the absence of an actin-binding site in the C-terminal region of all merlin proteins from various species but the presence of a conserved internal binding site in the N-terminal domain of the merlin and ERM proteins. In addition, a more conserved pattern of amino acid residues is found in the region containing the so-called "Blue Box," although some amino acid substitutions in this region exist in the merlin sequences of worms, fish, and Ciona. Examination of sequence variability at functionally significant sites, including the serine-518 residue, the phosphorylation of which modulates merlin's intra-molecular association and function as a tumor suppressor, identifies several potentially important sites that are conserved among all merlin proteins but divergent in the ERM proteins. Secondary structure prediction reveals the presence of a conserved alpha-helical domain in the central to C-terminal region of the merlin proteins of various species. The conserved residues and structures identified correspond to the important sites highlighted by the available crystal structures of the merlin and ERM proteins. Furthermore, analysis of the merlin gene structures from various organisms reveals the increase of gene length during evolution due to the expansion of introns; however, a reduction of intron number and length appears to occur in the merlin gene of the insect group.ConclusionOur results demonstrate a monophyletic origin of the merlin proteins with their root in the early metazoa. The overall similarity among the primary and secondary structures of all merlin proteins and the conservation of several functionally important residues suggest a universal role for merlin in a wide range of metazoa.

Project description:Recognition of foreign antigens by B cell receptor (BCR) on mature B cells leads to their clonal expansion, which is critically important for the effective host defence of the organism. However, excessive antigenic responses or reaction of B cells against bodyâs own components frequently lead to diverse immune diseases, such as B-cell lymphoma or autoimmunity, that often affect humans. Identification of genes that restrain uncontrolled proliferation of B cells is therefore an important goal towards understanding the origin of such diseases. Here we identify Ptger4 as a negative feedback regulator of B-cell proliferation in response to BCR triggering, and show that its encoded EP4 receptor is a principal molecule conveying the growth-suppressive effect of prostaglandin E2 (PGE2). In controlled in vitro assays, Ptger4-/- B cells showed augmented proliferative response and increased expression of activating genes upon BCR stimulation. Stable knock-down of Ptger4 in B-cell lymphoma markedly accelerated tumour spread in mice, while Ptger4 overexpression yielded significant protection. Lack of Ptger4 rendered mouse B cells completely resistant to proliferation arrest signalled by PGE2, and we find by transcriptional profiling that intrinsic activity of Ptger4 and PGE2-EP4 signalling target a similar set of activating genes. We further show that Ptger4 inhibits mouse B-cell activation in vivo and find it significantly downregulated in human B-cell lymphoma. Our results demonstrate that Ptger4 functions in B cells as a candidate tumour suppressor whose activity is regulated by the presence of PGE2 in the microenvironment. These findings suggest that targeting EP4 receptor for prostaglandin may present a novel strategy for treatment of B-cell diseases. Keywords: time course, cell type comparison, compound treatment design, microarray experiment record B cells were extracted from spleen of Ptger4+/+ and Ptger4-/- mice, and incubated in vitro for the indicated period with or without anti-IgM (Fab')2 antibody fragments and co-treated with or without PGE2. Total RNA was extracted, amplified, labelled with Cy3 or Cy5, and hybridized to mouse 24k oligo-arrays using a dye-swap strategy.

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Neurofibromatosis type 2 tumor suppressor protein is expressed in oligodendrocytes and regulates cell proliferation and process formation.

Publications

Neurofibromatosis type 2 tumor suppressor protein is expressed in oligodendrocytes and regulates cell proliferation and process formation.

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