title: THOC5, a member of the mRNA export complex, contributes to processing of a subset of wingless/integrated (Wnt) target mRNAs and integrity of the gut epithelial barrier.
abstract: BACKGROUND
  THO (Suppressors of the transcriptional defects of hpr1 delta by overexpression) complex 5 (THOC5), an mRNA export protein, is involved in the expression of only 1% of all genes. Using an interferon inducible knockout mouse system, we have previously shown that THOC5 is an essential element in the maintenance of hematopoietic stem cells and cytokine-mediated hematopoiesis in adult mice. Here we interrogate THOC5 function in cell differentiation beyond the hematopoietic system and study pathological changes caused by THOC5 deficiency.
  
  
  RESULTS
  To examine whether THOC5 plays a role in general differentiation processes, we generated tamoxifen inducible THOC5 knockout mice. We show here that the depletion of THOC5 impaired not only hematopoietic differentiation, but also differentiation and self renewal of the gut epithelium. Depletion of the THOC5 gene did not cause pathological alterations in liver or kidney. We further show that THOC5 is indispensable for processing of mRNAs induced by Wnt (wingless/integrated) signaling which play key roles in epithelial cell differentiation/proliferation. A subset of Wnt target mRNAs, SRY-box containing gene 9 (Sox9), and achaete-scute complex homolog 2 (Ascl2), but not Fibronectin 1 (Fn1), were down-regulated in THOC5 knockout intestinal cells. The down-regulated Wnt target mRNAs were able to bind to THOC5. Furthermore, pathological alterations in the gastrointestinal tract induced translocation of intestinal bacteria and caused sepsis in mice. The bacteria translocation may cause Toll-like receptor activation. We identified one of the Toll-like receptor inducible genes, prostaglandin-endoperoxidase synthase 2 (Ptgs2 or COX2) transcript as THOC5 target mRNA.
  
  
  CONCLUSIONS
  THOC5 is indispensable for processing of only a subset of mRNAs, but plays a key role in processing of mRNAs inducible by Wnt signals. Furthermore, THOC5 is dispensable for general mRNA export in terminally differentiated organs, indicating that multiple mRNA export pathways exist. These data imply that THOC5 may be a useful tool for studying intestinal stem cells, for modifying the differentiation processes and for cancer therapy.
authors.affiliation: Institut fuer Biochemie, Medizinische Hochschule Hannover, OE4310 Carl-Neuberg-Str, 1, Hannover D-30623, Germany. tamura.teruko@MH-Hannover.de.
authors.forename: Shashank
authors.initials: S
authors.lastname: Saran
authors.forename: Doan D H
authors.initials: DD
authors.lastname: Tran
authors.forename: Sabine
authors.initials: S
authors.lastname: Klebba-Färber
authors.forename: Patricia
authors.initials: P
authors.lastname: Moran-Losada
authors.forename: Lutz
authors.initials: L
authors.lastname: Wiehlmann
authors.forename: Alexandra
authors.initials: A
authors.lastname: Koch
authors.forename: Himpriya
authors.initials: H
authors.lastname: Chopra
authors.forename: Oliver
authors.initials: O
authors.lastname: Pabst
authors.forename: Andrea
authors.initials: A
authors.lastname: Hoffmann
authors.forename: Robert
authors.initials: R
authors.lastname: Klopfleisch
authors.forename: Teruko
authors.initials: T
authors.lastname: Tamura
mesh_terms: D000818:Animals; D018988:Bacterial Translocation; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D004926:Escherichia coli / Q000254:growth & development; D004927:Escherichia coli Infections / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics*; D011485:Protein Binding; D034443:RNA Transport; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism; D018805:Sepsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D015398:Signal Transduction; D051153:Wnt Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D051546:Cyclooxygenase 2; D005353:Fibronectins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D055758:SOX9 Transcription Factor; D051153:Wnt Proteins; C489311:Ascl2 protein, mouse; C527933:Sox9 protein, mouse; C559981:THOC5 protein, mouse; C077623:Ptgs2 protein, mouse