title: A functional connectome: regulation of Wnt/TCF-dependent transcription by pairs of pathway activators.
abstract: BACKGROUND
  Wnt/β-catenin signaling is often portrayed as a simple pathway that is initiated by Wnt ligand at the cell surface leading, via linear series of interactions between 'core pathway' members, to the induction of nuclear transcription from genes flanked by β-catenin/TCF transcription factor binding sites. Wnt/β-catenin signaling is also regulated by a much larger set of 'non-core regulators'. However the relationship between 'non-core regulators' is currently not well understood. Aberrant activation of the pathway has been shown to drive tumorgenesis in a number of different tissues.
  
  
  METHODS
  Mammalian cells engineered to have a partially-active level of Wnt/β-catenin signaling were screened by transfection for proteins that up or down-regulated a mid-level of TCF-dependent transcription induced by transient expression of an activated LRP6 Wnt co-receptor (∆NLRP).
  
  
  RESULTS
  141 novel regulators of TCF-dependent transcription were identified. Surprisingly, when tested without ∆NLRP activation, most up-regulators failed to alter TCF-dependent transcription. However, when expressed in pairs, 27 % (466/1170) functionally interacted to alter levels of TCF-dependent transcription. When proteins were displayed as nodes connected by their ability to co-operate in the regulation of TCF-dependent transcription, a network of functional interactions was revealed. In this network, 'core pathway' components (Eg. β-catenin, GSK-3, Dsh) were found to be the most highly connected nodes. Activation of different nodes in this network impacted on the sensitivity to Wnt pathway small molecule antagonists.
  
  
  CONCLUSIONS
  The 'functional connectome' identified here strongly supports an alternative model of the Wnt pathway as a complex context-dependent network. The network further suggests that mutational activation of highly connected Wnt signaling nodes predisposed cells to further context-dependent alterations in levels of TCF-dependent transcription that may be important during tumor progression and treatment.
authors.affiliation: School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
authors.forename: Jamie
authors.initials: J
authors.lastname: Freeman
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
authors.forename: David
authors.initials: D
authors.lastname: Smith
authors.affiliation: School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
authors.forename: Branko
authors.initials: B
authors.lastname: Latinkic
authors.affiliation: School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
authors.forename: Ken
authors.initials: K
authors.lastname: Ewan
authors.affiliation: School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
authors.forename: Lee
authors.initials: L
authors.lastname: Samuel
authors.affiliation: Department of Molecular Medicine and Biotechnology and Centro di Ingegneria Genetica e Biotecnologia Avanzate, Federico II, Via Pansini 5, 80131, Naples, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Zollo
authors.affiliation: Department of Molecular Medicine and Biotechnology and Centro di Ingegneria Genetica e Biotecnologia Avanzate, Federico II, Via Pansini 5, 80131, Naples, Italy.
authors.forename: Natascia
authors.initials: N
authors.lastname: Marino
authors.affiliation: School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
authors.forename: Lorraine
authors.initials: L
authors.lastname: Tyas
authors.affiliation: Department of Mathematics, Imperial College, London, SW7 2AZ, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Jones
authors.affiliation: School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, Wales, UK. daletc@cardiff.ac.uk.
authors.forename: Trevor C
authors.initials: TC
authors.lastname: Dale
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D053263:Gene Regulatory Networks; D057809:HEK293 Cells; D006801:Humans; D060066:Protein Interaction Maps; D051820:TCF Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D051153:Wnt Proteins / Q000502:physiology*; D060449:Wnt Signaling Pathway / Q000187:drug effects*; D014982:Xenopus laevis
chemical_list: D000970:Antineoplastic Agents; D051820:TCF Transcription Factors; D051153:Wnt Proteins