beta-Catenin is not necessary for maintenance or repair of the bronchiolar epithelium

Am J Respir Cell Mol Biol. 2009 Nov;41(5):535-43. doi: 10.1165/rcmb.2008-0407OC. Epub 2009 Feb 12.

Abstract

Signaling by Wnt/beta-catenin regulates self-renewal of tissue stem cells in the gut and, when activated in the embryonic bronchiolar epithelium, leads to stem cell expansion. We have used transgenic and cell type-specific knockout strategies to determine roles for beta-catenin-regulated gene expression in normal maintenance and repair of the bronchiolar epithelium. Analysis of TOPGal transgene activity detected beta-catenin signaling in the steady-state and repairing bronchiolar epithelium. However, the broad distribution and phenotype of signaling cells precluded establishment of a clear role for beta-catenin in the normal or repairing state. Necessity of beta-catenin signaling was tested through Cre-mediated deletion of Catnb exons 2-6 in airway epithelial cells. Functional knockout of beta-catenin had no impact on expression of Clara cell differentiation markers, mitotic index, or sensitivity of these cells to the Clara cell-specific toxicant, naphthalene. Repair of the naphthalene-injured airway proceeded with establishment of focal regions of beta-catenin-null epithelium. The size of regenerative epithelial units, mitotic index, and restoration of the ciliated cell population did not vary between wild-type and genetically modified mice. Thus, beta-catenin was not necessary for maintenance or efficient repair of the bronchiolar epithelium.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bronchioles / drug effects*
  • Bronchioles / metabolism
  • Bronchioles / pathology
  • Cell Differentiation
  • Cell Proliferation
  • Gene Expression Regulation, Developmental
  • Gene Knockout Techniques
  • Integrases / genetics
  • Lac Operon
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Mitotic Index
  • Naphthalenes / toxicity
  • Phenotype
  • Promoter Regions, Genetic
  • RNA, Messenger / metabolism
  • Rats
  • Regeneration* / drug effects
  • Regeneration* / genetics
  • Respiratory Mucosa / drug effects*
  • Respiratory Mucosa / metabolism
  • Respiratory Mucosa / pathology
  • Signal Transduction* / drug effects
  • Signal Transduction* / genetics
  • Stem Cells / drug effects*
  • Stem Cells / metabolism
  • Stem Cells / pathology
  • TCF Transcription Factors / genetics
  • Time Factors
  • Transcription Factor 7-Like 2 Protein
  • Uteroglobin / genetics
  • beta Catenin / genetics
  • beta Catenin / metabolism*

Substances

  • CTNNB1 protein, mouse
  • Naphthalenes
  • RNA, Messenger
  • Scgb1a1 protein, mouse
  • TCF Transcription Factors
  • Tcf7l2 protein, mouse
  • Transcription Factor 7-Like 2 Protein
  • beta Catenin
  • naphthalene
  • Uteroglobin
  • Cre recombinase
  • Integrases