Identification of three genes of known function expressed by alveolar epithelial type I cells

Am J Respir Cell Mol Biol. 2003 Jul;29(1):98-105. doi: 10.1165/rcmb.2002-0196OC. Epub 2003 Feb 14.


To identify genes of known function expressed by type I (AT1) cells, changes in gene expression during transdifferentiation of alveolar epithelial cells (AEC) in primary culture from type II (AT2) to type I-like cell phenotype were evaluated. Total RNA from AEC on Day 0 or Day 8 was hybridized to a rat microarray for screening. Eight upregulated genes on Day 8 were selected for further investigation. Northern analysis confirmed upregulation of three of these genes, PAI-1, P2X4, and P15INK4B. The corresponding proteins were evaluated in cultured AEC and results correlated with expression in AT1 cells. In AEC monolayers, all three proteins increased between Day 1 and Day 8. In mixed populations of freshly isolated rat lung cells, concurrent labeling with the AT1 cell-specific antibody, VIIIB2, localized these proteins to AT1 cells. In whole lung, all three proteins were detected in alveolar epithelium in a location consistent with expression in AT1 cells. Identification of novel AT1 cell genes of known function suggests an active role for AT1 cells in alveolar homeostasis. Furthermore, expression of these gene products in AT1-like cells, in freshly isolated AT1 cells, and AT1 cells in whole lung indicates that AT1-like cells reflect many of the properties of AT1 cells in situ.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blotting, Northern
  • Blotting, Western
  • Cell Cycle Proteins / genetics*
  • Cell Cycle Proteins / metabolism
  • Cell Differentiation / genetics
  • Cells, Cultured
  • Cyclin-Dependent Kinase Inhibitor p15
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics*
  • Cyclin-Dependent Kinase Inhibitor p16 / metabolism
  • Gene Expression Regulation
  • Lung / metabolism
  • Male
  • Microscopy, Fluorescence
  • Oligonucleotide Array Sequence Analysis
  • Plasminogen Activator Inhibitor 1 / genetics*
  • Plasminogen Activator Inhibitor 1 / metabolism
  • Pulmonary Alveoli / cytology*
  • Pulmonary Alveoli / physiology*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Purinergic P2 / genetics*
  • Receptors, Purinergic P2 / metabolism
  • Receptors, Purinergic P2X4
  • Reproducibility of Results
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Suppressor Proteins*
  • Up-Regulation


  • Cdkn2b protein, rat
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor p15
  • Cyclin-Dependent Kinase Inhibitor p16
  • P2rx4 protein, rat
  • Plasminogen Activator Inhibitor 1
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2X4
  • Tumor Suppressor Proteins