Published ahead of print on September 7, 2006, doi:10.1165/rcmb.2006-0207OC Am. J. Respir. Cell Mol. Biol., Volume 36, Number 2, February 2007, 213-225 A more recent version of this article appeared on February 1, 2007
Submitted on June 8, 2006 Thyroid Transcription Factor in Differentiating Type II Cells: Regulation, Isoforms and Target GenesVenkatadri Kolla1,1 Department of Pediatrics, Division of Neonatology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA, 2 The University of Pennsylvania, Institute for Environmental Medicine, Philadelphia, PA, USA, 3 Department of Pediatrics, Division of Neonatology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA; The University of Pennsylvania School of Medicine, Philadelphia, PA, USA * To whom correspondence should be addressed. E-mail: ballardp{at}email.chop.edu.
Thyroid transcription factor-1 (TTF-1, product of the Nkx2.1 gene) is essential for branching morphogenesis of the lung and enhances expression of surfactant proteins by alveolar type II cells. We investigated expression of two TTF-1 mRNA transcripts, generated by alternative start sites and coding for 42 and 46 kDa protein isoforms in the mouse, during hormone-induced differentiation of human fetal lung type II cells in culture. Transcript for 42 kDa TTF-1 was 20-fold more abundant than TTF-146 mRNA by RT-PCR. Only 42 kDa protein was detected in lung cells and its content increased during in vivo development and in response to in vitro glucocorticoid plus cAMP treatment. To examine TTF-1 target proteins, recombinant, phosphorylated TTF-142 was expressed in nuclei of cells by adenovirus transduction. By microarray analysis, 14 genes were comparably induced by rTTF-1 and hormone treatment, and 9 additional hormone-responsive genes, including surfactant proteins-A/B/C, were partially induced by rTTF-1. The most highly (~10-fold) TTF-1-induced genes were DC-LAMP (LAMP3) and CEACAM6 with induction confirmed by Western analysis and immunostaining. Treatment of cells with hormones plus siRNA directed toward TTF-1 reduced TTF-1 content by ~50% and inhibited hormone induction of the 23 genes induced by rTTF-1. In addition, knockdown of TTF-1 inhibited 72 of 274 other genes induced by hormones. We conclude that 42 kDa TTF-1 is required for induction of a subset of regulated genes during type II cell differentiation.
This article has been cited by other articles:
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
