Thyroid transcription factor in differentiating type II cells: regulation, isoforms, and target genes.
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-kD protein isoforms in the mouse, during hormone-induced differentiation of human fetal lung type II cells in culture. Transcript for 42-kD TTF-1 was 20-fold more abundant than TTF-1(46) mRNA by RT-PCR. Only 42-kD 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-1(42) was expressed in nuclei of cells by adenovirus transduction. By microarray analysis, 14 genes were comparably induced by recombinant TTF-1 (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 (approximately 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 small inhibitory RNA directed toward TTF-1 reduced TTF-1 content by approximately 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-kD TTF-1 is required for induction of a subset of regulated genes during type II cell differentiation.
Kolla
Venkatadri
V
Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, USA.
Gonzales
Linda W
LW
Gonzales
John
J
Wang
Ping
P
Angampalli
Sreedevi
S
Feinstein
Sheldon I
SI
Ballard
Philip L
PL
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000256:Adenoviridae; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D058851:GPI-Linked Proteins; D005786:Gene Expression Regulation / Q000187:drug effects; D005865:Gestational Age; D006367:HeLa Cells; D006801:Humans; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D051379:Mice; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D020033:Protein Isoforms / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000187:drug effects / Q000196:embryology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014161:Transduction, Genetic
D015703:Antigens, CD; C504117:CEACAM6 protein, human; D015815:Cell Adhesion Molecules; D058851:GPI-Linked Proteins; D051907:Lysosomal Membrane Proteins; C000614412:NKX2-1 protein, human; C000614414:Nkx2-1 protein, mouse; D009687:Nuclear Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003907:Dexamethasone