Iroquois genes influence proximo-distal morphogenesis during rat lung development.
Lung development is a highly regulated process directed by mesenchymal-epithelial interactions, which coordinate the temporal and spatial expression of multiple regulatory factors required for proper lung formation. The Iroquois homeobox (Irx) genes have been implicated in the patterning and specification of several Drosophila and vertebrate organs, including the heart. Herein, we investigated whether the Irx genes play a role in lung morphogenesis. We found that Irx1-3 and Irx5 expression was confined to the branching lung epithelium, whereas Irx4 was not expressed in the developing lung. Antisense knockdown of all pulmonary Irx genes together dramatically decreased distal branching morphogenesis and increased distention of the proximal tubules in vitro, which was accompanied by a reduction in surfactant protein C-positive epithelial cells and an increase in beta-tubulin IV and Clara cell secretory protein positive epithelial structures. Transmission electron microscopy confirmed the proximal phenotype of the epithelial structures. Furthermore, antisense Irx knockdown resulted in loss of lung mesenchyme and abnormal smooth muscle cell formation. Expression of fibroblast growth factors (FGF) 1, 7, and 10, FGF receptor 2, bone morphogenetic protein 4, and Sonic hedgehog (Shh) were not altered in lung explants treated with antisense Irx oligonucleotides. All four Irx genes were expressed in Shh- and Gli(2)-deficient murine lungs. Collectively, these results suggest that Irx genes are involved in the regulation of proximo-distal morphogenesis of the developing lung but are likely not linked to the FGF, BMP, or Shh signaling pathways.
van Tuyl
Minke
M
Program in Lung Biology, Hospital for Sick Children Research Inst., Toronto, Ontario, Canada.
Liu
Jason
J
Groenman
Freek
F
Ridsdale
Ross
R
Han
Robin N N
RN
Venkatesh
Vikram
V
Tibboel
Dick
D
Post
Martin
M
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D047108:Embryonic Development / Q000187:drug effects / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005346:Fibroblast Growth Factors / Q000378:metabolism; D015870:Gene Expression; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins / Q000235:genetics*; D066298:In Vitro Techniques; D051741:Kruppel-Like Transcription Factors / Q000172:deficiency / Q000235:genetics; D008168:Lung / Q000002:abnormalities / Q000196:embryology*; D008297:Male; D008648:Mesoderm / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D009154:Mutation; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics; D000075746:Zinc Finger Protein Gli2
D015415:Biomarkers; C525810:Bmp4 protein, mouse; C525811:Bmp4 protein, rat; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; C000618551:Gli2 protein, mouse; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D051741:Kruppel-Like Transcription Factors; D016376:Oligonucleotides, Antisense; C465570:Shh protein, mouse; D015534:Trans-Activators; D000075746:Zinc Finger Protein Gli2; D005346:Fibroblast Growth Factors