Expression of Iroquois genes is up-regulated during early lung development in the nitrofen-induced pulmonary hypoplasia.
OBJECTIVE
Iroquois homeobox (Irx) genes have been implicated in the early lung morphogenesis of vertebrates. Irx1-3 and Irx5 gene expression is seen in fetal lung in rodents up to day (D) 18.5 of gestation. Fetal lung in Irx knockdown mice shows loss of mesenchyme and dilated airspaces, whereas nitrofen-induced hypoplastic lung displays thickened mesenchyme and diminished airspaces. We hypothesized that the Irx genes are up-regulated during early lung morphogenesis in the nitrofen-induced hypoplastic lung.


METHODS
Pregnant rats were exposed either to olive oil or nitrofen on D9. Fetal lungs harvested on D15 were divided into control and nitrofen groups; and the lungs harvested on D18 were divided into control, nitrofen without congenital diaphragmatic hernia (CDH[-]), and nitrofen with CDH (CDH[+]). Irx gene expression levels were analyzed by reverse transcriptase polymerase chain reaction. Immunohistochemistry was performed to evaluate protein expression of Irx family.


RESULTS
Pulmonary Irx1-3 and Irx5 messenger RNA expression levels were significantly up-regulated in nitrofen group compared with controls at D15. On D15, Irx immunoreactivity was increased in nitrofen-induced hypoplastic lung compared with controls.


CONCLUSIONS
Overexpression of Irx genes in the early lung development may cause pulmonary hypoplasia in the nitrofen CDH model by inducing lung dysmorphogenesis with thickened mesenchyme and diminished airspaces.
National Children's Research Centre, Our Lady's Children's Hospital, Dublin, Ireland.
Takashi
T
Doi
Aušra
A
Lukošiūtė
Elke
E
Ruttenstock
Jens
J
Dingemann
Prem
P
Puri
D000199:Actins / Q000235:genetics; D000818:Animals; D047108:Embryonic Development / Q000235:genetics; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D005325:Fetal Organ Maturity / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D005865:Gestational Age; D006548:Hernia, Diaphragmatic / Q000235:genetics; D065630:Hernias, Diaphragmatic, Congenital; D018398:Homeodomain Proteins / Q000235:genetics*; D008168:Lung / Q000002:abnormalities* / Q000196:embryology*; D009024:Morphogenesis / Q000235:genetics*; D010647:Phenyl Ethers; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000502:physiology; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000235:genetics*
D000199:Actins; D018398:Homeodomain Proteins; D010647:Phenyl Ethers; D012333:RNA, Messenger; C007350:nitrofen