Quantification of Hox and surfactant protein-B transcription during murine lung development.
BACKGROUND
Genetic processes underlying fetal lung development and maturation are incompletely understood. Better knowledge of these processes would provide insights into the causes of lung malformations and prevention of respiratory distress syndrome and the potential adverse effects of glucocorticoids. Hox genes are involved in the lung branching morphogenesis and maturation of respiratory epithelium, but their expression pattern remains to be defined.


OBJECTIVE
We hypothesized that genes involved in lung branching would be downregulated during early development, whereas those involved in maturation would be unchanged or upregulated.


METHODS
TaqMan real-time primers and probes were designed for all 39 murine Hox genes, and the murine SP-B gene and transcription profiles of these genes were obtained from whole lungs isolated at e14.5, e16.5, e18.5, e19.5 and postnatal days 1 and 20.


RESULTS
Hox genes in clusters A and B, specifically those between paralog groups 3 and 7, were the most represented, with Hoxa4 and Hoxa5 being the most highly transcribed. A wave of reduced transcription in 16 Hox genes, coincident with increased SP-B transcription, was observed with advancing gestation. Consistently high transcription of Hoxa5 from e14.5 to postnatal day 20 may indicate that sustained transcription is required for normal lung maturation. When e15.5 lungs were cultured with dexamethasone, Hoxb6, Hoxb7 and Hoxb8 levels were significantly upregulated, creating the potential for modulation of diverse downstream target genes.


CONCLUSIONS
Improved understanding of the genetic processes underlying lung development afforded by our Q-PCR platform may allow development of more specific methods for inducing fetal lung maturation.
Grier
David G
DG
Regional Neonatal Unit, Royal Maternity Hospital, Grosvenor Road, Belfast BT12 6BB, UK. grier@doctors.org.uk
Thompson
Alexander
A
Lappin
Terence R J
TR
Halliday
Henry L
HL
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005325:Fetal Organ Maturity / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D005938:Glucocorticoids / Q000494:pharmacology; D018398:Homeodomain Proteins / Q000235:genetics*; D008168:Lung / Q000737:chemistry* / Q000196:embryology* / Q000254:growth & development; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009924:Organ Culture Techniques; D010750:Phosphoproteins / Q000235:genetics; D016133:Polymerase Chain Reaction; D037701:Pulmonary Surfactant-Associated Protein B / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D018398:Homeodomain Proteins; C484111:Hoxa4 protein, mouse; C059637:Hoxa5 protein, mouse; D010750:Phosphoproteins; D037701:Pulmonary Surfactant-Associated Protein B; D012333:RNA, Messenger; D014157:Transcription Factors; D003907:Dexamethasone