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A4651 - Transcriptome Dynamics During Prenatal-to-Postnatal Lung Development in Nfe2l2 (Nrf2)-Sufficient and -Deficient Mice
Author Block: H. Cho, L. DeGraff, S. R. Kleeberger; Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC, United States.
Rationale: Progressive phases (embryonic-pseudoglandular-canalicular-saccular-alveolar) drive structural lung development through gestation and after birth and functional lung maturation requires surfactant production from later gestation to postnatal period. The molecular basis of lung development is not fully understood, and the role for an antioxidant transcription factor Nrf2 is unknown. Methods: We investigated transcriptomics during prenatal-to-postnatal lung development and the consequence of Nrf2 deletion using cDNA microarrays on Nrf2-knockout (Nrf2-/-) and wild-type (Nrf2+/+) mouse lungs at embryonic (E) days 13.5 (pseudoglandular),15.5 (pseudoglandular/canalicular), and 17.5 (canalicular/saccular), and postnatal (P) days 0 (saccular), 1 (saccular), 4 (saccular/alveolar), 14 (alveolar), and 42 (mature). Data were analyzed by GeneSpring and Ingenuity Pathway Analysis. Results: The lung transcriptomics were differentiated by age and genotype. In wild-type fetus, transcriptome variation was utmost at E13.5 compared to P0, and cell cycle/cellular arrangement (midkine, centromere proteins, collagens, claudin 6) and transporter (embryonic hemoglobin, alpha fetoprotein) genes were significantly abundant at E13.5-E15.5. They were steadily suppressed toward P0, supporting roles in pseudoglandular branching and type 2 pneumocyte differentiation. Significantly suppressed genes at E13.5-E15.5 were involved in immunity (uteroglobin, toll-like receptor 4 and accessories), redox (aldehyde dehrogenases, glutathione-S-transferases, cytochrome P450), and surfactants. Their marked upregulation toward birth mirrored club cell maturation. Increased surfactant and related enzymes (phospholiphases) from E15.5/E17.5 implied surfactant synthesis/storage in type 2 cells. Fetal lung-rich keratin and myosin transcripts were diminished from P1, indicating decreased interstitium or thinning of alveolar walls, while immune system and lipid transporter genes (immunoglobulins, albumin) were markedly elevated from P1. Upregulated cytokinesis and developmental genes at P4 suggested continued type 1 cell lining and saccule maturation to functioning alveolus. Elevation of glucose metabolism and cytotoxicity transcripts from P14 were concurrent with developmental gene suppression. At E13.5-15.5, transcriptome variation in Nrf2+/+ and Nrf2-/- was minute as explained by Nrf2 induction from E15.5. At E17.5, Nrf2-deficiency raised liver X receptor/retinoid X receptor signaling (apolipoproteins) and chemotaxis (toll-like receptors) genes and suppressed keratins suggesting abnormal lipid/glucose metabolism, immunity, and tissue development. At birth, Nrf2-/- lungs showed dysregulated expression of cell cycle (cell cycle dependent kinases), cholesterol synthesis (acyl-CoA synthetases), and connective tissue differentiation (Eph receptors) genes. During postnatal lung development, Nrf2-/- transcriptome displayed suppressed redox system (P1-P14) and increased cell death/abnormality (P1-P14) and muscle contraction/hypertrophy (P14). Conclusions: Murine lung transcriptome profiles corresponded to developmental dynamics and elucidated novel genes. Nrf2-dependent transcriptomics provided insights into the role for Nrf2 in prenatal-to-postnatal lung development and in mature lung homeostasis.