Autophagy is required for lung development and morphogenesis
Behzad Yeganeh, … , Cameron Ackerley, Martin Post
Behzad Yeganeh, … , Cameron Ackerley, Martin Post
Published July 1, 2019; First published June 4, 2019
Citation Information: J Clin Invest. 2019;129(7):2904-2919. https://doi.org/10.1172/JCI127307.
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Categories: Research Article Development Pulmonology

Autophagy is required for lung development and morphogenesis

Abstract

Bronchopulmonary dysplasia (BPD) remains a major respiratory illness in extremely premature infants. The biological mechanisms leading to BPD are not fully understood, although an arrest in lung development has been implicated. The current study aimed to investigate the occurrence of autophagy in the developing mouse lung and its regulatory role in airway branching and terminal sacculi formation. We found 2 windows of epithelial autophagy activation in the developing mouse lung, both resulting from AMPK activation. Inhibition of AMPK-mediated autophagy led to reduced lung branching in vitro. Conditional deletion of beclin 1 (Becn1) in mouse lung epithelial cells (Becn1Epi-KO), either at early (E10.5) or late (E16.5) gestation, resulted in lethal respiratory distress at birth or shortly after. E10.5 Becn1Epi-KO lungs displayed reduced airway branching and sacculi formation accompanied by impaired vascularization, excessive epithelial cell death, reduced mesenchymal thinning of the interstitial walls, and delayed epithelial maturation. E16.5 Becn1Epi-KO lungs had reduced terminal air sac formation and vascularization and delayed distal epithelial differentiation, a pathology similar to that seen in infants with BPD. Taken together, our findings demonstrate that intrinsic autophagy is an important regulator of lung development and morphogenesis and may contribute to the BPD phenotype when impaired.

Authors

Behzad Yeganeh, Joyce Lee, Leonardo Ermini, Irene Lok, Cameron Ackerley, Martin Post

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Figure 1

Autophagy activity during embryonic mouse lung development.

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Autophagy activity during embryonic mouse lung development. (A) Represen...
(A) Representative immunoblots of the autophagy proteins ATG7, ATG5–12, BECN1, and LC3B-II (lower band) in mouse lung lysates during lung development. (B and C) Densitometric measurements of ATG7, ATG5–12, BECN1, and LC3B-II proteins at various gestation points relative to E11.5 lung. ACTB was used as a protein loading control. Results are expressed as the mean ± SEM from 3 separate experiments. *P < 0.05 versus E11.5. (D) IF confocal microscopic images showing the autophagosome marker LC3B (red) and the epithelial marker E-cadherin (CDH1, green) during lung development. Nuclei were stained with DAPI (blue). (E) Representative TEM images from embryonic (E12.5 and E17.5) and postnatal (P0) mouse lungs. Arrows indicate autophagosomes present in the epithelial cells of the lungs. Scale bars: 500 nm and 250 nm (insets). Graph shows quantitative analysis of the number of autophagosomes per epithelial cell (≥10 micrographs per gestational age for 2 mice; autophagic vacuoles were counted from 8 to 10 randomly selected fields). Results are expressed as the mean ± SEM. *P < 0.05 versus E12.5. Statistical significance for all data was determined by 1-way ANOVA followed by Tukey’s post hoc test.