Mitochondrial integrated stress response controls lung epithelial cell fate

Area of Science:

• Cell Biology
• Developmental Biology
• Metabolic Regulation

Background:

• Alveolar epithelial type 1 (AT1) and type 2 (AT2) cells are vital for lung function and repair.
• The metabolic regulation of lung epithelial cell fate remains largely unexplored.
• AT2 cells act as stem cells for AT1 cell production during lung development and repair.

Purpose of the Study:

• To investigate the role of mitochondrial metabolism in lung epithelial cell fate during postnatal development.
• To identify the specific mitochondrial components regulating cell differentiation and survival.
• To understand the mechanisms linking metabolic dysfunction to developmental defects in the lung.

Main Methods:

• Generated mouse models with targeted deletion of mitochondrial electron transport chain subunits (Ndufs2, Sdhd) in lung epithelial cells.
• Utilized single-cell RNA sequencing to analyze gene expression changes in affected cells.
• Employed interventions including yeast NADH dehydrogenase (NDI1) expression, ISR inhibitors, and NAD+ precursors.

Main Results:

• Loss of Ndufs2 in lung epithelial cells caused lethal defects in alveolar development, characterized by hypertrophic transitional cells.
• Conditional expression of NDI1 rescued alveolar development and lethality, indicating the importance of NAD+ regeneration.
• Transitional cells showed enrichment of integrated stress response (ISR) genes; ISR inhibition or NAD+ precursor administration partially rescued lethality.

Conclusions:

• Mitochondrial complex I-dependent NAD+ regeneration is essential for directing cell fate during postnatal alveolar development.
• Pathological induction of the integrated stress response is a key mechanism underlying developmental defects caused by complex I dysfunction.
• Targeting NAD+ metabolism and the ISR pathway offers potential therapeutic strategies for lung developmental disorders.