Single-cell sequencing of mouse lung epithelial cells after bleomycin injury and modulation of IRE1α

Epithelial cells that are committed to a differentiated state in homeostasis can change their identity in response to injury. In the lung, alveolar type 2 (AT2) cells are the resident secretory epithelial cells of the alveolus, and after injury can proliferate and differentiate into type 1 cells. This inducible plasticity is central to alveolar regeneration, fibrosis, and malignancy, but the regulatory pathways that govern the balance between fate maintenance and differentiation are incompletely understood. Epithelial cells that are committed to a differentiated state in homeostasis can change their identity in response to injury. In the lung, alveolar type 2 (AT2) cells are the resident secretory epithelial cells of the alveolus, and after injury can proliferate and differentiate into type 1 cells. This inducible plasticity is central to alveolar regeneration, fibrosis, and malignancy, but the regulatory pathways that govern the balance between fate maintenance and differentiation are incompletely understood. IRE1α is an ER transmembrane protein conserved throughout eukaryotes that senses misfolded protein in the ER lumen and initiates cellular efforts to regain protein folding homeostasis through its cytosolic kinase and RNase domains. We previously showed that IRE1α pharmacologic or genetic loss of function decreased the accumulation of damage-associated transient progenitors (DATPs), and also promoted their differentiation into new alveolar epithelial cells. To further detail the functions of IRE1α after AT2 injury, we performed single-cell transcriptome profiling of the AT2-to-AT1 transition after bleomycin injury, with pharmacologic or epithelial-specific genetic loss of IRE1α function.