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A molecular circuit regulates fate plasticity in emerging and adult AT2 cells [scRNA-seq]

ABSTRACT: Alveolar AT1 and AT2 cells are vital for gas exchange in the lung and become compromised in several common and deadly diseases. While the signals driving differentiation of either cell type have been identified, it remains unclear when and how fate plasticity is regulated in the emerging and adult alveolar epithelium. Here we show AT2s first emerge as singletons at zones between the proximal stalks and distal tips of the embryonic lung that quickly extrude and can traverse the interstitium to connect with nearby epithelium, a process we term interlumenal junctioning. Throughout the late embryonic and early perinatal period, we find that a window of AT2 fate plasticity exists that is closed by the bZIP transcription factor C/EBPα, mediated by its transcriptional suppression of the Notch signaling regulator DLK1. C/EBPα acts on Dlk1 at a novel regulatory site. Further, both Dlk1 and Cebpa are regulated by the polycomb repressive complex (PRC2), and together constitute a novel incoherent feedforward loop that generates a Dlk1 pulse upon downregulation of PRC2. We propose these form a “pulse generator” circuit capable of generating a timed activation of Notch signaling, resulting in a “salt and pepper” pattern of AT1 and AT2 fate. Following injury in the adult lung, we found that C/EBPα downregulation is required for re-accessing AT2 fate plasticity and is mediated by the dominant negative C/EBP family member CHOP. Finally, we observe Cebpa loss also activates a “defender” AT2 state enriched in interferon-stimulated antipathogenic gene expression that is distinct from its reparative state and propose AT2s toggle between these states following infection to robustly protect and repair alveoli.

ORGANISM(S): Mus musculus

PROVIDER: GSE295269 | GEO | 2025/07/30

REPOSITORIES: GEO

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Project description:Alveoli are thin-walled sacs that serve as the gas exchange units of the lung. They are affected in devastating lung diseases including COPD, Idiopathic Pulmonary Fibrosis, and the major form (adenocarcinoma) of lung cancer, the leading cause of cancer deaths. The alveolar epithelium is composed of two morphologically distinct cell types: alveolar type (AT) 1 cells, exquisitely thin cells across which oxygen diffuses to reach the blood, and AT2 cells, specialized surfactant-secreting cells. Classical studies suggested that AT1 cells arise from AT2 cells during development and following injury, but more recent studies suggest other sources. Here we use histological and marker analysis, lineage tracing, and clonal analysis in mice to identify alveolar progenitor and stem cells and map their locations and potential in vivo. The results show that AT1 and AT2 cells arise independently during development from a bipotential progenitor. After birth, new AT1 cells derive from rare, long-lived, self-renewing AT2 cells, each producing a slowly expanding clonal focus of regenerated alveoli contiguous with the founder AT2 cell. This stem cell function of AT2 cells is broadly activated by diffuse AT1 cell injury, and AT2 self-renewal can be induced in vitro by EGF ligands and permanently activated in vivo by AT2 cell-specific targeting of the oncogenic KrasG12D allele, efficiently transforming AT2 cells into monoclonal adenomatous tumors that rapidly enlarge and prove fatal. Thus, there is a developmental switch in alveolar progenitor cells after birth, when mature AT2 cells function as facultative stem cells that contribute to local alveolar renewal, repair, and cancer. We propose that short-range signals from dying AT1 cells regulate AT2 stem cell activity: a signal transduced by EGFR-KRAS controls AT2 self-renewal and is hijacked during oncogenic transformation, and a separate signal controls reprogramming to AT1 cell fate. To compare expression between ATII and E18 BP populations, RNA was isolated from either population purified by FACS. Two populations are analyzed with 3 biological replicates per population.

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A molecular circuit regulates fate plasticity in emerging and adult AT2 cells [scRNA-seq]

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