Neuroendocrine cells can originate from club cells, but this potential is normally suppressed by Hes1 during lung development and homeostasis.

The binary cell fate decision between neuroendocrine (NE) and club cell lineages is fundamental to lung development and epithelial homeostasis, yet the mechanisms that maintain these lineages remain incompletely understood. Here, we show that Hes1, a Notch target gene, maintains club cell identity by suppressing neuroendocrine differentiation. Lineage-tracing analyses revealed that Scgb1a1-expressing club cells give rise to NE cells following Hes1 loss during development and adulthood. Single-cell RNA sequencing of endogenous NE (eNE) cells and induced NE (iNE) cells generated by Hes1 loss uncovered substantial heterogeneity within the iNE populations and transitional cells expressing Notch-associated genes and keratins. Lineage tracing further showed that iNE cells integrate into neuroepithelial bodies (NEBs), and iNE cells reconstructed cell-cell communication networks that closely resemble those of eNE cells. These findings indicate that club cells, including Scgb1a1-positive club cell progenitors and mature club cells, retain latent potential to adopt an NE fate, which is normally suppressed by Hes1. Our results identify club cells as a previously unrecognized cellular source of NE cells and reveal a key mechanism that preserves epithelial lineage identity in the lung.