Disruption of Krox20-Notch1 signaling blocks meibomian gland development and homeostasis leading to dry eye disease.

Meibomian gland dysfunction (MGD) is the leading cause of Dry Eye Disease (DED), accounting for approximately 90% of DED cases worldwide. The transcription factor KROX20 has been shown to mark stem cells that play a critical role in Meibomian gland (MG) development and homeostasis, however, the molecular mechanisms underlying these processes are not well understood. In this report, we used multiple Krox20 lineage tracing and ablation studies to investigate lineage commitment during MG morphogenesis and homeostasis. KROX20 marks MG stem cell pools, and regulates cellular contributions to the glands, as loss of Krox20 leads to MG atrophy, while its overexpression results in MG enlargement. We also found that Notch1 signaling is regulated by KROX20 and that ablation of the Notch1 gene in KROX20-expressing cells leads to MG atrophy, while Notch1 overexpression partially rescues MG atrophy caused by the loss of Krox20. Together, these results reveal a critical Krox20-Notch1 regulatory pathway in MG stem cells. Activation of Notch1 signaling may offer a novel approach to preventing or treating DED caused by depletion of the MG stem cell pool that can occur with ageing.