KROX20-Notch1 Network Transcriptionally Regulates Meibomian Gland Stem Cells for Its Development and Homeostasis

Meibomian gland dysfunction is the leading cause of Evaporative Dry Eye Disease (EDED), and accounts for approximately 90% of dry eye disease 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 the process that governs lineage commitment during MG morphogenesis and homeostasis. Krox20 marks MG stem/progenitor cell pools, and it 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/progenitor cells. Activation of Notch1 signaling may offer a novel approach to preventing and treating EDED caused by the depletion of the MG stem cell pool that can occur with aging.