DAPL1 inhibits epithelial-mesenchymal transition of retinal pigment epithelial cells by regulating the TGF-β/MITF pathway

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is a critical factor in the development of retinopathies, including proliferative vitreoretinopathy (PVR) and age-related macular degeneration (AMD), which are the leading causes of blindness worldwide. Deficiency in DAPL1 can induce RPE-EMT in vivo, and Dapl1 knockout mice (Dapl1 -/-) are prone to PVR, while aged Dapl1 -/- mice display AMD-like pathological features. However, the molecular mechanisms through which DAPL1 regulates RPE-EMT remain largely unknown. Here, using Dapl1 -/- mice and DAPL1 knockdown or overexpression RPE cells, we show that DAPL1 inhibits RPE-EMT by regulating the TGF-β/MITF signaling pathway, a critical signaling pathway/transcription factor in RPE cells. Overexpression of DAPL1 inhibits TGF-β-induced RPE-EMT, while deletion of Dapl1 in mice activates TGF-β signaling, decreases MITF expression, and promotes RPE-EMT under physiological or PVR pathological conditions. Gene therapy demonstrates that transgenic overexpression of MITF in Dapl1 -/- mice inhibits RPE-EMT in vivo and prevents retinal detachment-induced PVR pathological progress, offering hope for future treatment. Similarly, pharmacological therapy with Isoviolanthin, a flavonoid glycoside isolated from traditional medicinal herbs, inhibits TGF-β signaling and increases MITF expression in RPE cells in Dapl1 -/- mice, which then effectively rescues experimental PVR in Dapl1 -/- mice. These results suggest that DAPL1 regulates RPE-EMT at least partial through the TGF-β/MITF pathway and that targeting the TGF-β/MITF pathway could be a potential therapeutic strategy to treat Dapl1 deficiency-induced RPE-EMT-related retinal diseases, instilling hope for the future of retinal disease treatment.