Generation of a Novel <scp> <i> Col8a2 ^{P2A‐CreERT2} </i> </scp> Mouse Line Enables Targeted Genetic Manipulation of Corneal Endothelial Cells and Modeling of Endothelial Decompensation

The corneal endothelium is a monolayer of specialized cells that maintains stromal deturgescence and transparency, functions essential for vision. Despite its clinical importance, the developmental origins and homeostatic programs of the endothelium remain poorly understood, in part due to the lack of a lineage-specific genetic driver. To overcome this limitation, we generated a Col8a2^P2A-CreERT2 knock-in mouse line that enables selective genetic manipulations of corneal endothelial cells. Cre activity was validated with reporter alleles and functional importance was assessed by conditional ablation of Col8a2⁺ cells in adulthood, with phenotypic outcomes evaluated by histology, immunofluorescence, and in vivo imaging. We found that Col8a2^P2A-CreERT2 drives robust and specific recombination in corneal endothelial cells. Functional assays demonstrated that Col8a2⁺ cells contribute continuously to Descemet's membrane synthesis and are essential for maintaining endothelial integrity. Ablation disrupted endothelial density and barrier function, resulting in phenotypes resembling human endothelial dystrophies, including features of Fuchs' endothelial corneal dystrophy and posterior polymorphous corneal dystrophy. These findings identify Col8a2⁺ cells as indispensable regulators of endothelial development, homeostasis, and disease pathogenesis. The Col8a2^P2A-CreERT2 line provides the first corneal endothelium-specific genetic driver, establishing a platform for mechanistic investigation and therapeutic discovery in endothelial disorders.