ZO-1/Tjp1 and ZO-2/Tjp2 deletion in retinal pigment epithelium causes progressive retinal degeneration.

Tight junction protein-1 and -2 (Tjp1/ZO-1 and Tjp2/ZO-2) function as scaffold proteins within the tight junction complexes of the blood-retinal barrier (BRB). Although the breakdown of the BRB is implicated in retinopathies, the contribution of ZO-1/2 in the pathogenesis of retinopathies is unknown. To understand their role, we generated RPE-specific conditional ZO-1/2 single KOs (T1KO/T2KO) and ZO-1/2 double knockout (DKO) mice. While T1KO and T2KO did not exhibit overt retinal phenotypes, DKO demonstrated a strong retinal phenotype from 1-month post-KO induction. This includes the loss of RPE integrity and retinal thinning. Furthermore, RPE in DKO re-entered the cell cycle with upregulated YAP. At 12 months, we observed severe structural and functional retinal deterioration. In response to laser-induced damage, RPE displayed persistent hyper-proliferation, delayed wound repair, and the up-regulation of YAP. These studies confirmed the critical role of ZO-1/2 in maintaining an intact BRB and revealed a role of ZO-1/2 in wound healing.