Their involvement in several retinal diseases has been implied, such as diabetic retinopathy and age-related degeneration, and in vitro studies from human retinal pigment epithelial cells have described protection by PACAP against several harmful effects (Fabian et al. 2019; Maugeri et al. 2017, 2019a). The gene discussed is ADCYAP1; the disease is diabetic retinopathy.