Cldn3 knockout mice exhibit enamel defects caused by excess accumulation of extracellular matrix proteins in the forming enamel and mutations in CLDN19 are associated with Amelogenesis Imperfecta, a genetic disorder characterized by tooth enamel defects (Bardet et al., 2017; Yamaguti et al., 2017). Here, CLDN19 is linked to amelogenesis imperfecta.