In response to various injury-inducing stimuli (e.g., hyperoxia, ventilation, and septic shock), claudin 4 expression has been shown to be downregulated in mice, although an early upregulation of claudin 4 mRNA level was observed at 4 h in a ventilation-induced ALI mouse model (Wray et al., 2009; Cohen et al., 2010; Herrero et al., 2018; Vyas-Read et al., 2018). The gene discussed is CLDN4; the disease is acute respiratory distress syndrome.