In the lung, YAP1 activation in alveolar epithelial stem cells and ECs promotes post-PNX lung growth (Liu et al., 2016; Mammoto T. et al., 2019), while deregulation of YAP1 contributes to chronic obstructive pulmonary disease (Makita et al., 2008) and pulmonary fibrosis (Liu et al., 2015; Panciera et al., 2017). Here, YAP1 is linked to pulmonary fibrosis.