mTORC1 signaling facilitates differential stem cell differentiation to shape the developing murine lung and is associated with mitochondrial capacity

Formation of branched organs requires sequential differentiation of stem cells. In this work, we find that the conducting airways derived from SOX2+ progenitors in the murine lungs fail to form without mTOR complex 1 (mTORC1) signaling and are replaced by lung cysts. Proximal-distal patterning through transitioning of distal SOX9+ progenitors to proximal SOX2+ cells is disrupted. Mitochondria number and ATP production are reduced. Compromised mitochondrial capacity results in a similar defect as that in mTORC1-deficient lungs. This suggests that mTORC1 promotes differentiation of SOX9+ progenitors to form the conducting airways by modulating mitochondrial capacity. Surprisingly, in all mutants, saccules are produced from lung cysts at the proper developmental time despite defective branching. SOX9+ progenitors also differentiate into alveolar epithelial type I and type II cells within saccules. These findings highlight selective utilization of energy and regulatory programs during stem cell differentiation to produce distinct structures of the mammalian lungs. Lung branching requires differentiation of progenitor cells to be coordinated with morphogenetic events. Zhang et al. find that loss of mTORC1 signaling in the distal SOX9+ lung progenitors reduces mitochondrial capacity and ATP production, thus disrupting the formation of the conducting airways without affecting the development of the gas exchange unit.