<p>Yeast Atg1 initiates autophagy in response to nutrient limitation. The <i>Ulk</i> gene family encompasses the mammalian orthologs of yeast <i>ATG1</i>. We created mice deficient for both <i>Ulk1</i> and <i>Ulk2</i> and found that the mice die within 24 h of birth. When found alive, pups exhibited signs of respiratory distress. Histological sections of lungs of the <i>Ulk1/2</i> DKO pups showed reduced airspaces with thickened septae. A similar defect was seen in <i>Atg5</i>-deficient pups as both <i>Ulk1/2</i> DKO and <i>Atg5</i> KO lungs show numerous glycogen-laden alveolar type II cells by electron microscopy, PAS staining, and increased levels of glycogen in lung homogenates. No abnormalities were noted in expression of genes encoding surfactant proteins but the ability to incorporate exogenous choline into phosphatidylcholine, the major phospholipid component of surfactant, was increased in comparison to controls. Despite this, there was a trend for total phospholipid levels in lung tissue to be lower in <i>Ulk1/2</i> DKO and <i>Atg5</i> KO compared with controls. Autophagy was abundant in lung epithelial cells from wild-type mice, but lacking in <i>Atg5</i> KO and <i>Ulk1/2</i> DKO mice at P1. Analysis of the autophagy signaling pathway showed the existence of a negative feedback loop between the ULK1 and 2 and MTORC1 and 2, in lung tissue. In the absence of autophagy, alveolar epithelial cells are unable to mobilize internal glycogen stores independently of surfactant maturation. Together, the data suggested that autophagy plays a vital role in lung structural maturation in support of perinatal adaptation to air breathing.</p
