Lung alveolar epithelial genes upregulated in terrestrialized lungfish included npc2 (NPC intracellular cholesterol transporter 2), which has a role in lung lipid metabolism and is associated with Niemann–Pick disease characterized by alveolar proteinosis59, and the antioxidant enzyme genes mgst1 (microsomal glutathione S-transferase 1) and prdx1 (peroxiredoxin-1) (Fig. 2c). Here, NPC2 is linked to Niemann-Pick disease.