Genetic regulation of neonatal pulmonary surfactant deficiency has been suggested by studies of gender, genetic linkage, recurrent familial cases, targeted gene ablation in murine lineages, and by racial disparity in risk of neonatal respiratory distress syndrome. Successful fetal-neonatal pulmonary transition requires production of the pulmonary surfactant, a phospholipid-protein film that lines alveoli and maintains alveolar patency at end expiration. Our goal is to understand the genetic mechanisms that disrupt pulmonary surfactant metabolism and cause neonatal respiratory distress syndrome. Studies in human newborn infants have demonstrated that 3 genes are critical for surfactant metabolism: surfactant protein B (SFTPB), surfactant protein C (SFTPC), and an ATP-binding cassette transporter, ABCA3 (ABCA3). To understand genetic regulatory mechanisms, we will investigate the contribution of variation in each of these genes to risk of neonatal respiratory distress syndrome by testing the hypothesis that genetic variants in the SFTPB, SFTPC, and ABCA3 disrupt pulmonary surfactant metabolism. Using high throughput automated sequencing to genotype, multidimensional protein identification technology to assess quantitative and qualitative differences in surfactant protein B and C expression, in vivo metabolic labeling with stable isotopically labeled precursors to estimate surfactant protein B and C and phospholipid metabolic rates, and cohort sizes that provide statistical power (0.8), we will use race-specific, severity-stratified case-control (N=480) and case comparison (N=250) designs to understand genetically regulated, metabolic mechanisms that cause surfactant deficiency by disrupting expression or altering processing of surfactant proteins B or C or by disrupting surfactant phospholipid composition in human newborn infants. Improved understanding of genetic regulation of surfactant deficiency will suggest novel diagnostic strategies to identify and categorize high risk infants and therapeutic strategies that target discrete steps in pulmonary surfactant metabolism to improve outcomes of infants with neonatal respiratory distress syndrome.