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1Pulmonary-Critical Care Medicine Branch and 2Office of Biostatistics Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
Submitted 10 August 2006 ; accepted in final form 26 October 2006
Surfactant protein B (SP-B) is an essential component of surfactant that promotes adsorption and spreading of surfactant phospholipids and stabilizes the phospholipid monolayer. SP-B is essential for respiratory function in newborn humans and mice; adult mice with levels of SP-B below 25% of wild-type develop fatal respiratory distress syndrome. A potential regulatory function of the C/A(18) single nucleotide polymorphism (SNP) in the promoter of the SP-B gene was examined. Transcriptional analysis and ELISA on bronchoalveolar lavage fluid revealed that the presence of the C allele correlated with more SP-B promoter activity and protein. There was approximately threefold difference in amounts of SP-B in bronchoalveolar lavage fluid from CA(18) and AA(18) individuals. By EMSA, Sp1 bound more tightly to the C allele sequence than to the A allele sequence, perhaps accounting for the differences in transcription. Genotyping of a normal volunteer population showed
31% of the population were AA homozygotes, suggesting that these individuals produce less SP-B. Differences in amounts of SP-B resulting from the promoter SNP could affect the clinical presentation of pulmonary disease.
electrophoretic mobility shift assay; enzyme-linked immunosorbent assay; respiratory function; SFTPB
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