An allelic variant of the 6A gene for human surfactant protein A

Two human surfactant protein A (SP-A) cDNA clones (1A and 6A) encoding human SP-A genes have previously been identified and characterized by our laboratory. The present study was undertaken to assess potential heterogeneity in the 6A locus among specimens from white adults and infants with respiratory distress syndrome (RDS) as well as black adults. The entire and/or a portion of the published SP-A gene was amplified from different genomic DNAs using the polymerase chain reaction (PCR), cloned, and sequenced. The data revealed the presence of a variant (6A¹) of the 6A gene with characteristics of the 1A gene. The most notable changes were a one-base change in exon 1 and an 11-base insertion in the 3' untranslated region (3'UT). Both changes are found in 1A gene. Analysis of the reverse- transcribed (RT) PCR products from lung mRNAs using 6A specific oligos showed that the 6A¹ variant is transcribed. The prevalence of each SP-A allele was then assessed in a group of 20 Nigerian Blacks and 43 Whites (26 infants with RDS and 17 adults). Although the data did not reach statistical significance, a trend was shown where the 6A/6A genotype appeared with higher frequency in Blacks.