High resolution mapping of the human sp-a and sp-d loci

The human pulmonary surfactant protein A (SP-A) locus has been assigned to chromosome 10q22-23 and consists of two nearly identical genes, SP-A1 and SP-A2, as well as a truncated pseudogene. SP-A belongs to the family of C-type lectins along with another surfactant associated protein, SP-D, which has also been mapped to the long arm of chromosome 10. Here we report the relative location of each of the human SP-A and SP-D genomic sequences. Characterization of two overlapping genomic clones revealed that the SP-A pseudogene lies in a reverse orientation 15kb away from the 5' side of SP-A1. This finding was verified by the amplification of the entire SP-A pseudogene / SP-A1 intergenic region using long range PCR with genomic DNA as template. The relative locations of SP-A2 and SP-D were then determined by testing a number of sequence tagged sites (STSs) against the Stanford G3 and TNG3 radiation hybrid panels. The radiation hybrid mapping data showed that both SP-A2 and SP-D are on the 5" side of SP-A1 at approximate distances of 40kb and 120kb, respectively. The SP-A and SP-D loci were also oriented relative to the centromere. The overall order was found to be: centromere-SP-D-SP-A2-pseudogene-SPA1-telomere. Supported by NIH grant HL49823.