HUMAN SURFACTANT PROTEIN-C - GENETIC HOMOGENEITY AND EXPRESSION IN RDS - COMPARISON WITH OTHER SPECIES

Human surfactant protein C (SP-C) mRNA is detected early during fetal lung development before the differentiation of the type II cell and th e need for surfactant. Later in life SP-C contributes to the surface-l owering properties of surfactant, as shown by several investigators. I n this study we sequenced both coding and noncoding regions of 12 geno mic SP-C clones from several human groups including RDS, whites, and b lack Nigerians, and examined the expression of SP-C in tissues front R DS and from non-RDS. The data showed that all clones had identical DNA sequences, not only within coding regions, consistent with previous o bservations, but also within intervening 5' flanking, and 3' untransla ted regions. Some differences from the previously published sequence w ere noted. The expression of sp-e in tissues from RDS and non-RDS as d etermined by tissue in situ hybridization was comparable between the t wo groups, suggesting that altered SP-C expression, the result of pret ranslational regulatory abnormalities, is an unlikely contributor to t he pathogenesis of RDS. II addition the results show, using genomic bl ot analysis, that a remarkable conservation within coding and 5' flank ing but not within 3' untranslated sequences exists in all mammalian s pecies examined. These data taken together suggest that strong evoluti onary pressures have been exerted on SP-C to maintain conservation, no t only among humans but also among species, which may underscore impor tant roles of SP-C in as yet unknown developmental/functional lung pro cesses.