Expression and cDNA sequence of helix destabilizing protein (HDP) in rat lung

The current study was undertaken to investigate genes that show alteration in expression during late fetal rat lung development. Using the differential display (DD) method, an initially unknown transcript was found to be abundant on day 18 compared to day 22 of gestation. This finding was confirmed by RNA blot analysis. Subsequent screening of a rat lung cDNA library with the unknown DD cDNA as a probe revealed a clone that encodes helix destabilizing protein (HDP), similar to that reported in rat brain (J Biol Chem. 1986, 261:3536-3543). Although there were several differences between lung and brain cDNAs at the 3' untranslated region (UTR), the 5' end was well conserved. There was a gradual decrease in HDP mRNA content beyond day 18 of gestation, as lung maturation increased. Similarly, a lower content of HDP mRNA was observed in maternal heart and brain tissues than in fetal heart and brain tissues from day 18 of gestation. Maternal dexamethasone treatment that promotes lung maturation did not have an impact on HDP expression. Because of the much higher abundance of HDP mRNA during fetal organ development compared to adult tissues, we speculate that HDP plays an important role during lung development. A portion of this work was previously presented (FASEB J. 1996;10:A26).