IDENTIFICATION OF GENES INVOLVED IN THE ADAPTATION OF THE LUNG TO THE AIR ENVIRONMENT. ▴ 354

Abstract

We are using the technique of differential display RT-PCR in order to identify genes important in lung development. We are particularly interested in genes whose products are essential to mesenchymal-epithelial interactions in late gestation lung. We isolated 38 cDNA probes representing mRNAs whose expression is modulated by glucocorticoid (GC) and dihydro-testosterone (DHT) in days 19-20 fibroblasts (fib) or epithelial cells (epi) of fetal rat lung. Among 18 fib-specific sequences, 16 represented mRNAs whose expression is increased in the presence of GC and decreased in the presence of DHT. This pattern of expression is expected for FPF, an activity generated by fibs which augments epi surfactant production. Twenty sequences were epi-specific and represent mRNAs meeting criteria for GC receptor (GR) stimulating factor (an activity produced by epi which stimulates fib GR). We sequenced 20 (15 epi, 5 fib) subclones (18 novel). Nine showed interesting homologies to sequences in Genbank. The predicted protein product of one epi-clone had 66-70% homology(over 60 residues) to 70 bacterial flagellins but had no identified homologs in eukaryotes. This suggests a novel protein, perhaps a precursor of a lung ciliary protein. The predicted protein products of 3 epi-clones had primary sequence homology or protein structural motifs suggestive of transcriptional regulators. One clone had homology to rat/mouse progesterone receptor (a stage and tissue-specific transcriptional regulator). Another had homology to yeast HPR1 protein (a positive transcriptional regulator). A third clone had a region with a leucine-zipper motif, a motif common to transcriptional activators. Transcriptional regulatory sequences are of interest as regulation of transcription is likely a key mechanism in the modulation of gene expression in late gestation lung development. These findings open new areas for the study of regulation of fetal lung maturation.