Gene expression analysis of rat tracheal epithelial cells following exposure to ionizing radiation

This study involved the use of differential display (DD) to investigate gene expression in rat tracheal epithelial cells following exposure to ionizing radiation. Previous work in X ray response research has provided useful information using cell lines and classical molecular biology techniques. However, the specific molecular mechanisms of the cellular response to ionizing radiation remain unclear. The development of DD (Liang and Pardee, 1992) provided a new means for studying changes in gene expression. In addition, the use of primary rat tracheal epithelial cells in X ray induced transformation studies (Terzaghi-Howe, 1990) provided a model cell population that more closely resembles in vivo conditions than do cell lines. DD was used to analyze gene expression in rat tracheal epithelial cells, revealing six potential X ray responsive gene fragments. Sequence analysis revealed that four of the six cDNA clones had significant sequence identity to known genes involved in growth and differentiation. These include a embryogenic preimplantation gene (Temeles et al, 1994), a human interferon related gene (Tirone et al, 1989), a mouse zinc finger mRNA (Mardon et al, 1990), and elongation factor 1 δ(Sanders et al, 1993). Enhanced expression was not detect by northern blot analysis using the cDNA fragments as probes. Two independent clones were isolated from 2 the original DD cDNA fragments to check the efficiency of reamplification and TA cloning. The secondary clones produced distinct sequences and Northern blot patterns. These clones showed significant identity to cyclin A and rat repetitive mRNA. Despite the inconsistencies, DD remains promising as a means for studying the molecular response of cells to ionizing radiation.