The goals of this project are (1) to understand the structure of two genes of which expression is controlled by retinoic acid and (2) to identify cis-acting DNA elements involved in the collagen IV and another differentiation gene during F9 stem cell differentiation. I plan to examine the restriction maps of these two F9 differentiation specific genes, identify the structural regions and more specifically the '5 end transcription cap sites. Different sizes of '5 flanking regions of two genes will be linked to Beta-globin structure gene of which promotor and '3 end of gene has been deleted. Transfection assays by using hybrid gene-SV40 vector as donor will be performed in F9 stem cells. The retinoic acid sensitive DNA elements will be determined in the transfected cells when higher degree of expression of Beta-globin gene is detected at the differentiated stage of F9 cells. These series of experiments will allow me to identify the retinoic acid regulated sequences directly or indirectly. Retinoic acid has been implicated in the control of differentiation in epithelial tissues and in some other cell types. The mechanism by which retinoic acid induce differentiation of teratocarcinoma cells is not well understood. Investigation in this field speculate that retinoic acid may act in a manner analogous to steroid hormones. However, the experimental data is too preliminary to make any firm conclusions. The studies of differentiation genes by using molecular cDNA as probe and further identifications of retinoic acid regulatory elements will inform us of the underlying mechanism of the action of retinoic acid. In addition, the understanding of early embryonic differentiation may also facilitate the understanding of oncogenesis which results from dedifferentiation in some cases.
