Embryonic tissues of a multicellular eukaryote diverge through the selective expression of their common genetic constitution. The long term goal of this research is to understand the basis of cell specific gene expression during differentiation. Dr. Ratner's experimental system is the cellular slime mold, Dictyostelium discoideum, in which spore and stalk cells develop from common vegetative precursors. Dr. Ratner is studying the regulation of prespore gene expression. Several prespore genes require developmental protein synthesis for their transcription; in the case of another gene, transcripts are made but quickly decay. Dr. Ratner has cloned one gene of the first class, and shall obtain a genomic clone of the latter type. Both genes will be analyzed by restriction mapping and sub-cloning, RNase mapping, and DNA sequencing. Presumptive control regions will be mutagenized in vitro, ligated to a unique "reporter" DNA fragment, and transformed back into amoebae. In vivo transcript levels will be measured by RNA hybridization in order to identify cis-acting regulatory sequences essential for DNA transcription or mRNA stability. Any essential DNA sequence thus discovered will be used, in gen retardation assays, to search for DNA binding trans-regulatory proteins. %%% During the development of any complex, multicellular organism, genetically identical cells descended from a single fertilized egg somehow differentially regulate the expression of their common genomes so as to achieve diverse forms and functions. This project exploits the simple slime mold as a model to try to understand how this differential gene expression is controlled.
