One of the major challenges of developmental biology is to understand how cellular diversity is generated. Ultimately, cellular differentiation is the result of differential gene expression controlled at the level of transcription. Thus, to understand cellular differentiation, one must understand how transcription factors control tissue-specific transcription in different developmental contexts. The goal of the proposed research is to understand how glial cell differentiation is accomplished by deciphering how glial-specific gene transcription is executed. Previous investigations identified the glial cells missing (gcm) gene as a "master regulator" of glial cell fate in the fruit fly Drosophila. gcm encodes a novel DNA-binding transcription factor that is required for the development of nearly all embryonic glia. In the presence of Gcm protein, neural cells develop into glia, while in its absence they become neurons. However, Gcm is also expressed in and required for the development of larval macrophages and tendon cells, and lamina neurons in the adult CNS. Thus, Gcm protein activates the transcription of different sets of genes in different developmental contexts. How Gcm regulates these different outcomes is not known. Different collaborators, co-activators, and/or repressors must be involved in regulating Gcm target genes in different tissues. The primary aim of the proposed research is to identify collaborators that act with Gcm to promote the transcriptional activation of Gcm target genes specifically in glial cells, or prevent their activation in the other tissues in which Gcm is expressed. The specific objectives of the proposed research is to understand how the transcription of the glial-specific Gcm target gene repo is regulated by Gcm and other factors. Experiments are designed to define cis-regulatory elements necessary for repo activation and repression and to identify factors that interact with these elements, using genetic, biochemical and bioinformatic approaches. Currently there is a limited understanding of the architecture and composition of transcriptional regulatory elements, as well as the general problem of how developmental context determines transcriptional output at the level of the individual promoter. The analysis of Gcm-dependent transcriptional regulation will provide a useful paradigm for deciphering these developmental problems. The proposed research will provide training opportunities in cell, molecular and developmental biology for undergraduate and graduate students. In addition, the incorporation of materials developed through this research in courses for undergraduate students will expose students to basic molecular biology research and foster interest in research-related careers.
