Regulators of repo: A Search for gcm/repo Transcription Factors
The role of the Drosophila melanogaster gene glial cells missing (gcm) is that of a binary switch in both the central nervous system (CNS) and the peripheral nervous system (PNS) in specification of the glial fate for multipotent precursor cells. However, Gcm is also essential for maturation of hematocytes and tendon cells ( Alfonso and Jones, 2002; Jones, et al., 1995; Hosoya et al., 1995; Soustell et al., 2004). The varied outcomes of gcm expression imply the interaction of co-factors capable of giving the Gcm protein different "meanings" in different developmental contexts. The Gcm target repo is expressed exclusively in glial cells and its protein is essential for differentiation and migration of glia (Yausa et al., 2003; Lee and Jones, 2005). Defining the transcriptional role of Repo can be of significance in understanding glial specific gene expression. Systematic analysis of the repo cis-regulatory DNA indicate that a 98 base-pair region recapitulates endogenous repo expression with only a single Gcm binding site (Lee and Jones, 2005; Johnson et al. , 2011). This 98 bp Epi Repressor fragment was used as "bait" in a Double Interaction yeast screen to identify collaborating factors of Gcm. Fusion proteins recovered in the screen include gcm, groucho, and three proteins annotated to trichogen cell phenotypes that may function in macrochaetae development. Three confirmed positives may be related to chromatin remodeling: the co-repressor groucho, Rm62, and histone 4R. CG6770 and Groucho, were selected for further study and exhibited in vivo interactions with gcm.
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