Lysine Specific Demethylase-1 and the Brahma Chromatin Remodeling Complex Regulate Conserved Signaling Pathways During Drosophila Wing Development

The conserved SWI/SNF chromatin remodeling complex uses the energy from ATP hydrolysis to alter local chromatin environments by disrupting DNA-histone contacts. The Drosophila SWI/SNF counterpart, the Brahma complex, has been shown to have an essential role in regulating the proper expression of many developmentally important genes, including those required for eye and wing tissue morphogenesis. A temperature sensitive mutation in one of the core subunits, SNR1 (SNF5/Ini1/SMARC B1), results in reproducible wing patterning phenotypes that can be enhanced and suppressed by extragenic mutations. SNR1 functions as a regulatory subunit to modulate chromatin remodeling activities of the Brahma complex on target genes, including both activation and repression. To help identify both targets and cofactors of the Brahma complex, I took advantage of the weak dominant nature of the snr1E1 mutation to carry out an unbiased enhancer and suppressor screen using overlapping chromosomal deficiencies. I identified histone lysine demethylase enzymes as potential co-regulators of the Brahma complex and found that these demethylases were important for normal wing pattern development. Specifically, I identified Lysine Specific Demethylase-1 (LSD1) as a potential co-regulator of a subtype of Brahma complex, the PBAP complex, remodeling activities. I found that LSD1 has an important role in cell-fate determination during pupal wing development. Mutation or loss of Co-RE1 Silencing Transcription Factor (CoREST), an accessory protein required for LSD1 demethylase activity, results in a similar wing patterning phenotypes, suggesting that demethylase activity is required for proper cell-fate specification. By utilizing a variety of biochemical and genetic approaches, I found that the LSD1/CoREST repressor complex regulates the evolutionarily conserved TGFβ/DPP signaling pathway, in a cell-type specific manner. My dissertation project has provided the framework for understanding how chromatin remodeling complexes and epigenetic modifying enzymes collaborate to regulate target genes and has broader applications in many fields including development, gene expression, and cell cycle regulation