These data suggest that Brm likely acts upstream of Sox14 to control its expression but appears to not directly regulate the expression of mical, a Sox14 target gene, in ddaC neurons. Thus, Brm appears to play a specific role in regulating the expression of Sox14, but not some other components of the EcR-B1/Sox14/Mical pathway. We next examined Brm expression and compared its expression pattern with EcR-B1. Brm was KPT-330 manufacturer expressed and localized in the nuclei of ddaCs and other dorsal da neurons (Figure S2B), whereas it was absent in brm MARCM ddaC clones ( Figure S2D). In contrast to drastic upregulation of EcR-B1 from the early third instar larval (eL3) stage to the
WP stage in ddaCs ( Kirilly et al., 2009), Brm levels remained largely constant ( Figures S2G and S2H). Consistently, inhibition of ecdysone signaling by EcRDN overexpression had no effect
on the expression levels of Brm in the WP ddaCs ( Figure S2F). These data indicate that Brm is expressed independently of ecdysone signaling. The observation that the Brm remodeler regulates dendrite pruning prompted us to systematically investigate the involvement of histone modifiers, including histone acetyltransferases/deacetylases and methyltransferases/demethylases in ddaC dendrite pruning. We examined 49 genes that potentially regulate enzymatic functions and assembly of various histone modification complexes click here (Table S1; also see Supplemental Experimental Procedures) via RNAi. From these HATs, CBP was the only gene we isolated that was required for ddaC dendrite pruning. CBP functions as a HAT as well as a transcriptional coactivator during gene activation ( Bantignies et al., 2000). Perturbation of its histone acetyltransferase activity is implicated in
neurological disorders, such as Rubinstein-Taybi syndrome (RTS) ( Wang et al., 2010) and polyglutamine expansion diseases ( Steffan et al., 2001). CBP RNAi knockdown with two independent RNAi lines, GD3787 (#1) and KK105115 (#2) ( Dietzl et al., 2007), resulted in severe dendrite pruning defects in ddaC neurons: an average of 9 (n = 21; Figures 3B, 3B′, and 3F) and 12 Ergoloid (n = 30; Figures 3C, 3C′, and 3F) primary and secondary dendrites, respectively, persisted at 18 hr APF. Using a third CBP RNAi line (#3) that was previously published ( Kumar et al., 2004), the knockdown of CBP exhibited a similarly strong dendrite pruning defect, with an average of 11.9 primary and secondary dendrites (n = 29; Figures 3D, 3D′, and 3F), whereas all dendrites were pruned in the wild-type ddaC neurons (n = 15; Figures 3A, 3A′, and 3F) at 18 hr APF. The larval dendrites of CBP RNAi ddaCs were largely removed by 30 hr APF (n = 6; Figure S3A), similar to those of BrmDN-overexpressing ddaCs.