Interestingly, the dGcn5 HAT is not important for ddaC dendrite pruning,

despite its role in facilitating ecdysone signaling and the onset of metamorphosis ( Carré et al., 2005). No pruning defects were observed in dGcn5 RNAi knockdown ddaC neurons (data not shown) or in the MARCM ddaC clones of two dGcn5 null/strong alleles (n = 5; Figure S3D; Table S3). Thus, CBP, but not dGcn5, is required for ddaC dendrite pruning during early metamorphosis. To further verify the requirement of CBP Selleck Ibrutinib for pruning, we overexpressed the dominant-negative form of CBP, which lacks the C-terminal transactivation domain (CBP-ΔQ; Kumar et al., 2004), in ddaC neurons. A strong dendrite-pruning defect was observed with an average of 8.3 primary and secondary dendrites attached in CBP-ΔQ-expressing ddaC neurons (n = 26; Figures 3E, 3E′, and 3F), resembling the CBP RNAi phenotype. We did not recover MARCM ddaC clones using several CBP null/strong

hypomorphic alleles, which was consistent with a previous finding that CBP is essential for cell viability in the eye discs ( Kumar et al., 2004). Further, overexpression of the first exon of mutant Huntingtin (Httex1), with an expanded polyglutamine repeat (Httex1p-Q93; Steffan et al., 2001) that has been reported to sequestrate CBP protein and abolish its HAT activity in both flies and mammals, also resulted in a strong pruning defect (n = 7; Figure S3B) and loss of CBP VRT752271 mw protein (n = 13; Figure S3C) in ddaC neurons. About 13.8 primary and secondary dendrites remained connected in Httex1p-Q93-overexpressing ddaC neurons, whereas all dendrites were pruned in the Httex1p-Q20-overexpressing control ( Figure S3B). Similar to Brm, CBP appears to not be crucial for the development of major larval ddaC dendrites, because RNAi knockdown of CBP did not obviously affect the number of their primary and secondary dendrites of WP ddaC neurons

( Figures 3B–3D). CBP null mutant (nej3) ddaC neurons exhibited normal outgrowth of their embryonic dendrites at 17–18 hr APF (n = 24) and normal major dendrites with slightly simple terminals at 18–19 hr APF (n = 23), compared to the controls (n = 26 and n = 28, respectively; Figure S3E). The expression levels of Thymidine kinase Cut and Knot (n = 4 and n = 7, respectively; Figure S3F) were not affected in CBP RNAi ddaC neurons. Finally, CBP knockdown did not affect regrowth of ddaC dendrites at 76 hr APF (n = 11; Figure S3G). However, the involvement of CBP in dendritic morphology/connectivity of adult ddaCs remains unknown. In summary, CBP appears to be a specific HAT required for ddaC dendrite pruning during the larval-to-pupal transition. Both dendrite pruning of ddaD/E neurons and apoptosis of ddaF neurons are also dependent on EcR-B1 and Sox14 functions (Kirilly et al., 2009 and Williams and Truman, 2005a).