expression were apparent, such as the loss of aminioserosa (AS) or the block in germ-band retraction (resulting in the U-shaped phenotype commonly observed in embryos deficient for function of genes involved in germ-band retraction). However, Nintra/ NICD over-expression at later stages (stages 13–14) suppressed actin levels. B. Excess canonical Notch signaling due to expression of a hyper-active classical allele l(1)NB also did not result in increased actin level. Embryonic stages 13–14 are shown. All embryos were from the same experiment and were processed identically. (TIF) Figure S8 cl-8+S2 cell mixtures do not show evidence of cell fusion. CellTracker Red labeled cl-8 cells were treated with References 1. Le Sommer C, Lesimple M, Mereau A, Menoret S, Allo M-R, et al. (2005) PTB regulates the processing of a 39-terminal exon by repressing both splicing and polyadenylation. Mol. Cell. Biol 25: 9595–9607. 2. Castelo-Branco P, Furger A, Wollerton M, Smith C, Moreira A, et al. 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