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Fig. 7 Roles of the octamer sequences in the transcriptional regulation by the proximal upstream DNA. A-L: GFP-2.2 or its mutated constructs were introduced into embryos and examined for their green fluorescent protein (GFP) expression at early somite stages. Deletion of the intervening sequences little affected the expression (B,C), while disruption of any of the four octamer sequences abrogated the brain expression, but gave rise to ectopic expression in the caudal region (thick arrows, D-J). Deletion of IS2 from GFP-2.2 lacking the octamer sequences eliminated the ectopic expression in the caudal region (K,L). M-R: The expression of GFP-2.2, which was restricted to the dorsal blastoderm at 50% epiboly (M), and to the brain at the bud (O) and three-somite stages (N), was expanded significantly by pou2 overexpression by mRNA injection (P-R), as was revealed both by GFP fluorescence (M,N,P,Q) and whole-mount in situ hybridization (O,R). S-U: The expression of GFP-2.2 (S,T) and GFPΔIS2 (U) in embryos injected with MO-con (S) or MO-pou2 (T,U).