Fig. 6. Identification of the early Pax2 enhancer. (A) Transgenic constructs and statistics. ‘Early’ refers to expression in the anterior neural plate of presomitic embryos and ‘late’ to expression at the MHB beyond the four-somite stage. B, BsrD1; Bu, Bsu36I; Bs, BsmI; Ps, PshAI; Sc, ScaI. (B,C) Transgenes containing the intermediate homology region of Pax2 are expressed already in the neural plate of presomitic embryos. (D,E) Loss of the early (D) but not late (E) MHB-specific expression in a permanent transgenic line lacking the intermediate homology region. (F,G) The 120 bp intermediate homology region together with the Pax2 promoter suffices for anterior neural plate expression (F), but fails to maintain expression in the MHB region (G, arrowhead) at later stages of the same permanent transgenic line. All embryos are shown in lateral view. op, otic placode.