Fig. 5. Presence of a second late MHB enhancer in the Pax2 upstream region. (A) Transgenic constructs and statistics. Ap, ApoI; B, BsrD1; Bh, BssHII; Bs, BsmI; K, KpnI; Sc, ScaI; Sp, SapI; Sm, SmaI; Ss, SspI. (B,C) Transgene #17 lacking the proximal enhancer was still expressed in the MHB region (arrowhead). (D,E) Four (* in A) of five embryos expressed transgene #19 only in the ventral MHB region at E10 to E10.5, indicating that the conserved 102 bp sequence in the distal homology region of mammalian and Fugu Pax2 genes (Fig. 1B) is required for maintaining lacZ expression in the dorsal region of the MHB. Embryos are shown in frontal (B), dorsolateral (D) or lateral (C,E) view.