Fig. 3. Schematic diagram of the lacZ transgene constructs used to identify cis-acting regions throughout the Fotx2 genomic locus. The translational start site is indicated (0). Each fragment examined for cis-activity is denoted by the bars marked F1-F13. Restriction enzyme sites used are indicated above. The colored genomic fragments consistently display specific lacZ activity at 10.5 dpc. By contrast, the fragments in black possess no cis-acting ability at 10.5 dpc. Tissues in which expression is driven by these fragments are indicated in colored letters below. The number of lacZ-positive embryos in the specific regions among transgenic embryos is indicated on the right with transgene names. In all these embryos, the patterns of expression were reliably identical although their levels were variable. B, BamHI; Bs, BstEII; EV, EcoRV; N, NotI; Ns, NspV; X, XbaI.