Expression of the lacZ reporter gene driven by the conserved downstream segments in transgenic mice. (A) Structure of the reporter construct. Each transgene construct was made by insertion of one of the conserved segments into plasmid pIZ (Hatano et al. 1998). (B) Representative patterns of lacZ staining in 12- to 12.5-dpc embryos. CS1 transgenes reproducibly stained the ganglionic placodes of the facial nerve (near the first branchial groove) and the inferior edge of the maxillary prominences. CS3 transgenes were expressed in the sclerotome, and CS4 transgenes in the liver and the epithelial layer of the gut. CS5 directed lacZ expression in the neural tube floor plate as well as in the ectoderm of the limb buds. Both CS6 and CS9 transgenes expressed lacZ in the myotome and the rib primordia. CS7 transgenes were expressed in the mesenchyme condensations at the bases of the limb buds. The expression patterns were confirmed by histological examinations.
