Fig. 2. Localization of separate elements carrying hindbrain cis-regulatory activities. (A) Schematic representation of the chick Krox20 locus and genomic fragments tested by in ovo electroporation and mouse transgenesis. All fragments, except fragments 10 and 13, were cloned upstream of the lacZ reporter gene driven by a human ß-globin minimal promoter. Fragments 10 and 13 were tested by transgenesis after co-injection with a reporter fusion gene, Krox20/lacZ. In all cases, transcriptional activity of the elements was evaluated by X-gal staining of the embryos. The table indicates the construct number, the presence (+) or absence (–) of activity in r3 and/or r5 in electroporated chick embryos (in ovo), the number of E8.5 transgenic embryos analysed (n) and the number of transgenic embryos expressing in r3 and r5 (r3/r5), the r3 to r5 region (r3-r5) or r5 only (r5). (B-I) Electroporated chick embryos (B-E) and transgenic mouse embryos (F-I), for the indicated constructs. r, rhombomere; ov, otic vesicle; ND, not determined.