Fig. 1. The regulatory region at -58/-48 kb upstream of Myf5. (A) Schematic representation of the different fragments of the -58/-48 kb region and its upstream extension to -63 kb, which are subcloned in front of the Myf5-nlacZ cassette (2.6 kb, including a branchial arch element, neural tube element and the Myf5 promoter) (Hadchouel et al., 2000; Summerbell et al., 2000). For each construct, the cloned region is indicated by a black line. Distances in kb are from the Myf5 Cap site. (B) The nlacZ expression pattern, revealed by X-gal staining, is shown for an embryo at E11.5 (40-45 somites) with a -58/-48 tk-nlacZ transgene, where the region between -58 kb and -48 kb has been placed in front of a heterologous thymidine kinase promoter.