Fig. 7. Multiple deletions within the -63 kb to -48 kb interval reveal interactions between different regulatory regions. Comparison of Myf5-nlacZ expression profiles between BAC195APZ63-48 (A,E), 59-54 (B,F), 54-49 (C,G) and p8.8 (D,H) constructs. At E9.5 (A-D), deletion of the entire -63 kb to -48 kb region (A) or the -59 kb to -54 kb region (B) results in a marked caudal somitic expression in the dermomyotome, reminiscent of the expression pattern obtained with plasmid p8.8 (D), and driven by the intragenic enhancer element (Summerbell et al., 2000). Deletion of the -54 kb to -49 kb region does not seem to affect the expression pattern at this stage, as it results in a similar pattern to the wild type. This suggests that the -59 kb to -54 kb interval contains the predicted suppressor of the dermomyotome element. At E11.5 (E-H), limb expression is missing in the -63 kb to -48 kb deletion (E), whereas expression in both limbs is seen with both the half-deletion constructs (F,G). In the -59 kb to -54 kb deletion (F), expression in the hindlimb is stronger, whereas in the -54 kb to -48 kb deletion, the relative intensity of expression between fore- and hindlimbs is reversed. This suggests that both regions are required for the full recapitulation of limb expression at this stage. (H) The intragenic region in p8.8 directs a pronounced band of labeling in the myotome of more mature somites.