Fig. 7. Regulatory organisation of paralogous group 4 Hox genes in the mouse. (A) A revised version of Fig. 1A incorporating the data presented in this study. The spatial and temporal specificities of regulatory regions are indicated below the Hoxb4 locus. Red and yellow boxes indicate neural and paraxial mesodermal specificity, respectively. Early and late regulatory elements have been more precisely mapped within region A and are indicated accordingly (Gould et al., 1997; Gould et al., 1998). (B) Comparison of the regulatory organisation of Hoxa4, Hoxb4 and Hoxd4. Black boxes represent the coding sequences of each gene. The question mark represents the ambiguous role of the Hoxa4 intron (see Discussion). Asterisks indicate that enhancer activity may be located in either or both of the regions 3' of Hoxd4. M, maintenance. This diagram incorporates data from Behringer et al. (Behringer et al., 1993), Keegan et al. (Keegan et al., 1997), Morrison et al. (Morrison et al., 1997), Sharpe et al. (Sharpe et al., 1998), Whiting et al. (Whiting et al., 1991) and Zhang et al. (Zhang et al., 1997).