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Fig. 2 Restriction of erm expression to narrow stripes at the centres of rhombomeres 2-7 is dependent on Notch signaling. In situ hybridisation analysis of erm expression in (A,C,E,G,I) wild-type sibling and (B,D,F,H,J) homozygous mind bomb mutant embryos, at 24 hpf (A,B), 27 hpf (C,D,G,H) and 30 hpf (E,F,I,J). Dorsal views of hindbrain are shown in panels A-F. Transverse sections through rhombomere 5 are shown in panels G-J. The hindbrain of wild-type sibling embryos (A,C,E) exhibits narrow stripes of erm expression at 24, 27 and 30 hpf that are restricted to rhombomere centres. However, in 24, 27 and 30 hpf mind bomb mutant embryos, erm is expressed in much broader domains within rhombomeres (B,D,F), forming a near-continuous domain of erm expression that extends across rhombomeres 2-7. In transverse sections through the hindbrain of 27 and 30 hpf mind bomb mutant embryos (H,J), a recognisable ventricular zone cannot be distinguished and erm expression is restricted to a central territory within hindbrain tissue, being most intense at the midline. By contrast, in age-matched wild-type sibling embryos (G,I), erm expression is restricted to the clearly recognisable ventricular zone.