Fig. 2. Maintenance of rhombomere identities after AP axial rotation of R4 to R7. The AP axis of the hindbrain, R4-R7, is reversed at E1.5. (A) An E1.5 embryo showing EphA4 expression in R3 and R5. The red rectangle indicates the region of hindbrain that is rotated. (B) EphA4-positive R5 is located next to the anterior half of the otocyst in controls. EphA4 is also expressed in R3 and otocysts. (C) EphA4 expression in R5 is relocated (R-R5) to the posterior half of the otocyst after AP rotation. (D,E) Hoxb1-positive R4 is located rostral to the otocyst in controls (D), but is relocated (R-R4) caudal to the otocyst after AP rotation (E). White and black brackets indicate otic locations. Scale bars: 200 µm in A; in B, 200 µm for B-E.