Fig. 2. Rhombomere grafts in the pre-otic region. (A) Transplant of r3 at level of r5 (r3/r5) and of r5 at level of r3 (r5/r3). (B-N) Flat mount of E6 chick/quail chimera hindbrains in situ hybridised with probes for Islet2, Hb9, Hoxa3 or Hoxb3 as indicated. Labels in white bars above each panel indicate the type of graft and embryonic stage at which the graft was undertaken. Asterisk indicates grafted rhombomere. (G,N) Additional immunostaining of the embryos in F and M, respectively, with anti-quail cell antibodies (QCPN) to show position of the graft. (J,K) Higher magnification of H and I, respectively. (O-S) Double-immunostaining (except S; single immunostaining) on sections of an E6 embryo that had received an r5 in r3 graft at stage 10; transverse cryostat sections through r3 (O-Q) or parasagittal vibratome sections (R,S). (S) Higher magnification of R. Antibodies as indicated: QCPN, anti-quail cells; NF, anti-neurofilament; QN, anti-quail axons; Islet2, anti-Islet2. r, rhombomere; HH indicates Hamburger/Hamilton staging of embryo. White arrows indicate: (O,Q-S) axonal bundles from the graft joining the host abducens (Abd); (P) r5^* Islet2-positive motoneurones. Scale bar: 580 µm for B,E,F-I,L-N; 400 µm for C,D,J,K; 240 µm for O,Q; 120 µm for P; 500 µm for R; 350 µm for S.

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