Fig. 3. Rhombomere grafts in the post-otic region. (A) Transplant of r3 or r4 at level of anterior (r8a) or posterior (r8p) r8. (B-J) Flat mounts of E6 chick/quail chimera hindbrain preparations containing rhombomere grafts, in situ hybridised with probes for Islet2, Hb9, Hoxa3 or Hoxd4 as indicated by blue type. Labels in white bars above each panel indicate the type of graft and embryonic stage at which the graft was undertaken. E,G and H show only the r8 region. Asterisk indicates grafted rhombomere. Double-headed arrows indicate rostrocaudal extent of grafted rhombomere. (D) Higher magnification of C showing immunofluorescent QCPN staining (red) of grafted r3. (J) Higher magnification of I showing immunofluorescent QCPN staining (red) of grafted r4. (K-O) Double-immunostaining on transverse serial cryostat sections (level of r8p) of E6 embryo that had received an r4 in r8p graft at stage 10. Antibodies as indicated as in Fig. 2, with the addition of anti-Islet1/2 and anti-Lim3 antibodies. White arrow (K) indicates quail axons from r4^* leaving the neuroepithelium ventrally and joining host hypoglossal axons. (P) Diagram of a transverse section level of r8p summarising normal Lim code in host r8p versus grafted r4^*. Scale bar: 580 µm for B,C,F,I; 190 µm for E,G,H,J; 140 µm for D; 340 µm for K; 120 µm for L,N; 60 µm for M,O.

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