Hindbrain patterning in wild-type and nls embryos. In situ hybridisation of wild type (upper panels in A,C,E,G,I,K,M,O,Q.S) and nls (lower panels in B,D,F,H,J,L,N,P,R,T) embryos with markers expressed in the hindbrain and spinal cord. (A,B) valentino expression in r5/r6 is expanded along the AP axis (see also r3-r7 in Figs 2D,F,J); myoD expression abuts r7 in wild type and r6 and r7 in nls. (C,D) Expression of ephrin b2 appears normal in r4 and r7 in nls. (E-H) hoxb3 expression in r5/r6 and in the migrating postotic neural crest (arrows in G,H). (I-L) hoxb4 expression (blue) in the neural tube is absent in a 12 hpf nls embryo; krox20 expression (red) is expanded; myoD (red) counterstain identifies nls embryos (I,J). At 16 hpf, neural hoxb4 expression is initiated with an anterior expression boundary at r6/r7 (arrowheads), yet it is not fully expanded caudally (K.L). (M,N) RARa is expressed caudally to the r6/r7 boundary in the neural tube (arrows) in wild type; nls embryos are devoid of neural expression, while expression is unaffected or slightly elevated in more rostral regions of the neural tube (arrowheads). (O-R) tbx-c expression in interneurones of the anterior spinal cord (arrows) is reduced in nls; (Q,R) cross sections show tbxc expression in the spinal cord (arrows). (S,T) Immunostaining with the Zn8 antibody of spinal cord neurones at the level of the pectoral fins (arrows) shows loss of these neurones in nls. ov, otic vesicle. Embryonic stages: 24 hpf in A,B,E-H; 10 somite stage in C,D; 12 hpf in I,J,M,N; 16 hpf in K,L; 33 hpf in O-T. Lateral (C-F,I-L,O,P) and dorsal (A,B,G,H,M,N,S,T) views, anterior towards the left.