Figure 5
Analysis of the effects of attenuation of Wnt signalling on facial branchiomotor (FBM) migration. (A, B) Control hindbrain explant (A) and secreted frizzed-related protein (SFRP)-treated explant (B) immunostained for Islet-1/2 after 48 hours in vitro. (C) Quantification of FBM migration in hindbrain explants treated with SFRPs. SFRP-treated versus control p < 0.01 (indicated by asterisk), n = 10 explants in each group. (D, E, G-M) Analysis of mutant phenotypes by in situ hybridisation with Islet-1 probe. (D, E, G-I) Flat-mounted hindbrains of embryonic stage (E)12.5 mouse embryos of Wnt5A+/+ (wild type) and homozygote mutant litter-mates Wnt5A-/- in which a stream of cells (arrowheads in (G-I)) is located in rhombomere (r)5 and does not reach their final position in r6 compared to wild type (D). (E, H) Higher magnifications of FBM neurons in wild type and homozygote mutant showing a decompacted nucleus in the latter. (F) Quantification of the migration defect by measurement of the width of the FBM migratory stream showing this is increased in Wnt5A mutants. N = 8; p < 0.05 (error bars = sems). (J, L) Flat-mounted hindbrains of E11.5 mouse embryos of Fz3+/+ (wild type) and its Fz3-/- litter-mate homozygote mutant in which a striking loss of migration of the FBM population can be observed. In the Fz3-/- mutant a much reduced stream of cells migrated caudally into r5 (asterisk) and there is aberrant dorsolateral migration of FBM neurons in r4 (arrowhead). (K, M) At E14.5, FBM neurons in homozygote Fz3-/- hindbrains (M) contain an FBM nucleus in r6 that is much smaller than in the wild-type (K) and there are ectopic dorsal nuclei in r4 and r5 (arrowheads). Brackets in (K, M) indicate the smaller size of the FBM nucleus in Fz3-/- mutant. Scale bars: in (B), 250 μm and applies to (A, B); in (G), 375 μm and applies to (D, G, I,); in (H), 125 μm and applies to (E, H); in (M), 375 μm and applies to (J, M). FN, facial nucleus; TN, trigeminal nucleus.