Fig. 5.

The periodicity of cLfng oscillations slows later in development following dramatic downregulation of cWnt3a expression in the tail bud. (A, B) Fix and culture assays performed on chick explants at different stages of development. (A) Two day old explants showing progression through one complete cycle of cLfng and formation of an extra somite within 90 min in the cultured half. Both explants show onset of phase I. (B) Chick explants dissected from HH stage 22 showing progression from phase I on the fixed side to phase III on the cultured side within 90 min i.e. the cultured explant does not complete a full oscillation in this time period. (C, D) Chick explant pairs cultured in Wnt3a conditioned media, 10 mM LiCl, control media alone or control media supplemented with KCl respectively. (C) Treatment with Wnt3a media did not affect the oscillation period of cLfng. (D) Treatment with LiCl did not affect the oscillation period of cLfng. (E–G) HH stage 20–23 chick embryos hybridised for cWnt3a expression showing broad expression in the tail bud at HH stage 20 (E) becomes dramatically reduced (F, G). (H) Western blot analysis where each lane contains protein extracted from the PSM of 5 E2 chick embryos cultured in control or Wnt3a media. Top row shows GAPDH as loading control. Middle row shows total β-catenin. Bottom row shows β-catenin when phosphorylated on the three residues targeted by GSK3β (S33, S37-P, T41-P). Dashed line indicates control. Red dots demarcate somites. Arrow heads highlight tail bud expression domain of Wnt3a.