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Fig. 5 Msgn1 controls cell movements in the neighbourhood of the tailbud. (A) An 8-somite stage Kaede-injected zebrafish embryo with a patch of tailbud cells freshly photoactivated (red), imaged in the plane of the notochord and adaxial cells [i.e. in the superficial layer of the maturation zone (MZ)]. (B-C′′) Dispersion of the photoactivated tailbud cells imaged in this plane in controlMO (B-B′′, Movie 1) and msgn1MO (C-C′′, Movie 3) morphants. (E) An 8-somite stage embryo with photoactivated tailbud cells (red) imaged in a deeper layer, ~20 μm ventral to the notochord and adaxial cells (i.e. in a deep layer of the MZ). (F-G′′) Dispersion of the photoactivated tailbud cells imaged in this plane in controlMO (F-F′′, Movie 2) and msgn1MO (G-G′′, Movie 4) morphants. (D,H) z-position of individual Kaede photoactivated tailbud cells tracked over time in controlMO (D) and msgn1MO (H) morphants. Each colour represents an individual cell. Loss of msgn1 leads to failure of ventral diving and of the subsequent lateral dispersion. Scale bars: 50 μm.