Neural crest cells lacking Sip1 exhibit reductions in detachment, directional migration, and overall displacement. Time-lapse imaging of the midbrain regions of living embryos starting at HH10. (A and B) Snapshots of embryos electroporated with Sip1MO-FITC + pCS2-memRFP show electroporated cells that are able to delaminate from the neural tube (NT) and migrate laterally (LE, leading edge). However, they remain connected to each other (asterisks) near the midline and form clumps of cells relative to ContMO-injected cells (E and F). (C and D) Cell tracking and net displacement over time (t = 295 min) shows that Sip1MO-injected cells are unable to migrate long distances away from the midline and in a directional manner as is seen in ContMO embryos (G and H; t = 245 min). (H) Displacement of ContMO-injected cells demonstrates that NC cells near the LE actively migrate away from the midline while the NT appears to move away from the NC cells due to growth and movement. (I and J) Confocal imaging of a histological section from an embryo electroporated on the left side with memRFP + nucRFP and on the right side with Sip1MO + memRFP + nucRFP reveals that Sip1MO-treated cells remain clumped next to the midline (arrows). NT, neural tube; LE, leading edge. (C and G) white dots represent final time points for each track. (A and B) z = 8 µm; (E and F) z = 10 µm; (I and J) z = 6 µm. Bars, 30 µm. See also Videos 1–6. The data shown are representative of multiple repeats (experiment was repeated five [Sip1MO] and four [ContMO] times).