Glypican 4 is required for efficient convergence and extension movements of cells of the anterior endoderm during early segmentation. Epifluorescence time-lapse experiments performed on the anterior endoderm of one- to six-somite stage (s) Tg(sox17:EGFP) embryos (Movie 1). (A-B′) Representative still images from movies at 1s (A,B) and 6s (A′,B′). Dashed squares indicate locations in which cell migration was analyzed. (C,D) Representative migration tracks of two populations of endodermal cells detected in A and in B. Blue and magenta tracks represent cells that migrate primarily in the anterior and medial directions, respectively. Solid circles indicate the endpoint of migration. N, notochord. (E-G) Characteristics of migration. Six embryos of each genotype were analyzed, and the number of cells analyzed for each genotype is indicated in the graph. (E) Total and net speeds of convergence and extension. (F) Persistence index for migration. ****P<0.0001; Student's t-test. (G) Direction of cell migration during the time-lapse period (5 min intervals, grouped into 30° sectors). A, anterior; P, posterior; ML, medial-lateral.
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