Radial cell movement in paraxial mesoderm. Radial cell movement in paraxial mesoderm. Graph showing the numbers of cells that moved in or out of a 12-16 μm region, located 12 μm deep to the surface endoderm, during a 2-hour time-lapse sequence. Data are represented as the mean±s.d.; numbers on each bar represent the number of observations made on n=8 embryos for WT and n=6 embryos for the Ptk7 mutant. Bars marked with different letters are significantly different from one another (one-way ANOVA followed by the Student-Newman-Keuls test, P>0.01). Wei Wei Yen et al. Development 2009;136:2039-2048 © 2009.