Fig. 3. A posterior FGF8 gradient modulates endoderm tensional gradient to control collective cell movements.
a, Coelectroporation of DUSP6-mScarlet reporter and control CAG nTagBFP (n = 7). Scale 100 μm. b-c, Normalized DUSP6 activity (b) and gradient shape parameter ι (c, GFP: green, n = 7, FGF8: red, n = 5); mean ±s.d., unpaired two-tailed t-test. d, Representative cell tracks (HH14 to HH16) of GFP electroporated embryos in 0.1% DMSO (n = 0/3 affected) or 50 μM SU5402 (n = 3/3 affected), or electroporated with dnFGFR1-IRES-GFP or FGF8-IRES-GFP. Scale 100 μm. e, Average cell velocity (n = 4 embryos each). mean ±s.d., 1-way ANOVA, Tukey’s correction. f, Transverse sections through posterior HH18 embryos; For GFP n= 5/5 formed hindgut, vs. n= 3/12 for dnFGFR1-IRES-GFPand n= 8/21 FGF8-IRES-GFP; D/V = dorsal/ventral. Scale = 10 μm. g, Relative tension at HH15, n = 10 embryos each; mean ±s.d., 1-way ANOVA, Tukey’s correction; *P vs. GFP. h- i, Cell density (h, ≥1,000 cells each from n= 6 GFP and dnFGFR1, and n = 4 FGF8) and area (i, ≥1,000 cells each from n = 6 GFP, n = 7 dnFGFR1, and n = 8 FGF8) at HH15; mean ±s.d., 2-way ANOVA, Tukey’s correction. */+ vs GFP/posterior-most bin per treatment. j, Membrane stain PKH26 with mosaic expression of GFP (top-left) and dnFGFR1-IRES-GFP (bottom-left) at HH15; cell area quantification (right) in GFP+ and (-) cells with GFP (197 cells, n = 3) and dnFGFR1 IRES GFP (209 cells, n = 4) electroporation; mean ±s.d., 2-way ANOVA, Tukey’s correction, */+ vs. GFP(+)/dnFGFR1-IRES-GFP(-); A/P = anterior/posterior. k, Cell tracks (HH14 to HH16) with anteriorly grafted PBS (left, n = 0/3 disrupted) or rhFGF8 soaked (right, n = 4/7 disrupted) beads. Scale 100 μm. l, εyy heat maps for PBS and rhFGF8 soaked beads (n = 1/5 and n = 4/6 ectopic compaction strains, respectively); bead marked by white circle. Scale 100 μm.