Extended Data Fig. 7: Somite surface tension facilitates length adjustment.
From: Left–right symmetry of zebrafish embryos requires somite surface tension
(A) (a) Schematic of somite dimensions. (b) Normal stress on somite surface due to surface tension. Surface tension forces Fj (red) and Fk (green) acting on the light blue surface i are proportional to the surface edge lengths Lj and Lk. The normal stress σi is then normal force per surface area Ai from which we obtain Eqs. 9, 10 and 11 (see Supplementary Note). (c) Contacts (red) with PSM and anterior somite result in normal stress σa. (d) Left, constraint l(t) imposed on LDV by neural plate and yolk. Right, snapshot of somite 3 from a 3-somite stage embryo. Scale bar, 100 μm. (B,D) 3D plot of relative cell nucleus movements for a representative explant (B) and in vivo somite (D). (C,E) MSRD measurement for 2 explants (C) and two in vivo somites (somite 3) (E). Red line indicates diffusive behaviour and black line indicates the square of typical cell size. (F) Explanted somites contain a Fibronectin-rich extracellular matrix. Fibronectin-mKIK fusion protein from mRNA injected in embryos localizes to somite and notochord boundaries as expected. Red box points to zoomed-in images (right) of the middle and ventral regions of a somite. Scale bar, 50 μm. (G) Fibronectin-mKIK is observed with a similar distribution around explanted somites. Blue, Fn1a-mKIK; yellow, explant manually outlined from Utr:mCherry channel. Scale bar, 25 μm. (H) Representative data for cumulative shape change of cells and somites along AP, ML and DV dimensions. Further details on statistics and reproducibility can be found in the Methods section.
