Fig. 6

Figure 6. Magnetic bead pulling induces interstitial fluid accumulation at the yolk syncytial layer-deep cell boundary

(A) Schematic of mechanical induction of interstitial fluid (IF) relocalization by a controlled displacement of a magnetic bead, implanted at the YSL (yolk syncytial layer)-deep cell (DC) boundary of an MZoep embryo, using a focused magnetic field; embryo was held by a blunt micropipette (d = 80 μm); EVL, enveloping layer.

(B, B′, E, and E′) Representative cross-sections of the magnetic tweezer experiments with unpulled (B and B′) and pulled magnetic beads (E and E′) at the start of the experiment (B and E) and 15′ later (B′ and E′); dashed white line outlines the IF accumulation at the YSL-DC boundary; scale bars, 200 μm.

(C and F) Representative cross-section images of non-pulled (C) and pulled (F) magnetic beads at the YSL-DC boundary where the trajectory of bead movement is projected over a period of 15′; time is color-coded; dashed white line marks the position of the magnetic tweezer; scale bars, 250 μm.

(D and G) Representative kymographs of IF accumulation relative to the position of the magnetic bead, either unpulled (D) or pulled (G), via a focused magnetic field.

(H) Schematic illustrating the embryo orientation during IF relocalization by a controlled displacement of a magnetic bead, implanted at the YSL-DC boundary of an MZoep embryo; AV, animal-vegetal axis.

(I and J) Maximum intensity projections and single cross-sections (S, sagittal view) of MZoep;gsc::caax-EGFP embryos injected with fluorescent dextran to mark IF during mechanical induction of interstitial fluid (IF) at the beginning of the experiment (I) and 15′ after the pull (J); dashed white circles outline implanted magnetic beads; dashed blue lines outline the IF at the EVL-DC boundary; dashed pink lines outline the IF at the YSL-DC boundary (sagittal view, S); scale bars, 100 μm.

(I′ and J′) IF distribution profiles along the axis of controlled displacement of a magnetic bead at the beginning of the experiment (I′) and 15′ after the pull (J′); multi-color curves represent average values of n = 3 independent embryo replicates of the position of magnetic bead (black lines) and IF distribution at the EVL-DC (blue lines) and YSL-DC (pink lines) boundaries; arrowheads (pink) indicate the IF accumulation ahead of the ppl.

See also Video S6.