Fig. 5

AVC-specific fibronectin synthesis is dependent on blood flow forces.

(a) Fibronectin staining (magenta) is lost in the absence of heart contraction (fli:nEGFP, sih^-/- embryos) (n=6/6). (b) fli:nlsmCherry embryos injected with gata1, gata2 or myh6 morpholinos to alter blood flow forces were fixed at 48 hpf and anti-fibronectin immunofluorescence analysis was performed. Alterations in flow forces impacted fibronectin synthesis (cyan) in the AVC of gata1, gata2 or myh6 morphants. (c) Quantification of extent of fibronectin (Fn)-positive staining confirms an increase in gata1 morphants and a reduction in both gata2 and myh6 morphants. (d) fli:nlsmCherry (magenta) embryos were incubated with 0.1% tricaine between 48-52 and 48-56 hpf to stop heart contraction. When necessary, heart contraction was restored at 52 hpf by washing out tricaine and embryos were left to develop under normal conditions until 56 hpf. Yellow font shows embryonic age at fixation. Anti-fibronectin immunofluorescence (green) shows the flow-responsive nature of fibronectin in the AVC. (e) Quantification of extent of fibronectin-positive staining confirms the restoration of fibronectin synthesis following restoration of heart contraction. Control (ctrl) samples were not incubated in 0.1% tricaine. Student’s t-test ***P<0.005, **P<0.01, *P<0.05. Scale bars, 10 µm.