|
Fig. 7 Smooth muscle contraction drives epithelial invasion but does not alter tissue rigidity.
(A–C) Lateral views of live 5 dpf larvae injected with Sma or control morpholino. (A) Sma knockdown has no effect on WT intestinal morphology. (B) Control morpholino injection in mlt. (C) Sma knockdown rescues invasion in mlt. Residual invasive cells persist in this Sma deficient mlt larva (arrowhead). (D–I) Histological cross-sections through the posterior intestine of 74 hpf WT and mlt larvae immunostained with anti-keratin (red) and anti-laminin (green) antibodies. (D) WT. (E, F) mlt larvae injected with control (E) and Sma (D, F) morpholinos. Invasive cells in mlt (arrowheads, E) are rescued by Sma knockdown. (G, H) Injection of a morpholino targeting the high molecular weight isoform of Caldesmon (cald) has no effect on WT intestinal morphology but induces invasion (arrowhead) and stratification (asterisk) in an mlt heterozygote. (I) Treatment of an mlt heterozygote with L-NAME causes invasion (arrowhead) and epithelial stratification (asterisk). (J) Force displacement measurements show identical compliance of intestines dissected from mlt and WT larvae before the phenotype develops at 70 hpf, and a modest increase in compliance at the outer surface of the intestine (<4 micron indentation) when invasion is present at 74 hpf. (K) Compliance is indicated by Young′s modulus, which is proportional to the slope of the Force versus Tissue indentation curve.