Figure 7. Noncanonical Wnt Signaling Is Required for the Formation of the Asymmetric Bilateral Body Plan (A) Spindle orientations during AB4-AB8 division. Schematic representation of left side views. The Wnt signal from C that leads to spindle rotation in ABar is highlighted in blue. Note that all other AB spindles are parallel. (B) RNAi of Wnt-signaling components and their effect on asymmetric midline placement. 3D projection stills, left side views, fluorescent markers are plasma membrane (red) and nuclei (green). Dashed lines indicate the orientation of the midline, numbers indicate the angle between the midline and the AP axis (n = 3; mean ± SD). Large double arrows indicate spindle orientations of ABal and ABar, respectively. Small arrows indicate the interface of ABal/pl where filopodial protrusions are normally observed in wild-type embryos. (C) Effects of
mom-2 RNAi on individual cellular paths. Displacement of AB nuclei in AP and DV direction during chiral morphogenesis are shown as in Figure 6D for five wild-type and five
mom-2 RNAi embryos. (D) Severe impairment of apical NMY-2 accumulation in
gsk-3 RNAi-treated embryos. 3D projection still, left side view. Plasma membrane is shown in red and the actomyosin cortex (NMY-2) in green. Arrows indicate the interface of ABal/pl where filopodial protrusions are normally observed in wildtype embryos. The asterisk points to the center of the apex of ABpl. (E) Quantification of the
gsk-3 RNAi phenotype relative to wild-type. Graphs displaying cortical NMY-2::GFP fluorescence intensity as measured on a line parallel to the AP axis that transects the center of ABpl (as shown in the inset on the upper right) for a representative wild-type (gray) and
gsk-3 RNAi embryo (red). (F) Flowchart of the components and processes leading to LR mechanical differences, chiral morphogenesis, and asymmetric midline placement. Wild-type behaviors are depicted in green. The behavior in mutants with inverted chiral morphogenesis is shown in red. Size of fonts depicts the degree of cortical contractility. Solid lines represent AP axes; dashed lines represent midlines.