Fig. 4. Gene perturbation selectively eliminates muscle.

Wild-type animals are shown in the upper row panels and mutant animals in the lower row panels. a e-protein−/− mutant: Phalloidin staining in control (upper) and mutant (lower). b nem64−/− mutant: Control animals (upper) show extended tentacles with intact phalloidin-positive retractor muscles, whereas mutant animals (lower) exhibit droopy nonresponsive tentacles and the absence of phalloidin-positive muscle within the tentacle retractors. c Structural marker genes (myhc-st, melc4) are lost within the tentacles of nem64−/− mutant animals (bottom). Outline of animal indicated with a dashed line, arrows: tentacles. d Single-cell sequencing of nem64−/− animal heads lose the retractor muscle cluster present in the wild type (TR & MR: top), but the retractor muscle signal is present in a few cells of the gastrodermis (MR). e Mapping mutant cells onto the wild-type UMAP confirms the presence of MR cells but the loss of TR cells. f The distribution of cell types is otherwise similar between wild type and mutant heads. Scale bars are 100 µm (embryos) and 20 µm (confocal images).