Fig. 6

Expression of Pdu-Tcf in the adult worm. a 3D reconstruction of a confocal z-stack of several adult Platynereis trunk to tail segments showing the expression of Pdu-Tcf by fluorescent in situ hybridization (red) together with DAPI (blue) and β-catenin immunostaining (green) to visualize cell nuclei and surface; ventral view, anterior up. Sagittal section of the z-stack from (a) through the midline from ventrolateral (b) or lateral (c) view, ventral to the left, anterior up. Strong Pdu-Tcf expression signal in the intestine and constrictions of the gut between segments are apparent. d Lateral view of the same z-stack; ventral down, anterior to the left. e Transverse section through the middle of segment marked in (c) with the planes of coronal sections in (f–h) indicated. f Coronal section of the z-stack from (a) on the level of the ventral nerve cord (VNC), as indicated in (e). Some in situ signal is present in the VNC and weakly in muscles. g Another coronal section deeper in the body through the intestinal wall. In situ signal can be seen in the gut and in few cells around the base of chatae. β-catenin staining is strongest on the surface of the body and the gut epithelium. h Coronal section through the middle of the gut demonstrates strong Pdu-Tcf intestinal expression, especially on the luminal side, and in the intersegmental clusters of mesodermal cells (marked by yellow arrowheads), most probably the excretory system. ch chaetae, iss intersegmental septum, pp parapodia, vnc ventral nerve cord